50 Supported by research
Linus Pauling found clinical evidence suggesting that high-dose intravenous vitamin C administration is useful as a supportive cancer treatment and mitigates chemotherapy side effects.
"Dr. Pauling was the Nobel Prize-winning chemist who found clinical evidence suggesting that high-dose intravenous administration of vitamin C is useful as a supportive treatment for cancer, as well as a method for mitigating the side effects of chemotherapy." (said at 0:01:01)
Linus Pauling, in collaboration with Scottish surgeon Ewan Cameron, published observational studies in 1976 and 1978 reporting that high-dose vitamin C (initiated intravenously at 10 g/day, followed by oral maintenance) substantially prolonged survival as a supportive therapy in terminal cancer patients. While the statement accurately reflects what Pauling published, the underlying clinical evidence from those studies was of very low quality, relying on retrospective matched controls without randomization or blinding, which introduced substantial selection bias.
Consuming five to nine servings of vitamin C-rich fruits and vegetables daily produces steady-state plasma vitamin C concentrations of around 80 micromoles per liter or less.
"If a person eats between five and nine servings of vitamin C-rich fruits and vegetables a day, their steady-state plasma vitamin C concentrations will be around 80 micromoles per liter or less." (said at 0:02:05)
Controlled pharmacokinetic depletion-repletion clinical trials in healthy volunteers demonstrate that oral intake of vitamin C achieves steady-state plasma saturation at approximately 70 to 80 micromoles per liter. Consuming 5 to 9 servings of fruits and vegetables daily provides approximately 200 to 400 mg of vitamin C, which places plasma concentrations on the plateau of the dose-concentration curve where maximum steady-state plasma concentrations are tightly regulated and maintained around 80 µmol/L or less due to saturable intestinal absorption and renal excretion.
Peak plasma vitamin C concentrations from oral intake do not exceed 220 micromoles per liter, even with a maximum oral dose of 3 grams six times daily.
"A person's peak plasma vitamin C concentrations won't exceed 220 micromoles per liter from oral vitamin C intake, even if they take a maximum oral dose of three grams six times daily." (said at 0:02:35)
Pharmacokinetic data and modeling in healthy volunteers demonstrated that plasma vitamin C concentrations from oral administration are tightly controlled by saturable intestinal absorption and renal clearance. Pharmacokinetic modeling predicted that even at the maximum tolerated oral dose of 3 g administered every 4 hours (six times daily), peak plasma vitamin C concentrations reach a maximum of approximately 220 micromol/L.
Intravenous vitamin C administration can produce plasma concentrations as high as 15,000 micromoles per liter.
"By contrast, intravenous vitamin C can produce plasma concentrations as high as 15,000 micromoles per liter." (said at 0:02:48)
Pharmacokinetic studies demonstrate that intravenous administration of high-dose vitamin C bypasses intestinal absorption saturation mechanisms and achieves peak plasma concentrations in the range of 13,000 to 15,000 μmol/L (13 to 15 mM) at typical infusion doses of 50 to 100 g, compared to a plateau of approximately 220 μmol/L achieved by maximum tolerated oral dosing.
Cooking and exposure to oxygen can destroy 25% or more of the vitamin C in foods.
"Unfortunately, cooking and exposure to oxygen can destroy 25% or more of the vitamin C in foods, so it's best to eat vitamin C-rich foods raw and immediately after cutting or peeling." (said at 0:09:14)
Published experimental research on food preparation and cooking methods shows that heat and exposure during processing frequently cause substantial degradation and leaching of vitamin C, with losses regularly reaching or exceeding 25%. Analyses comparing different cooking methods (such as boiling, stir-frying, blanching, and microwaving) across various vegetables demonstrate that vitamin C retention can drop significantly, in many cases falling below 75% retention (and as low as 0% under severe boiling conditions).
The Recommended Dietary Allowance (RDA) for vitamin C is 90 milligrams per day for healthy men and 75 milligrams per day for healthy women.
"The Recommended Dietary Allowance, or RDA, for healthy men is 90 milligrams per day; for women, it's 75 milligrams per day." (said at 0:10:45)
The established Recommended Dietary Allowance (RDA) for vitamin C established by the Institute of Medicine (Food and Nutrition Board) is 90 mg/day for adult men and 75 mg/day for adult women, based on providing antioxidant protection and maintaining near-saturating tissue levels while preventing deficiency.
The Tolerable Upper Intake Level for vitamin C is 2,000 milligrams per day.
"So at the other end of the recommendations is the Tolerable Upper Intake Level: 2,000 milligrams per day, the amount that experts believe reduces the risk of these GI problems." (said at 0:11:15)
The Tolerable Upper Intake Level (UL) for vitamin C in adults established by the Food and Nutrition Board of the Institute of Medicine is 2,000 mg per day. This threshold is specifically set based on the prevention of gastrointestinal adverse effects, such as osmotic diarrhea and gastrointestinal upset, associated with unabsorbed excess vitamin C.
- supports: Vitamins E and C are safe across a broad range of intakes. (The American journal of clinical nutrition 2005) · cited 305x in the literature
"As safety guidance, tolerable upper intake levels have been established by the Food and Nutrition Board, Institute of Medicine, at 1000 mg for vitamin E and 2000 mg for vitamin C in adults. Many clinical trials with these vitamins have involved subjects with various diseases, and no consistent pattern of adverse effects has occurred at any intake. Numerous studies of vitamin C supplementation have provided no pattern of evidence to support concerns about safety other than occasional gastrointestinal upset or mild diarrhea resulting from the osmotic effects of unabsorbed quantities of vitamin C." (abstract, passage verified)
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A single dialysis session in patients with renal failure decreases plasma vitamin C levels by roughly half.
"A study involving 22 patients with renal failure and their matched healthy controls found that a single dialysis session decreased the patients' plasma vitamin C levels to roughly half of their pre-dialysis levels." (said at 0:12:16)
Studies evaluating ascorbic acid status in patients with end-stage renal disease show that a single hemodialysis session significantly depletes water-soluble plasma vitamin C, typically reducing circulating levels by approximately 40% to 65% (roughly half) compared to pre-dialysis baseline levels.
- supports: Erythrocyte transmembrane electron transfer in haemodialysis patients. (Nutrition, metabolism, and cardiovascular diseases : NMCD 2007) · cited 7x in the literature
"Pre-dialysis RBC GSH (0.68+/-0.13 vs 0.80+/-0.13 mg/mL, p<0.01), P SH (266+/-74 vs 406+/-78 micromol/L, p<0.01) and plasma vitamin C (7.0+/-5.1 vs 21.5+/-8.5mg/L, p<0.001) were lower than in 25 age-sex-matched healthy controls; [...] Following dialysis, RBC vfcy (to 8.9+/-4.5 mmol/mL/h, p<0.001) decreased, as well as P MDA, RBC MDA and plasma vitamin C (to 2.5+/-1.4 mg/L, p<0.001)" (abstract, results)
pubmedfull study (doi) - supports: Reduced Plasma Ascorbate and Increased Proportion of Dehydroascorbic Acid Levels in Patien… (Life (Basel, Switzerland) 2021) · cited 7x in the literature
"After dialysis, there was a 40% reduction in the plasma total ascorbate levels." (abstract, results, passage verified)
pubmedfull study (doi)
Consuming less than 10 milligrams of vitamin C daily causes scurvy.
"Getting less than 10 milligrams of vitamin C daily is thought to cause scurvy." (said at 0:14:00)
The statement that consuming less than 10 mg/day of vitamin C causes scurvy is supported by classic depletion-repletion clinical trials and established nutritional guidelines. Human experimental studies (most notably the Medical Research Council Sheffield trial) demonstrated that a daily intake of approximately 10 mg of vitamin C is the minimum threshold required to prevent and cure clinical symptoms of scurvy.
A cross-sectional study of 149 patients admitted to a teaching hospital found that 60% had low vitamin C levels and 19% were deficient at levels approaching scurvy.
"A population-based cross-sectional study of 149 patients admitted to a large teaching hospital found that 60% of the patients had low vitamin C levels and 19% were deficient, with levels approaching those associated with scurvy." (said at 0:14:00)
A 2008 cross-sectional study of 149 medical patients admitted to a Canadian university teaching hospital evaluated plasma vitamin C levels shortly after admission. The study found that 60% of hospitalized patients had subnormal vitamin C levels (<28.4 µmol/L) and 19% had frank vitamin C deficiency (<11.4 µmol/L, a concentration associated with clinical scurvy). As this is an observational, single-center cross-sectional survey, the GRADE certainty is low.
A specific polymorphism in the sodium-dependent vitamin C transporter gene reduces vitamin C cellular transport capacity by 40% to 50%.
"For example, one polymorphism in the sodium-dependent vitamin C transporter results in a protein with 40 to 50 percent decreased ability to transport vitamin C into the cell." (said at 0:15:30)
Genetic variation in the sodium-dependent vitamin C transporter gene (SLC23A1, encoding the SVCT1 transporter) functionally impairs vitamin C transport and significantly alters systemic vitamin C concentrations. Large-scale genetic analyses demonstrate that specific nonsynonymous single-nucleotide polymorphisms in SLC23A1 (such as the missense variant rs33972313) lead to reduced active transport capacity and reliably lower circulating L-ascorbic acid levels in humans.
Red blood cells transport dehydroascorbic acid only and generate ascorbate via intracellular recycling, rather than transporting ascorbate directly.
"Red blood cells transport dehydroascorbic acid only, and they generate their own ascorbate via recycling." (said at 0:16:00)
Mature human erythrocytes lack functional sodium-dependent vitamin C transporters (such as SVCT2), which are lost during maturation from erythroblasts to reticulocytes. Consequently, red blood cells cannot actively transport ascorbate directly. Instead, they take up the oxidized form, dehydroascorbic acid (DHA), via the abundant glucose transporter GLUT1, and rapidly reduce it internally to generate ascorbate using glutathione and intracellular reductase enzymes.
Single-dose oral vitamin C bioavailability maxes out at approximately 200 milligrams.
"That's because vitamin C's bioavailability maxes out at about 200 milligrams when given as a single dose. At 500 milligrams, the bioavailability decreases, and excess vitamin C gets excreted." (said at 0:17:00)
A landmark pharmacokinetic depletion-repletion clinical trial in healthy volunteers established that oral vitamin C bioavailability is 100% (complete) at a single dose of 200 mg. At single oral doses of 500 mg and above, fractional intestinal absorption (bioavailability) declines substantially, and circulating vitamin C that exceeds the renal threshold is excreted in the urine.
In a study of 20 people, a single 10-gram dose of liposomal vitamin C increased plasma levels to 300 micromoles per liter, took an hour longer to reach peak concentration, and had a half-life two hours longer than non-encapsulated vitamin C.
"A slightly larger study with 20 people showed that a single 10-gram dose of liposomal vitamin C increased plasma levels to 300 micromoles, a concentration that is higher than the established peak concentration of 220 micromoles per liter. Not only that, the liposomal form took about an hour longer to reach the maximum vitamin C blood concentration, and its half-life was two hours longer compared to free vitamin C, indicating increased bioavailability." (said at 0:19:29)
Published pharmacokinetic evidence confirms that liposomal encapsulation enhances the oral bioavailability of vitamin C compared to standard, non-encapsulated forms. A scoping review of clinical pharmacokinetic trials investigating doses up to 10 g found that 9 of 10 studies demonstrated significantly higher peak plasma concentrations (Cmax, 1.2- to 5.4-fold higher) and overall systemic exposure (AUC, 1.3- to 7.2-fold higher) with liposomal delivery. While specific kinetic parameters vary depending on formulation characteristics, liposomal encapsulation typically delays time to peak concentration (Tmax) and prolongs plasma elimination half-life relative to unencapsulated ascorbic acid.
In a study of 12 young adults, a 1.25-gram oral dose of vitamin C produced plasma levels of 135 micromoles per liter compared to 885 micromoles per liter for the same intravenous dose.
"For example, a clinical study involving 12 young adults found that plasma levels of vitamin C after taking a 1.25-gram dose of oral vitamin C reached about 135 micromoles per liter of blood, but they reached 885 micromoles per liter of blood with an intravenous administration of the same dose." (said at 0:20:31)
A pharmacokinetic study by Padayatty et al. (2004) evaluating oral versus intravenous vitamin C administration found that a 1.25 g oral dose achieved mean peak plasma concentrations of 134.8 ± 20.6 µmol/L, compared with 885 ± 201.2 µmol/L following intravenous administration of the same dose.
A meta-analysis of 29 trials with over 11,000 participants found that prophylactic vitamin C reduced the relative risk of catching a cold by 4%.
"A larger meta-analysis of 29 trials involving more than 11,000 participants also looked into the use of vitamin C as a prophylactic. Doses ranged from 200 milligrams to 2 grams per day for two weeks to six months. The relative risk of catching a cold when taking the prophylactic dose only decreased by 4%—not much of an effect" (said at 0:24:34)
The speaker's statement accurately summarizes the Cochrane systematic review by Hemilä and Chalker (2013). The meta-analysis evaluated regular prophylactic vitamin C supplementation across 29 trial comparisons involving 11,306 participants using doses of at least 200 mg/day. It found that regular prophylactic supplementation did not meaningfully reduce cold incidence in the general population, showing only a non-significant ~3% to 4% relative risk reduction (pooled risk ratio of 0.97, 95% CI 0.94 to 1.00 in general community trials).
Six trials in over 600 marathon runners, skiers, and soldiers showed a 50% reduction in cold incidence with supplemental vitamin C.
"Six trials involving more than 600 marathon runners, skiers, and soldiers reported 50% fewer colds among those who took supplemental vitamin C, suggesting that people who frequently participate in high-endurance exercise might be more responsive to supplemental vitamin C than others." (said at 0:26:36)
The claim accurately reflects findings from the Cochrane Systematic Review on vitamin C and the common cold. In the 2007 Cochrane update by Douglas et al. (and slightly updated in 2013 by Hemilä and Chalker), a subgroup meta-analysis of six placebo-controlled trials involving 642 marathon runners, skiers, and soldiers on subarctic exercises found that regular vitamin C supplementation reduced the incidence of colds by 50% (pooled relative risk 0.50, 95% CI 0.38 to 0.66).
In a prospective study of over 19,000 people followed for 16.5 years, those with the highest blood vitamin C concentrations were 15% less likely to develop respiratory conditions and 46% less likely to die of lung cancer compared to those with the lowest levels.
"One very large study looked at the relationship between blood vitamin C concentrations and incidence of respiratory disease in more than 19,000 people between the ages of 40 and 79 years without histories of respiratory diseases... The people with the highest blood vitamin C concentrations were 15% less likely to develop respiratory conditions and were 46% less likely to die of lung cancer compared to those with the lowest blood vitamin C levels." (said at 0:29:07)
The statement accurately reflects findings from the EPIC-Norfolk prospective cohort study (Myint et al., 2019). In this study of 19,357 adults aged 40–79 followed for an average of over 16 years, individuals in the highest quartile of baseline plasma vitamin C concentrations had a 15% lower risk of developing non-cancerous respiratory diseases (HR 0.85, 95% CI: 0.77–0.95) and a 46% lower risk of lung cancer mortality (HR 0.54, 95% CI: 0.35–0.81) compared to those in the lowest quartile, after controlling for confounders. The authors note plasma vitamin C served as a biomarker for fruit and vegetable intake.
A single 3-gram intravenous dose of vitamin C produces peak plasma concentrations of approximately 1,760 micromoles per liter.
"Even when they increased the dose to 3 grams taken every four hours, peak blood concentrations with oral vitamin C only reached 220 micro moles per liter, but they reached 1,760 micromoles per liter for a single 3-gram intravenous dose." (said at 0:21:03)
The host's statement accurately reflects published pharmacokinetic data on vitamin C administration. In a study evaluating oral versus intravenous vitamin C pharmacokinetics in healthy volunteers, oral administration at the maximum tolerated dose of 3 g every 4 hours was predicted to yield peak plasma concentrations of 220 µmol/L due to tightly controlled absorption mechanisms. In contrast, a single intravenous dose of 3 g was reported/modeled to achieve peak plasma concentrations of approximately 1,760 µmol/L (Padayatty et al., 2004).
A comparison of 12 clinical trials found that vitamin C supplementation reduced cold duration by 13.5% in children and 8% in adults.
"And a comparison of 12 trials found a 13.5% reduction in cold duration among children compared to an 8% reduction in adults." (said at 0:26:36)
A systematic review and meta-analysis of placebo-controlled trials published in the Cochrane Database of Systematic Reviews evaluated the effect of regular vitamin C supplementation on common cold duration. Meta-analyses of these trials demonstrated that regular vitamin C prophylaxis shortened cold duration by approximately 8% in adults and 13.6% to 14% in children.
The highest tissue concentrations of vitamin C in the body are found in the brain and adrenal glands, while the lowest concentrations are found in muscle, heart, and kidneys.
"The concentration in different tissues varies, with the lowest amounts found in muscle, heart, and kidneys, and the highest amounts found in the brain and adrenal glands." (said at 0:16:42)
Published pharmacological research confirms that vitamin C (ascorbate) tissue distribution is highly compartmentalized. Tissue concentrations at homeostasis reach their highest levels in the brain and adrenal glands (up to ~10 mM) and their lowest levels in tissues such as muscle and heart (around 0.2 mM).
- supports: The Pharmacokinetics of Vitamin C. (Nutrients 2019) · cited 342x in the literature
"Moreover, the tissue specific expression levels and subtypes of these SVCTs result in a compartmentalized distribution pattern with a diverse range of organ concentrations of vitC at homeostasis ranging from about 0.2 mM in the muscle and heart, and up to 10 mM in the brain and adrenal gland." (abstract, passage verified)
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A meta-analysis of six studies found that patients mechanically ventilated for more than 24 hours who were given vitamin C spent 18% less time on mechanical ventilation compared to controls.
"A meta-analysis of six studies found a significant difference in the effect of vitamin C on the duration of mechanical ventilation between patients on ventilation for more than 24 hours compared to those on ventilation for less than 24 hours. In three of those trials, two of which utilized intravenous vitamin C, patients were ventilated for more than 24 hours, and given vitamin C, spent 18% less time on mechanical ventilation compared to controls." (said at 0:30:09)
The statement accurately reflects the results of a 2019 meta-analysis by Hemilä and Chalker evaluating controlled trials of vitamin C in intensive care settings. In their analysis of trials reporting mechanical ventilation duration, three trials involved patients ventilated for more than 24 hours, where vitamin C supplementation shortened ventilation time by 18.2% (95% CI: 7.7% to 27%, p = 0.001).
Three randomized controlled trials investigating vitamin C as a prophylactic treatment against pneumonia each found an 80% lower incidence of pneumonia in people taking vitamin C compared to controls.
"Three of the studies investigated the use of vitamin C as a prophylactic treatment against pneumonia, and each found the incidence of pneumonia was 80% lower in people who took vitamin C compared to those who did not." (said at 0:32:13)
A Cochrane systematic review identified three controlled prophylactic trials assessing vitamin C for pneumonia prevention (encompassing 2,335 participants and 37 cases of community-acquired pneumonia). Each of the three trials reported an 80% or greater reduction in pneumonia incidence in the vitamin C group compared to controls. However, the review authors noted that only one trial was satisfactorily randomized, double-blind, and placebo-controlled, and all three evaluated specific high-risk or historical cohorts (military recruits and boarding school students in World War II-era Britain with potentially low baseline intake), meaning the overall quality of evidence is limited and cannot be generalized broadly.
- supports: Vitamin C for preventing and treating pneumonia. (The Cochrane database of systematic reviews 2013) · cited 198x in the literature
"We identified three prophylactic trials which recorded 37 cases of community-acquired pneumonia in 2335 people. Only one was satisfactorily randomised, double-blind and placebo-controlled. Two trials examined military recruits and the third studied boys from "lower wage-earning classes" attending a boarding school in the UK during World War II. Each of these three trials found a statistically significant (80% or greater) reduction in pneumonia incidence in the vitamin C group." (abstract, results, passage verified)
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A therapeutic trial in 57 elderly patients diagnosed with bronchitis or bronchopneumonia found that 200 milligrams of vitamin C daily improved respiratory function compared to controls.
"A therapeutic trial involving 57 elderly patients diagnosed with either bronchitis or bronchopneumonia found that patients who took 200 milligrams of vitamin C per day showed improvements in respiratory function compared to the patients who were not administered vitamin C." (said at 0:32:44)
A double-blind, placebo-controlled trial in 57 elderly hospitalised patients with acute respiratory infections (bronchitis and bronchopneumonia) found that 200 mg of oral vitamin C daily significantly improved clinical respiratory symptom scores compared to placebo, particularly among patients who were most severely ill at baseline.
In a study of 300 asthma patients, daily supplementation with 1 gram of vitamin C and 450 milligrams of magnesium chelate for 16 weeks showed no beneficial effects on asthma control.
"But a separate study involved 300 asthma patients between the ages of 18 and 60 years who took 1 gram of vitamin C and 450 milligrams of magnesium chelate or a placebo daily for 16 weeks... At the end of the study, there was no evidence of beneficial effects on any outcome measure of asthma control." (said at 0:34:18)
A double-blind, randomized, placebo-controlled trial in 300 adult asthma patients (aged 18–60 years) evaluated 16 weeks of daily supplementation with 1 g/day of vitamin C, 450 mg/day of magnesium chelate, or matched placebo. The study found no beneficial effect of either supplement on any outcome measure of asthma control, including lung function (FEV1, FVC, peak flow), airway responsiveness, symptom scores, or bronchodilator use.
A meta-analysis of 14 studies comprising over 6,000 lung cancer cases found that for every 100-milligram daily increase in vitamin C intake among men, the risk of lung cancer decreased by 7%.
"A meta-analysis of 14 studies comprising more than 6,000 lung cancer cases found that vitamin C was not only protective, but also showed a dose-dependent effect: for every 100-milligram increase in daily vitamin C intake among men, the risk of developing lung cancer decreased 7%." (said at 0:34:49)
A 2014 dose-response meta-analysis by Luo et al. evaluated the association between vitamin C intake and lung cancer risk. In their dose-response analysis, they identified a linear relationship where each 100 mg/day increase in vitamin C intake was associated with a 7% reduction in lung cancer risk (RR = 0.93, 95% CI: 0.88–0.98). Because this finding is derived from observational case-control and cohort studies that are subject to residual confounding (such as smoking status and overall diet quality), the GRADE certainty is low.
A meta-analysis of three placebo-controlled studies found that 0.5 to 2 grams of vitamin C taken immediately before exercise for two weeks reduced the exercise-induced FEV1 decline by more than 8%.
"A meta-analysis of three placebo-controlled studies found that when men and women between the ages of 7 and 28 years took between 0.5 and 2 grams of vitamin C immediately before exercise for two weeks, vitamin C reduced the FEV1 decline by more than 8%, indicating that vitamin C might help alleviate respiratory problems caused by exercise." (said at 0:35:50)
A 2013 meta-analysis of three placebo-controlled trials (totaling 40 participants aged 7 to 28 years) evaluated 0.5 to 2 g of vitamin C administered before exercise. It found that vitamin C administration reduced the post-exercise decline in forced expiratory volume in 1 second (FEV1) by a pooled arithmetic difference of 8.4 percentage points (95% CI: 4.6% to 12.1%), corresponding to a 48% relative reduction in exercise-induced bronchoconstriction. The overall certainty is low due to the very small pooled sample size.
In a randomized controlled trial of 54 young adults, taking 1 gram of vitamin C with 235 milligrams of vitamin E daily for 11 weeks decreased markers of mitochondrial biogenesis compared to placebo during exercise training.
"For example, in a randomized controlled trial of 54 young men and women who took either 1 gram of vitamin C with 235 milligrams of vitamin E or a placebo for 11 weeks, both groups saw similar improvement in VO2 max compared to their pre-supplementation levels, but markers of mitochondrial biogenesis decreased in those who took vitamin C and E and increased in the placebo group" (said at 0:37:53)
A double-blind randomized controlled trial by Paulsen et al. (2014) in 54 young men and women evaluated 1,000 mg of vitamin C and 235 mg of vitamin E daily versus placebo during 11 weeks of endurance training. Both groups achieved similar increases in VO2 max (8 ± 5% in each group). However, markers of mitochondrial biogenesis in the vastus lateralis muscle (COX4 and cytosolic PGC-1α) increased significantly in the placebo group (+59% and +19%) while decreasing in the antioxidant group (-13% and -13%; P <= 0.03 between groups).
- supports: Vitamin C and E supplementation hampers cellular adaptation to endurance training in human… (The Journal of physiology 2014) · cited 325x in the literature
"Fifty-four young men and women were randomly allocated to receive either 1000 mg of vitamin C and 235 mg of vitamin E or a placebo daily for 11 weeks... Participants in the vitamin C and E group increased their VO2 max (mean ± s.d.: 8 ± 5%) and performance in the 20 m shuttle test (10 ± 11%) to the same degree as those in the placebo group (mean ± s.d.: 8 ± 5% and 14 ± 17%, respectively). However, the mitochondrial marker cytochrome c oxidase subunit IV (COX4) and cytosolic peroxisome proliferator-activated receptor-γ coactivator 1 α (PGC-1α) increased in the m. vastus lateralis in the placebo group by 59 ± 97% and 19 ± 51%, respectively, but not in the vitamin C and E group (COX4: -13 ± 54%; PGC-1α: -13 ± 29%; P ≤ 0.03, between groups)." (abstract, results, passage verified)
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In a study of 40 men completing an exercise program, taking 500 milligrams of vitamin C twice daily along with 400 IU of vitamin E prevented exercise-induced improvements in insulin sensitivity.
"For example, a study involving 40 men, 20 untrained and 20 pre-trained, found that 500 milligrams of vitamin C taken twice a day along with 400 IU of vitamin E reduced insulin sensitivity compared to a placebo. All the men in this study participated in an exercise training program of approximately one hour of cycling or running plus circuit training five days a week for four weeks along with daily supplementation. The exercise improved the men's insulin sensitivity only in the absence of antioxidants." (said at 0:40:27)
The statement accurately reflects the design and results of a landmark 2009 clinical trial by Ristow and colleagues (PMID: 19433800). In the study, healthy young men (untrained and pretrained) underwent a 4-week exercise regimen with or without daily supplementation of 1,000 mg vitamin C (given as 500 mg twice daily) and 400 IU vitamin E. Exercise significantly improved glucose infusion rates and plasma adiponectin (markers of insulin sensitivity) only in the groups not receiving antioxidants, whereas antioxidant supplementation blocked these adaptations.
A study of 21 physically active men taking 500 milligrams of vitamin C and 400 IU of vitamin E daily at breakfast for 16 weeks showed no effect of supplementation on insulin sensitivity.
"But another study in 21 physically active men between the ages of 18 and 40 years who took 500 milligrams of vitamin C and 400 IU of vitamin E or a placebo every day for 16 weeks showed that antioxidant supplementation had no effect on insulin sensitivity." (said at 0:41:29)
A randomized controlled trial evaluated 21 healthy young men undergoing an intense endurance training program who received either daily antioxidant supplementation (500 mg vitamin C and 400 IU vitamin E) or a placebo. The study lasted 12 weeks (rather than 16 weeks). Insulin-stimulated glucose uptake measured by hyperinsulinemic-euglycemic clamp increased similarly in both the antioxidant group (17.2%) and the placebo group (18.9%), confirming that antioxidant supplementation had no effect on the training-induced improvement in insulin sensitivity.
- supports: Effect of antioxidant supplementation on insulin sensitivity in response to endurance exer… (American journal of physiology. Endocrinology and metabolism 2011) · cited 85x in the literature
"To assess the effect of antioxidant supplementation during endurance training on insulin-stimulated glucose uptake, 21 young healthy (age 29 ± 1 y, BMI 25 ± 3 kg/m(2)) men were randomly assigned to either an antioxidant [AO; 500 mg vitamin C and 400 IU vitamin E (α-tocopherol) daily] or a placebo (PL) group that both underwent a supervised intense endurance-training program 5 times/wk for 12 wk... Although plasma levels of vitamin C (P < 0.05) and α-tocopherol (P < 0.05) increased markedly in the AO group, insulin-stimulated glucose uptake increased similarly in both the AO (17.2%, P < 0.05) and the PL (18.9%, P < 0.05) group in response to training... Our results indicate that administration of antioxidants during strenuous endurance training has no effect on the training-induced increase in insulin sensitivity in healthy individuals." (abstract, results and conclusions, passage verified)
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In a study of 22 adults, fat utilization during exercise was 25% lower in individuals with marginal vitamin C status (below 34 micromoles per liter) compared to those with adequate levels.
"15 of the people in the study had marginal vitamin C blood levels, less than 34 micromoles per liter, and 7 had adequate vitamin C levels, greater than 34 micromoles per liter. As a part of the study, all participants completed a 60-minute treadmill walk at 50% of their VO2 max. Fat utilization during exercise was 25% lower among the people with marginal vitamin C status" (said at 0:47:09)
A 2006 study by Johnston et al. evaluated 22 young adults (15 with marginal vitamin C status and 7 with adequate status) during a 60-minute submaximal treadmill walk. The researchers reported that participants with marginal vitamin C status oxidized 25% less fat per kilogram of body weight during exercise compared to those with adequate vitamin C levels. Because this specific finding is based on a small preliminary study (n = 22), the certainty of the broader evidence is low.
Studies in newborn guinea pigs demonstrated that prenatal and postnatal vitamin C deficiency stunted hippocampal development by 10% to 30%.
"For example, studies in newborn guinea pigs have demonstrated that prenatal and postnatal vitamin C deficiency stunted hippocampal development in newborn guinea pigs by 10 to 30%." (said at 0:49:12)
Controlled animal studies in guinea pigs (which, like humans, cannot synthesize vitamin C endogenously) show that prenatal and postnatal vitamin C deficiency impairs hippocampal development. Specifically, early postnatal vitamin C deficiency was found to reduce hippocampal neuron counts by approximately 30% and impair spatial memory, while maternal (prenatal) deficiency resulted in significantly reduced postnatal hippocampal volume (typically around 10–15% smaller) and reduced neuronal migration that was not rescued by postnatal vitamin C repletion. Because this evidence is derived entirely from animal models, the GRADE certainty is very low.
In the CITRIS-ALI trial of over 160 ICU patients with sepsis-induced acute respiratory failure, 28-day mortality was less than 30% in the intravenous vitamin C group compared to nearly 50% in the placebo group.
"One study involved more than 160 patients admitted to the ICU for treatment of sepsis-induced acute respiratory failure. The patients were randomized to receive either a placebo or intravenous vitamin C at 50 milligrams per kilogram of body weight every six hours for 96 hours. What's interesting is that the study revealed no differences in the primary outcomes of organ failure, inflammation, or vascular injury, but 28 days after beginning of the study, nearly half of the patients in the placebo group died compared to less than 30% in the intravenous vitamin C treated group." (said at 0:53:50)
In the CITRIS-ALI trial (Fowler et al., JAMA 2019), 167 intensive care unit patients with sepsis and acute respiratory distress syndrome (ARDS) were randomized to receive intravenous vitamin C (50 mg/kg every 6 hours for 96 hours) or placebo. The trial found no statistically significant difference in its primary endpoints (change in modified SOFA organ dysfunction score, CRP, or thrombomodulin levels). However, as a secondary outcome, 28-day all-cause mortality was 29.8% (25 of 84) in the vitamin C group compared with 46.3% (38 of 82) in the placebo group.
- supports: Effect of Vitamin C Infusion on Organ Failure and Biomarkers of Inflammation and Vascular … (JAMA 2019) · cited 839x in the literature
"The CITRIS-ALI trial was a randomized, double-blind, placebo-controlled, multicenter trial conducted in 7 medical intensive care units in the United States, enrolling patients (N = 167) with sepsis and ARDS present for less than 24 hours... Patients were randomly assigned to receive intravenous infusion of vitamin C (50 mg/kg in dextrose 5% in water, n = 84) or placebo (dextrose 5% in water only, n = 83) every 6 hours for 96 hours. The primary outcomes were change in organ failure as assessed by a modified Sequential Organ Failure Assessment score... and plasma biomarkers of inflammation (C-reactive protein levels) and vascular injury (thrombomodulin levels)... There were no significant differences between the vitamin C and placebo groups in the primary end points" (abstract, methods and results, passage verified)
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In a study of 13 infertile men taking 1 gram of oral vitamin C twice daily for two months, sperm count increased by 58% and sperm motility increased by 48%.
"A study in 13 infertile men between the ages of 25 and 35 years who took 1 gram of oral vitamin C twice a day for two months found that, compared to baseline measurements, the men's sperm count increased 58% and sperm motility increased 48%, indicating improved semen quality." (said at 0:57:56)
The speaker accurately describes the results of an open-label study by Akmal et al. (2006). In that trial, 13 infertile men aged 25 to 35 years with oligozoospermia received 1,000 mg of oral vitamin C twice daily for 2 months. Mean sperm count increased from 14.3 × 10⁶ to 32.8 × 10⁶/mL and mean motility increased from 31.2% to 60.1%. However, because this was a very small, uncontrolled pre-post trial (n=13) without a placebo comparison group, the certainty of evidence for vitamin C's therapeutic efficacy is very low.
A meta-analysis of 29 randomized placebo-controlled clinical trials found that an average of 500 milligrams of oral vitamin C daily for eight weeks significantly decreased blood pressure in hypertensive patients.
"A meta-analysis of 29 randomized, placebo-controlled clinical trials involving more than 1,400 participants demonstrated that patients with high blood pressure who took an average of 500 milligrams of oral vitamin C per day for about eight weeks showed significant decreases in blood pressure compared to those who took a placebo." (said at 0:58:57)
A 2012 meta-analysis of 29 randomized controlled trials by Juraschek et al. (totaling 1,407 participants) examined the effect of oral vitamin C supplementation on blood pressure. The median dose across trials was 500 mg per day and the median duration was 8 weeks. Overall, vitamin C significantly lowered systolic blood pressure (SBP by -3.84 mm Hg, P < 0.01) and diastolic blood pressure (DBP by -1.48 mm Hg, P = 0.04). Among trials specifically evaluating hypertensive participants, SBP was significantly reduced by -4.85 mm Hg (P < 0.01), while the reduction in DBP (-1.67 mm Hg) was not statistically significant (P = 0.17).
In a study of 39 terminal cancer patients, receiving 10 grams of intravenous vitamin C twice a week and 4 grams of oral vitamin C daily for a week improved quality of life and reduced fatigue, nausea, vomiting, pain, and appetite loss.
"A study involving 39 patients diagnosed with terminal cancer who received 10 grams of intravenous vitamin C twice a week and 4 grams of oral vitamin C daily for a week found that patients reported improvement in physical, emotional, and cognitive status, as well as reduced fatigue, nausea, vomiting, pain, and appetite loss." (said at 0:56:44)
A prospective study of 39 terminal cancer patients (Yeom et al., 2007) evaluated quality of life using the EORTC QLQ-C30 questionnaire before and after administering 10 g of intravenous vitamin C twice (with a 3-day interval) alongside 4 g of oral vitamin C daily for one week. The authors observed statistically significant improvements in physical, role, emotional, and cognitive functioning, as well as significant reductions in reported fatigue, nausea/vomiting, pain, and appetite loss. However, because this was an uncontrolled, unblinded single-arm study, the overall certainty regarding the efficacy of vitamin C for quality of life is very low due to the high risk of placebo effects and response bias in subjective symptom reporting.
- supports: Changes of terminal cancer patients' health-related quality of life after high dose vitami… (Journal of Korean medical science 2007) · cited 148x in the literature
"All patients were given an intravenous administration of 10 g vitamin C twice with a 3-day interval and an oral intake of 4 g vitamin C daily for a week... In functional scale, the patients reported significantly higher scores for physical, role, emotional, and cognitive function after administration of vitamin C (p<0.05). In symptom scale, the patients reported significantly lower scores for fatigue, nausea/vomiting, pain, and appetite loss after administration of vitamin C (p<0.005)." (abstract, results, passage verified)
pubmedfull study (doi)
An observational study of 125 breast cancer patients found that receiving 7.5 grams of intravenous vitamin C once weekly alongside chemotherapy and radiation improved quality of life compared to standard therapy alone.
"Another observational study of 125 patients diagnosed with breast cancer, 53 of whom received 7.5 grams of intravenous vitamin C once per week in conjunction with their standard chemotherapy and radiation therapies, noted improved quality of life compared to patients who only received chemotherapy and radiation." (said at 0:57:15)
A retrospective multicenter cohort study of 125 breast cancer patients (53 who received 7.5 g intravenous vitamin C as Pascorbin alongside standard adjuvant therapy, and 72 who received standard therapy alone) evaluated treatment-related complaints and quality of life. The study found that patients receiving adjunctive intravenous vitamin C experienced significant reductions in chemotherapy- and radiation-induced complaints, including fatigue, nausea, appetite loss, depression, and sleep disorders. Because this was a retrospective observational study without randomization or blinding, the body of evidence carries low certainty.
- supports: Intravenous vitamin C administration improves quality of life in breast cancer patients du… (In vivo (Athens, Greece) 2011) · cited 148x in the literature
"Data from 125 breast cancer patients in UICC stages IIa to IIIb were selected for the study. A total of 53 of these patients were treated with i.v. vitamin C (supplied as Pascorbin® 7.5 g) additional to standard tumour therapy for at least 4 weeks (study group) and 72 without this additional therapy (control group)... Comparison of control and study groups revealed that i.v. vitamin C administration resulted in a significant reduction of complaints induced by the disease and chemo-/radiotherapy, in particular of nausea, loss of appetite, fatigue, depression, sleep disorders, dizziness and haemorrhagic diathesis." (abstract, results, passage verified)
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In a mouse model of Werner syndrome, vitamin C supplementation extended average lifespan, corrected age-related metabolic diseases, and increased levels of PPAR-alpha.
"In addition, a mouse model of Werner syndrome, a genetic disorder characterized by premature aging, demonstrated that vitamin C supplementation lengthened the average lifespan of the mice and corrected many of their age-related metabolic diseases. The supplemented mice also exhibited increased levels of PPAR-alpha, a protein that regulates fat metabolism by increasing uptake and utilization." (said at 0:46:36)
In a 2010 study using a mutant mouse model of Werner syndrome (Wrn-null/helicase-deficient mice), vitamin C supplementation normalized the animals' shortened mean lifespan, corrected age-associated metabolic abnormalities (including adipose tissue abnormalities and metabolic dysfunction), and elevated hepatic levels of the lipid metabolism transcriptional regulator PPAR-alpha. Because these findings are derived from an animal model, the certainty of evidence for human clinical application is very low.
Statins reduce C-reactive protein levels by roughly 17%.
"That's roughly the same amount that statins reduce C-reactive protein." (said at 1:01:33)
Extensive randomized controlled trial evidence and large meta-analyses confirm that statin therapy significantly lowers serum C-reactive protein (CRP) levels, independent of LDL cholesterol reduction. In clinical trials and systematic reviews, statins reduce CRP concentrations by absolute amounts of approximately 0.65 to 0.80 mg/L, which typically corresponds to relative median reductions of roughly 15% to 35% depending on the specific statin molecule and dose intensity.
- supports: Statins influence biomarkers of low grade inflammation in apparently healthy people or pat… (Cytokine 2019) · cited 28x in the literature
"When we combined 21 effect sizes from 16 studies, we observed a significant reduction in circulating levels of CRP following administration of statins [Weighted Mean Difference (WMD): -0.80; 95% CI: -1.05, -0.56]." (abstract, results, passage verified)
pubmedfull study (doi) - supports: Reduction of C-reactive protein, low-density lipoprotein cholesterol, and its relationship… (Medicine 2022) · cited 8x in the literature
"Compared with placebo treatment, statins and ezetimibe treatments resulted in a significant decrease in LDL-C level (statins: WMD -47.94 mg/dL, 95% CI -51.21 to -44.67 mg/dL; ezetimibe: WMD -22.84 mg/dL, 95% CI -26.76 to -18.92 mg/dL) and CRP level (statins: WMD -0.67 mg/L, 95% CI -0.90 to -0.45 mg/dL; ezetimibe: -0.64 mg/L, 95% CI -1.07 to -0.21 mg/dL)." (abstract, results, passage verified)
pubmedfull study (doi) - supports: Effect of lipid-lowering therapies on C-reactive protein levels: a comprehensive meta-anal… (Cardiovascular research 2024) · cited 64x in the literature
"A total of 171 668 subjects from 53 RCTs were included. CRP levels (mg/L) were significantly decreased by statins [-0.65 (-0.87 to -0.43), bempedoic acid; -0.43 (-0.67 to -0.20), ezetimibe; -0.28 (-0.48 to -0.08)], and omega-3 fatty acids [omega3FAs, -0.27 (-0.52 to -0.01)]." (abstract, results, passage verified)
pubmedfull study (doi)
Neutrophils and leukocytes maintain intracellular vitamin C concentrations 50 to 100 times higher than plasma concentrations.
"vitamin C is highly concentrated in immune cells, with neutrophils and leukocytes having 50 to 100 times higher vitamin C concentrations than plasma." (said at 1:02:40)
Published biochemical and physiological literature supports the claim that immune cells, including leukocytes and neutrophils, actively accumulate and maintain intracellular vitamin C (ascorbate) concentrations roughly 50 to 100 times higher than circulating plasma levels. Human plasma physiological vitamin C concentrations typically range between 50 and 80 µmol/L, whereas resting neutrophils and mononuclear leukocytes maintain intracellular ascorbate levels in the low millimolar range (~1 to 4 mmol/L, or approximately 0.35 nmol per 10^6 cells) via active transport through sodium-dependent vitamin C transporters (SVCT2) and dehydroascorbic acid recycling.
- supports: Vitamin C and Immune Function. (Nutrients 2017) · cited 2021x in the literature
"Vitamin C accumulates in phagocytic cells, such as neutrophils, and can enhance chemotaxis, phagocytosis, generation of reactive oxygen species, and ultimately microbial killing." (abstract, passage verified)
pubmedfull study (doi) - supports: The Role of Physiological Vitamin C Concentrations on Key Functions of Neutrophils Isolate… (Nutrients 2019) · cited 63x in the literature
"We found that neutrophils isolated from healthy individuals already had replete ascorbate status (0.35 nmol/10 6 cells), therefore they did not uptake additional ascorbate. However, they readily took up dehydroascorbic acid, thus significantly increasing their intracellular ascorbate concentrations" (abstract, results, passage verified)
pubmedfull study (doi) - supports: Neutrophils Isolated from Septic Patients Exhibit Elevated Uptake of Vitamin C and Normal … (Antioxidants (Basel, Switzerland) 2021) · cited 9x in the literature
"Neutrophils isolated from septic patients had comparable intracellular ascorbate content to healthy volunteers (0.33 vs. 0.35 nmol/10 6 cells, p > 0.05), despite significantly lower plasma concentrations than the healthy controls (14 vs. 88 µmol/L, p < 0.001)." (abstract, results, passage verified)
pubmedfull study (doi)
In vitamin C-deficient mice with elevated pro-inflammatory cytokines, vitamin C administration normalizes cytokine production.
"In mouse models in which mice are vitamin C deficient and have increased pro-inflammatory cytokines, giving the mice vitamin C normalized cytokine production." (said at 1:04:06)
Studies using Gulo(-/-) knockout mice (which, like humans, cannot synthesize vitamin C internally) show that vitamin C deficiency leads to elevated levels of pro-inflammatory cytokines such as TNF-α and IL-6 during stress or inflammatory challenge, and that vitamin C supplementation normalizes or prevents these elevations. Because this evidence comes entirely from animal models, the overall certainty for human extrapolation is very low.
- supports: Vitamin C prevents stress-induced damage on the heart caused by the death of cardiomyocyte… (Free radical biology & medicine 2013) · cited 37x in the literature
"Moreover, lipid peroxidation and the production of tumor necrosis factor-alpha (TNF-α) in the heart were increased. Finally, all vitamin C-insufficient Gulo(-/-) mice were expired within 2 weeks. Interestingly, all of the findings in vitamin C-insufficient Gulo(-/-) mice were completely prevented by the supplementation of a sufficient amount of vitamin C." (abstract, results, passage verified)
pubmedfull study (doi) - supports: Preventive Effect of Vitamin C on Dextran Sulfate Sodium (DSS)-Induced Colitis via the Reg… (International journal of molecular sciences 2022) · cited 19x in the literature
"comparing vitamin C-insufficient Gulo(-/-) mice to vitamin C-sufficient Gulo(-/-) mice and wild-type mice, the insufficient group faced a decrease in mucin-1 expression, accompanied by an increase in IL-6 production, followed by the activation of the STAT3 and Akt pathways. The results suggest that vitamin C insufficiency induces severe colitis, meaning vitamin C could also take on a preventative role by regulating the production of cytokines and the induction of inflammation." (abstract, results and conclusions, passage verified)
pubmedfull study (doi)
Vitamin C is involved in the production of interferon cytokines in mice.
"Vitamin C is also involved in the production of interferon in mice. Interferon is a type of cytokine that signals the body to initiate antiviral defenses." (said at 1:04:15)
Animal research in mice supports the claim. In Gulo(-/-) knockout mice (which cannot synthesize their own vitamin C, mimicking human physiology), vitamin C deficiency led to decreased production of antiviral interferons (IFN-α/β) during early influenza A infection, whereas adequate vitamin C promoted IFN-α/β production and antiviral immune defense. Because this evidence is derived solely from animal models, the overall GRADE certainty is very low.
In vitro studies show that importing dehydroascorbic acid into cancer cells induces oxidative stress and decreases cancer cell viability.
"And in vitro studies suggested that the import of dehydroascorbic acid into cancer cells can cause oxidative stress and decrease cancer cell viability." (said at 1:05:07)
In vitro experimental evidence demonstrates that the uptake of dehydroascorbate (DHA)—the oxidized form of vitamin C—into cancer cells through glucose transporters (such as GLUT1) causes intracellular oxidative stress. As intracellular DHA is reduced back to ascorbic acid, it depletes glutathione reserves and generates reactive oxygen species, leading to metabolic disruption, energetic crisis, and reduced cancer cell viability.
Intravenous doses of vitamin C greater than 1 gram generate hydrogen peroxide, whereas physiological concentrations around 50 micromolar act primarily as an antioxidant.
"While vitamin C acts primarily as an antioxidant at physiological concentrations of approximately 50 micromoles per liter, pharmacologic doses of intravenous vitamin C greater than 1 gram generate hydrogen peroxide, a type of reactive oxygen species that can damage DNA, RNA, and proteins, leading to tissue damage." (said at 1:05:38)
Published pharmacokinetic and mechanistic studies confirm that ascorbic acid functions primarily as an antioxidant at physiological plasma concentrations (~50–100 μM), whereas high intravenous doses that produce millimolar extracellular concentrations act as a pro-oxidant prodrug, generating ascorbate radicals and hydrogen peroxide (H₂O₂) in extracellular and interstitial fluid.
An in vitro study showed that 2.5 millimoles per liter of vitamin C eliminated 90% of influenza virus and 20 millimoles per liter completely blocked viral replication.
"Another in vitro study showed a dose-dependent effect of vitamin C to kill influenza viruses, with a vitamin C concentration of 2.5 millimoles per liter eliminating 90% of the virus present and a concentration of 20 millimoles per liter fully blocking viral replication." (said at 1:07:23)
A 2012 in vitro study evaluating the effects of pharmacological ascorbate (vitamin C) on influenza A (H1N1) in normal human bronchial epithelial cells found a dose-dependent antiviral effect. The study reported that 2.5 mmol/L ascorbic acid eliminated 90% of the virus and 20 mmol/L completely blocked viral replication in vitro, mediated by extracellular hydrogen peroxide generation. Because these data are derived strictly from in vitro cell culture experiments, clinical applicability in humans cannot be established from this evidence alone.
In a vitamin C-deficient mouse model of viral infection, deficient mice had a 10- to 15-fold increase in lung viral titers and 100% mortality after one week, while 100% of normal mice survived.
"A really interesting study using a vitamin C-deficient mouse model demonstrated that these mice had increased pro-inflammatory cytokines and a 10- to 15-fold increase in viral titers in their lungs during viral infection compared to normal mice. One week after the mice developed a viral infection, all of the vitamin C-deficient mice had died, but all of the normal mice survived." (said at 1:07:43)
The speaker accurately describes the findings of an animal study using gulonolactone oxidase-knockout (Gulo-/-) mice, which cannot synthesize vitamin C. When infected with influenza A virus (H3N2), vitamin C-insufficient mice showed markedly increased lung viral titers, elevated pro-inflammatory cytokines (such as TNF-α and IL-1α/β), and 100% mortality within one week, whereas vitamin C-sufficient mice survived. Because these findings come from an animal model, certainty regarding direct translation to human viral infections is very low.
- supports: Vitamin C Is an Essential Factor on the Anti-viral Immune Responses through the Production… (Immune network 2013) · cited 183x in the literature
"First, we found that vitamin C-insufficient Gulo (-/-) mice expired within 1 week after intranasal inoculation of influenza virus (H3N2/Hongkong). Viral titers in the lung of vitamin C-insufficient Gulo (-/-) mice were definitely increased but production of anti-viral cytokine, interferon (IFN)-α/β, was decreased. On the contrary, the infiltration of inflammatory cells into the lung and production of pro-inflammatory cytokines, tumor necrosis factor (TNF)-α and interleukin (IL)-α/β, were increased in the lung." (abstract, results, passage verified)
pubmedfull study (doi)
Supplementing vitamin C-deficient mice with vitamin C prior to viral infection achieved plasma levels of 80 to 100 micromolar, prevented increased lung viral titers, increased antiviral cytokines, and protected against death.
"When vitamin C-deficient mice were supplemented with vitamin C prior to viral infection to achieve plasma levels of approximately 80 to 100 micromoles, similar to that of normal mice, there was no increase in viral titers in their lungs and the production of antiviral cytokines increased. This study showed that supplementation with vitamin C prior to viral infection protected the formerly deficient mice from death." (said at 1:08:14)
The statement accurately reflects findings from an animal study using L-gulonolactone oxidase knockout (Gulo -/-) mice, which cannot synthesize vitamin C endogenously. In this model, vitamin C-insufficient mice showed impaired antiviral cytokine production (interferon-alpha/beta), increased viral titers in the lungs, and died within one week of influenza A virus (H3N2) infection. Prior supplementation with vitamin C restored normal plasma levels, promoted interferon-alpha/beta production, suppressed lung viral loads, and prevented mortality. Because this evidence comes exclusively from a rodent knockout model, certainty is rated very low regarding direct extrapolation to human viral infections.
The established tolerable upper intake level for oral vitamin C in healthy adults is 2,000 milligrams per day.
"a tolerable upper intake of 2,000 milligrams of oral vitamin C per day has been established because vitamin C can sometimes cause GI problems such as diarrhea for most people." (said at 1:08:44)
The Food and Nutrition Board of the Institute of Medicine established a Tolerable Upper Intake Level (UL) of 2,000 mg/day for vitamin C in adults. The primary adverse effect used as the basis for establishing the UL is osmotic gastrointestinal disturbance, specifically symptoms such as diarrhea, abdominal cramps, and nausea, caused by unabsorbed ascorbic acid in the intestine.
- supports: The antioxidants--vitamin C,vitamin E, selenium, and carotenoids. (Journal of agromedicine 2003) · cited 75x in the literature
"In April of 2000, the Food and Nutrition Board of the National Academy of Sciences released Dietary Reference Intakes for Vitamin C, Vitamin E, Selenium, and Carotenoids. ... for the first time upper tolerable levels of ingestion (UL) were established to prevent the harmful effects of over consumption of essential nutrients, such as vitamin C, vitamin E, and selenium." (abstract, passage verified)
pubmedfull study (doi) - supports: Vitamins E and C are safe across a broad range of intakes. (The American journal of clinical nutrition 2005) · cited 305x in the literature
"As safety guidance, tolerable upper intake levels have been established by the Food and Nutrition Board, Institute of Medicine, at 1000 mg for vitamin E and 2000 mg for vitamin C in adults. ... Numerous studies of vitamin C supplementation have provided no pattern of evidence to support concerns about safety other than occasional gastrointestinal upset or mild diarrhea resulting from the osmotic effects of unabsorbed quantities of vitamin C." (abstract, passage verified)
pubmedfull study (doi)
High doses of intravenous vitamin C have been observed to cause oxalate nephropathy in patients with preexisting kidney impairment.
"A small number of case reports indicate that a condition called oxalate nephropathy, in which oxalate calcium crystals form in the kidney, has been observed when patients with kidney impairment were given high doses of intravenous vitamin C." (said at 1:10:49)
The speaker's statement accurately reflects the published medical literature. Ascorbic acid is metabolized to oxalate, and multiple published case reports document secondary acute oxalate nephropathy—characterized by intratubular calcium oxalate crystal deposition and acute renal failure—following high-dose intravenous vitamin C administration, especially in patients with preexisting renal dysfunction.
The most commonly reported side effects of intravenous vitamin C administration are mild to moderate nausea, headache, and dry mouth, while less common side effects include fatigue, hypertension, loss of appetite, and hyperglycemia.
"Intravenous vitamin C is well-tolerated and has low toxicity. The most commonly reported side effects include mild to moderate nausea, headache, and dry mouth. Less common side effects include fatigue, hypertension, loss of appetite, and hyperglycemia." (said at 1:09:15)
Published systematic reviews and phase I clinical trials of pharmacological intravenous (IV) vitamin C demonstrate that IV ascorbate is generally well-tolerated with low systemic toxicity. Across clinical studies, reported adverse events are typically mild-to-moderate and transient, with the most frequent infusion-related effects including nausea, headache, lightheadedness, and dry mouth/thirst (often related to the hyperosmolar infusion). Less frequent effects documented across safety trials include fatigue, transient blood pressure alterations (hypertension/hypotension), appetite changes, and transient hyperglycemia or false glucose elevation on point-of-care monitoring.
- supports: Pharmacological ascorbate with gemcitabine for the control of metastatic and node-positive… (Cancer chemotherapy and pharmacology 2013) · cited 308x in the literature
"Adverse events attributable to the drug combination were rare and included diarrhea (n = 4) and dry mouth (n = 6). Dose-limiting criteria were not met for this study." (abstract, results, passage verified)
pubmedfull study (doi) - supports: Systematic Review of Intravenous Ascorbate in Cancer Clinical Trials. (Antioxidants (Basel, Switzerland) 2018) · cited 110x in the literature
"Overall, vitamin C has been shown to be safe in nearly all patient populations, alone and in combination with chemotherapies." (abstract, conclusions, passage verified)
pubmedfull study (doi) - supports: The Effect of Vitamin C (Ascorbic Acid) in the Treatment of Patients with Cancer: A System… (Nutrients 2019) · cited 159x in the literature
"Nevertheless, treatment with vitamin C is safe with minimal side effects." (abstract, results, passage verified)
pubmedfull study (doi)
Unverified means no publication matching the claim was located; it does not prove the claim false. Spotted an error? See the corrections policy - disputes from the people quoted are prioritized.