Vitamins E and C are safe across a broad range of intakes.
Level 5 - mechanism / opinion, no new human data
Narrative review of safety data without systematic review or meta-analytic methodology described.
PubMed 15817846 · doi:10.1093/ajcn/81.4.736
What was done
The authors reviewed clinical trial evidence and safety databases evaluating dietary supplementation of vitamins E and C across a range of intakes in adults.
What was found
The abstract reports no consistent pattern of adverse events across clinical trials. Vitamin C supplementation showed occasional gastrointestinal upset or mild diarrhea from unabsorbed quantities, but theoretical risks concerning iron absorption and metabolism were not confirmed. Evidence of bleeding or other harms from high vitamin E was judged unconvincing. The review concluded that vitamin E up to 1600 IU (1073 mg RRR-alpha-tocopherol) and vitamin C up to 2000 mg/day appear safe for most adults. No numerical effect sizes, sample counts, or statistical analyses are reported in the abstract.
Why it matters
It synthesizes clinical safety data supporting tolerable upper intake levels for two of the most widely consumed dietary antioxidant supplements.
Limits
The abstract does not state the number of studies reviewed, search criteria, inclusion criteria, or trial durations. As a narrative review, it lacks formal risk-of-bias assessment and quantitative meta-analysis of rare or long-term adverse events.
Cited by
- supports The Tolerable Upper Intake Level for vitamin C is 2,000 milligrams per day.
- supports The established tolerable upper intake level for oral vitamin C in healthy adults is 2,000 milligrams per day.