Huberman Lab · 2026-04-13 · Andrew Huberman (host), Natalie Crawford

How Women Can Improve Their Fertility & Hormone Health | Dr. Natalie Crawford

82 research-tied claims examined: 8 contradicted 9 overstated 8 context 53 supported 4 unverified

8 Contradicted by research
0:10:37Natalie Crawfordcontradictedhigh

Hormone replacement therapy in women provides cardioprotection, reduces the risk of Alzheimer's disease, and protects bone density.

"I mean, for women we see it be cardioprotective, it can help lower the risk of Alzheimer's disease, of course it can be protective for your bones." (said at 0:10:37)

The speaker bundles three distinct claims regarding hormone replacement therapy (HRT): cardiovascular protection, reduction in Alzheimer's disease/dementia risk, and bone protection. Per systematic review and randomized controlled trial (RCT) evidence (e.g., the Women's Health Initiative and Cochrane reviews), HRT is supported for protecting bone mineral density and reducing fractures. However, the claims of cardioprotection and dementia reduction are contradicted by high-certainty RCT evidence: combined HRT increases the risk of stroke, venous thromboembolism, coronary events, and probable dementia (in older women), leading major health bodies to advise against HRT for the primary prevention of cardiovascular disease or cognitive decline. Because the cardioprotective and dementia-preventive assertions are contradicted by randomized trials, the bundled claim receives an overall verdict of contradicted.

  • contradicts: Long-term hormone therapy for perimenopausal and postmenopausal women. (The Cochrane database of systematic reviews 2017)
    "In relatively healthy postmenopausal women (i.e. generally fit, without overt disease), combined continuous HT increased the risk of a coronary event (after 1 year's use: from 2 per 1000 to between 3 and 7 per 1000), venous thromboembolism (after 1 year's use: from 2 per 1000 to between 4 and 11 per 1000), stroke (after 3 years' use: from 6 per 1000 to between 6 and 12 per 1000)... Women over 65 years of age who were relatively healthy and taking continuous combined HT showed an increase in the incidence of dementia (after 4 years' use: from 9 per 1000 to 11 to 30 per 1000)... Risk of fracture was the only outcome for which strong evidence showed clinical benefit derived from HT" (abstract, results, passage verified)
    pubmedfull study (doi)
  • contradicts: Hormone Therapy for the Primary Prevention of Chronic Conditions in Postmenopausal Persons… (JAMA 2022) · cited 69x in the literature
    "Risks, per 10 000 persons, were significantly increased for invasive breast cancer (242 vs 191 cases; 51 more [95% CI, 6-106]), gallbladder disease (723 vs 463 cases; 260 more [95% CI, 169-364]), stroke (187 vs 135 cases; 52 more [95% CI, 12-104]), and venous thromboembolism (246 vs 126 cases; 120 more [95% CI, 68-185]) over 5.6 years; probable dementia (179 vs 91 cases; 88 more [95% CI, 15-212]) over 4.0 years" (abstract, results)
    pubmedfull study (doi)
0:36:40Natalie Crawfordcontradictedmoderate

In approximately 80% of recurrent pregnancy loss cases, all diagnostic test results are normal, while roughly 20% show an identifiable cause.

"If I look across somebody who has recurrent pregnancy loss, I say, 80% of the time, every test will come back normal. But 20% is a big number." (said at 0:36:40)

Standard clinical guidelines (ASRM, ESHRE) and systematic reviews indicate that conventional diagnostic evaluation identifies an abnormal finding or probable cause in approximately 45% to 60% of recurrent pregnancy loss (RPL) cases, leaving roughly 37% to 50% classified as unexplained (normal test results). Furthermore, when comprehensive genetic testing of products of conception (miscarriage tissue) is added, an identifiable cause is found in up to 90% to 95% of cases. The claim that 80% of cases return completely normal results with only 20% yielding an identifiable cause substantially understates the diagnostic yield of standard evaluation and contradicts published epidemiological and clinical evidence.

0:44:50Natalie Crawfordcontradictedmoderate

The male genome does not activate until day three after fertilization, meaning embryo development during the initial days is entirely controlled by maternal factors.

"In fact, the male genome doesn't even kick in until day three after fertilization. All those first few days are 100% maternal." (said at 0:44:50)

The speaker's assertion that the male genome 'doesn't even kick in until day three' and that early development is '100% maternal' is inaccurate. While the canonical wave of 'major' embryonic genome activation (EGA) occurs around the 4- to 8-cell stage (approximately day 3 in humans), transcription from the paternal genome initiates much earlier during minor/immediate EGA at the 1-cell (pronucleate) stage, including demonstrated transcription of paternal Y-linked genes (such as ZFY) within 20–24 hours post-fertilization. Furthermore, early embryo development is not '100% maternal': critical paternal factors are required immediately upon fertilization, including sperm-derived phospholipase C-zeta (PLC-zeta) to trigger calcium oscillations and oocyte activation, as well as the sperm centriole/centrosome, which organizes the mitotic spindle for the first cleavage divisions.

0:45:05Natalie Crawfordcontradictedhigh

Primary oocytes inside the ovary are arrested in metaphase of meiosis II until ovulation.

"So an interesting fact is that inside the egg, it is frozen in metaphase of meiosis II for whatever reason. And so the chromosomes have met in the middle and they're held apart by those meiotic spindles and they do not separate until you ovulate." (said at 0:45:05)

The speaker confuses the two meiotic arrest stages of female gametogenesis. Inside the ovary, primary oocytes are arrested in prophase I (specifically the dictyate stage of meiosis I) from fetal life until the ovulatory LH surge triggers the resumption of meiosis. Progression into metaphase of meiosis II (MII) occurs around ovulation, and the oocyte remains arrested at metaphase II until fertilization by a sperm, not until ovulation.

1:26:10Natalie Crawfordcontradictedhigh

After removal of a progesterone IUD, endometrial receptivity is altered for at least six months, leading to lower conception rates during the first six months.

"But when you stop the IUD, we do see a change in endometrial receptivity at least for 6 months after it's been removed, and it can take time to build that lining back up. So I always recommend that a progesterone IUD is removed at least 6 months before you want to get pregnant. Give the endometrium time to rebuild and regrow, and then you'll have better odds at conceiving. We do see a little bit of lower pregnancy rates in those first 6 months of conceiving in women coming off of the IUD." (said at 1:26:10)

The claim that endometrial receptivity remains altered for at least six months after removal of a progestin-releasing IUD (such as the LNG-IUD), causing lower conception rates and requiring removal six months in advance, is contradicted by published clinical evidence. Randomized comparative trials and systematic reviews demonstrate that the endometrium recovers quickly after LNG-IUD removal, ovulation and fertility return rapidly, and 12-month post-removal pregnancy rates (~80-90%) are comparable to non-hormonal IUDs and other contraceptive methods.

1:33:25Natalie Crawfordcontradictedmoderate

Gonadotropins FSH and LH are released from the brain during the early morning hours.

"Your gonadotropins, so FSH and LH, are released from the brain in the early morning hours. So, when you don't sleep long enough, you're not going to have the same hormonal response." (said at 1:33:25)

The claim that gonadotropins (luteinizing hormone [LH] and follicle-stimulating hormone [FSH]) are primarily released in the early morning hours and blunted by short sleep is contradicted by neuroendocrine studies in adults. LH and FSH are secreted in pulsatile bursts across the entire 24-hour cycle from the anterior pituitary gland. While prominent nocturnal/sleep-entrained increases in LH pulsatility occur during puberty, this pattern diminishes in adulthood. In adult humans under constant routine protocols, circadian studies show either an absence of endogenous circadian rhythmicity for LH and FSH or peak levels (acrophase) occurring in the afternoon, not the early morning. Furthermore, sleep restriction studies in young adults show that partial sleep deprivation during the second half of the night does not suppress LH or FSH secretion (LH concentrations increase or remain preserved, while FSH remains unchanged). The speaker may have conflated gonadotropins with downstream hormones like testosterone or cortisol, which exhibit prominent morning peaks.

1:42:05Andrew Huberman (host)contradictedmoderate

Nattokinase supplementation can naturally help reduce LDL cholesterol levels.

"As a result, I decided to start supplementing with nattokinase, which can naturally help reduce LDL cholesterol, and it did." (said at 1:42:05)

A systematic review and meta-analysis of randomized controlled trials (RCTs) evaluating nattokinase supplementation found that it does not lower LDL cholesterol; in fact, low doses were associated with a slight increase in LDL cholesterol compared to control, and higher doses showed no statistically significant effect on LDL-C. Clinical trials that observed substantial LDL reductions evaluated combination formulations containing red yeast rice (which contains naturally occurring lovastatin), whereas nattokinase monotherapy failed to demonstrate a significant lipid-lowering effect compared to placebo.

2:30:15Natalie Crawfordcontradictedmoderate

Insufficient intake of unsaturated fats reduces progesterone production necessary for embryo implantation.

"And in fact, if you don't intake enough, you're not going to make progesterone as well. It'll be really minute. You need progesterone for implantation; don't have enough unsaturated fat in your diet, you're not going to make as much progesterone." (said at 2:30:15)

Progesterone is a steroid hormone synthesized from cholesterol, not from dietary unsaturated fatty acids. While progesterone is biologically necessary for endometrial receptivity and embryo implantation, human prospective studies and intervention trials do not support the claim that low intake of unsaturated fats severely impairs or reduces progesterone synthesis to 'minute' levels. In cohort evaluations such as the BioCycle study (PMID 26843151), total fat and polyunsaturated fatty acid intakes showed no general association with circulating luteal progesterone levels. Furthermore, interventional supplementation trials with omega-3 polyunsaturated fatty acids found no significant alterations in sex steroid levels (PMID 30773100).

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.