Can Vitamin B6 Alter Menstrual Cycles?
Vitamin B6 does not fundamentally alter the timing or regularity of menstrual cycles in healthy women, but it can modulate premenstrual symptoms and potentially influence reproductive hormone levels at higher doses.
Evidence on Menstrual Cycle Regularity
The most rigorous evidence examining vitamin B6's effects on actual menstrual cycle function comes from a prospective cohort study that found no associations between vitamin B6 intake and risk of anovulation among 259 healthy, regularly menstruating premenopausal women tracked across two complete cycles 1. This study specifically evaluated whether B6 intake affected ovulatory function—the core mechanism determining cycle regularity—and found it did not 1.
Hormonal Effects of Vitamin B6
While B6 doesn't disrupt cycle timing, it does appear to have modest effects on reproductive hormones:
- Higher vitamin B6 intakes were suggestively associated with higher follicle-stimulating hormone (FSH) levels, though this did not reach statistical significance (0.63% difference per 0.1 mg increase, p=0.06) 1
- One older study reported that vitamin B6 at doses of 200-800 mg/day reduced blood estrogen and increased progesterone in women with premenstrual anxiety symptoms, though this was in a specific subgroup with presumed hormonal imbalance 2
- The 2020 prospective study found that riboflavin (not B6) was inversely correlated with estradiol levels, but vitamin B6 itself showed minimal hormonal effects at typical dietary intakes 1
Important caveat: The hormonal effects reported in the 1983 study 2 used extremely high doses (200-800 mg/day) that far exceed current safety recommendations and carry significant toxicity risk. Clinical guidelines indicate that prolonged intakes of just 100 mg/day have been associated with neurological toxicity 3.
Effects on Premenstrual Symptoms (Not Cycle Timing)
The evidence on B6 for premenstrual syndrome is mixed but suggests symptom improvement without altering cycle characteristics:
- A 2020 randomized controlled trial found that vitamin B6 (80 mg/day) reduced PMS symptoms with medium effect sizes (ES = 0.43-0.56), with 60% of participants achieving full remission after three cycles 4
- However, a 1985 double-blind crossover trial found vitamin B6 (100 mg/day) was no better than placebo for premenstrual tension 5
- A 2012 trial showed vitamin B6 significantly decreased premenstrual syndrome scores, though the study design had limitations 6
These studies evaluated symptom severity, not menstrual cycle regularity or timing 4, 5, 6.
Clinical Interpretation
The distinction is critical: Vitamin B6 may help manage premenstrual symptoms in some women, but this represents symptomatic treatment rather than alteration of the underlying menstrual cycle physiology. The cycle itself—ovulation timing, cycle length, hormonal patterns—remains fundamentally unchanged in healthy women 1.
Safety Considerations for Higher Doses
If considering B6 supplementation for premenstrual symptoms:
- Doses above 100 mg/day carry significant risk of peripheral neuropathy, including numbness, paresthesia, motor ataxia, and loss of deep tendon reflexes 3
- Even "low-dose" supplementation (6-40 mg/day) has caused toxicity in case reports 7
- The recommended daily intake is only 1.3-1.7 mg/day for adults, with an upper tolerable limit of 100 mg/day 7
- Neurological recovery after B6 toxicity may take several weeks to months, and some nerve damage may persist permanently 3, 7
Bottom Line
Vitamin B6 supplementation does not alter menstrual cycle regularity or ovulatory function in healthy women 1. Any perceived "cycle changes" are more likely related to symptom improvement rather than actual cycle disruption. The doses required to potentially influence reproductive hormones (200-800 mg/day) 2 are dangerously high and should be avoided due to severe neurotoxicity risk 3, 7.