NutriStack
Combined Oral Contraceptive and Vitamin B9, a synergy.
A systematic review and meta-analysis of 17 studies found that women using combined oral contraceptives had significantly lower serum and red-cell folate than non-users. This matters most for women who may conceive shortly after stopping the pill, because low folate at conception raises neural tube defect risk.
One pair, every claim cited. The two substances, the type, the mechanism, the recommendation, and the primary literature.
Same shape as the other 1,729 pairs in the public database.
From the interaction database
What the row says.
Every entry follows the same shape: what is happening, the mechanism, the recommendation, and the primary literature.
At a glance
- Substances
- Combined Oral Contraceptive and Vitamin B9
- Pair type
- Synergy
- Evidence (highest tier)
- Strong
- Source citations
- 2 sources
- Stack Score effect
- +2 to your Stack Score (per scored synergy row).
- Scope
- Supplement × Prescription
- Last verified
- May 30, 2026
Synergy · Strong evidence
Synergy
What is happening. A systematic review and meta-analysis of 17 studies found that women using combined oral contraceptives had significantly lower serum and red-cell folate than non-users. This matters most for women who may conceive shortly after stopping the pill, because low folate at conception raises neural tube defect risk.
Mechanism. Estrogens increase hepatic folate-binding protein synthesis and may alter folate catabolism and renal clearance, lowering circulating folate. Some progestins also impair folate-dependent one-carbon metabolism.
Recommendation. Take a daily folate-containing multivitamin (400-800 mcg of folic acid or 5-MTHF) while on combined oral contraception, especially in the year before any planned pregnancy. The folate can be taken with or without the pill.
Sources (2)
- Shere M, Bapat P, Nickel C, Kapur B, Koren G. Association Between Use of Oral Contraceptives and Folate Status: A Systematic Review and Meta-Analysis. J Obstet Gynaecol Can. 2015;37(5):430-438. PMID 26168104
- Palmery M, Saraceno A, Vaiarelli A, Carlomagno G. Oral contraceptives and changes in nutritional requirements. Eur Rev Med Pharmacol Sci. 2013;17(13):1804-13. PMID 23852908
Stack Score
How this pair moves the number.
Effect on the composite score
If both Combined Oral Contraceptive and Vitamin B9 are in the same stack, this pair applies +2 to your Stack Score (per scored synergy row).
The full algorithm, the clamping rules, and four worked stacks are documented at /methodology/stack-score.
Check your full routine
One pair was the worked example. NutriStack runs every pair in your stack at once.
Drop in your supplements and prescriptions and the public database surfaces every interaction, synergy, timing rule, and contraindication, every one linked to its primary source.