MTHFR and Breastfeeding

MTHFR and Breastfeeding

Product Recommendations

L Methylfolate 15 mg - A Mood-Boosting Supplement

Methylfolate 15 mg

$76.00

  • Professional Strength - Ask Your Doctor
  • High-Dose L Methylfolate 15 Mg for Natural Mood Support²
  • 3rd-Party Tested for Purity, Potency & Safety
  • 90 Vegan, Non-GMO, Chewable Mint Tablets
Katie Stone - Naturopath

Written By:

Katie Stone - Naturopath
Kari Asadorian - BSN, RN

Medical Reviewer:

Kari Asadorian - BSN, RN
Dr. Nare Simonyan - PhD Pharmaceutical Science

Edited By:

Dr. Nare Simonyan - PhD Pharmaceutical Science
Last updated:

Folate plays an important role in the production and nutritional content of breastmilk. Research has suggested that certain genetic variants involved in folate metabolism, such as MTHFR, may impact breastfeeding.


Pregnant and breastfeeding women are routinely prescribed folic acid to support the body’s folate requirements. However, common MTHFR variants such as C677T reduce MTHFR enzyme activity, which can lead to low folate levels, higher homocysteine, and higher levels of unmetabolized folic acid (UMFA) when taking folic acid supplements.1

Research has shown that taking folic acid above the recommended 400 µg/d can lead to increased levels of unmetabolized folic acid (UMFA) and reduce the proportion of active, reduced folate forms.2


The MTHFR C677T genotype is associated with lower levels of folate, higher homocysteine, and altered red blood cell folate vitamer distribution.3

Recommended Supplements When Breastfeeding

The composition of breast milk largely depends on the mother’s diet and nutritional status. Studies show that dietary intake, particularly fatty acids, and some micronutrients, such as fat-soluble vitamins, vitamin C, and some B vitamins are associated with micronutrient content in breast milk.4 These micronutrients and vitamins are essential for the development and growth of babies, particularly neural development, metabolic processes, development of soft tissues and muscles, transport of oxygen and synthesis of DNA.5


Nutritional demands during breastfeeding are considerably higher than during pregnancy, and inadequate intake of vitamins and minerals can have a negative impact on the health of both the mother and the child.6


Iodine: Recommended intake 250 µg/day 

Iodine is essential for synthesis of thyroid hormones (thyroxine and triiodothyronine), which are required for metabolism and growth of the infant. Iodine requirements are especially high in babies due to high turnover of thyroid hormones, and they rely entirely on this through breastmilk.
Inadequate iodine intake during pregnancy and breastfeeding reduces thyroxine synthesis, which may then impair brain development and lead to long-term deficits in cognitive function.7


Vitamin D: 600 IU per day for mothers plus 400 IU daily supplement for infants.

Vitamin D is essential for calcium absorption and bone mineralization in both mother and baby. Vitamin D content in human breast milk is often insufficient, so supplementation is recommended.8


Omega-3 fatty acids (DHA/EPA): Recommended intake 200-300 mg daily 

DHA is a structural component of the brain and retina, required for nerve myelination, neurodevelopment, and overall cognitive function.9 Supplementation during breastfeeding improves the DHA status both in the mother and her child as it is transferred through breast milk.10


Vitamin B12: Recommended intake 2.8 mcg for breastfeeding mothers, 0.4 mcg for infants 6 months and under.

Vitamin B12 is essential for DNA synthesis, red blood cell formation, and neurological function. B12 deficiency in mothers during breastfeeding lactation can impair red blood cell development and cognitive development in infants, potentially leading to developmental regression and megaloblastic anemia.11

Taking Methylfolate While Breastfeeding

Methylfolate is the active form of folate and the main form in breast milk; breastfed infants predominantly ingest L-5-MTHF. However, only folic acid is approved for the use in infant formula.12

When taken as a supplement, methylfolate is immediately available for use in the body without further conversion, which makes it ideal for those with MTHFR variants. Unlike folic acid, it has not been shown to cause UMFA.13

Methylfolate can be taken in prenatal and breastfeeding supplements. Folate is required for healthy DNA synthesis in all growing cells, and higher levels of folate during pregnancy are associated with a lower risk of preterm birth, low birth weight, and small-for-gestational-age births. 

A 2023 study found that higher concentrations of methylfolate in breast milk led to higher folate in infants at 4 months of age. The transfer of folate into breastmilk is favored, even when the mother is deficient. This leads to a depletion of the mother’s supply, highlighting the importance of folate supplementation while breastfeeding.14 

Folic acid supplementation, however, had almost no effect on folate concentrations in breastmilk. The researchers concluded that folate supplementation during lactation can ensure an adequate supply of folate to prevent the depletion of maternal folate and provide sufficient folate intake to their breastfed infants.15

Taking Folic Acid While Breastfeeding

Folic acid supplementation during lactation has minimal effect on total breastmilk folate content, though it may improve the mother’s levels (depending on her genetic profile).16

A 2023 RCT found that folic acid supplementation at 0.6 mg/day resulted in significantly higher (11 nmol/L) UMFA in breastmilk compared to methylfolate supplementation.17 UMFA (unmetabolized folic acid) is a synthetic form that cannot be properly utilized and may compete with active folate for transport and binding sites. Animal studies have associated UMFA with altered one-carbon metabolism and potentially adverse effects on cognitive development in offspring.18

Taking B12 While Breastfeeding

Taking B12 with folate while breastfeeding is generally recommended by health professionals as both are required for growth and development in infancy, including DNA synthesis, cell division, formation of red blood cells, and myelination of the nervous system.19


Methylcobalamin is the main form of vitamin B12 in human milk, followed by 5΄-deoxyadenosylcobalamin and small amounts of hydroxocobalamin and cyanocobalamin, all bound to haptocorrin.20

Breast milk is considered a good source of folate but it is generally low in B12, which can be a concern for babies fed exclusively on breast milk. The vitamin B12 content of breast milk depends on the mother’s own B12 levels, which depends on her B12 intake (from food or supplements) during pregnancy and lactation. The B12 content in breast milk also declines during the first 4-6 months of lactation.21


Research has suggested that low vitamin B12 levels are common in exclusively breastfed infants, both in low- and high-income populations.22

Taking B12 supplements during lactation improves breast milk concentration and infant vitamin B12 levels. This data was based on high-dose supplementation (50–250 µg/d) that began in early pregnancy and continued until 6-12 weeks postpartum.23

MTHFR and Breastfeeding

Key Takeaways

  • Icon Folate is essential for a baby’s growth and development, and is transferred via breastmilk even if the mother’s own folate stores are low.
  • Icon Supplementing with folic acid may lead to unmetabolized folic acid in the breastmilk.
  • Icon Methylfolate is the predominant form of folate in breastmilk and supplementation may be preferable to folic acid while breastfeeding.

Product Recommendations

L Methylfolate 15 mg - A Mood-Boosting Supplement

L Methylfolate 15 mg - A Mood-Boosting Supplement

$76.00

  • Professional Strength - Ask Your Doctor
  • High-Dose L Methylfolate 15 Mg for Natural Mood Support²
  • 3rd-Party Tested for Purity, Potency & Safety
  • 90 Vegan, Non-GMO, Chewable Mint Tablets

Frequently Asked Questions about MTHFR and Breastfeeding

Does MTHFR affect breastfeeding?

The MTHFR genetic mutation can affect the body’s ability to properly process folic acid. Some research has shown that taking folic acid during pregnancy and breastfeeding can result in unmetabolized folic acid (UMFA) in breastmilk. UMFA is not bioavailable to the baby, and there are some concerns about the long-term effects of UMFA in both mother and baby. UMFA can be avoided by taking methylfolate, the active form of folate that requires no further metabolism in the body, regardless of MTHFR.

Is it safe to take methylfolate while breastfeeding?

Yes, methylfolate is safe to take while breastfeeding. It is actually the predominant form of folate in breastmilk. Unlike folic acid, methylfolate is absorbed immediately by the body and requires no further enzymatic alteration, so it is ideal for those with MTHFR genetic variants. During breastfeeding, methylfolate is transferred to the baby via the breastmilk where it plays a key role in growth and development, especially in cognitive functions.

Can you take folic acid when breastfeeding?

Yes, folic acid is often recommended while breastfeeding to support the mother’s folate stores. However, it’s important to note that high-dose folic acid can lead to a buildup of unmetabolized folic acid both in the mother and the breastmilk, especially in people with MTHFR variants. Some clinicians may recommend active forms of folate (methylfolate) for this reason.

Can you take folate while breastfeeding?

Yes, taking folate while breastfeeding is both safe and recommended. The active form of folate (methylfolate) is often preferred over folic acid as it passes into breast milk without requiring further conversion in the mother’s body. Folate is essential for the normal growth and development of the baby, and supplementation during breastfeeding can help to maintain healthy levels in breastmilk.

References

  1. Rachael Page, Alex Wong, Tye E Arbuckle, Amanda J MacFarlane; "The MTHFR 677C>T polymorphism is associated with unmetabolized folic acid in breast milk in a cohort of Canadian women"; Am J Clin Nutr.; 2019 Apr

    https://pmc.ncbi.nlm.nih.gov/articles/PMC6669053/

  2. Rachael Page, André Robichaud, Tye E Arbuckle, William D Fraser, Amanda J MacFarlane; "Total folate and unmetabolized folic acid in the breast milk of a cross-section of Canadian women"; Am J Clin Nutr.; 2017 May

    https://pubmed.ncbi.nlm.nih.gov/28298392/

  3. Rachael Page, Alex Wong, Tye E Arbuckle, Amanda J MacFarlane; "The MTHFR 677C>T polymorphism is associated with unmetabolized folic acid in breast milk in a cohort of Canadian women"; Am J Clin Nutr.; 2019 Apr

    https://pmc.ncbi.nlm.nih.gov/articles/PMC6669053/

  4. Mojtaba Keikha, Maryam Bahreynian, Mohammad Saleki, Roya Kelishadi; "Macro- and Micronutrients of Human Milk Composition: Are They Related to Maternal Diet? A Comprehensive Systematic Review"; Breastfeed Med.; 2017 Nov

    https://pubmed.ncbi.nlm.nih.gov/28880568/

  5. Mojtaba Keikha, Ramin Shayan-Moghadam, Maryam Bahreynian, Roya Kelishadi; "Nutritional supplements and mother’s milk composition: a systematic review of interventional studies"; Int Breastfeed J.; 2021 Jan

    https://pmc.ncbi.nlm.nih.gov/articles/PMC7780633/

  6. Mojtaba Keikha, Ramin Shayan-Moghadam, Maryam Bahreynian, Roya Kelishadi; "Nutritional supplements and mother’s milk composition: a systematic review of interventional studies"; Int Breastfeed J.; 2021 Jan

    https://pmc.ncbi.nlm.nih.gov/articles/PMC7780633/

  7. Zheng Feei Ma, Louise Brough; "Effect of Iodine Nutrition During Pregnancy and Lactation on Child Cognitive Outcomes: A Review"; Nutrients; 2025 Jun

    https://pmc.ncbi.nlm.nih.gov/articles/PMC12196286/

  8. CDC; "Vitamin D and Breastfeeding"; U.S. Centers For Disease Control and Prevention; 2026 Jul

    https://www.cdc.gov/breastfeeding-special-circumstances/hcp/diet-micronutrients/vitamin-d.html

  9. Sanjay Basak, Rahul Mallick, Asim K Duttaroy; "Maternal Docosahexaenoic Acid Status during Pregnancy and Its Impact on Infant Neurodevelopment"; Nutrients; 2020 Nov

    https://pmc.ncbi.nlm.nih.gov/articles/PMC7759779/

  10. Sanjay Basak, Rahul Mallick, Asim K Duttaroy; "Maternal Docosahexaenoic Acid Status during Pregnancy and Its Impact on Infant Neurodevelopment"; Nutrients; 2020 Nov

    https://pmc.ncbi.nlm.nih.gov/articles/PMC7759779/

  11. Cezary Dubaj, Katarzyna Czyż, Wanda Furmaga-Jabłońska; "Vitamin B12 deficiency as a cause of severe neurological symptoms in breast fed infant – a case report"; Italian journal of pediatrics; 2020 Mar

    https://pmc.ncbi.nlm.nih.gov/articles/PMC7106665/

  12. Barbara Troesch, Johann Demmelmair, Martina Gimpfl, Christina Hecht, Goran Lakovic, Robert Roehle, Ljilja Sipka, Branka Trisic, Milica Vusurovic, Rotraut Schoop, Sznezana Zdjelar, Berthold Koletzko; "Suitability and safety of L-5-methyltetrahydrofolate as a folate source in infant formula: A randomized-controlled trial"; PLOS ONE; 2024 Jul

    https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0216790

  13. Fulvia Draicchio, Jeanette Hausser, Mastaneh Sharafi, Adeline Grier-Welch, Arianne Vance, Nima Alamdari, Itamar D. Futterman, Scott Chudnoff, Olga Malysheva, Marie A. Caudill, Isabelle Hanson, Xinyin Jiang; "Using 6S-5-methyltetrahydrofolate instead of folic acid in prenatal multivitamin reduces unmetabolized folic acid concentrations in the mother-fetus dyad: a 24-week randomized controlled trial"; Front. Nutr.; 2026 Mar

    https://www.frontiersin.org/journals/nutrition/articles/10.3389/fnut.2026.1679067/full

  14. Rima Obeid, Ines Warnke, Igor Bendik, Barbara Troesch, Rotraut Schoop, Elodie Chenal, Berthold Koletzko; "Infants’ Folate Markers and Postnatal Growth in the First 4 Months of Life in Relation to Breastmilk and Maternal Plasma Folate"; Nutrients; 2023

    https://www.mdpi.com/2072-6643/15/6/1495

  15. Rima Obeid, Ines Warnke, Igor Bendik, Barbara Troesch, Rotraut Schoop, Elodie Chenal, Berthold Koletzko; "Infants’ Folate Markers and Postnatal Growth in the First 4 Months of Life in Relation to Breastmilk and Maternal Plasma Folate"; Nutrients; 2023

    https://www.mdpi.com/2072-6643/15/6/1495

  16. Page Rachael, Robichaud André, Arbuckle Tye E, Fraser William D, MacFarlane Amanda J; "Total folate and unmetabolized folic acid in the breast milk of a cross-section of Canadian women"; The American Journal of Clinical Nutrition; 2017 May

    https://www.sciencedirect.com/science/article/pii/S0002916522048778

  17. Kelsey M Cochrane, Rajavel Elango, Angela M Devlin, Jennifer A Hutcheon, Crystal D Karakochuk; "Human milk unmetabolized folic acid is increased following supplementation with synthetic folic acid as compared to (6S)-5-methyltetrahydrofolic acid"; Scientific reports; 2023 Jul

    https://pmc.ncbi.nlm.nih.gov/articles/PMC10338559/

  18. Franziska Delgas, Lisa Bitsch, Laura Maria König, Damaris Elisabeth Beitze, Veronika Scherbaum, Maren C Podszun; "Dietary supplement use among lactating mothers following different dietary patterns – an online survey"; Matern Health Neonatol Perinatol.; 2024 Feb

    https://pmc.ncbi.nlm.nih.gov/articles/PMC10832081/

  19. Julia L Finkelstein, Amy Fothergill, Sudha Venkatramanan, Alexander J Layden, Jennifer L Williams, Krista S Crider, Yan Ping Qi; "Vitamin B12 supplementation during pregnancy for maternal and child health outcomes"; Cochrane Database Syst Rev.; 2024 Jan

    https://pubmed.ncbi.nlm.nih.gov/38189492/

  20. Daniela Hampel, Daphna K Dror, Lindsay H Allen; "Micronutrients in Human Milk: Analytical Methods"; Adv Nutr.; 2018 May

    https://pubmed.ncbi.nlm.nih.gov/29846527/

  21. Sigrun Henjum, Mari Manger, Daniela Hampel, Anne Lise Brantsæter, Setareh Shahab-Ferdows, Nasser E. Bastani, Tor A. Strand, Helga Refsum, Lindsay H. Allen; "Vitamin B12 concentrations in milk from Norwegian women during the six first months of lactation"; European Journal of Clinical Nutrition volume; 2020 Jan

    https://www.nature.com/articles/s41430-020-0567-x

  22. Beate S Solvik, Kjersti S Bakken, Adrian McCann, Per M Ueland, Sigrun Henjum, Tor A Strand; "Breastfeeding and biomarkers of folate and cobalamin status in Norwegian infants: a cross-sectional study"; J Nutr Sci.; 2024 Sep

    https://pmc.ncbi.nlm.nih.gov/articles/PMC11428113/

  23. Beate S Solvik, Kjersti S Bakken, Adrian McCann, Per M Ueland, Sigrun Henjum, Tor A Strand; "Breastfeeding and biomarkers of folate and cobalamin status in Norwegian infants: a cross-sectional study"; J Nutr Sci.; 2024 Sep

    https://pmc.ncbi.nlm.nih.gov/articles/PMC11428113/

Katie Stone - Naturopath

About the Author

Katie is a qualified Naturopath (BNatMed) and freelance writer from New Zealand. She specializes in all things health and wellness, particularly dietary supplements and nutrition. Katie is also a dedicated runner and has completed more half-marathons than she can count!

Related Articles

Trusted by Experts. Backed by Science.

Trusted professionals crafting original content backed by verified research. Since 2012, Methyl-Life® has been dedicated to providing evidence-based education to help individuals better understand methylation and nutritional wellness.

  • Expert-authored education

    Expert-authored education

    Every article and guide is written or reviewed by professionals specializing in methylation science and nutritional biochemistry.

  • Research-verified information

    Research-verified information

    Our content references peer-reviewed studies and verified data, ensuring accuracy, integrity, and real-world relevance.

  • Educational leadership since 2012

    Educational leadership since 2012

    A founder-led team collaborating with clinicians, researchers, and health writers to make complex science accessible and actionable.

  • Transparent and trustworthy

    Transparent and trustworthy

    All educational materials undergo internal review for scientific accuracy, compliance, and clarity before publication.

Blog Categories

Table of Contents