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Folate
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In one pass Folate is vitamin B9: cell division and DNA-making depend on it, which is also why it is the vitamin people are told again and again to take before pregnancy.
Educational content, not medical advice — consult a clinician.
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Chapter 1
Leafy B9
Folate is vitamin B9: cell division and DNA-making depend on it, which is also why it is the vitamin people are told again and again to take before pregnancy.
The name folate comes from the Latin word for leaf. Dark leafy greens (see Spinach · see Kale · see Broccoli), legumes (see Lentils), asparagus, avocado (see Avocado), citrus, and animal liver (Organ Meat) are all common sources.
Food contains natural, reduced forms of folate; supplements and fortified foods use a synthetic form called folic acid. The synthetic form is more stable and better absorbed, which is why pregnancy supplements and grain fortification both use it.
The name folate comes from the Latin word for leaf. Dark leafy greens (see Spinach · see Kale · see Broccoli), legumes (see Lentils), asparagus, avocado (see Avocado), citrus, and animal liver (Organ Meat) are all common sources.
Food contains natural, reduced forms of folate; supplements and fortified foods use a synthetic form called folic acid. The synthetic form is more stable and better absorbed, which is why pregnancy supplements and grain fortification both use it.
Numbers · How to read DFE on a folate label
Folate on a nutrition label can mean three different things with completely different conversion factors, which makes it one of the most easily misread items on a label.The three forms:
Food folate (natural): several polyglutamate forms, which have to lose their extra glutamates in the gut before they can be absorbed; about 50% bioavailableFolic acid (synthetic, used in fortified foods and supplements): an oxidized single-unit form that is absorbed easily; close to 100% bioavailable on an empty stomach and about 85% with food (5-methyltetrahydrofolate, often sold as "active folate"): enters the circulation directly in its active form, skipping the reduction step done by dihydrofolate reductase (DHFR); about 85% bioavailable
How dietary folate equivalents () convert:
1 µg DFE = 1 µg of food folate1 µg DFE = 0.6 µg of folic acid taken with food1 µg DFE = 0.5 µg of folic acid taken on an empty stomach
So 400 µg of folic acid taken with food in pregnancy equals 400 / 0.6 ≈ 666 µg DFE, well above the number the label seems to show.
Recommended Dietary Allowances (US ):
Adults: 400 µg DFE/dayPregnancy: 600 µg DFE/dayBreastfeeding: 500 µg DFE/dayPlanning a pregnancy: in 2023 the US Preventive Services Task Force (USPSTF) gave an A-grade recommendation (high certainty of a substantial net benefit) that everyone planning or able to become pregnant take 400–800 µg of folic acid a day, starting at least 1 month before conception, on top of food folate
On people with TT homozygosity who are planning a pregnancy: some doctors suggest switching to 5-MTHF, because folic acid must first be reduced by DHFR before it enters the circulation, and TT homozygotes have lower MTHFR enzyme activity. But the 2013 guideline of the American College of Medical Genetics and Genomics (ACMG) holds that folic acid works regardless of MTHFR genotype; most TT homozygotes have healthy babies on ordinary folic acid, and 5-MTHF is more of an insurance policy than a necessity.
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Chapter 2
Carrying carbon pieces for DNA
Folate's core job is carrying one-carbon units: methyl (CH₃), methylene (CH₂), and formyl (CHO), small fragments with a single carbon.
These one-carbon units go to two places:
Raw material for DNA: making thymidylate (TMP) and purines from scratch both need carbon fragments delivered by folateThe methylation cycle: 5-methyltetrahydrofolate hands its methyl group to , which turns back into methionine, and methionine is then made into , the body's all-purpose methyl donor
That is why the fastest-dividing tissues suffer most when folate runs short: blood-making in the bone marrow, the fetal neural tube, and the renewal of the gut lining all need a steady supply of DNA building blocks. Without folate, DNA synthesis stalls and cells grow but cannot divide; this is the cellular basis of megaloblastic anemia (red blood cells that are too large and too few).
These one-carbon units go to two places:
Raw material for DNA: making thymidylate (TMP) and purines from scratch both need carbon fragments delivered by folateThe methylation cycle: 5-methyltetrahydrofolate hands its methyl group to , which turns back into methionine, and methionine is then made into , the body's all-purpose methyl donor
That is why the fastest-dividing tissues suffer most when folate runs short: blood-making in the bone marrow, the fetal neural tube, and the renewal of the gut lining all need a steady supply of DNA building blocks. Without folate, DNA synthesis stalls and cells grow but cannot divide; this is the cellular basis of megaloblastic anemia (red blood cells that are too large and too few).
Clinical · Methotrexate and folate
Methotrexate (MTX) is the most important folate antagonist in clinical use: both a chemotherapy drug and a first-line treatment for rheumatoid arthritis, psoriasis, and inflammatory bowel disease ().Mechanism: MTX looks very like folate and competitively inhibits dihydrofolate reductase (DHFR), so tetrahydrofolate (THF) cannot be regenerated, which blocks DNA synthesis (especially of thymidylate, TMP). Fast-dividing cancer cells and activated immune cells are hit hardest.
It is used in two ways, in completely different clinical settings.
High-dose chemotherapy:
Used for acute lymphoblastic leukemia (ALL), osteosarcoma, and some lymphomasDoses of 500–5000 mg/m² (far above the 15–25 mg/week used in rheumatology)24–48 h after MTX, intravenous leucovorin (folinic acid) is usually given as a rescue to protect normal cells from the DNA-synthesis blockMistakes in timing or dose can be fatal
Low-dose anti-inflammatory use:
Used for rheumatoid arthritis, psoriasis, psoriatic arthritis, and IBDDoses of 7.5–25 mg/week (by mouth or injection under the skin)Usually paired with folic acid (1 mg a day, or 5 mg once a week) to reduce nausea, mouth ulcers, raised liver enzymes, bone-marrow suppression, and other side effects. The Shea 2013 Cochrane systematic review pooled randomized trials and found that this pairing reduces gut side effects and abnormal liver enzymes without affecting disease control
Practical points: people on MTX should take folic acid as prescribed (not folinic acid, unless the doctor specifies it); do not raise the folic acid dose on your own, since that may weaken MTX's anti-inflammatory effect; pregnancy is an absolute contraindication, because MTX causes birth defects and raises the risk of miscarriage, and stopping it for at least 3 months before trying to conceive is usually advised.
This is a clear example that more folate is not always better: with certain drugs and diseases, different forms of folate carry completely different clinical meanings.
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Chapter 3
MTHFR genetics
(methylenetetrahydrofolate reductase) is a key enzyme in the folate cycle: it reduces 5,10-methylenetetrahydrofolate to 5-methyltetrahydrofolate, the active form that the methylation cycle uses.
The C677T variant: how often people are TT homozygous varies sharply by ancestry. NIH ODS gives about 25% of Hispanic people, about 10% each of White and Asian people, and about 1% of African Americans. In TT homozygotes, MTHFR activity is markedly lower than in the usual (wild-type) form, with CT heterozygotes in between. When folate intake is short, less 5-methyltetrahydrofolate is made, methylation slows, and blood rises.
What it means in practice:
With enough folic acid in the diet, most TT homozygotes show no obvious consequencesThe risk grows mainly when folate intake is borderlineSome studies suggest some TT homozygotes may benefit from supplements, but the evidence is not settled
Note: an MTHFR variant is not a disease gene. The actual risk for a TT homozygote still depends on overall folate status, and the market overstates what MTHFR testing means clinically.
The C677T variant: how often people are TT homozygous varies sharply by ancestry. NIH ODS gives about 25% of Hispanic people, about 10% each of White and Asian people, and about 1% of African Americans. In TT homozygotes, MTHFR activity is markedly lower than in the usual (wild-type) form, with CT heterozygotes in between. When folate intake is short, less 5-methyltetrahydrofolate is made, methylation slows, and blood rises.
What it means in practice:
With enough folic acid in the diet, most TT homozygotes show no obvious consequencesThe risk grows mainly when folate intake is borderlineSome studies suggest some TT homozygotes may benefit from supplements, but the evidence is not settled
Note: an MTHFR variant is not a disease gene. The actual risk for a TT homozygote still depends on overall folate status, and the market overstates what MTHFR testing means clinically.
Myth · Does an MTHFR variant need special supplements?
testing is one of the genetic tests most prone to hype in marketing channels, and the gap between the sales pitch and medical consensus is wide.The direct-sales pitch goes roughly like this: you have an MTHFR mutation, your detox is impaired, you must take plus a range of methylation supplements, avoid ordinary folic acid, and go through detox protocols. Along the way it ties MTHFR to chronic fatigue, autism, depression, miscarriage, anxiety, and dementia, and sells the lot as a pricey personalized package.
Mainstream medical consensus (the 2013 guideline of the American College of Medical Genetics and Genomics, ACMG, updated in 2020) is far more restrained:
The MTHFR variants C677T and A1298C are common polymorphisms, not disease genesTT homozygosity is not rare in most populations (NIH ODS: about 10% each of White and Asian people, about 25% of Hispanic people)The clinical association with the most support is that TT homozygotes whose folate intake is borderline show moderately raised blood (Hcy) and a slightly higher risk of neural tube defectsEvidence linking MTHFR to miscarriage, autism, and depression is weak and inconsistentIt is not recommended as a routine test in assessing infertility, depression, or cardiovascular diseaseThere is no need to avoid folic acid: ACMG states that folic acid works regardless of MTHFR genotype
The MTHFR intervention that actually helps is plain: get folate intake up to the of 400 µg /day (leafy greens, fortified foods, and a supplement if needed); keep B12 adequate so methylation can work; do not smoke, drink less, control blood sugar, and exercise regularly. These matter far more than genotype.
On whether TT homozygotes must take 5-MTHF: they need not; folic acid lowers homocysteine too. 5-MTHF takes a more direct path, skipping the DHFR and MTHFR steps. Patanwala 2014 sampled blood straight from the portal vein and found that most swallowed folic acid is not reduced in the gut but reaches the liver unchanged, where it depends on the liver's DHFR, which is not very active and varies a lot between people; natural reduced folates, by contrast, are almost all converted to 5-MTHF in the gut. If you choose 5-MTHF, 400–800 µg a day is enough; it usually costs more, and there is no need to pay extra for a special formula.
MTHFR is a real metabolic variant, but testing MTHFR-positive means you need a complex personalized supplement plan is an overreach; the great majority of TT carriers do fine with a sensible diet plus ordinary folic acid.
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Chapter 4
Without B12, folate gets stuck
B12 is the cofactor for methionine synthase (MTR). Without B12, 5-methyltetrahydrofolate cannot hand its methyl group to , and folate gets stuck in that form; this is called the methyl-folate trap.
The result is counterintuitive: blood folate looks ample, but the forms of folate that cells actually use to make DNA run short, so DNA synthesis still fails, and B12 deficiency and folate deficiency show a similar megaloblastic anemia.
The more serious clinical trap: high-dose folic acid can correct the anemia caused by B12 deficiency, but it cannot repair the nerve damage that B12 deficiency causes. Folic acid does not harm nerves itself; the problem is that it masks the B12 deficiency. The blood count looks better while nerve damage keeps progressing behind the illusion that the anemia has improved, and if it goes on long enough it may not be reversible. Numbness or tingling in the hands and feet, an unsteady walk, or worsening memory are reasons to get B12 checked, not to add folic acid on your own.
People at high risk of B12 deficiency: long-term vegans, older adults (less stomach acid and intrinsic factor), long-term users of proton pump inhibitors () or H2 blockers, and long-term users of metformin.
The result is counterintuitive: blood folate looks ample, but the forms of folate that cells actually use to make DNA run short, so DNA synthesis still fails, and B12 deficiency and folate deficiency show a similar megaloblastic anemia.
The more serious clinical trap: high-dose folic acid can correct the anemia caused by B12 deficiency, but it cannot repair the nerve damage that B12 deficiency causes. Folic acid does not harm nerves itself; the problem is that it masks the B12 deficiency. The blood count looks better while nerve damage keeps progressing behind the illusion that the anemia has improved, and if it goes on long enough it may not be reversible. Numbness or tingling in the hands and feet, an unsteady walk, or worsening memory are reasons to get B12 checked, not to add folic acid on your own.
People at high risk of B12 deficiency: long-term vegans, older adults (less stomach acid and intrinsic factor), long-term users of proton pump inhibitors () or H2 blockers, and long-term users of metformin.
Evidence · Why folic acid fortification is debated
Folic acid fortification is one of the most successful interventions in public health, and one of the most argued over.Who fortifies by law: several dozen countries. Since 1998 the US has required synthetic folic acid in enriched cereal-grain products, at 140 µg per 100 g; Canada, Chile, Brazil, Australia, Indonesia, South Africa, and others followed. The goal is preventing neural tube defects (NTDs): about half of pregnancies are unplanned, and starting folate once the pregnancy is discovered is too late (the neural tube closes 21–28 days after conception). The effect: the rate of NTDs in the US fell by about 28% (Williams 2015, data from the US Centers for Disease Control and Prevention, CDC, across all surveillance programs; about 35% in programs with prenatal diagnosis).
Many countries do not fortify: most of Europe (France, Germany, the Nordic countries, and others) worries that it could mask B12 deficiency and harm older people's nerves, and that the long-term effects of unmetabolized folic acid (UMFA) are unknown. China does not require fortification, but prenatal care includes folic acid supplements. Japan does not fortify and advises people to supplement on their own.
The argument centers on three points.
First, masking B12 deficiency: large amounts of folic acid can correct megaloblastic anemia, which hides the earliest sign of B12 deficiency, while the nerve damage it causes keeps progressing as peripheral neuropathy, spinal cord damage, and cognitive problems. US surveys of older adults suggest that undiagnosed B12 deficiency may have increased after fortification, but the data are inconsistent and the question is still debated.
Second, the unknown long-term effects of unmetabolized folic acid. A single intake of more than about 200 µg of folic acid may exceed the body's capacity to reduce it, so unmetabolized folic acid stays in the blood: in studies summarized by NIH ODS, common single doses of 300 or 400 µg already produce measurable levels. Patanwala 2014 found that the human gut has very limited capacity to reduce folic acid, leaving most of the work to the liver, which may explain why UMFA appears. Some studies have linked UMFA to lower numbers and activity of natural killer (NK) cells, a kind of immune cell; what it does to the body in the long run is unclear, but this is the main basis for Europe's caution.
Third, the two faces of colorectal cancer: by mechanism, adequate folate may reduce DNA damage early on, but in people who already have precancerous lesions such as adenomas, large amounts may speed progression instead. In the randomized trial by Cole 2007 (JAMA), people with a recent history of colorectal adenomas who took 1 mg of folic acid a day had no fewer adenoma recurrences, and more often had 3 or more adenomas. It is a textbook case of dose plus timing deciding benefit and harm.
A balanced practical approach: fortified foods plus food sources, for a total of 400–600 µg a day, is safe and effective; extra supplements make sense mainly when planning a pregnancy and in early pregnancy, and others do not need them without a diagnosed deficiency; when older adults have folate tested, test B12 as well, and do not take high-dose folic acid alone; people with a history of, or high risk for, colorectal cancer should discuss their folate intake with a doctor.
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Chapter 5
Why it matters before pregnancy
Folate's strongest public-health evidence sits before pregnancy and in early pregnancy. The neural tube closes within 21–28 days after fertilization, and by the time many people realize they are pregnant, that window has already passed.
So guidelines stress: anyone who could become pregnant should have enough folate at least 1 month before conception. The US Preventive Services Task Force (USPSTF) 2023 A-grade recommendation (high certainty of a substantial net benefit) is that everyone planning or able to become pregnant take 400–800 µg of folic acid a day. The US FDA's requirement to fortify grain with folic acid rests on the same timing logic.
Dose: the adult is 400 µg /day; supplements for planning a pregnancy and for pregnancy usually contain 400–800 µg of folic acid; people who have had a pregnancy affected by a neural tube defect, and people taking anti-seizure drugs, should use a high-dose regimen such as 4000 µg/day under a doctor's guidance, not raise the dose on their own.
This is not prenatal supplement marketing; it is a real limit set by the timing of fetal development.
So guidelines stress: anyone who could become pregnant should have enough folate at least 1 month before conception. The US Preventive Services Task Force (USPSTF) 2023 A-grade recommendation (high certainty of a substantial net benefit) is that everyone planning or able to become pregnant take 400–800 µg of folic acid a day. The US FDA's requirement to fortify grain with folic acid rests on the same timing logic.
Dose: the adult is 400 µg /day; supplements for planning a pregnancy and for pregnancy usually contain 400–800 µg of folic acid; people who have had a pregnancy affected by a neural tube defect, and people taking anti-seizure drugs, should use a high-dose regimen such as 4000 µg/day under a doctor's guidance, not raise the dose on their own.
This is not prenatal supplement marketing; it is a real limit set by the timing of fetal development.
Clinical · Folate from planning to breastfeeding
Below is a timeline of folate across pregnancy and breastfeeding, drawing on recommendations from the US USPSTF, the World Health Organization (WHO), and others.Planning a pregnancy (1–3 months before conception):
Every woman who could become pregnant: 400–800 µg of folic acid a dayBuild the dietary base at the same time (leafy greens, legumes, fortified grains)Make sure B12 is adequate too, especially for vegetarians
Early pregnancy (weeks 0–12):
Continue 400–800 µg of folic acid a day, plus food folateThe neural tube closes 21–28 days after conception, the most critical stretch of the whole windowUsually continued through week 12
Mid and late pregnancy (weeks 13–40):
The is 600 µg /day (roughly 400 µg of folic acid plus food)Most pregnant women reach it with a prenatal vitamin plus fortified foodsKeep B12 adequate
Breastfeeding:
The RDA is 500 µg DFE/dayFolate in breast milk is kept up as a priority, possibly at the cost of the mother's own stores
The following high-risk groups usually need a high-dose prevention regimen of 4–5 mg a day (about 10 times the routine dose). Doses like these exceed the upper limit for folic acid and should only be used under a doctor's guidance:
People who have had a pregnancy affected by a neural tube defect: 4 mg a day in the next pregnancy, from 1 month before conception to the end of early pregnancy. The main evidence is the MRC 1991 randomized trial: in women at high risk of recurrence because of a previous affected pregnancy, high-dose folic acid cut neural tube defects by 72%A personal or first-degree family history of neural tube defectsLong-term anti-seizure medicines (valproate, carbamazepine, phenytoin)Diabetes, especially when blood sugar is poorly controlledWithin 1–3 months of stopping methotrexate
The 2025 guideline from England's NICE also lists diabetes and taking anti-seizure medicines as reasons for a high dose (5 mg). People who smoke heavily, drink heavily, or eat poorly overall should first make sure of the basic dose, and leave any increase to a doctor's assessment.
When to stop: after week 12 the risk window for neural tube defects has passed; continuing a folate-containing prenatal vitamin after that is about meeting pregnancy's higher folate needs. After weaning, go back to the routine RDA.
A few common misconceptions:
Eating lots of spinach means I do not need a supplement: food folate is only about 50% bioavailable, so reaching 600 µg reliably from food alone is hardI will start once I am pregnant: the 21-day window may already have passedMy periods are regular, so I do not need to supplement while planning: even with regular cycles, about half of pregnancies are unplanned, so building in a safety margin is wiser
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Chapter 6
Not more is better
Folate from natural foods is very safe; what deserves attention is long-term high-dose folic acid.
The adult tolerable upper intake level () for folic acid is 1000 µg/day. It counts only the synthetic folic acid in supplements and fortified foods, not food folate. There are three main concerns:
1. Masking B12 deficiency (covered in the chapter on B12)
2. Rising unmetabolized folic acid (UMFA): a large dose of folic acid outruns the body's capacity to reduce it (DHFR), the unmetabolized part goes straight into the blood, and its long-term effects are still unknown
3. Some studies suggest that high UMFA is linked to changes in immune-cell activity, but the clinical meaning has not been settled
In practice: build on dark leafy greens and legumes, use fortified grains as a top-up, take supplements in pregnancy or when a doctor specifically advises them, and do not chase more is better.
The adult tolerable upper intake level () for folic acid is 1000 µg/day. It counts only the synthetic folic acid in supplements and fortified foods, not food folate. There are three main concerns:
1. Masking B12 deficiency (covered in the chapter on B12)
2. Rising unmetabolized folic acid (UMFA): a large dose of folic acid outruns the body's capacity to reduce it (DHFR), the unmetabolized part goes straight into the blood, and its long-term effects are still unknown
3. Some studies suggest that high UMFA is linked to changes in immune-cell activity, but the clinical meaning has not been settled
In practice: build on dark leafy greens and legumes, use fortified grains as a top-up, take supplements in pregnancy or when a doctor specifically advises them, and do not chase more is better.
Myth · Is synthetic folic acid harmful?
Natural folate good, synthetic folic acid bad is a hot topic in the supplement market. Here is the evidence, point by point.The forms compared:
Food folate (several polyglutamate forms): from greens, legumes, liver, and fortified grains; it must lose its extra glutamates before absorption; about 50% bioavailable; safe in any amount from foodFolic acid (synthetic, pteroylglutamic acid): the standard supplement form; after absorption it is converted by DHFR and into active ; 85–100% absorbed; 1000 µg/day; very high doses produce UMFA5-MTHF (L-methylfolate, levomefolate): already in methylated form, so it needs no conversion by DHFR or MTHFR; about 85% absorbed; usually more expensive than folic acid
Does the claim that folic acid is unnatural and harmful hold up? Point by point:
The case for avoiding it comes down to three arguments: UMFA's long-term effects are unknown, so apply the precautionary principle; MTHFR TT homozygotes convert it less efficiently; and a philosophical preference that the body should stay close to nature.
The rebuttals are clear: counting from the start of mandatory fortification in the US in 1998, mass consumption of folic acid has now run for more than a generation without clear long-term harm; the clinical meaning of UMFA is still unestablished; folic acid still works in TT homozygotes (ACMG 2013); and 5-MTHF's advantages remain mostly theoretical, with clinical evidence comparable to folic acid.
Practical recommendations: for most people folic acid is perfectly fine, and cheap; 5-MTHF is fine if you prefer it, but it does not justify spending more; food folate should be the base, with supplements as a top-up; what really should be avoided is long-term high-dose folic acid (> 1000 µg/day) without a reason.
This is at heart a tension between personalized nutrition and public health: public-health data support that folic acid fortification has saved many babies; at the individual level, 5-MTHF is an option, not a necessity.
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References · 10
- National Institutes of Health, Office of Dietary Supplements. (2022). Folate — Fact Sheet for Health Professionals. ods.od.nih.gov/factsheets/Folate-HealthProfessional
- Crider, K. S., Bailey, L. B., & Berry, R. J. (2011). Folic acid food fortification—its history, effect, concerns, and future directions. Nutrients, 3(3), 370–384. 10.3390/nu3030370
- Allen, L. H., Miller, J. W., de Groot, L., et al. (2018). Biomarkers of Nutrition for Development (BOND): vitamin B-12 review. The Journal of Nutrition, 148(suppl_4), 1995S-2027S. 10.1093/jn/nxy201
- Patanwala, I., King, M. J., Barrett, D. A., Rose, J., Jackson, R., Hudson, M., et al. (2014). Folic acid handling by the human gut: implications for food fortification and supplementation. American Journal of Clinical Nutrition, 100(2), 593–599. Crossover study in 6 patients with a TIPS shunt (which allows portal-vein sampling), physiological oral doses of labelled folic acid vs 5-formylTHF. Fifteen minutes after folic acid, 80 +/- 12% of labelled folate in the portal vein was unmodified folic acid; after 5-formylTHF only 4 +/- 18% was unmodified. Conclusion: the human gut reduces folic acid poorly (limited mucosal DHFR), leaving the liver to do it. Not a trial in MTHFR TT carriers - genotype is not mentioned (abstract, PMID 24944062). 10.3945/ajcn.113.080507
- Stabler, S. P. (2013). Clinical practice. Vitamin B12 deficiency. The New England Journal of Medicine, 368(2), 149–160. 10.1056/NEJMcp1113996
- National Institutes of Health, Office of Dietary Supplements. (2024). Vitamin B12 — Fact Sheet for Health Professionals. Fact sheet (updated July 2, 2025; Wayback snapshot 20 September 2026): multivitamin/mineral supplements typically contain 5 to 25 mcg B12, B-complex products 50 to 500 mcg, B12-only supplements typically 500 to 1,000 mcg; absorption is only about 2% at 500 mcg and 1.3% at 1,000 mcg; a 2018 Cochrane review of 3 RCTs (153 participants) compared very high oral doses (1,000-2,000 mcg) with intramuscular B12; high oral doses (e.g. 1,000 mcg/day) might be equally effective in Crohn's disease and appear as effective as hydroxocobalamin injections after Roux-en-Y bypass. These are product contents and trial doses; the sheet gives no recommended daily supplement range (fact sheet). ods.od.nih.gov/factsheets/VitaminB12-HealthProfessional
- Williams, J., Mai, C. T., Mulinare, J., et al. (2015). Updated estimates of neural tube defects prevented by mandatory folic acid fortification — United States, 1995–2011. MMWR, 64(1), 1-5. www.cdc.gov/mmwr/preview/mmwrhtml/mm6401a2.htm
- Cole, B. F., Baron, J. A., Sandler, R. S., et al. (2007). Folic acid for the prevention of colorectal adenomas: a randomized clinical trial. JAMA, 297(21), 2351–2359. 10.1001/jama.297.21.2351
- Czeizel, A. E., & Dudás, I. (1992). Prevention of the first occurrence of neural-tube defects by periconceptional vitamin supplementation. The New England Journal of Medicine, 327(26), 1832–1835. 10.1056/NEJM199212243272602
- US Preventive Services Task Force. (2023). Folic acid supplementation to prevent neural tube defects: US Preventive Services Task Force reaffirmation recommendation statement. JAMA, 330(5), 454-459. Grade A: all persons planning or capable of pregnancy take a daily supplement with 400-800 mcg folic acid. 10.1001/jama.2023.12876