Folate (B9)
Supplements · Vitamins · Supplement, Typed Supps
Easy to confuse with folic acid, which is the synthetic version.
Stage by stage
- Intake (Tablet (folate or folic acid)): Methylfolate skips a conversion step that synthetic folic acid requires.
- Small intestine (Absorbed): Absorbed and carried in blood to cells throughout the body.
- Bloodstream (Carried to cells): Carried in the blood to cells throughout the body.
- Cells (DNA synthesis): Needed for DNA synthesis and red blood cell formation.
What the evidence supports
- Preventing neural tube defects when taken before and in early pregnancy — strong evidence. One of the strongest findings in all of nutrition, and the reason many countries fortify flour. The window is before conception and the first weeks — after that it is too late.
- Correcting folate-deficiency anaemia — strong evidence. Well established.
- Lowering homocysteine — strong evidence. The biochemical effect is reliable. Whether lowering it prevents heart attacks is the part that has not held up.
- Preventing cardiovascular events by lowering homocysteine — insufficient evidence. Large trials lowered homocysteine successfully and did not reduce heart attacks or strokes.
Typical dose
400 mcg daily; 400–800 mcg for anyone who could become pregnant
Upper limit: 1,000 mcg daily of folic acid from supplements and fortified food (no limit on food folate)
Timing
With food, standard dosing.
Time to effect
- Weeks: Blood levels and red blood cell changes.
Medication interactions
- Methotrexate: Folate interacts directly with how it works. It is often prescribed deliberately alongside it, but only on a schedule your prescriber sets. (high)
- Anti-seizure medication (phenytoin, carbamazepine, valproate): Interaction runs both ways — folate can lower drug levels, and these drugs deplete folate. (high)
- Sulfasalazine: Blocks folate absorption. (moderate)
Common myth
“Folic acid and folate are interchangeable.” In reality: High-dose folic acid can mask the blood signs of a B12 deficiency while nerve damage continues — worth knowing your B12 status first.
Food sources
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