Folate

What Is Folate (Vitamin B9)?

Folate is the name for a family of B9 compounds. Its core job is carrying single carbon units from one molecule to another, a process called one-carbon metabolism. Cells use those carbon units to make the building blocks of DNA and RNA, so any tissue that divides quickly, such as bone marrow or a growing embryo, depends on folate.

Folate also turns homocysteine, an amino acid that builds up in the blood when folate is short, back into methionine. Too little folate shows first in the blood: red blood cells come out large and few, a condition called megaloblastic anemia, with tiredness, weakness and shortness of breath.

Food Folate, Folic Acid, and DFE

Food folate is fragile. It breaks down with heat, light and storage and leaks into cooking water. Folic acid, the form in supplements and fortified foods, is stable and better absorbed. Since 1998 the US has required folic acid in enriched flour, bread, pasta and rice, and several other countries, including Canada, do the same.

That difference is why labels use dietary folate equivalents (DFE). A supplement with 400 mcg of folic acid is listed as 680 mcg DFE, because folic acid taken with food counts 1.7 times. Taken on an empty stomach it counts twice. The figures on this page and in the Caltide food library are total folate, not DFE.

Folate in a Day of Food Without Beans

One ordinary day built only from foods in the Caltide food library, in usual portions, with greens but no beans, lentils or enriched grains. No supplements.

The day clears the EU label reference of 200 mcg but reaches about 66% of the US amount of 400 mcg DFE. A cup of lentils at lunch would close the gap.

Why Folate Timing Matters in Pregnancy

The neural tube, which becomes the baby's brain and spinal cord, closes within about four weeks of conception. Low folate in those weeks raises the risk of neural tube defects such as spina bifida. Because many pregnancies are not planned, women who could become pregnant are advised to take 400 mcg of folic acid a day from supplements or fortified food, on top of the folate in their diet.

How Folate and Vitamin B12 Work Together

Folate and vitamin B12 (cobalamin) work in the same reaction, and a lack of either causes the same large-cell anemia. Large doses of folic acid can correct that anemia while a B12 shortage goes on damaging nerves unnoticed. This masking is the main reason the folic acid upper limit exists.

Who Is Most Likely to Be Low in Folate

People who drink heavily, since alcohol blocks folate absorption and speeds its loss; people with celiac disease or other conditions that damage the gut; and women in their childbearing years who eat few beans, greens or fortified foods. Iron deficiency is a separate cause of anemia; a blood test tells them apart, because folate shortage makes red cells large and iron shortage makes them small.