The big picture: Vitamin B9, commonly known as folate, is essential for energy production, DNA, RNA synthesis, and red blood cell formation. Its deficiency can lead to anemia, heart disease, and developmental issues during pregnancy, making its adequate intake vital for overall health.

Folate vs folic acid: While the terms "folate" and "folic acid" are often used interchangeably to refer to vitamin B9, there's a key distinction: folate is the natural form found in foods, whereas folic acid is a synthetic, oxidized version not naturally occurring.

Folate is found in green leafy vegetables, citrus fruits, nuts, and beans.
Folic acid, a synthetic form with higher bioavailability, is added to many foods and supplements.

By the numbers: Adults typically store 1,000-20,000 mcg of vitamin B9, with varying daily requirements based on age, sex, and pregnancy status. Levels of vitamin B9 in the blood reflect recent intake and tissue stores over a period of about 120 days so deficiency can take 8-16 weeks to become apparent.

Heart health link: Low levels of vitamin B9 can increase heart disease risk due to its role in homocysteine metabolism. Studies indicate that managing homocysteine levels can significantly reduce the risk of heart-related issues.

Vitamins B9, B12, and B6 work together to control blood levels of homocysteine, an amino acid. So a low B9 status may result in elevated homocysteine.
Meta-analyses of 30 prospective and retrospective studies (n=16,786) show the risk of any coronary heart disease event increased approximately 20% for each increase of 5 μmol/L of homocysteine. Furthermore, lowering homocysteine by 25% or 3 μmol/L was associated with a 11% lower risk of ischemic heart disease and 19% lower risk of stroke.
Increases in homocysteine levels is an early indicator of reduced vitamin B9.

Beyond heart health: Deficiency in vitamin B9 can lead to other health problems, including megaloblastic anemia, pancytopenia, oral ulcers, fetal neural tube defects, and neuropsychiatric symptoms like depression and insomnia.

Pregnancy: High vitamin B9 levels in women of childbearing age can reduce the risk of neural tube defects (NTDs) like spina bifida. Deficiency post-first trimester is linked to maternal anemia, low birth weight, and premature delivery.

The B9-B12 Connection: Vitamin B9 interacts closely with vitamin B12. A deficiency in one can hide a deficiency in the other, particularly in vegans/vegetarians, certain ethnic groups, and the elderly. Importantly, supplementing B9 without addressing B12 deficiency can exacerbate neurological issues.