This is the most that can legally be added to a vitamin, as there is a concern that folate could mask vitamin B12 deficiency — which is not a problem if the supplement also has high levels of B12. Optimal levels of folic acid (folate) are critical because of its role in immune function.
The benefits of folate begin early in life. Folic acid is known to protect against serious neural tube birth defects that develop in the earliest weeks of pregnancy. For this reason, doctors recommend that women who are pregnant or trying to get pregnant take a vitamin supplement that includes folic acid.
Mothers-to-be with lower levels of the vitamin folate in their body during early pregnancy are also more likely to have low birth-weight babies. A review of many studies suggests that taking 800 mcg of folic acid per day was associated with a 15% lower risk of heart attack and a 24% reduction in stroke. Folate may also increase bone strength, along with vitamin B12, and vitamin B6, lowering the risk of life-threatening hip fractures.
Interestingly, since food makers began adding extra folate to flour in 1998 to prevent birth defects, heart disease, stroke, blood pressure, colon cancer and osteoporosis have all fallen. Researchers are now advocating that the current fortification level, 140 micrograms of folic acid per 100 grams of grain, should be doubled. Supplementing with 800 mcg of folate a day can also help memory. In one study, 818 cognitively healthy people ages 50 to 75 took either folic acid or placebo for three years. On memory tests, the supplement users had scores comparable to people 5.5 years younger.
In addition, low folate is associated with Alzheimer's. In a study of over 1,400 participants, the participants who had intakes at or above the 400 microgram recommended dietary allowance of folate had a 55% reduction in the risk of developing Alzheimer's. Folate may also decrease the risk of ovarian cancer and hypertension.