Vitamin B9 (folate, folic acid) works with vitamins B6 and B12 (cobalamin) and other nutrients to control blood levels of the amino acid homocysteine.
Elevated homocysteine levels in blood are a risk factor for cardiovascular disease. Although B vitamin supplementation has been proven effective to control homocysteine levels, current data from intervention trials have not shown that lowering homocysteine levels decreases cardiovascular disease risk. Researchers are not sure whether homocysteine is a cause of heart disease or just a marker that indicates someone may have heart disease.
Recommended Dietary Allowance (RDA) - the average daily dietary nutrient intake level sufficient to meet the nutrient requirement of nearly all - ~97% - healthy individuals in a particular life stage and gender group.
The process for setting the RDA depends on being able to set an Estimated Average Requirement (EAR). If an EAR cannot be set, no RDA will be set. The EAR is the daily intake value of a nutrient that is estimated to meet the nutrient requirement of half the healthy individuals in a life stage and gender group.
The RDA is set at the EAR plus twice the standard deviation (SD) if known (RDA = EAR + 2 SD). If data about variability in requirements are insufficient to calculate a standard deviation, a coefficient of variation for the EAR of 10% is ordinarily assumed (RDA = 1.2 x EAR).
The RDA for a nutrient is a value to be used as a goal for dietary intake by healthy individuals. The RDA is not intended to be used to assess the diets of either individuals or groups or to plan diets for groups.