What is the US prevalence of folic acid deficiency?

Updated: Sep 14, 2018
  • Author: Katherine Coffey-Vega, MD; Chief Editor: Emmanuel C Besa, MD  more...
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United States

The current standard of practice is that serum folate levels less than 3 ng/mL and a red blood cell (RBC) folate level less than 140 ng/mL puts an individual at high risk of folate deficiency. The RBC folate level generally indicates folate stored in the body, whereas the serum folate level tends to reflect acute changes in folate intake.

Data from the National Health and Nutrition Examination Survey (NHANES) 1999-2000 indicate the prevalence of low serum folate concentrations (< 6.8 nmol/L) decreased from 16% before folic acid fortification to 0.5% after folic acid fortification. [17] In elderly persons, the prevalence of high serum folate concentrations (>45.3 nmol/L) increased from 7% before fortification to 38% after fortification.

Subsequent to the initial NHANES studies, subjects in the 2003-2006 cohort were asked about their daily supplement use in order to better quantify their total daily intake of folic acid. [1] It was discovered that 34.5% of the participants took supplements containing folic acid. Certain groups were over-supplementing, while other groups were still receiving inadequate doses. The participants ages 51-70 years took the highest doses of folate (combined food and supplement), with 5% exceeding the tolerable upper intake level. Two groups were most likely to consume inadequate folate (below the recommended dietary allowance): women of childbearing age (17-19%) and non-Hispanic black women (23%). The study authors concluded that efforts need to be made both to monitor for over-supplementation in certain groups and to target increased supplementation in the groups at risk for deficiency.

Several studies have demonstrated that high-dose folate may increase the risk of cancer. [10, 11, 12, 13, 14, 15, 18] Specifically, increased risks of prostate and colorectal cancer have been noted. However, despite experimental evidence suggesting increased risk of breast cancer progression, [12] a comparison of 2,491 breast cancer cases individually matched to 2,521 controls in the European Prospective Investigation into Cancer and Nutrition (EPIC) found that plasma levels of folate were not significantly associated with the overall risk of breast cancer. [19]

It is particularly concerning that the groups who are over-supplementing are among the highest risk for accelerating the growth of malignancy through overuse of folic acid, while many in the groups that are under-supplementing are women who could confer benefits of folic acid supplementation to a developing fetus. Clearly, folic acid supplementation continues to be an important primary care and public health issue.

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