A comparison of folate status in women of child-bearing age in Korea and in the United States

Abstract

Background: Even though several studies have demonstrated that periconceptional supplementation with folic acid (FA) reduces the occurrence of neural tube defects, FA fortification has been a topic of intense debate due to the possible adverse effects of higher folate status on several health conditions. Several countries, including Korea, have been indecisive as to whether fortification is warranted or not. It is therefore helpful for these countries to compare folate concentrations in their populations with populations exposed to mandatory FA fortification.

Purpose: To evaluate the differences in the distribution of circulating concentrations of folate in Korea and the United States (US) at different time points.

Methods: The Korean study populations consisted of women of child-bearing age recruited in 1999 and in 2009. The US study populations consisted of women of child-bearing age recruited in the post FA fortification era (2005 and 2009). Plasma and red blood cell (RBC) folate concentrations were measured using the Lactobacillus casei microbiological assay.

Results: The percentage of US women with neural tube defect-protective levels of RBC folate was significantly higher compared to Korean women in 1999 and 2009. However, in 2009, when FA supplements became readily available for Koreans, 50% of Korean women in the study achieved the neural tube defect-protective level of RBC folate; 11% of them demonstrating supraphysiologic concentrations of plasma folate. Even though FA fortification in the US resulted in more than 80of women achieving >400 ng/mL of RBC folate by 2009, nearly 50% also demonstrated having supraphysiologic concentrations of plasma folate, which prompted some researchers to raise concerns about possible adverse effects of higher folate status on several health conditions.

Conclusion: Encouraging Korean women of reproductive age to take FA supplements and evaluating the outcome of such efforts would be worthwhile prior to implementing a population-wide mandatory FA fortification in Korea.