Does obesity modify the association of supplemental folic acid with folate status among nonpregnant women of childbearing age in the United States?
BACKGROUND
Obesity is associated with an increased risk of having a pregnancy affected by a neural tube defect (NTD). It is not clear whether the amount of folic acid required by obese women to protect against NTDs is the same as that for nonobese women.


METHODS
We analyzed data from the National Health and Nutrition Examination Survey, representative of the noninstitutionalized civilian U.S. population, to assess whether body mass index (BMI; normal weight, overweight, and obese categories) modified the association between supplemental folic acid intake and folate status. We estimated the geometric mean concentration among nonpregnant women of childbearing age (15-44 years) during the postfortification period of: serum folate (2003-2008); red blood cell (RBC) folate (2007-2008); and plasma total homocysteine (tHcy; 2003-2006), adjusted for age, race and ethnicity, and total dietary folate expressed as dietary folate equivalents for strata of supplement use and BMI.


RESULTS
BMI was inversely associated with serum folate among women who did not use supplements containing folic acid; no differences between women in different BMI categories were observed among supplement users. Regardless of supplement use, obese women had the highest RBC folate concentrations. There were no differences in tHcy by BMI, regardless of supplement use.


CONCLUSIONS
These results do not support a straightforward modification of the relationship between supplemental folic acid intake and folate status by BMI. In this population, BMI may affect the body distribution of folate, as reflected by lower serum and higher RBC folate levels in obese women who do not use supplements.
National Center on Birth Defects and Developmental Disabilities, Centers for Disease Control and Prevention, Atlanta, GA, USA. Zzu9@cdc.gov
Sarah C
SC
Tinker
Heather C
HC
Hamner
Robert J
RJ
Berry
Lynn B
LB
Bailey
Christine M
CM
Pfeiffer
D000293:Adolescent; D000328:Adult; D000367:Age Factors; D015992:Body Mass Index; D019587:Dietary Supplements / Q000706:statistics & numerical data*; D005260:Female; D005492:Folic Acid / Q000008:administration & dosage* / Q000097:blood; D006801:Humans; D009436:Neural Tube Defects / Q000209:etiology; D009749:Nutrition Surveys; D009752:Nutritional Status / Q000502:physiology*; D009765:Obesity / Q000097:blood / Q000150:complications* / Q000453:epidemiology; D011247:Pregnancy; D011295:Prenatal Care / Q000379:methods / Q000706:statistics & numerical data; D012307:Risk Factors; D014481:United States / Q000453:epidemiology; D055815:Young Adult
D005492:Folic Acid