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J Am Coll Nutr. 2017 Sep-Oct;36(7):572-578. doi: 10.1080/07315724.2017.1333929. Epub 2017 Sep 12.

Association between Serum Unmetabolized Folic Acid Concentrations and Folic Acid from Fortified Foods.

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a Department of Clinical and Toxicological Analysis, Faculty of Pharmaceutical Sciences , University of São Paulo , São Paulo , Brazil.
b Department of Food and Experimental Nutrition, Faculty of Pharmaceutical Sciences , University of São Paulo , São Paulo , Brazil.
c Department of Nutrition, School of Public Health , University of São Paulo , São Paulo , Brazil.
d National Center for Environmental Health , Centers for Disease Control and Prevention , Atlanta , Georgia , USA.



To investigate the association between serum unmetabolized folic acid (UMFA) concentrations and folic acid from fortified foods and nutrients known as dietary methyl-group donors (folate, methionine, choline, betaine and vitamins B2, B6 and B12) in participants exposed to mandatory fortification of wheat and maize flours with folic acid.


Cross-sectional study carried out with 144 healthy Brazilian participants, both sexes, supplement nonusers. Serum folate, UMFA, vitamin B12 and total plasma homocysteine (tHcy) were biochemically measured. Dietary intake was assessed by 2 non-consecutive 24-hour dietary recalls (24-HRs) and deattenuated energy-adjusted nutrient data were used for statistical analysis.


Ninety eight (68.1%) participants were women. Median (interquartile range) age was 35.5 (28.0-52.0) years. Elevated serum folate concentrations (>45 nmol/L) were found in 17 (11.8%), while folate deficiency (<7 nmol/L) in 10 (6.9%) participants. No one had vitamin B12 deficiency (<148 pmol/L). An elevated serum UMFA concentration was defined as > 1 nmol/L (90th percentile). UMFA concentrations were positively correlated with folic acid intake and negatively correlated to choline, methionine and vitamin B6 intakes. Participants in the lowest quartile of UMFA concentrations had lower dietary intake of total folate (DFEs) and folic acid, and higher dietary intake of methionine, choline and vitamin B6 than participants in the highest quartile of UMFA. Folic acid intake (OR [95% CI] = 1.02 [1.01-1.04)] and being a male (OR [95% CI] = 0.40 [0.19-0.87) were associated with increased and reduced odds for UMFA concentrations > 0.55 nmol/L (median values), respectively.


UMFA concentrations were directly influenced by folic acid intake from fortified foods in a healthy convenience sample of adult Brazilians exposed to mandatory flour fortification with folic acid.


Folic acid; dietary intake; fortification; micronutrients; unmetabolized folic acid

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