Little research has been conducted to determine the effect of chronic folic acid (FA) intake on folate receptors (FR). We aimed to determine if long‐term supplementation with FA (140 or 400 μg/d) changes expression of FRα in blood. Samples from a 40‐wk randomized placebo controlled trial in 144 reproductive aged females were used. Plasma FRα was determined by ELISA, plasma folate vitamer concentrations by LC‐MS/MS, and red blood cell (RBC) folate by microbiologic assay. The geometric mean (SD) FRα concentration was 12.4 (1.7) nmol/L at baseline and 13.2 (1.6) nmol/L at 40‐wks. There were no significant correlations between FRα and any blood folate indices at baseline, however, after 40‐wks, FRα was significantly correlated with RBC folate (Spearman’s r = 0.217, P = 0.021). In a multivariable model, FRα at baseline significantly predicted FRα at 40‐wks (Ratio 2.41, 95% CI 2.23 – 2.60, P < 0.001). While there was no overall effect of treatment (P = 0.124), exploratory subgroup analysis revealed a borderline association of 400 μg/d FA with FRα at 40‐wks (Ratio 1.10, 95% CI 1.00‐1.20, P = 0.043), yet no effect of 140 μg/d FA (Ratio 1.04, 95% CI 0.95‐1.13, P = 0.414). This suggests that FRα in plasma, which may reflect FRα from decomposed RBCs and neutrophils, may be slightly increased by long‐term FA supplementation. Larger studies are needed to determine effects of chronic FA exposure on FR expression, including in other tissues.Grant Funding Source: Supported by University of Otago Research Grant
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