Folate receptor (FR)-blocking autoantibodies (FR-autoantibodies) have been reported in women with neural tube defect-affected pregnancies and subfertility and in children with progressive neurodevelopment disorders. We investigated their prevalence and association with folate status and milk intake in adults unexposed to folic acid fortification. A cross-sectional study of a randomly selected representative sample of a Spanish population (aged 18-75 y) stratified by age and gender was performed. Plasma and red cell folate, plasma cobalamin, fasting plasma total homocysteine (tHcy) concentration, methylenetetrahydrofolate reductase C677T polymorphism, and FR-autoantibody titer were determined in blood samples from 787 fasting participants. Lifestyle data were collected and milk intake estimated from a 3-d dietary record. FR-autoantibody prevalence was 7.2% [0.30 +/- 0.27 nmol (mean +/- SD) FR blocked/L], equally affecting men and women of all ages. Plasma and red cell folate and tHcy did not differ between carriers and noncarriers of FR-autoantibodies. Milk intake was higher in carriers (225 +/- 199 g/d) than in noncarriers (199 +/- 147 g/d) (P < 0.01). The risk of having FR-autoantibodies increased progressively with increasing quintile of milk intake and was significant in the highest quintile (> or =307 g/d) compared with the lowest (< or =67 g/d) [odds ratio (OR), 2.41 [95% CI: 1.02, 5.69]; P < 0.05; linear trend, P = 0.02]. We concluded that FR-autoantibodies occur in men and women of all ages and do not affect indicators of folate status such as plasma and red cell folate and tHcy. Higher milk intake is associated with increased risk of having FR-autoantibodies.