Iron, vitamin B-12 and folate status in Mexico: associated factors in men and women and during pregnancy and lactation.

To determine the prevalence and causes of anemia in rural Mexico, blood samples and longitudinal dietary data were collected from 187 women, some pregnant and then lactating, and from 72 men. Blood was used to measure anemia, mean cell volume, and plasma ferritin, folate and vitamin B-12. Anemia was found in 33% of the men, 54% of nonpregnant, nonlactating women, 35% of pregnant women and 41% of lactating women, and varied by season. Low iron stores (ferritin) accompanied anemia in only 8% of men compared with 38-67% of women. Low meat intake and poor dietary iron bioavailability were associated with anemia in women. There were no cases of low plasma folate. Low plasma vitamin B-12 was common in all groups, and the incidence increased from 15% at 7 mo of pregnancy to 30% at 7 mo of lactation. Vitamin B-12 was lower in the plasma and milk of anemic lactating women than in plasma and milk of non-anemic lactating women and was classified as deficient in 62% of breast milk samples.