Variation in plasma folate levels among groups of healthy persons

Levels of plasma folate, erythrocyte folate and serum vitamin B12 were measured in 106 essentially healthy persons grouped both as to race and economic--educational status. Whereas the mean values of the three assays did not differ significantly among groups, values of plasma folate below the usual limits of normal were more prevalent in the migrant worker and urban clinic groups. Persons with low plasma folate levels did not have symptomatic deficiency as evaluated by hematocrit, peripheral blood smears and erythrocyte folate levels. The interpretation of the plasma folate requires reference values from a healthy population selected to be comparable to the study group. The diagnosis of deficiency, or at least the degree of deficiency, requires clinical and laboratory evaluations beyond the plasma folate.