Blood selenium values in an adult Auckland population group.

New Zealand top soils are low in selenium with some regional variation. Grain and cereal products are the main source of dietary selenium intake but in New Zealand their content is low due to widespread top soil deficiency. Whole blood levels reported from Oago, 68 +/- 13ng/ml, are a half to one-third of those in North America and also lower than in Auckland residents, 79 +/- 15.7ng/ml. The variation between New Zealanders is due to regional differences in top soil levels and grass content affecting secondary selenium sources such as sheep meat and beef. Regular consumption of selenium rich chicken and fish is associated with a significant increase above average values, but age, sex, smoking, alcohol and the use of oral contraceptives, are unimportant factors.