Selenoprotein P concentration in plasma is an index of selenium status in selenium-deficient and selenium-supplemented Chinese subjects.

Selenoprotein P, a selenium-rich plasma protein, is an index of selenium status in rats. Antibodies against human selenoprotein P were raised to study the protein and to develop a radioimmunoassay for it. A single collection of plasma from a healthy person in the United States contained 1.84 mumol selenium/L and was defined as containing 1 Unit (U) selenoprotein P/L. Removal of selenoprotein P from the reference plasma by an antibody column indicated that 0.81 mumol selenium/L, or 44% of the plasma selenium, was present as selenoprotein P. Work by others had determined that glutathione peroxidase accounted for 12% of plasma selenium. Stored plasma samples from selenium-deficient (Dechang County) and selenium-supplemented (Mianning County) populations in China were assayed for selenoprotein P. Boys aged 8-12 y had selenoprotein P concentrations of 0.10 +/- 0.04 U/L (n = 22) in Dechang and 0.39 +/- 0.17 U/L (n = 17) in Mianning. Supplementation with 100 micrograms selenium as selenate per day for 14 d raised those levels to 0.51 +/- 0.13 U/L in Dechang and to 0.76 +/- 0.27 U/L in Mianning. Similar results were obtained in men, and plasma selenium concentrations correlated with selenoprotein P concentrations. A study comparing indices of selenium status was conducted in the two counties. Selenoprotein P concentration in Dechang subjects (n = 79) was 36% of that in Mianning subjects (n = 117). For plasma glutathione peroxidase activity the value was 54%; for plasma selenium, 47%; and for whole blood selenium, 64%. We conclude that selenoprotein P is the major selenoprotein in human plasma and that its concentration is an index of selenium nutritional status that appears to be as sensitive as other indices in common use.

Dietary assessment methods evaluated in the Malmö food study.

A study to evaluate the relative validity of two dietary assessment methods, to be used in a prospective cohort study on diet and cancer, was conducted in a random sample of the Malmö population during 1984-1985. The study compared (i) a long, self-administered 'food-use questionnaire' (about 250 food items), asking for frequency of consumption of food and beverages and for usual portion size estimated with the help of a booklet of food pictures, and (ii) a combined method involving a shorter food frequency questionnaire (about 130 food items) and a 2-week diet diary, with (iii) a reference method requiring 18 days of weighed food records. The results indicated that subject compliance was quite good for both methods and, in particular, that the diet diary was well accepted. Both methods produced fairly good correlations with the reference method, of the order of 0.40 to 0.60 for most nutrients after adjustment for energy. Both methods tended to overestimate intake of fat, protein and carbohydrates as well as of vitamins and minerals.