Toenail selenium as an indicator of selenium intake among middle-aged men in an area with low soil selenium

Toenail selenium concentration has been proposed as a long-term (6-12 mo) indicator of human selenium status. This study investigated the association between toenail selenium concentration and selenium intake and other dietary factors among 166 urban men aged 55-69 y. The dietary information was collected by food records covering a 6-mo period. Toenail clippings were collected by mail 9-10 mo after food recording. The mean selenium intake from food was 42.5 micrograms/d and the dietary intake was equal to that of users and nonusers of selenium supplements. The mean toenail selenium concentration was 0.47 mg/kg. The mean selenium intake from supplements was 29.7 micrograms/d among supplement users. In the analysis of covariance the best predictors of toenail selenium concentration were selenium intake from supplements and food, and among supplement users dietary beta-carotene also.

Seasonal variation of serum concentrations of beta-carotene and alpha-tocopherol

We studied the seasonal variation in serum concentrations of beta-carotene and alpha-tocopherol (HPLC) in 17,247 Finnish men who smoked. Month of blood sampling was a statistically significant determinant of serum concentration of beta-carotene in a regression model including age, body mass index, alcohol and fat intakes, total serum cholesterol, and daily cigarettes as covariates. The serum concentrations were lowest in April-June and highest in October-November. The 1.5-fold increase in the serum concentration of beta-carotene during the fall reflects the seasonality of dietary sources of carotenoids in Finland. The serum concentrations of alpha-tocopherol demonstrated no seasonal variation but remained close to 27.6 mumol/L throughout the year. The results indicate that the seasonal variation of serum concentrations of beta-carotene should be taken into account in long-term studies in which comparison of groups or individuals is based on serum concentrations.

Lifetime menstrual activity--indicator of breast cancer risk

A case-control study of 67 cases of breast cancer and 157 controls was conducted to investigate the role of different behavioral, reproductive, and hormonal factors and to develop a unifying indicator of breast cancer risk. The results confirm previous reports of the influence of smoking on the risk of breast cancer. Age at menarche was found to be a risk factor among the premenopausal women. Late age at menopause was suggestive of an increase in risk. Long use of oral contraceptive or estrogen supplementation were risk-enhancing both pre- and postmenopausally. Lifetime duration of menstrual activity (LMA) combines age at menarche and menopause, parity, and lactation into a biologically plausible model. Our findings concerning LMA support its role as a determinant of breast cancer.

Serum beta-carotene before and after beta-carotene supplementation

A two-month double-blind, placebo-controlled supplementation study of oral beta-carotene (20 mg daily) was conducted. Two hundred and twenty two 30-69 year old men were randomized into either a beta-carotene or placebo group, and serum samples were obtained at baseline, follow-up (2 months), and up to 12 weeks post-supplementation. Serum beta-carotene increased on average 10-fold in the beta-carotene group, from 0.53 +/- 0.32 mumol/l (mean +/- SD) at baseline to 4.99 +/- 2.47 mumol/l at follow-up (P less than 0.0001), and beta-carotene levels remained elevated up to 12 weeks post-supplementation (0.61 +/- 0.15 mumol/l). No changes in serum retinol, alpha-tocopherol, or total cholesterol were observed. At baseline, serum beta-carotene levels were positively correlated with dietary beta-carotene (r = 0.29) and inversely correlated with body mass index and serum gamma-glutamyltransferase (r = -0.33 and r = -0.40, respectively). The inverse association with body mass index and serum gamma-glutamyltransferase persisted during active supplementation, whereas the positive association with dietary beta-carotene disappeared. In multivariate analysis, serum cholesterol was also positively associated with serum beta-carotene levels both before and after supplementation. Baseline serum beta-carotene was the factor most strongly associated (positively) with serum beta-carotene after supplementation. Our study highlights the importance of several factors which affect serum beta-carotene.