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.