Sex and seasonal variations of plasma retinol, α-tocopherol, and carotenoid concentrations in Japanese dietitians

Aim: To clarify sex and seasonal variations of plasma antioxidant concentrations among middle-aged Japanese. Subjects and Methods: We investigated sex and seasonal variations of plasma antioxidant concentrations, including retinol, α-tocopherol, and carotenoids (α-carotene, β-carotene, β-cryptoxanthin, lutein and lycopene), in 55 middle-aged dietitians (46 women and 9 men) in Aichi Prefecture, Central Japan, who took no supplements from autumn 1996 to summer 1997. Reversed-phase high performance liquid chromatography was used to measure plasma antioxidant concentrations in overnight-fasting blood samples. Results: Plasma levels of α-tocopherol, α-/β-carotene, β-cryptoxanthin and lutein were significantly influenced by sex, being significantly higher for women than men in each corresponding season; retinol and lycopene, however, showed no such difference. For women, winter values of α-tocopherol, α-/β-carotene, lutein and lycopene were significantly lower than corresponding summer values, and had reached their annual lowest. Retinol failed to show any significant seasonal variation, whereas the winter value of β-cryptoxanthin had reached its annual highest. For men, β-cryptoxanthin exhibited significant seasonal changes and was also highest in winter. Winter values of α-tocopherol, α-/β-carotene and lycopene were lower compared with other seasons, but not statistically significant, probably due to the small sample size. Conclusions: The findings indicate that sex and seasonal variations of plasma antioxidant concentrations should be taken into account in nutritional epidemiologic studies.