AbstractWe conducted a double-blind, placebo-controlled trial to evaluate the effect of heat-killed cells ofLactococcus lactisstrain H61 on various skin properties of Japanese women. Volunteers (age 31–62 years) were randomly assigned to receive test food with or without 60 mg of heat-killed strain H61 (fifteen women in each group; H61 and control groups, respectively) daily for 8 weeks. Results were analysed for three age categories (30s, 40s and 50–60s). Compared with that at week 0, skin hydration at the inner forearm at weeks 4 and 8 decreased in all volunteers (except those in their 50–60s) because of the environmental change from autumn to winter. The oldest H61 group maintained skin hydration at the inner forearm throughout the study. Skin elasticity and melanin content in the cheek decreased and sebum content increased throughout the test period due to seasonal environmental change, regardless of age or H61 treatment. Self-evaluation scores for apparent hair follicles and dryness of the throat at week 8 were higher in the overall H61 group than in the combined placebo group. The 30s H61 group noted marked improvements in self-surveyed skin elasticity at week 8 compared with at week 0 and with the placebo group at week 8. The results of the present study indicate that oral intake of heat-killed cells ofL. lactisstrain H61 can improve some skin properties and body characteristics in women. This strain would probably be useful in increasing the quality of life in an ageing population.