Nutritional supplement foods containing antioxidant vitamins and minerals and fish oil (mainly docosahexaenoic acid, DHA, C22:6n-3), referred to as capsules, were administered to seven smokers every day for 34 days. Concentrations of antioxidant vitamins and minerals in serum, activity of superoxide dismutase in plasma and the concentration of 8-isoprostane (8-epi-prostaglandin F₂ α) in the urine showed an increase or a tendency to increase after the end of administration. The frequency of subjects showing poor state of psychological health evidenced by a total score of 8 points or more on the General Health Questionnaire (30-item edition) scale was 42.9%, although there was a significant decrease to 14.3% upon completion of administration of the capsules. These biochemical and psychological changes were mostly returned to the basal level one month after the end of administration of the capsules. The results suggest that administration of antioxidant vitamins and minerals and fish oil to smokers resulted in an increase in antioxidant capacity. Effectiveness in alleviating psychosocial stress likely to be attributable to DHA was also observed.