Dietary supplement consumption among urban adults influenced by psychosocial stress: its pronounced influence upon persons with a less healthy lifestyle.

In order to examine the consumption of dietary supplements among urban adults and the impact of psychological stress on supplement use in relation to lifestyle, 375 interviews of a population-based sample of urban Japanese in 2002 were analysed. The usage of various supplements, stress process (daily stressors, psychological moderators, stress outcomes), personal health practices (smoking, alcohol drinking, physical exercise, fruit and vegetable juice consumption, health-conscious eating habits) and other background factors were measured. We examined the impacts of stress on the use of vitamin tablets and capsules, vitamin-enriched health drinks and health drinks for intestinal adjustment. The percentages of these three categories of supplement user were 26.9, 18.7 and 35.7%, respectively. After adjusting for potential confounders, subjects with 'two or more' daily stressors out of the eight stressors investigated consistently showed 2-fold higher levels of consumption of either vitamin tablets and capsules or vitamin-enriched drinks compared with their counterparts with 'one or less' daily stressors. Stress-outcome indicators also related, to a greater or less extent, to the elevated consumption of various supplements. Further lifestyle-stratified analyses revealed that the stress-supplementation relationships were weaker in subjects fulfilling more than three of the five investigated health practices (i.e. the healthy lifestyle group), but stronger in subjects with fewer than two healthy practices (i.e. the less healthy lifestyle group). In conclusion, dietary supplement consumption is independently associated with stress in urban adults. The uncontrolled use of supplements for the self-medication of stress or to compensate for unhealthy behaviour represents a health concern for the general population.