Can supplements alone prevent chronic diseases?

A new French study claims that the use of dietary supplements may not improve general well-being. Experts criticize the study’s poor validity.

To evaluate the relationship between supplement use and health-related quality of life, the state of health of 8,112 volunteers who took either a capsule containing vitamin C (120 mg), vitamin E (30 mg), beta-carotene (6 mg), selenium (100 µg) andzinc (20 mg), or a placebo every day for over six years was assessed (1). The state of the participants’ health was assessed at the beginning and end of the trial with a quality of life survey designed to measure everything from mobility and pain to vitality and mental health. The study results showed that, after six years, the number of participants who had developed serious illnesses, such as cancer or heart disease, was almost the same in the supplement (30.5%) and the placebo group (30.4%). There were 120 cases of cancer and 65 cases of heart disease in the supplement group and a respective 139 and 57 cases in the placebo group.

The researchers concluded that long-term supplementation with antioxidant vitamins and minerals may not have a beneficial effect on health-related quality of life. The conventional beliefs and claims that supplemen-tation improves general well-being would not be supported by this trial.

Experts criticized that the study does not reveal that antioxidant supplements have no health benefits. Measurable effects would depend on the micronutrient dose, the duration of supplement use, and the micronutrient status of the user. The finding that supplements had no impact on how the study’s participants perceived their health was to be expected and would not show that taking supplements is ineffective. Supplements do not have a measurable impact on how people feel on a day-to-day basis but ensure that people are receiving their recommended micronutrient levels to support disease prevention. Dietary supplements alone would never claim to be a magic recipe for preventing the development of multifactorial chronic diseases.

1. Briançon S. et al. Long-term antioxidant supplementation has no effect on health-related quality of life: The randomized, double-blind, placebo-controlled, primary prevention SU.VI.MAX trial. Int. J. Epidemiol. 2011 ; 40(6):1605–1616.