Myths and realities about preventive vitamin supplementation

The vitamins and the trace elements have antioxidant and other effects that could be useful in patients with multiple diseases. Many studies have been conducted to determine whether and how much they can reduce both morbidity and mortality in various diseases. However, it is not known whether vitamins and minerals can prevent future disease. Nevertheless, there is a steady increase in the consumption of these substances in the developed world. On the occasion of the publication of 2 studies (randomised clinical trials), one of the world's leading pathology journals, the Annals of Internal Medicine, devoted an entire issue to this topic.

People who have suffered heart attack have a high chance of having a heart attack again in the near and distant future. The same applies to other cardiovascular conditions such as vascular stroke. Researchers from the US and Canada tried to answer the question of whether vitamins can help people who have already had a history of a heart attack in a study involving about 1700 people. The researchers randomly divided patients who had had a heart attack up to 9 years earlier into 2 groups: one that took daily pills containing high doses of multivitamins and minerals and one that took a daily placebo. Patients had to take the pills for up to 5 years. Every time a patient had an episode was recorded as an episode in one group or the other. An episode was defined as another heart attack (chest pain that required hospitalization or a cardiac catheterization), a new stroke, or death. Neither the patients, nor the researchers, nor the doctors caring for the patients knew which of the patients were taking the placebo or the multivitamins and minerals.

After a mean follow-up period of about 55 months, the occurrence of another heart attack, strokes and deaths did not differ significantly between the two groups. The group taking the multivitamins and minerals had no more side effects than the group taking the placebo. The main limitation of the study was that many people in both groups stopped taking the pills, or did not take them as often as they were instructed (75% took them for up to a year and only 50% for up to 3 years), resulting in them dropping out of the study before the prescribed end date. Therefore, it is difficult to draw clear conclusions about what multivitamins and minerals can do. So it seems that although multivitamins and minerals do not appear to be harmful, they did not reduce heart attacks, strokes or deaths after a first heart attack.

In the 2nd study with similar methodology, the researchers tried to see if multivitamins could reduce the progression of Alzheimer's disease and dementia in general in medical patients over 65 years of age. After an average of 12 years of taking multivitamins, no evidence was found that multivitamins reduce cognitive decline. The pros of the study were that the patients regularly took their prescribed formulations, the large sample size and the sufficient length of stay in the study. It therefore appears that in people with an adequate diet, the administration of multivitamins is not associated with a reduction in the likelihood of developing dementia.

In the editors' text accompanying these studies, the authors were unequivocal. Under the title "Enough is enough, stop throwing money away by buying vitamins and minerals", they listed a series of studies and reviews which showed that nowhere does it follow that someone who regularly takes vitamin supplements will be able to prevent in the first or second degree any health problem (i.e. before the onset of the disease or reduce the likelihood of its recurrence). In contrast, there is data showing a trend towards a higher incidence of lung cancer and an increase in mortality in people who regularly took beta-carotene, vitamin E and possibly vitamin A.

In conclusion, the authors' message is simple: in people on a complete diet, vitamin supplements do not prevent chronic diseases (including cardiovascular, dementia and cancer), their widespread use is not justified by the available data, there is no evidence to support further investigation with more clinical trials, and therefore they should be avoided.

Source: www.annals.org