A new Japanese study suggests that vitamin supplement use in women might reduce the risk of cardiovascular disease and elevate the risk of cancer. Experts doubt the conclusions.
In the observational study, 28,903 men and 33,726 women were asked about their use of vitamin supplements and cases of cancer and cardiovascular disease (CVD) in two surveys (1). The participants were categorized into four groups based on their habits – never used, past user, recent user, and consistent user – and then tracked for several years. The analysis of the data showed no association of vitamin supplement use with the risk of cancer or CVD in men. In women, consistent use was associated with a lower risk of CVD, whereas past and recent use was associated with a higher risk of cancer.
The researchers commented that the elevated risk of cancer associated withpast and recent use of vitamin supplements in women may be partly explained by preexisting diseases (e.g. hypertension, hyperlipidemia, and diabetes) or an unhealthy background (higher body mass index, greater likelihood of smoking, and medication use). It may also be caused by a pro-oxidant effect of supplementation with antioxidants producing DNA damage. Further research with detailed, long-term data regarding components, doses, and patterns of vitamin supplement use would be needed to confirm these findings.
Experts criticized the study for only measuring the use of vitamin supplement twice and for asking different questions in the two surveys. Aside from the vast number of lifestyle factors and genetic dispositions influencing chronic disease risk, the inconsistent use of various vitamin supplements in the study – only 4.1% of men and 5.8% of women continued to use vitamin supplements from the first to the second survey period – would make it impossible to draw any robust conclusions regarding supplement use and disease risk. What remains would be a hypothesis based on statistical shortcomings and not a proof of causal relations.
According to the experts, vitamin supplements can close nutrition gaps in people with insufficient dietary vitamin intakes. Since adequate micronutrient intakes would be an essential part of a holistically healthy life, supplements can contribute to the maintenance of health. Supplements alone cannot prevent chronic diseases or compensate for an unhealthy lifestyle. By the same token, supplements cannot be held responsible for the development of complex chronic diseases.