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Multivitamins, Heart Disease and Cancer

Neither reduce nor increase risk

Source: Archives of Internal Medicine, Feb 9; 2009

It is estimated that about half of the entire adult US population uses dietary supplements of some sort. This is also the trend in other western countries. Trouble is; there are few evidence-based guidelines for the use of these supplements.

Vitamin supplements to reduce risk of heart disease and cancer

Many adults take multivitamins with the belief that they can prevent significant health problems, such as cancer and cardio-vascular diseases (CVD). The current study of the Women Health Initiative (WHI) cohort addresses this issue. The WHI program is funded by the US National Heart, Lung, and Blood Institute, National Institutes of Health, US Department of Health and Human Services.

The WHI study is most famous for its look at the issue of the safety and risks associated with use of Hormone Replacement Therapy, the results of which were first published in 2003. However, the WHI researchers have used this huge cohort to study other health-related aspects. One of the issues looked at has been the use of multivitamins among this group of women and its impact or otherwise on cancer and cardiovascular disease trends.

161,000 study participants

The study included 161,808 participants, all being post-menopausal women, from the WHI. Detailed data were collected on multivitamin use at baseline and follow-up time points, with enrolment occurring between 1993 and 1998 and a median follow-up period of around eight years. Just over 4 out of every 10  (41.5%) of these women reported using multivitamins on a regular basis.

Trends of diseases looked at included cancers of the breast (invasive), bowel (colon and rectum), endometrium (lining of the womb), kidney, bladder, stomach, ovary, and lung. Other conditions analysed were heart attacks (myocardial infarction), cerebro-vascular accidents (stroke), venous thrombo-embolism); and total mortality.

No difference in cancer and heart attack cases or death rates

There were 9619 cases of cancer, 8751 CVD events, and 9865 deaths reported over the follow-up period. Analyses revealed no association of multivitamin use with risk of any cancer, cardio-vascular diseases or total mortality. In other words, the taking of the multivitamins neither conferred any protection against these conditions nor increased their risk.

Dietary supplements industry unregulated

The authors of the report concluded that this is further evidence that these pills are of little if any benefit. They also expressed concern with the state of affairs in the United States on the issue of dietary supplements. They particularly cited the deregulation of the supplement industry that occurred in the US in the early 1990s with the introduction of the Dietary Supplement and Health Education Act.

The bottom line on multivitamins

There are few evidence-based guidelines for the use of dietary supplements.

Current recommendations include folic acid supplements for women with childbearing potential on the basis of its proven benefit in reducing the risk of neural tube defects such as spina bifida.  Another evidence-based recommendation is the avoidance of high-dose beta-carotene supplements in smokers.

This study fails to find a significant benefit or risk between the use of multivitamins and cancer or CVD in postmenopausal women.

Note: Advice on the use of various types of nutritional supplements in pregnancy is discussed in this section. Click to get there.

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