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.