RSS feedAt the 7th Annual American Association for Cancer Research International Conference on Frontiers in Cancer Prevention Research (AACR FCPR 2008) held last week in Washington, D.C, several papers were presented on the role of vitamin supplementation in the prevention of cancers.
Researchers from Harvard University studied the potential benefits of vitamins E and C supplements on 14,461 male physicians, 50 years or older, who participated in the Physicians’ Health Study II. Participants were given 400 IU of vitamin E every other day or placebo and 500 mg of vitamin C daily or placebo. They were followed for a mean of 8 years. After 8 years, taking vitamin E supplements had no effect on the incidence of prostate cancer. Vitamin C supplementation had no effect on total cancers or on specific cancers such as colorectal, lung or prostate.
In another study, the Calcium Polyp Prevention Study, from the Vanderbilt University, 930 men were randomized to receive placebo or calcium supplementation (1,000 mg daily for 4 years) to see if calcium supplementation could prevent colorectal adenoma recurrence. (Colorectal adenomas are precursors to colorectal cancers.) The researchers found that calcium supplementation only reduced polyp recurrence in people whose dietary ratio of calcium to magnesium intake was low before treatment and remained low during treatment. Among those with baseline calcium to magnesium ratio below the median, calcium supplementation reduced the risk of adenoma recurrence by 32%.
In a separate published study from the Harbor-UCLA Medical Center, 36,282 postmenopausal women, who were enrolled in a Women’s Health Initiative clinical trial, were randomly assigned to 1000mg of elemental calcium with 400 IU of vitamin D3 daily or placebo for a mean of 7 years (J Natl Cancer Inst 2008; 100: 1581 – 1591). This study was carried out to look at the effects of supplement use on the incidence of hip fracture with incidence of invasive breast cancer as a secondary outcome. At the end of the study period, the incidence of invasive breast cancer in postmenopausal women was not affected by calcium and vitamin D supplementation.
An interesting study on the protective effects of consuming cruciferous vegetables in smokers was presented at the AACR FPCR 2008. Researchers from Roswell Park Cancer Institute in Buffalo, New York, studied 948 patients diagnosed with primary lung cancer and 1743 healthy controls between 1982 and 1998. The researchers found that there was a strong linear inverse association between intakes of fruit, total vegetables and cruciferous vegetables and the risk for lung cancer (odds ratio range 0.53 – 0.70). The study results suggest that the risk of developing lung cancer among smokers was reduced by 22 – 50 % if they consumed at least 4.5 servings of raw cruciferous vegetables per month compared to those who ate less than 2.5 servings per month. This inverse association of reduced lung cancer was only seen for squamous or small cell cancer, the 2 subtypes of lung cancer most commonly associated with heavy smoking. [The same group of researchers had demonstrated that the intake of raw cruciferous vegetables, including broccoli, broccoli sprouts, cabbage and cauliflower, was associated with a reduced risk for bladder cancer (Cancer Epidemiol Biomarkers Prev 2008; 17: 938 – 944). The protective action of cruciferous vegetables is derived from isothiocyanates, a group of phytochemicals which can be degraded by cooking.]
At present it is reasonable to conclude that supplementing with individual vitamins may not be sufficient to prevent cancer. Chemoprevention of cancer probably depends on a combination of vitamins and minerals. As yet we do not posses the knowledge to formulate the correct combination that works. Do multivitamin supplements work better? We do not have the answer yet. What we do know is that Mother Nature has perfected the combination in the form of fruits and vegetables. Seriously, why would you choose to take pills when you can enjoy the taste of fresh fruits and vegetables!
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