I felt that it was important to post this article I saved from a few weeks back in it’s entirety. Since I share so many complimentary medicine and nutritional tips on our site, running this is an “equal time” sort of thing…
By Charles Bankhead, Staff Writer, MedPage Today
Consumers need more information and guidance about the potential risks, as well as the benefits, of using dietary supplements for cancer prevention, authors of a review concluded.
Emerging evidence has shown that high doses of certain supplements can actually increase the risk of cancer, Maria Elena Martinez, PhD, of the University of California San Diego, and co-authors wrote in a commentary published online in the Journal of the National Cancer Institute.
Aside from a role in treating a few uncommon nutrient deficiencies, dietary supplements have minimal supporting data for health benefits in disease prevention, particularly cancer.
“Despite this evidence [of potential harm], marketing claims by the supplement industry continue to imply anti-cancer benefits,” Martinez and co-authors wrote. “Insufficient government regulation of the marketing of dietary supplement products may continue to result in unsound advice to consumers. Both the scientific community and government regulators need to provide clear guidance to the public about the use of dietary supplements to lower cancer risk.”
The 2003 to 2006 National Health and Nutrition Examination Survey showed that half of U.S. adults use one or more dietary supplements, primarily multivitamin/multimineral supplements (NCHS Data Brief. 2011; 61: 1-8).
In the absence of data from observational studies or clinical trials, use of supplements has been fueled primarily by marketing-oriented claims of wide-ranging benefits, Martinez and co-authors wrote. As a result, sales of dietary supplements have grown into a $30-billion-a-year industry.
To assess the current state of evidence supporting use of supplements, Martinez and co-authors reviewed literature for “supplements that have been tested in adequately powered clinical trials or in large well-designed observational studies.”
The review encompassed supporting data for use of antioxidants, folic acid, vitamin D, and calcium to prevent cancer.
Preclinical studies suggested that dietary antioxidants — including beta-carotene, alpha-tocopherol, and vitamin C — encouraged growth of normal cells and tissue and inhibited growth of abnormal tissue. Clinical studies failed to support the favorable laboratory evidence:
- Beta-carotene did not prevent recurrence of nonmelanoma skin cancer
- Beta-carotene, alpha-tocopherol, and vitamin C failed to prevent recurrence of colonic adenomas
- Beta-carotene, vitamin A, and alpha-tocopherol did not prevent lung cancer
- Vitamins C and E did not protect against cancer
- Alpha-tocopherol, vitamin C, and beta-carotene had no effect on cancer incidence or mortality
- Beta-carotene and vitamins A, C, and E — alone or in combination — did not prevent gastrointestinal cancers
- Alpha-tocopherol and selenium failed to prevent prostate cancer in average-risk men
One exception to the negative studies of antioxidants was a prevention trial in China, which showed a 13% reduction in cancer mortality and a 21% reduction in gastric cancer mortality in participants randomized to a combination of beta-carotene, vitamin E, and selenium (J Natl Cancer Inst 1993; 85: 1483-1492).
However, a substudy of the Chinese investigation showed no effect of a multivitamin/multinutrient supplement on cancer incidence in participants with cytologic evidence of esophageal dysplasia (J Natl Cancer Inst 1993; 85: 1492-1498).
Several antioxidant trials have shown increased cancer risk with supplementation, the authors wrote. The most notable examples were two randomized trials of patients at high risk for lung cancer because of smoking or exposure to asbestos. Both trials showed an increased incidence of lung cancer in participants randomized to beta-carotene.
Laboratory and observational data had suggested a protective effect of folic acid against cancer, particularly colorectal cancer. However, a meta-analysis of randomized trials showed no effect of folic acid supplementation on development of colorectal adenomas (Int J Cancer 2011; 129: 192-203).
Two different randomized trials showed an increased risk of cancer (prostate) and precancerous lesions (colonic adenomas) in participants on long-term folic acid supplementation.
The Institute of Medicine recently updated its recommendations on vitamin D and calcium intake and found “there was not enough evidence to state that there is a causal association between low vitamin D intake and increased cancer risk.”
Epidemiologic studies have shown inverse associations between serum levels of 25-hydroxy (OH) vitamin D and several types of cancer. Three short-term randomized trials failed to demonstrate an effect of vitamin D supplementation on cancer incidence or mortality.
Observational studies have yielded conflicting data on the association between vitamin D concentrations and the risk of pancreatic cancer.
The authors concluded that more studies are needed to determine whether vitamin D has any preventive effects on cancer.
Despite their overall negative review, Martinez and co-authors said they have not given up on dietary supplements for cancer prevention.
“Given the current state of the evidence, do we need to conduct more randomized controlled trials of dietary supplements to assess their efficacy for cancer prevention?” they asked. “We do, but these trials must be designed strategically and in light of lessons learned from previous studies.”
“In the absence of convincing evidence that more will be better, we probably do not need more trials in nutrient-replete populations,” they added.
Using lots of supplements in large doses can be tricky, especially for a cancer patient. For the record, I use a lot of supplements. But I don’t take them in mega-doses. And I always seek outside guidance. Let’s face it, oncologists tend to be very busy. Their focus isn’t on supplements and nutrition. Instead, they spend hours and hours each week just trying to keep-up with the latest drug and therapy related developments.
So remember to check with your doctor and find one or more sources you can trust before adding a new supplement to your pill box.
I will follow-up on this tomorrow. Feel good and keep smiling! Pat