Years ago, researchers hypothesized that vitamin E and selenium supplements may protect against prostate cancer and other diseases. Not so, found one large study in 2008. Now, a longer study that continued to follow the same group of men suggests that vitamin E supplements may actually increase risk of prostate cancer.
The latest major study on supplements and cancer risk follows the approximately 35,000 men in the Selenium and Vitamin E Cancer Prevention Trial (SELECT). Starting a decade ago, participants were randomly placed in one of four groups: One group took daily selenium supplements; a second group took daily vitamin E supplements; the third took both supplements; and the fourth group consumed placebos.
The first report, published in 2008, found no reduction in risk of prostate cancer but there was a trend toward increased risk with vitamin E. The men were recommended to stop taking the supplements but researchers continued to track their health.
This study, published in the Journal of the American Medical Association, tracked the men's health through July 2011. Compared to those who had taken a placebo, the men who had taken vitamin E had a 17 percent increased risk of developing prostate cancer.
The findings suggest the health effects can continue even after men stop taking the supplement.
Currently, over half of adults in America take supplements, according to a Centers for Disease Control and Prevention survey conducted earlier this year. Below, AICR Nutrition Communications Manager Alice Bender, MS, RD, answers some questions on supplements and cancer.
Q: Some studies, like this one on vitamin E, show taking excessive amounts of single supplements actually increase the risk of cancer – and mortality – why would that be?
A: There are a lot of things that are good for us but getting too much of it is not always better. Studies looking at general vitamin and mineral supplementation are mixed. Some show no effect, a few show certain supplements may be helpful, and then others show some supplements may be harmful.
There are upper limits on specific nutrients so we know that too much can be dangerous. There's a balance we need to keep to stay healthy: For example, we talk about antioxidants being good but it's always a balance between oxidation and antioxidants and having too much of any one nutrient may end up being harmful rather than helpful.
Q: AICR recommends not to use supplements to protect against cancer and to get nutrients and phytochemicals from foods. Yet there are often studies suggesting a compound protects against cancer.
A: Yes, but the AICR recommendation comes from a review of the research around the world, and the evidence is continuously updated. There are many single studies showing a food component protects against cancer in animals, which are often genetically bred to get cancer. But humans are complex and we can't take away a public health recommendation from single studies.
"It's possible that the benefit of these foods comes from all the components working together to promote a healthy body that is better able to fight off cancer. "
The research does show that a diet with plenty of vegetables and fruits can lower risk for certain cancers, but scientists are still investigating how those foods work in the body to protect against cancer. It's possible that the benefit of these foods comes from all the components working together to promote a healthy body that is better able to fight off cancer.
Q: What would you say to the many Americans who do not eat the recommended amounts of fruits and vegetables and want to take a limited amount of supplements?
A: I would want to give people ways to get more plant-based foods in their diet because there are so many benefits to them, and they are delicious. Aside from the compounds, eating lots of fruits, vegetables and moderate amounts of whole grains also helps people get to and stay a healthy weight. And overweight and obesity are linked to increased risk of seven cancers.
One way to begin increasing the veggies and fruits in your diet is to make your portion size larger when you do eat them. You can also try eating different foods or fixing them in different ways.
Q: Are there certain populations you would suggest talk with their doctor or other health professional about taking supplements, such as cancer survivors?
A: There are some people who need to take vitamin or mineral supplements because they are not able to get enough of those specific nutrients for medical or other reasons. This includes people with certain digestive disorders and some elderly, who have a low calorie intake.
Cancer survivors undergoing treatment may have difficulty getting all of the nutrients so their doctor or dietitian may recommend a supplement. After treatment I would always go back to recommending whole foods first but survivors would need to consult their treatment team.
If you are generally healthy, you can use one of the many online diet analyses tools such as USDA's MyPlate, to see if you're meeting your nutrient needs. If you have a special medical concern, talk with a registered dietitian or other health care professional for guidance.
For more supplement information, below are highlights of supplement-related questions answered by AICR Nutrition Advisor Karen Collins, MS, RD, CDN.
Foods that claim to help our health also help the food companies make money, according to a new report from the Hudson Institute, a research organization.
Better-For-You Foods: It's Just Good Business analyzed sales and financial data from the largest 15 food and beverage companies, including Kellogg's, Nestle, Dannon, and Campbell Soup. Foods such as Cheerios, Lean Cuisine, and Coca-Cola Zero were included in the category termed Better-for-You (BFY).
The report found that between 2007 and 2011, BFY foods made up approximately 40 percent of sales but led to more than 70 percent of the growth in sales. Companies with more BFY sales returned more money to their shareholders, earned higher favorable marks among consumers, and outperformed the S&P 500 Index by a wider margin compared to those with a lower percentage of BFY sales.
The report received funding from the Robert Wood Johnson Foundation.
Source: Source: Hudson Institute. "Better-For-You Foods: It's Just Good Business." Obesity Solutions Initiative. October 2011.
Recent evidence shows that people who have type 2 diabetes have a significantly increased risk for many common cancers, such as pancreatic, endometrial, breast, and bladder. Now comes new evidence that diabetes also increases the risk of a highly fatal, not-so-common cancer related to our bile: cholangiocarcinoma or bile duct cancer.
Cholangiocarcinoma is a cancerous growth in one of the bile ducts, tubes that carry bile from the liver and gallbladder to the intestine. Bile is a fluid that helps digest fats in foods and carry out waste from the liver.
The recent study, published in the European Journal of Cancer Prevention, looked at all relevant population studies from 1966 to present day. The authors excluded studies that included diabetes beginning before age 30, in the attempt to focus entirely on type 2 diabetes, which generally occurs later in life. After analyzing the 15 studies, the researchers found that people with diabetes had a 60 percent increased risk of cholangiocarcinoma compared to those without diabetes.
Source: Jing W, Jin G, Zhou X, Zhou Y, Zhang Y, Shao C, Liu R, Hu X. "Diabetes mellitus and increased risk of cholangiocarcinoma: a meta-analysis." Eur J Cancer Prev. 2011 Aug 19 [Epub ahead of print]
Several studies among breast cancer survivors suggest that exercise may help in multiple ways, including improving women's quality of life and reducing risk of recurrence. It's not just conventional exercises that may help, suggests a small new study published in Clinical Breast Cancer.
The study focused on the physiologic effects of the martial art Tai Chi Chua on breast cancer survivors.
In the study, 19 breast cancer survivors were randomly assigned to either a Tai Chi group or a group that focused on coping strategies. None of the women were moderately active more than once a week. After meeting three times weekly for 12 weeks, researchers analyzed blood samples taken at the beginning and end of the study. Compared to the women who participated in Tai Chi, the women in the comparison group had higher levels of several biomarkers linked with increased risk of breast cancer. For example, while insulin levels remained stable in the Tai Chi group, it increased in the comparison group. The results are only preliminary, conclude the authors, but they are encouraging.
Source: Michelle C. Janelsins et al. "Effects of Tai Chi Chuan on Insulin and Cytokine Levels in a Randomized Controlled Pilot Study on Breast Cancer Survivors." Clin Breast Cancer. 2011 Jun;11(3):161-70. Epub 2011.
A new study that may help explain why whole foods can provide more benefits than supplements has found that that people who consume a broccoli supplement are missing a cancer-fighting phytochemical seen among broccoli sprout eaters.
The study was published in the Journal of Agricultural and Food Chemistry.
Broccoli and other cruciferous vegetables contain a large family of phytochemicals called glucosinolates. In laboratory studies, glucosinolates have reduced and prevented tumor incidence. In our bodies, glucosinolates are converted into a biologically active compound, such as sulforaphane. But in order for glucosinolates to transform into sulforaphane, it needs a protein called myrosinase, which is missing in many supplements.
This study gave healthy people either broccoli sprouts or broccoli supplements (no myrosinase). By studying urine samples, the researchers found that the broccoli consumers excreted higher amounts of two major compounds – sulforaphane and erucin – compared to the supplement takers.
Source: John D. Clarke, Ken Riedl, Deborah Bella, Steven J. Schwartz, Jan F. Stevens, Emily Ho. "Comparison of Isothiocyanate Metabolite Levels and Histone Deacetylase Activity in Human Subjects Consuming Broccoli Sprouts or Broccoli Supplement." Journal of Agricultural and Food Chemistry, 2011.