Study Warns of Hype about Ability of Some Foods to Protect Against Cancer

Dorian Martin Health Guide
  • So should you focus on your eating habits to lower your risk for cancer? Maybe add some soy? Perhaps add cinnamon to your coffee? Or should you avoid coffee and caffeine altogether?

    What you should – and shouldn’t eat – can get confusing. And now a new study out of Harvard throws some cold water on whether some specific foods can make a difference. "There's very strong evidence, and pretty strong expectation, that some nutrients in some foods would be related to cancer risk - either protecting or increasing the risk - but it's very hard to believe that almost anything would be associated with cancer," the study’s co-author Dr. John Ioannidis from the Stanford Prevention Research Center, told Reuters Health Information.

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    Ioannidis and the research team picked 50 common ingredients including meats, fish, vegetables, dairy products and spices from random recipes in a cookbook and then looked at studies that had been published in the past 35 years evaluating the relation of each ingredient to the risk of cancer. Their analysis found that while associations have been claimed that these ingredients affected cancer risk in either a positive or negative way, much of the evidence was weak. The researchers pointed out, though, that there was agreement in most of the studies that some foods, such as onions, carrots and tea, were linked to a decrease in cancer risk while foods such as sugar and bacon were found in almost all studies to increase the risk of this disease. Fruits and vegetables also have been found in studies to provide a beneficial effect.

    That last bit helps to underscore the findings from a new meta-analysis out of Brigham & Women’s Hospital and Harvard Medical School that looked at whether carotenoids, which are micronutrients in fruits and vegetables, could help reduce the risk of breast cancer.

    Researchers analyzed eight cohort studies that comprised more than 80 percent of prospective data on plasma or serum carotenoids and breast cancer that have been published. This data included 3,055 case subjects and 3,956 matched control subjects. In doing their analysis, researchers found a statistically significant association between increased levels of carotenoids and a decreased risk of breast cancer, especially for women who have the ER-negative breast cancers that don’t rely on estrogen for their growth.

    So if you’re worried about cancer. should you change your diet when you hear stories on the news? “Because people are interested in the possible links between specific foods, nutrients, or lifestyle factors and specific cancers, research on health behaviors and cancer risk is often reported in the news,” the American Cancer Society reports. “No one study, however, provides the last word on any subject, and single news reports may put too much emphasis on what appear to be conflicting results.”

    With that said, the American Cancer Society does point to some foods that have been found in multiple studies to either raise the risk or lower the risk of cancer. Foods that seem to protect against cancer include whole grains, vegetables, fruit and soy products. Foods that may raise the risk of cancer include alcohol (especially when combined with smoking), salt, processed meats and meats that have been preserved using smoke or salts. And some foods and nutrients, such as calcium, fats, selenium and folate have mixed results. Other foods such as fish, coffee, garlic, non-nutritive sweeteners, sugar substitutes, olive oil, organic foods, tea, spices,  and irradiated foods have not been found at this point to be associated with a change in risk status.


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    Genetically modified foods have not been found to increase the risk of cancer at this time. However, the American Cancer Society points out that lack of proof does not equal proof of safety and that there may be long-term health effects.

    And interestingly, supplements don’t seem to provide quite the protection as eating the foods that have those specific nutrients. For instance, the American Cancer Society points out that since eating vegetables and fruits has been linked to a lower risk of cancer, one might assume that taking large doses of beta-carotene in supplemental form would especially reduce the risk. However, two studies found that taking high-dose supplemental beta carotene actually led to a higher risk of lung cancer while a third study found that high-dose supplements neither raised nor lowered the risk of cancer.

    So what should you do? Some foods may prevent cancer, while others might help with Alzheimer’s or arthritis. Therefore, just focus on eating a healthy diet!

    Primary Sources for This Sharepost:

    American Cancer Society. (2012). ACS guidelines on nutrition and physical activity for cancer prevention.

    Eliaseen, A. H. (2012). Circulating carotenoids and risk of breast cancer: pooled analysis of eight prospective studies. JNCI Journal.

    Pittman, G. (2012). Treat nutrition and cancer research cautiously: study. MedlinePlus.

    Preidt, R. (2012). Nutrients in fruits, vegetables may help prevent breast cancer: study. MedlinePlus.

    Schoenfeld, J. D. & Ioannidis, J. P. A. (2012). Is everything we eat associated with cancer? A systematic cookbook review.  The American Journal of Clinical Nutrition.

Published On: December 12, 2012