You might think so if you listen to the news, read the paper, or pick up the latest magazine or medical journal. Headlines scream "Pomegranates can curb cancer" or "Potato chips cause cancer."
Anything connecting food and disease often garners a great deal of attention in the news media. Many times, however, the data is taken out of context or extrapoloated into something more than what is truly accurate.
I can personally attest to this. A little more than a year ago, I contributed to a blog post on the health benefits of blueberries. In the post, I stated that blueberries are healthy because they are full of antioxidants, which protect cells by stabilizing free radicals and can prevent some of the damage free radicals cause. The next thing I knew, other organizations had picked up that blog post and expanded on it to say that studies done at my institution had shown that as little as a cup a day can help prevent cell damage linked to cancer.
I am not a researcher, and no studies showing any such thing have been done here. But I received calls/emails from multiple organizations (including the Blueberry Council), magazines in Europe, and a national TV station wanting to do a piece on my so-called research.
Certainly, nutrition is very important in terms of cancer risk (increasing or decreasing it), but news reports often oversensationalize individual findings, rather than emphasizing evidence-based guidelines. This may be due not only to the desire for a good sound bite ("10 Worst Foods Ever") or a teaser for a story, but also to the conclusions reached by researchers themselves overemphasizing the potential effect of their findings.
This was highlighted by a recent study published in the American Journal of Clinical Nutrition that examined the conclusions and statistical significance in the literature of associations between specific foods and cancer risk. The authors selected 50 common ingredients from random recipes and searched for studies investigating the relation of each ingredient to cancer risk.
Eighty percent of the ingredients had at least one study investigating its relation to cancer risk, including bread, eggs, pork, butter, tomatoes, onions, milk, olives, cheese, bacon, nuts, wine, cinnamon, cayenne, and oranges.
Thirty-nine percent of the studies concluded that the ingredient contributed to an increased risk of malignancy. Thirty-three percent found evidence of a decreased risk, and 23 percent found no evidence of an increased or decreased risk. However, in three-quarters of the studies assigning risk, the effect was weak (0.05 > P ≥ 0.001) or of no statistical significance (P > 0.05).
This is not to discount by any means the importance of a healthy diet, along with a healthy lifestyle, in the prevention of cancer. Nutritional epidemiology is extremely important in identifying modifiable nutrition factors. But we should always be extremely cautious in interpreting study results and especially in communicating information to the public.
I like to discuss specific foods that have potential cancer-fighting properties, primarily to encourage the intake of healthy foods that people may not be eating (or to encourage the continued intake of those foods) and to discuss how they can be incorporated into a healthy diet. However, it is really the overall patterns of the diet that are most important, not always specific foods or ingredients.