Food Combinations for Higher Cancer Protection
July's newsletter reported on the benefits of low carb diets for weight loss, while pointing out that high protein diets may not represent the healthiest eating pattern over the long run. One shortfall of these diets is a lack of emphasis on cancer-preventing fruits and vegetables, and the importance of eating a produce-rich diet is underscored by recent research findings.
Broccoli and Tomatoes: Cancer Fighting Synergy
Combining broccoli and tomatoes in the diet may maximize the amount of cancer protection both foods afford, according to research presented by Dr. John Erdman at the AICR International Research Conference in Washington, D.C. last month. Both of these foods contain plant chemicals that have been shown to fight cancer - broccoli's glucosinolates and the lycopene found in tomatoes have been touted as powerful anti-cancer compounds on their own. Lycopene is an antioxidant, and glucosinolates break down into compounds that help enzymes flush carcinogens from the body before they can do harm. Dr. Erdman's team wanted to study whole food combinations "to learn more about real diets eaten by real people". While it's important to analyze how specific food components influence health, researchers want to know more about how these compounds interact.
The study, scheduled for publication in the December issue of the Journal of Nutrition, compared the effects of four different diets in laboratory animals: one with added freeze-dried tomato powder, another with broccoli powder, and a third that combined both the broccoli and tomato powders. A final group of rats was fed a normal diet supplemented with finasteride, a drug commonly prescribed to men who suffer from benign prostatic hyperplasia (BPH).
Surprisingly, each of the vegetable-supplemented diets was better able to suppress prostate tumor growth than the drug-added diet. In the group that ate the combination tomato-broccoli diets, the average tumor weight was significantly lower than the control group or the individual fruit (tomato) or vegetable (broccoli) groups.
Supplements are Important, but They Don't Replace Whole Foods
Dr. Erdman noted that the phenomenon of interaction was not unique to tomatoes and broccoli. "This interactivity is likely taking place in any diet high in a variety of plant foods - fruits, vegetables and whole grains". In fact an experimental study published last year by the United Kingdom-based Institute of Food Research found that two food components recognized for their potential cancer-protective effects were found to have a much bigger impact on genes that play a role in the formation, progression and spread of tumors, when combined. The two food components, sulforaphane (a glucosinolate) from broccoli paired this time with selenium, were many times more effective as anti-cancer agents when put to work together. In addition to broccoli, Brassica vegetables such as cauliflower, cabbage, kale and Brussels sprouts are good sources of glucosinolates, while selenium is found in particularly high levels in Brazil nuts, shellfish, mushrooms and broccoli as well.
The results are a good reminder that there are many nutrients and chemicals in whole foods, and cancer protection likely comes as a result of their complex interactions rather than just from isolated compounds. Taking a multi-nutrient supplement daily is an excellent strategy to make up dietary shortfalls of nutrients and to obtain more optimal intakes of nutrients known to be important such as selenium and lycopene. However it's important to remember that supplements can't totally replace cancer-fighting whole foods.
- Erdman, J. Tomato phytochemicals and reduction of prostate cancer risk. Abstract 24, WCRF/AICR International Research Conference on Food, Nutrition and Cancer, July 15-16, 2004.
- Zhang J et al. Synergy between sulforaphane and selenium in the induction of thioredoxin reductase 1 requires both transcriptional and translational modification. Carcinogenesis 24:497- 503, 2003.