From ASCO (American Society of Clinical Oncology)
A Menu for Cancer Risk Reduction?
Five truths about the role of food and diet in cancer prevention
March 15, 2017
Amanda Narod, MPS, ASCO Staff
“When it comes to maintaining a healthy diet, what is the trend ‘du jour? We have all heard the buzzwords: superfoods, gluten free, Mediterranean diet, high protein. The endless barrage of information and misinformation about cancer risk reduction and food often leave people confused about what to place on their plates. The bottom line is a healthy diet is a piece of the cancer prevention puzzle. Regular exercise, maintaining a healthy weight, and avoidance of tobacco products, along with a healthy diet, are all lifestyle choices that can help reduce one’s risk of cancer.”
•Merry Jennifer Markham, MD, ASCO Expert
Experts estimate that at least one-third of all adult cancer cases are linked to lifestyle choices and habits, which include diet.1 While numerous studies have looked at food and cancer, it’s challenging to come away with definitive conclusions.
Here are five commonly debated truths when it comes to food and cancer.
1. There is no proven diet to prevent cancer
The litany of factors associated with cancer risk make it nearly impossible to prevent cancer entirely. For example, some cancers are associated with inherited genetic mutations so it is possible someone can develop cancer, even while adopting a healthy diet and lifestyle.
There is some evidence, however, that the Mediterranean Diet – rich in vegetables, fruits, whole grains, olive oil and fish –may prevent breast cancer incidence rates, but not necessarily mortality rates. Nevertheless, researchers note that additional investigation is needed to confirm the findings.2
2. Your mom was right: eat your veggies
Vegetables – particularly those classified as cruciferous vegetables – are rich in nutrients and minerals. They include leafy greens such as kale, collard greens, broccoli and bok choy among others.
A protective effect of cruciferous vegetables has been shown for cancers of the mouth, pharynx, voice box, esophagus, and stomach. Several laboratory studies suggest that cruciferous vegetables help regulate the body's complex system of enzymes that defend against cancer. They also show that parts of the vegetables can stop cancer cell growth.
It’s important to remember, however, that these vegetables may not work the same or as well in people as they have in laboratory studies.3 In addition, people who eat cruciferous vegetables may also be more likely to have other healthy behaviors that reduce disease risk versus those who do not consume these vegetables.4
3. Soy may help women with breast cancer
Like many other foods, women often received mixed messages about consumption of soy as part of their diet. Research results are mixed, but one recent large study found that women with breast cancer who ate the most soy foods were 21% less likely to die over 9 ½ years than women who ate the least. Settling longstanding concerns, the study also found that soy had no detrimental effect on women with estrogen receptor-positive breast cancer.5
Studies among prostate cancer survivors indicate that eating soy foods may lower PSA levels. The effect was stronger in some men, but not all, making it unclear whether genetics or metabolism made a difference in lowering PSA levels.6
4. Order the coffee, but be careful when consuming hot beverages
The evidence on coffee and its relation to cancer risk can be confusing. Those who rely on that morning cup ‘o joe can sip and savor their drink. Just last year, the World Health Organization (WHO) reversed its longstanding labeling of coffee as a carcinogen. In fact, WHO performed a review of nearly 1,000 studies and pointed to evidence that coffee was associated with a risk reduction in liver and endometrial cancers.
Yet the WHO also stated that drinking very hot beverages, such as tea, is probably carcinogenic to humans. The classification change was based on limited evidence from epidemiological studies that showed positive associations between cancer of the esophagus and drinking very hot beverages. Studies in places such as China, the Islamic Republic of Iran, Turkey, and South America, where tea or maté is consumed at very hot temperatures, found that the risk of esophageal cancer increased with the temperature at which the beverage was consumed.7
5. Fire up the grill with caution
A recent study found that a high intake of grilled, barbecued or smoked meat may increase mortality after breast cancer, as these meats are a source of polycyclic aromatic hydrocarbon (PAH), a known carcinogen. However, population studies have not established a definitive link between a PAH exposure from cooked meats and cancer in humans. A challenge remains that people can be exposed to PAHs from other environmental sources, such as pollution and tobacco smoke. Researchers found that high consumption of well-done, fried, or barbecued meats was associated with increased risks of colorectal, pancreatic, and prostate cancer.8
To learn more about food and cancer prevention, visit Cancer.Net.
1. Parkin, D. M., et al. (2011). "16. The fraction of cancer attributable to lifestyle and environmental factors in the UK in 2010." Br J Cancer 105(S2): S77-S81.
2. Bloomfield HE, Koeller E, Greer N, MacDonald R, Kane R, Wilt TJ. Effects on Health Outcomes of a Mediterranean Diet With No Restriction on Fat Intake: A Systematic Review and Meta-analysis. Ann Intern Med. 2016;165:491-500. doi: 10.7326/M16-0361
3. Higdon JV, Delage B, Williams DE, Dashwood RH. Cruciferous Vegetables and Human Cancer Risk: Epidemiologic Evidence and Mechanistic Basis. Pharmacological research : the official journal of the Italian Pharmacological Society. 2007;55(3):224-236. doi:10.1016/j.phrs.2007.01.009.
4. C. Bosetti, M. Filomeno, P. Riso, J. Polesel, F. Levi, R. Talamini, M. Montella, E. Negri, S. Franceschi, C. La Vecchia; Cruciferous vegetables and cancer risk in a network of case–control studies. Ann Oncol 2012; 23 (8): 2198-2203. doi: 10.1093/annonc/mdr604
5. Zhang, F. F., Haslam, D. E., Terry, M. B., Knight, J. A., Andrulis, I. L., Daly, M. B., Buys, S. S. and John, E. M. (2017), Dietary isoflavone intake and all-cause mortality in breast cancer survivors: The Breast Cancer Family Registry. Cancer. doi:10.1002/cncr.30615
6. an Die, M. D., Bone, K. M., Williams, S. G. and Pirotta, M. V. (2014), Soy and soy isoflavones in prostate cancer: a systematic review and meta-analysis of randomized controlled trials. BJU Int, 113: E119–E130. doi:10.1111/bju.12435
7. Loomis, D., et al. "Carcinogenicity of drinking coffee, mate, and very hot beverages." The Lancet Oncology 17(7): 877-878.
8. Humberto Parada, Jr., Susan E. Steck, Patrick T. Bradshaw, Lawrence S. Engel, Kathleen Conway, Susan L. Teitelbaum, Alfred I. Neugut, Regina M. Santella, Marilie D. Gammon; Grilled, Barbecued, and Smoked Meat Intake and Survival Following Breast Cancer. J Natl Cancer Inst 2017; 109 (6): djw299. doi: 10.1093/jnci/djw299
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