Ask the Dietitian: Know the Myths and Facts about Cancer Prevention

cup of tea

February is Cancer Prevention Month. The American Institute for Cancer Research (AICR) is leading a national campaign to help Americans separate the myths from facts about cancer risk and to empower people with accurate information on cancer. Here, Karen Collins tackles some of these myths while answering your questions

Q: Does drinking tea reduce cancer risk?

A: Studies show potential for tea, especially green tea, as a helpful addition in a diet to lower cancer risk, but the research is currently inconclusive. Interest in green tea as a way to reduce cancer risk relates mainly to natural polyphenol compounds it contains, especially one known as EGCG (epigallocatechin gallate). Cell and animal studies show these tea polyphenols may be protective in several ways: they may support antioxidant defenses that protect our DNA from damage that begins cancer development; they may intervene directly in cancer cell growth and ability to spread; and they may increase self-destruction of abnormal cells..

The challenge, however, is to figure out whether these benefits hold true in humans. Some population studies do show a link between green tea, or total tea consumption and lower risk of colorectal, prostate, ovarian and some other cancers, yet the studies overall are inconsistent.

Researchers are working to determine whether the results of these studies are really reflecting the effects of some other diet or lifestyle choice, such as not smoking, not drinking alcohol or physical activity levels. It is also possible that the different methods of producing and brewing green tea, or individual differences in how compounds from tea are metabolized in the body, could lead to different results.

Cell studies are investigating whether other phytochemicals from plant foods might even enhance the availability of tea’s compounds in the body. Regardless, unsweetened tea is a good beverage choice, since it contains no calories and can replace sugary drinks, which can help weight management — a goal clearly important to lower cancer risk. But don’t count on tea as your primary strategy to reduce cancer risk.

Q: Does eating vegetables reduce risk of breast cancer?

A: Eating more vegetables (and fruits) may work in several ways as part of an overall healthy eating pattern and lifestyle to reduce breast cancer risk. Excess body fat does increase risk for postmenopausal breast cancer. Therefore, substituting low-calorie vegetables and fruits for foods high in calories can help, because research strongly supports this key step in weight management.

The AICR/WCRF Third Expert Report (Diet, Nutrition, Physical Activity and Cancer: a Global Perspective) concluded that consumption of non-starchy vegetables and fruits is linked to a lower risk of cancer, overall. For breast cancer specifically, the evidence is suggestive but limited. The impact may also be restricted to estrogen-receptor positive breast cancer. Other studies have shown a link between high blood levels of carotenoids and decreased breast cancer risk. High blood carotenoids are a marker of people consuming more vegetables and fruits, but could also reflect more use of nutrient-rich deep orange and dark green leafy vegetables. These carotenoids (including beta-carotene and several others) may offer both antioxidant protection and direct interference with cancer development. Some cruciferous vegetables, such as broccoli, Brussels sprouts and kale, are rich in carotenoids as well as compounds called glucosinolates that may reduce cancer risk.

Analysis from two large cohorts combined both cruciferous and yellow/orange vegetables with lower risk of breast cancer. However, people may differ in how much they benefit from these specific compounds, and researchers emphasize that no firm conclusions can be drawn yet about cruciferous vegetables and breast cancer risk. As you look for steps you can take to reduce your risk of post-menopausal breast cancer, by far the strongest effects seem to come from reaching and maintaining a healthy weight, getting regular physical activity and minimizing alcohol consumption. For all these reasons, eating more vegetables does make sense as one part of an overall lifestyle to reduce breast cancer risk and promote overall health.

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