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Nutrition Notes
Week of November 17, 2008
Contact: Sarah Wally, (202) 328-7744

Could Mushrooms Be Cancer-Fighters?

Karen Collins, MS, RD, CDN
American Institute for Cancer Research

The cancer-protective benefits of vegetables like garlic, broccoli and tomatoes are well known in the scientific community. Now, emerging evidence suggests that mushrooms may soon be included among the cancer-fighting plant foods. Human studies are just beginning, but laboratory studies suggest several ways that mushrooms may inhibit cancer development.

Previously published research has shown that mushroom extract can decrease tumor cell growth in mice and in cell cultures. Scientists speculate that natural compounds in mushrooms inhibit aromatase enzymes in the body, proteins that stimulate the production of estrogen, which can promote growth of some cancers, including breast cancer. Experts now suggest that vegetables that act as natural aromatase inhibitors might reduce the body’s production of estrogen and help prevent estrogen-sensitive breast cancer.

Mushrooms might also help prevent cancer by providing natural antioxidant compounds. Antioxidants work to neutralize free radicals (naturally occurring chemicals that can damage cells’ DNA and initiate the cancer process) and help to repair damage that has already occurred. In some laboratory studies, mushrooms displayed even more antioxidant power than tomatoes and carrots.

One antioxidant compound that gets a lot of attention, ergothionene, is found most readily in brown mushrooms (including portabella), shitake and other exotic mushrooms. But white mushrooms are still an important source, and also contain other antioxidant compounds called polyphenols, which fight cell damage and inflammation. All mushroom are also significant sources of the antioxidant mineral, selenium.

In addition to enzyme inhibition and antioxidant activity, other laboratory studies suggest that mushrooms might protect against cancer by acting through the immune system. Animal studies have shown that ingestion of dried white mushrooms increased immune function that has been linked to cancer protection. Scientists suggest that beta-glucans, a type of soluble dietary fiber in mushrooms, may somehow stimulate the protective immune function.

These laboratory studies show a variety of ways that mushrooms could provide cancer protection, but we need human studies to truly test the impact of mushrooms in our diet. Human clinical studies are currently underway at the City of Hope Comprehensive Cancer Center in California, the results of which will hopefully offer additional insight.

Meanwhile, mushrooms, along with a host of other vegetables, may help lower cancer risk by helping us avoid excess calorie consumption and thus supporting weight control. A 2008 study published in the journal Appetite found that participants who substituted mushrooms in dishes traditionally made with ground beef (lasagna and chili, for example) reported no difference in enjoyment or hunger satisfaction compared to those who dined on the meat-containing dishes, despite consuming from 300 to almost 600 fewer calories.

Adding mushrooms and other vegetables to soups, stews and casseroles is a great way to make a dish more filling with fewer calories. However, mushrooms are not nutritional substitutes for meat, since they are substantially lower in protein, iron, zinc and vitamin B-12. So, when adding mushrooms to add texture and flavor in place of meat, remember that dried beans, nuts, poultry or seafood should also be added in the meal to maintain equal nutrition.

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The American Institute for Cancer Research (AICR) is the cancer charity that fosters research on the relationship of nutrition, physical activity and weight management to cancer risk, interprets the scientific literature and educates the public about the results. It has contributed more than $100 million for innovative research conducted at universities, hospitals and research centers across the country. AICR has published two landmark reports that interpret the accumulated research in the field, and is committed to a process of continuous review. AICR also provides a wide range of educational programs to help millions of Americans learn to make dietary changes for lower cancer risk. Its award-winning New American Plate program is presented in brochures, seminars and on its website, www.aicr.org. AICR is a member of the World Cancer Research Fund International.

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