Packing for a picnic? Don't forget to pack crisp, fresh apples for your family and friends to munch on throughout the day. Food scientist Rui Hai Liu, M.D., Ph.D., Cornell University, says epidemiology studies involving hundreds of thousands of individuals document amazing stories of the health benefits of apples. Additional studies in Liu's own lab with rats suggest that an apple a day may even keep breast cancer away. Liu's review of the literature on apples was published online in the Nutrition Journal on May 12, 2004. His current research with rats was published in the Journal of Agricultural and Food Chemistry in March 2005.

Infoaging: Dr. Liu, can you explain what is so special about apples?

Dr. Liu: Apples — and especially apple peels — have been found to contain a high amount of plant chemicals called phytochemicals with potent antioxidant activity in that they mop up lots of harmful compounds in the body and inhibit the production of substances that damage normal cells.

Apples are a very significant source of two important groups of phytochemicals — flavonoids and phenolic acids. While other fruits and vegetables have protective health effects, apples were most consistently associated with reduced risk of certain chronic diseases in humans.

Infoaging: What kinds of health benefits might we derive from eating these fruits regularly?

Dr. Liu: Numerous studies show that apples have a particularly protective effect on our lungs. Eating this fruit has been inversely linked with asthma, bronchial hypersensitivity, and chronic obstructive pulmonary disease (COPD) and it is positively associated with general pulmonary health.

Studies involving tens of thousands of individuals also indicate that women eating the highest amounts of flavonoids had a significant reduction in the risk of cardiovascular events as well. The literature suggests that apples are also associated with a reduced risk of type II diabetes and with increased weight loss, when compared with other foods and other sources of flavonoids.

Infoaging: What benefits from apples have you found in your own research?

Dr. Liu: We have seen a potent antioxidant activity and antiproliferation activity from apple phytochemicals in cell cultures. My colleagues and I were able to show that phytochemicals in fresh apples could greatly inhibit the growth of liver and colon cancer cells.

Specifically, 50 mg of apple extracts from the skins inhibited colon cancer cells by 43 percent, while apple flesh extracts inhibited the colon cancer cells by 29 percent. The same dosage of apple extracts with skins also inhibited liver cancer cells by 57 percent, while the extracts from apple flesh inhibited liver cancer cells by 40 percent. We published these findings in an article in the journal Nature a few years ago.

Because of the effectiveness of whole-apple extracts in inhibiting the growth of cancer cells, we tested it in animals too. We randomly divided rats into different groups. We treated the rats with a known mammary carcinogen and then fed them either whole-apple extracts or control extracts. We were able to block mammary cancer formation in those rats fed apple extracts. We found that tumor incidence was reduced by 17, 39, and 44 percent in rats fed the human equivalent of one, three, or six apples a day, respectively, over 24 weeks. We also found that the number of tumors was reduced by 25, 25, and 61 percent in rats fed, respectively, the equivalent of one, three or six apples a day over 24 weeks.

This study demonstrates that whole-apple extracts effectively inhibited mammary cancer growth in the rat model. Thus, consumption of apples may be an effective strategy for cancer protection. This is the first study of the effects of apples on cancer prevention in animals.

The results you get from an animal model are different from those you get in a cell model, so it's one step closer to showing how it might work in humans. There is a good chance it will work in humans, too, but we still have to confirm this premise with additional tests.

Infoaging: You mentioned the potent nutritional power of apple peels. Can you tell us more about that?

Dr. Liu: Apple peels may have higher antioxidant activity, because they contain more antioxidant compounds — especially quercetin. In fact, depending on the variety of the apple and other factors, apple peels contain anywhere from two to six times more phenolic compounds than in the flesh. Peels also contain two to three times more flavonoids than in the flesh. Because of the powerful antioxidant activity of apple peels, we made apple peel powder as a value-added product here at Cornell.

Infoaging: What do we need to know about phytochemicals in general?

Dr. Liu: Approximately 8,000 phytochemicals are present in whole foods. That's why we recommend that you eat a wide variety of fruits, vegetables, and whole grains daily. The health benefits of eating fruits, vegetables, and whole grains extend beyond lowering the risk of developing cancer and cardiovascular diseases. It has been found that these foods have preventative effects for other chronic diseases such as cataracts, age-related macular degeneration, and central neurodegenerative diseases including Alzheimer's disease.

Phytochemicals vary in molecular size, polarity, and solubility. This could affect how they are absorbed and distributed in different cells, tissues, and organs. This balanced natural combination of phytochemicals present in fruits and vegetables cannot be mimicked by dietary supplements. There is considerable evidence showing that phytochemicals in whole foods have additive and synergistic effects. These pure compounds either lose their bioactivities in isolation or may not behave the same way as the compounds in complex whole foods.

We recommend people to obtain their antioxidants and other bioactive compounds from a balanced diet with a wide variety of fruits, vegetables, and whole grains daily to have the optimal health benefit.

Resources:
University of Michigan: Healing Foods Pyramid
http://www.med.umich.edu/umim/clinical/pyramid/index.htm

United States Department of Agriculture
Steps to a Healthier You — http://www.mypyramid.gov

University of Illinois Extension: Apples & More — http://www.urbanext.uiuc.edu/apples/