An Apple a Day

The anti-cancer activity Liu is referring to is made possible by substances called "phytochemicals," which are antioxidants that help fight cancer. Antioxidants work by intercepting free radicals, highly reactive molecules that can damage a cells membrane or DNA and render it more susceptible to cancer and other diseases.

image: WIXT

Cornell researchers tested the anti-cancer activity of Red Delicious apples by studying what happens to cancer cells when they are exposed to both apple flesh and skin. They found that colon cancer cells were inhibited by 43 percent when treated with 50 milligrams of apple skin extract, and 29 percent when treated with flesh extract.

They also tested the apple extract with liver cancer cells. These cells were inhibited by 57 percent when treated with skin extract and 40 percent when treated with extract from the fruit's flesh.

While it was previously thought that Vitamin C, a known antioxidant, might be responsible for this effect, this has turned out not to be the case. "Vitamin C in apples only provides a very small total of antioxidant activity," say Liu, noting that 100 grams of apples contains just 5.7 milligrams of Vitamin C. "But eating 100 grams of apples, like one serving of apples, provides you with a total antioxidant activity equal to 1,500 milligrams of Vitamin C."

The researchers say that for all fruits and vegetables, the total anti-cancer activity likely adds up to more than the sum of the parts. That's because the whole fruit contains a complex combination of phytochemicals, including flavonoids and phenolic acids. It is this combination that makes eating apples better than taking individual vitamin supplements. Taking too many supplements can sometimes lead to toxic side effects, something that doesnt happen with fruit because the effect of small amounts of vitamins is enhanced by the interaction of the phytochemicals. Interestingly, the amount of phytochemicals varied from year to year, season to season, and region to region.

The Cornell study, which was funded by the New York Apple Research Development Program and the New York Apple Association, is by no means the first research showing the health benefits of eating apples.

In 1997 a study published in the American Journal of Epidemiology involving almost 10,000 Finnish men found that eating apples appeared to reduce the incidence of lung cancer, due to a flavonoid called quercetin. Better lung function was also linked to eating about one apple a day in a study of 2,500 Welshman published in the British medical journal Thorax earlier this year.

Besides being beneficial to the lungs, apples have been shown to benefit the heart and brain, too. Last year, researchers at the University of California at Davis published findings in the journal Life Sciences which showed that apples and apple juice may help lower cholesterol buildupspecifically LDL, the "bad" cholesterolon artery walls. Last month, a study published in the European Journal of Clinical Nutrition following more than 9,000 Finnish men and women for more than 25 years showed that those who ate the most apples had the lowest risk of having a stroke.

But such benefits are not unique to apples. "I think all the fruits are very differentdifferent fruits having different phytochemicalsso I suggest people eat fruits and vegetables in a variety," says Liu. His group is now testing the anti-cancer activity of extracts from cherries, grapes, and cranberries.

In the meantime, the old adage still works. "I generally eat one apple a day," says Liu. "Sometimes I eat two."