An Apple A Day ...
An international team of researchers from Johns Hopkins University in Baltimore, Maryland and Tsukuba University in Tokyo, Japan, believe they have found some of the biochemical mechanisms by which fruits and vegetables are able to protect the body against cancer and other diseases.
Writing in the Proceedings of the National Academy of Sciences, Hopkins' Thomas Kensler and colleagues suggest that natural substances in fruits and vegetables called phase II enzymes may block the ability of some toxins to damage DNA and trigger cancer.
Previously, Japanese researchers led by Masayuki Yamamoto identified a protein known as Nrf2 that seems to increase in the presence of carcinogens. In laboratory experiments, they found that chemoprotective chemicals, such as those found in fruits and vegetables, seem to encourage cells to release Nrf2. This in turn provided an increasingly protective effect against the carcinogens.
Studies such as these are enabling researchers to unravel the biochemical mechanism of something that nutritionists have known all along-that a diet rich in fruits and vegetables provides myriad health benefits, including a lower risk of certain cancers.
A number of recent studies have focused on apples as a particularly rich source of antioxidants. Previous research has found that antioxidants reduce or prevent oxidation in certain cells, thus preventing cell or tissue damage that could lead to cancer.
For example, in a recent study published in the journal Nature, Dr. Rui Hai Liu of Cornell University and colleagues pointed out that the many antioxidants contained in fresh apples-phenolic acids and flavonoids-seem to work in synergy to inhibit the proliferation of tumor cells.
The researchers used extracts from Red Delicious apples to treat colon cancer cells in vitro and found that "cell proliferation was inhibited in a dose-dependent manner after exposure to apple-extract concentrations above 20 mg/ml." They had similar success in tests with human liver tumor cells.
They found that colon cancer proliferation was inhibited 57 percent with extract containing apple skin, and 40 percent by extract not containing skin.
About one serving (100 g) of fresh apple provides antioxidant activity equal to that of 1,500 mg of vitamin C, Liu noted. Apples contain almost 100 phytochemicals, he added, which may explain their remarkable antioxidant punch.
Another study by the National Cancer Institute reported that foods containing flavonoids like those found in apples may reduce the risk of lung cancer by as much as 50 percent. Apples have the highest concentration of flavonoids of any fruit.
Still other studies have found that eating an apple a day (literally) can reduce heart disease, prevent stroke, and even help women maintain estrogen during menopause.
The old adage not only still applies, but it may actually be an understatement.
SOURCES:
Proceedings of the National Academy of Sciences, March 13, 2001; 98(6):3410-3415
Nature, June 22, 2000; 405:902-904
The National Center for Complementary and Alternative Medicine, National Institutes of Health (http://www.nccam.nih.gov)
Washington Apple Commission (http://www.bestapples.com)