New Evidence in Colon Cancer Prevention Unveiled at American College of Nutrition.

Eating two servings of raisins a day may help lower the risk of colon cancer, according to newly released research at the Symposium on Advances in Clinical Nutrition. The study was designed to confirm an earlier hypothesis that the combination of dietary fiber and tartaric acid in sun-dried raisins plays an important role in colon function and health.

“We found a significant, positive correlation between consuming sun-dried raisins and a change in some colon cancer risk factors,” said Gene Spiller, Ph.D., lead study author and researcher at the Health Research and Studies Center in Los Altos, California.

“Eating as little as two servings—or ½ cup (84 grams) of raisins—resulted in beneficial changes in colon function that may help combat the estimated 130,000 new cases of colorectal cancer expected to be diagnosed this year.”

In this clinical study of 16 healthy men and women, beneficial colonic changes were measured. Two servings of raisins helped speed food and waste through the digestive system while decreasing the bile acids in the colon that may promote the growth of cancerous tumors.

Dr. Spiller said that the decreased transit time and increased fecal bulk mean that dietary carcinogens may be diluted and may have less time to act negatively on the colon wall.

“Also, the colon's pH may be lowered, modifying a risk factor for colon cancer. This means colonic diseases typical of a low-fiber diet, such as cancer and diverticular disease, may be prevented,” he said.

Raisins are unique in having this protective effect because they contain tartaric acid. According to a 1996 study by Dr. Spiller and his colleagues, tartaric acid—present in significant amounts only in raisins, grapes, and the tropical fruit tamarind—plays a significant role in decreasing the time it takes for food and waste to move through the digestive system and in reducing harmful bile acid concentrations.

“The combination of fiber and tartaric acid in raisins helped to speed transit time and decrease bile acids beyond what would be expected from fiber alone,” said Dr. Spiller.

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