Juicy anticancer prospects.

While using various juices to hide the taste of a test substance given to patients along with their drugs as part of a cancer trial, researchers at the University of Western Ontario in London noticed that the drugs seemed far more effective when the patients drank grapefruit juice.

The observation spurred Kenneth K. Carroll, director of the university's Centre for Human Nutrition, to explore why. He and his colleagues now report that certain fruit-derived flavonoids seem especially potent at halting the growth of cancer cells.

When administered to test-tube cultures of estrogen-insensitive human breast cancer cells, naringenin, a flavonoid in grapefruit juice, proved almost eight times more potent at halting the cells' growth than genestein, an estrogenlike flavonoid in soy that shows promise as a natural anticancer agent. Naringenin proved far less effective than genestein, however, at slowing the growth of breast cancer cells that depend on estrogen for growth.

The researchers proceeded to test other fruits. Individually, the best performers against both types of cells were tangeretin and nobiletin, a pair of flavonoids from tangerines. Each was about 250 times more potent than genestein in estrogen-insensitive cells and five to nine times more potent in estrogen-dependent cancer cells. Delivered together or with certain other fruit flavonoids, they proved still more potent. They also appeared to increase the efficacy of tamoxifen, the leading drug for halting breast cancer recurrence.

Orange juice outperformed grapefruit juice in two trials using rats. In cell tests, however, grapefruit's naringenin outperformed an orange-derived flavonoid, hesperetin. Carroll now plans to study the cancer-inhibiting effects of oranges-and perhaps tangerines-in mice injected with human cancer cells.