IU Research Links Dieting Habits With Risk For Estrogen-Responsive Cancers

INDIANAPOLIS-- It's still a bit premature to burn all diet books and disavow all attempts to lose weight, but Indiana University School of Medical researchers have completed initial research showing there may be a link between weight loss and some forms of cancer.

Preliminary studies reported in the March 1 issue of the journal, Cancer Research, "suggest a woman's dieting habits may become an important factor for determining risk of estrogen-responsive cancers," said Robert M. Bigsby, Ph.D., principal investigator.

Some environmental contaminants, such as DDT and forms of lindane, contain man-made estrogenic compounds, known as xenoestrogens. These contaminants, which are pervasive in nature, are fat soluble, meaning they are "stored" in fat cells. Dr. Bigsby and his colleagues looked at what happened to the xenoestrogens in female mice when the number of fat cells were reduced through weight loss.

Dr. Bigsby said that the xenoestrogens in DDT and lindane may be linked to the incidence of estrogen-responsive cancer. When the number of fat cells are reduced, the xenoestrogens stored there are released into the body. Some of the xenoestrogens lodge in adjacent fat cells, while others are released into the blood so that they can go to epithelial cells in the uterus, breast or other areas with estrogen sensitive tissue, Dr. Bigsby said. Epithelial cells are the cells in an organ that most often form tumors.

The research underway by Dr. Bigsby, an associate professor of obstetrics and gynecology and of physiology and biophysics at the IU School of Medicine, and his team also is concerned with the effect of these xenoestrogens on estrogen-sensitive tissue, such as that of the uterus. The study shows a marked change in the uterus of mice following periods of fasting.

This study demonstrated that when beta-HCH, a compound in lindane, is released from fat it has a larger effect on the uterine tissue than did DDT-- a now-banned insecticide-- but DDT did have some estrogenic effect on uterine tissue.

Beta-HCH is less fat soluble and therefore more water soluble than DDT so it can get into the blood and travel to the breast, uterus and liver.

In a December 1996 study in Cancer Research, Dr. Bigsby and his colleagues showed that beta-HCH and DDT stimulated the growth of breast tumor tissue that was grafted into mice. Since the epithelial cells of the breast are surrounded by fat cells the effect of a diet-induced loss of fat may be of special concern with regard to the release of these xenoestrogens.

The question that remains to be answered is whether these compounds can actually cause the growth of malignant cells.

It will take additional testing to determine if yo-yo dieting may be a culprit behind some forms of cancer, Dr. Bigsby said. The study results indicate that researchers now need to look at women and their blood levels before and after fasting, he said.

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