High fat, high cholesterol diet linked to increased breast cancer risk

Breast cancer rates are five times higher in Western countries than in other developed countries, and studies have shown that rates increase in immigrant communities who come from low-incidence areas. This has suggested to scientists that environmental factors play a high part in the progress of the disease.

Now a group of researchers from Jefferson University in the US has found that mice fed a western-style diet high in fat and cholesterol are more likely to develop breast cancer than mice placed on a control diet, and that breast cancer tumours are larger and grow faster.

Dietary fat and cholesterol have been shown to be important risk factors in the development and progression of a number of tumour types, but diet-based studies in humans have reached contradictory conclusions. This is why the scientists considered a mice-based study.

The mice were of a type believed to closely parallel the course of human breast cancer. One set were placed on a diet that contained 21.2 percent fat and 0.2 percent cholesterol, reflective of a typical Western diet, and another on a diet with 4.5 percent fat and negligible amounts of cholesterol. The researchers found that tumours began to develop quickly in mice fed the fat/cholesterol-enriched food. In this group, the number of tumours was almost doubled, and they were 50 percent larger than those observed in mice that ate a normal diet.

Commenting on the results, study leader Philippe G. Frank said: "The consumption of a Western diet resulted in accelerated tumour onset and increased tumour incidences, multiplicity, and burden, suggesting an important role for dietary cholesterol in tumour formation." He also noted that there was an increase in lung tumours in the mice fed the high fat diet.

The study noted that cholesterol levels dropped in those mice that developed the tumours. This suggests that the cholesterol is actually fuelling the development of the tumours. Thus an otherwise unexplained drop in blood cholesterol levels may provide a useful indicator of the development of cancer tumours.

The research team also discovered the same association between cholesterol and growth of prostate cancer in mice in a study published in the December issue of The American Journal of Pathology, as was the new study.

The results of these two new studies indicate, according to Dr. Frank, that "cholesterol does indeed seem to be an important factor in the regulation of tumour formation in several cancer types."

The Family GP