While a diet containing a wide variety of fruits, vegetables, grains, and animal products in the proportions recommended by the US Department of Agriculture (USDA) Food Guide Pyramid may help in the prevention of cancer, whey protein is being proven in clinical studies to be a powerful assistant in cancer prevention and treatment. Whey protein was found to inhibit the growth of breast cancer cells in a test tube, and another clinical study showed a regression in the size of tumours of some patients who were fed 30g of whey protein concentrate per day. In clinical studies in rats at the Arkansas Children's Research Institute, whey was proven to be twice as effective as soy in breast cancer prevention. Studies have also led researchers to the discovery that whey protein protects healthy cells while cancerous cells are being treated with chemotherapy. In order to increase the effects of radiation and chemotherapy on cancer patients, doctors must sufficiently reduce glutathione in tumour cells to weaken them, without placing healthy tissue at risk and putting the cancer patient in a worse condition. Whey protein appears to selectively deplete the cancer cells of their glutathione, while increasing or at least maintaining the levels of glutathione in healthy cells. These effects were not seen with other proteins. According to the whey producer NEXT Proteins, cancer patients undergoing radiation or chemotherapy often have difficulty in meeting their daily nutritional requirements due to nausea and lack of appetite, and can suffer from protein malnutrition. Whey is a good protein source for cancer patients because it is easy to digest and gentle to the system. While additional research is needed on the effects of whey protein and cancer treatment, early dietary intervention with whey protein can have positive health benefits.