Implicating insulin
Physician-scientist Charles Fuchs, wearing a Little League cap and always ready to play ball, studies how metabolic factors such as diet and exercise influence cancer development.
Insulin, a natural hormone made by the pancreas to regulate the body's uptake of sugar from the blood, can also promote cancer through molecular pathways.
For example, studies have shown that women with invasive breast cancer who also have high blood levels of insulin or c-peptide, a marker of insulin resistance, are almost three times more likely to die of the disease than breast cancer patients who have lower levels of these proteins.
When cancer cells are treated with insulin in the laboratory, they tend to grow faster. In overweight or obese people, insulin becomes less effective in moving sugar from the blood into cells, so the pancreas compensates by making more insulin. Over a period of years, the excess insulin accelerates cell growth, including abnormal cell proliferation that can lead to cancer.
Dietary choices can help or hinder. Fuchs says cancer risk, like diabetes, can be raised by foods that cause blood sugar to jump, such as pastries and sweet cereals, and some foods that elevate insulin, such as white bread, candy, and protein-rich items. "We're trying to come up with a dietary index that predicts your insulin levels based on individual foods," he says. Avoiding a high "insulin index" diet could substantially lower an individual's risk of several common cancers.
Another culprit is insulin-like growth factor 1 (IGF-1), which is made by the liver, pancreas, and other organs and stimulates growth. Higher levels of IGF-1 have been found in patients with breast, prostate, colorectal, and lung cancer. "One hypothesis is that a sedentary lifestyle and obesity drive up insulin and IGF-1, which have been shown in the laboratory to increase the growth of colon and pancreatic cancer cells," Fuchs says.
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