It’s even harder to imagine how seesawing blood sugar levels could possibly lead to cancer, but high insulin levels seem to promote an environment that makes it easier for certain tumors to grow. Research is still ongoing, and, unlike with heart disease and diabetes, it’s too early to make strong statements about the connection between blood sugar levels and cancer. But there is cause for concern with the following cancers.
Colon and rectal cancer. In the Health Professionals Follow-up Study conducted by the Harvard School of Public Health and involving more than 50,000 middle-aged men, those whose diets were most likely to raise blood sugar fast and high were 32 percent more likely to develop colon or rectal cancer over 20 years. The heavier the men, the stronger the effect. In the Women’s Health Study, funded in part by the U.S. National Cancer Institute, the rise in cancer risk was an astounding 185 percent higher over 8 years.
Breast cancer. In the Women’s Health Study, sedentary women who followed a blood sugar–boosting diet were 135 percent more likely to develop breast cancer over seven years than women whose diets were more blood sugar friendly. These women had not yet entered menopause. On the other hand, a Canadian study of nearly 50,000 women found no link to breast cancer before premenopause, but among postmenopausal women, there was an 87 percent increase in breast cancer risk — and it was even higher if the women did little or no vigorous exercise. A Mexican study comparing women who got breast cancer with those who didn’t found the risk was 62 percent greater with blood sugar–boosting diets. A similar Italian study found an 18 percent increase.
Endometrial cancer. In the Iowa Women’s Health Study, which involved more than 23,000 postmenopausal women, those who didn’t have diabetes and followed blood sugar–spiking diets were 46 percent more likely to get this cancer over 15 years. An Italian study that compared women who developed endometrial cancer with a similar group of women who didn’t found a 110 percent increase in risk linked to this type of diet.
Prostate cancer. An Italian study looked at men ages 46 to 74 who developed prostate cancer and compared their diets with those of a similar group of men who didn’t get the cancer. Those whose diets were most likely to spike blood sugar were 57 percent more likely to have prostate cancer. A similar Canadian study found a 57 percent increase in risk.
Pancreatic cancer. Even the organ that produces insulin may be more prone to cancer if it’s constantly bathed in that hormone. A study using data from the Nurses’ Health Study over 18 years found that women whose diets raised blood sugar the most were 53 percent more likely to develop pancreatic cancer than women whose diets raised it the least. Women in the first group who were overweight and physically inactive were 157 percent more likely to get the cancer than similar women in the second.