A major new study has added to evidence suggesting that high blood sugar and problems in sugar metabolism may increase cancer risk. The link between high blood sugar and cancer is not new. We don’t know whether risk comes from high blood sugar itself or from the elevated insulin levels that generally develop with it, which can lead to type 2 diabetes.
The latest research suggests that high blood sugar may increase cancer risk even before diabetes develops. Either way, since studies show that lifestyle dramatically lowers the risk of high blood sugar developing into diabetes, healthy eating and exercise offer the double benefit of reducing risk of diabetes and some types of cancer.
In the recent study, published in March, researchers found that women with the highest blood sugar showed a 26 percent increase in overall cancer risk compared to those with the lowest blood sugar. Overall cancer risk in men was not affected. In both men and women, however, the study confirmed an association between high blood sugar and increased pancreatic, kidney and urinary tract cancers, along with a doubled risk of melanoma.
The study spanned 13 years and followed more than 64,000 Swedish people. Blood sugar was measured after eight hours of fasting. Other studies have shown an increased cancer risk linked to type 2 diabetes. But this study found an increased cancer risk with pre-diabetics – people with smaller blood sugar elevations – as well as diabetics. High blood sugar is often related to overweight, but the link to cancer here was independent of weight. This is one of many studies investigating cancer risk as it relates to blood sugar and diabetes.
- Pancreatic cancer: In the March Swedish study, men and women with the highest levels of fasting blood sugar were almost 2.5 times as likely to develop pancreatic cancer as those with the lowest blood sugar. High-sugar diets, which can temporarily (but frequently) raise blood sugar, may also play a role in cancer risk. A 2006 study of almost 78,000 Swedish adults found that after 7 years, high consumption of sugar (including regular soft drinks) was associated with 70 to 90 percent increased risk of pancreatic cancer.
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- Endometrial cancer: The March Swedish study found a link between high blood sugar and endometrial (uterine) cancer. In another recent Swedish study of more than 36,000 women, diabetics were almost twice as likely to develop endometrial cancer compared to nondiabetic women. Sedentary or obese women with diabetes faced three to six times greater risk, and women having all three conditions (diabetes, inactivity and obesity) were almost ten times more likely to develop endometrial cancer as those with none of the conditions.
- Breast Cancer: Studies have shown conflicting findings on a link between high blood sugar and breast cancer. In the March Swedish study, higher blood sugar was linked to about double the breast cancer risk for women under age 49 (there was no link for overall breast cancer). Yet a large study of American women showed no tie between a marker of blood sugar levels and breast cancer risk.
- Colon Cancer: Colon cancer was not one of the cancers tied to blood sugar elevations in the March Swedish study. However, diabetes has been linked with colon cancer risk in other studies. In a 19-year study of more than 22,000 U.S. men, overweight and diabetes each increased risk of colon cancer 40 to 50 percent, respectively.
Blood sugar itself may not be the risk; in one study, blood sugars were only modestly related to colon cancer risk in a group of men. Elevated insulin levels and insulin resistance (which often accompany type 2 diabetes) increased risk of colorectal cancer about 85 percent.
Researchers say that we could probably reduce the risk of cancer linked to high blood sugar by following the same recommendations for preventing diabetes: maintain a healthy weight, get regular activity and eat a healthy diet, filled with fruits, vegetables and fiber, and scarce on saturated fat.