We’ve long known that smoking cigarettes dramatically increases the risk of developing lung cancer. However, new evidence suggests that certain dietary choices can also increase the risk for lung cancer, even for people who have never smoked before.
A research team at the University of Texas MD Anderson Cancer Center recently looked at the medical and dietary histories of over 1,900 people with lung cancer and over 2,400 people without. They honed in on foods with a high glycemic index, i.e. “poor quality” refined carbohydrates such as white bread, white potatoes, bran flakes, pretzels, and popcorn.
After ranking people in the study based on the amount of high glycemic food in their diet, the researchers discovered that those who were in the top fifth (that is, those who had the highest glycemic diets) were 49% more likely to develop lung cancer than those in the bottom fifth.
This trend was even more noticeable when researchers looked only at people who had never smoked. When controlling for cigarette smoking, people in the highest glycemic index group were more than twice as likely to develop lung cancer compared to those in the lowest glycemic index diet group.
Why Might High Glycemic Index Foods Increase Cancer Risk?
It is not fully understood why eating a diet high in refined, “poor quality” carbohydrates might increase the risk for lung cancer. However, the researchers hypothesize that the key might lie in the way high glycemic index foods affect the body’s insulin production. These carbohydrates raise blood glucose levels, which triggers the release of more insulin from the pancreas. Regularly eating a diet that is high in refined carbohydrates can lead to insulin resistance (essentially, the body’s insulin isn’t able to successfully convert blood glucose into energy), a precursor to diabetes.
Glycemic Index Chart of Foods
In previous studies, insulin disorders have been singled out as potential contributors to an increased risk for cancer. This might be because insulin resistance triggers certain “growth factor” chemicals in the body, which can lead to cancer.
Of course, more research needs to be done before we will know whether there truly is a causal relationship between a high glycemic index diet and lung cancer. The University of Texas researchers point out that their study had several limitations: they only looked at a non-Hispanic white population, and they didn’t control for other illnesses, such as high blood pressure, heart disease, and diabetes. They also relied on study participants to self-report their dietary choices, which could have led to recall errors. In future studies, the team hopes to incorporate other ethnic groups and to investigate the mechanism of action that might cause high glycemic index foods to increase cancer risk.