Glycemic Load, Overall Health, and a New Study on Colon Cancer Survival

“Glycemic index.”  It’s a term that likely rings a bell, but unless you’re a dietician or research scientist, you can certainly be excused for not knowing exactly what it is and why it’s even important.  But, like a lot of similar concepts, it’s really not that complicated once you look into it a little bit.

Basically, the glycemic index is a lot like the speedometer in your car.  While a speedometer measures how fast you’re moving, the glycemic index measures how fast a food you eat gets converted into glucose in your body.  The higher the number, the more quickly and strongly the food boosts blood glucose levels, which can cause a host of reactions that over the long run can lead to weight gain and an increased risk of heart disease and diabetes. Some studies have also linked diets filled with high glycemic index foods to an increased risk of some cancers, but this link isn’t perfectly clear and is an active area of research.

Adding to this science base, is a new study in the Journal of the National Cancer Institute that links diets high in high glycemic index foods and carbohydrates with the return of cancer and earlier death in patients with stage III colon cancer (study).

The study, part of the federally-sponsored Cancer and Leukemia Group B trial, followed a thousand colon cancer survivors for an average of seven years and looked at the carbohydrate intake and overall glycemic load of patients’ diets to see how this related to cancer recurrence and survival.  What the researchers found was that those patients with the highest overall glycemic load diets were almost twice as likely to have their cancer return (recurrence) compared to those with the lowest glycemic load diets. Overall carbohydrate intake had a similar effect.  Looking at overall survival, high glycemic load diets and high carbohydrate intake diets increased the risk of dying by 75 – 80 percent.  In the United States, the large majority of carbohydrates eaten are refined carbohydrates, which have a high glycemic index, so it’s not surprising that the results for carbohydrate intake tracked closely to those of overall glycemic load.

Exactly how a high glycemic load diet may promote cancer recurrence is unknown.  But, high glycemic index foods can cause spikes in blood glucose and insulin, which can have wide-ranging effects throughout the body that some lab studies suggest can lead to cancer cell growth and inhibit cancer cell death.

Though this study doesn’t provide concrete evidence that a high glycemic load diet hurts survival in colon cancer patients, it does add to overall evidence that a diet filled with low glycemic index foods is a healthy choice for everyone, and there’s good evidence that it’ll lower the risk of heart disease and diabetes, which are important concerns even for most cancer survivors.

In general, a diet with a lower glycemic load includes a lot of whole grains (like oatmeal, whole wheat, and wild rice) and whole fruits and vegetables. It’s also low in refined grains (like white bread, white rice, and regular pasta) and sugary foods (like sweets and soda). (See figure).

For more on healthy steps after a cancer diagnosis, see Cancer Survivors’ 8ight Ways to Stay Healthy After Cancer.  For general healthy steps, see 8ight Ways to Stay Healthy and Prevent Disease.