Reduced Glycemic Load Boosts Colon Cancer Survival

New research from Boston’s Dana-Farber Cancer Institute and Duke University Medical Center have determined that a diet with lower glycemic load foods – foods with a lower glycemic index – reduce the risk of recurring colon cancer.

Diet and cancer survival studied

The research analyzed the diets and cancer progression of 1,011 patients with stage 3 colon cancer for six months. The researchers reviewed their diets’ glycemic load, glycemic index, fructose content and carbohydrate content. They cross-referenced these parameters with the patients’ recurrence of cancer or lack thereof, and their survival rates. Colon cancer stage 3 patients have an average five-year survival expectancy in the 60% range.

The researchers discovered that those whose diets had the greatest levels of high glycemic foods had a 79% increased incidence of their colon cancers recurring, compared to those whose diets had the lowest (quartile) amounts of high glycemic foods. This link was seen greatest among those patients who were overweight or obese.

This confirms previous research that has associated higher insulin levels with higher incidence of colon cancer. Those with type-2 diabetes or high plasma C-peptide levels – indicating higher insulin production – have also been found to have lower colon cancer survival rates.

This research is also consistent with other studies that have found that Western diets – diets with increased levels of fried and sugary foods, and animal proteins – are also linked to increased risk of colon cancer, and greater risk of colon cancer recurrence.

Western diet worse for cancer

One of these studies – by some of the same researchers – also followed about 1,000 colon cancer patients. This study found that those patients whose diets were more Western diet oriented were over three times more likely to have colon cancer recurrence than those with the lowest levels of Western diet. Meanwhile, the highest Western diet eaters had almost a three times greater risk of dying compared to those who ate the least amount of Western dietary foods.

While many have showed surprise with this relationship, there is significant research linking colon cancer incidence with increased red meat and Western diets in general. In an extensive review of research from the Portuguese Oncology Institute, it was found that diets with high levels of red meat and processed meat had a 29% increased incidence of colon cancer when the results of sixteen case-control and cohort studies were averaged.

While this relationship between red and processed meat and colon cancer is widely accepted now – even by the American Cancer Society – the relationship between higher glycemic foods and colon cancer survival is relatively new. The mechanism is not well understood.

High glycemic foods are foods that increase the blood sugar levels higher and faster. This is measured by two general calculations – glycemic load and glycemic index. The glycemic load is the amount blood sugar increases after a meal. A range of 10-20 is considered moderate, while over 20 is considered high and under 10 is considered low.

Some fruits have low glycemic load

Low glycemic load foods will typically include high fiber foods such as whole grains, brown rice, apples, lettuce and so on. Foods with a high glycemic load will include sugary snacks and sodas. High sugar, low fiber foods usually have a high glycemic load. Glycemic load does not necessarily relate to sweetness. For example, many of the sweetest fruits have very low glycemic loads. Watermelon, one of the sweetest fruits, for example, has a glycemic load of 4.

Some have suggested that greater insulin levels may increase colon cell activity, thereby increasing the risk of recurrence.

However, the fact that most foods with lower glycemic loads also happen to have more fiber, higher antioxidant levels and/or greater levels of phytonutrients is not coincidental. Each of these elements have been independently found to decrease the risk of various cancers.

REFERENCES:

Meyerhardt JA, Sato K, Niedzwiecki D, Ye C, Saltz LB, Mayer RJ, Mowat RB, Whittom R, Hantel A, Benson A, Wigler DS, Venook A, Fuchs CS. Dietary Glycemic Load and Cancer Recurrence and Survival in Patients with Stage III Colon Cancer: Findings From CALGB 89803. J Natl Cancer Inst. 2012 Nov 7.

Meyerhardt JA, Niedzwiecki D, Hollis D, Saltz LB, Hu FB, Mayer RJ, Nelson H, Whittom R, Hantel A, Thomas J, Fuchs CS. Association of dietary patterns with cancer recurrence and survival in patients with stage III colon cancer. JAMA. 2007 Aug 15;298(7):754-64.