In the first study of its kind, a University of Sydney review has found conclusive evidence that foods with a high-glycemic index, which are those that quickly convert carbohydrates into glucose in the blood, heighten the risk of developing common diseases by interfering with the body's normal functions.
In contrast, low-GI foods (such as grainy food) made people feel full and broke down slowly during digestion, avoiding any sudden spikes in blood sugar levels.
The results, published in the American Journal of Clinical Nutrition, found that high blood glucose levels led to an increased risk of type 2 diabetes and heart disease and was also linked to some types of cancer and gall stones.
Researcher and dietitian Alan Barclay said that because GI ranked carbohydrates according to their effect on blood glucose levels, he was not surprised to a find a link between a high-GI diet and diabetes. However, he was surprised by the strong relationship between high GI and other diseases.
"If you have constantly high blood glucose and insulin levels due to a high-GI diet, you may literally wear out your pancreas over time," he said. "Eventually it may lead to type 2 diabetes in older age.
"But there's good evidence from studies that high-GI diets are linked to cancer as well because constant spikes in blood glucose that cause the body to release more insulin also increase a related substance called insulin-like growth factor one, or IGF-1.
"Both these hormones increase cell growth and decrease cell death, and have been shown to increase the risk of developing cancer."
Barclay said other research suggested that a high-GI diet tended to reduce HDL or "good" cholesterol, while raising triglycerides which were bad for cardiovascular health. People with low HDL and high triglycerides were more prone to gall stones. "Grandma was right -- you are what you eat," he said.
There is good evidence from studies that high-GI diets are linked to cancer as well.
From the March 17, 2008, Prepared Foods e-Flash