Eating white bread and sugary breakfast cereals can increase the risk of diabetes, heart disease and even cancer, new Australian research suggests.
A world-first study by Sydney scientists has found conclusive evidence that a high GI diet, generally rich in food that is burnt by the body quickly, leads to a higher risk of common lifestyle diseases.
The Glycaemic Index (GI) is a measure of how different foods affect your blood glucose levels, with those that are "low GI" released more slowly and deemed better for health.
A team of nutrition experts at the University of Sydney evaluated 37 diet studies involving nearly two million people worldwide to analyse the effect of eating high GI foods, which are usually highly processed.
The study, published in the American Journal of Clinical Nutrition, found a link between a high GI diet and a high risk of type 2 diabetes and heart disease.
The diet was also linked to gall stones and some types of cancer.
"The key message from this study," says lead author Alan Barclay, "is that the GI of your diet is a powerful predictor of disease risk.
"Grandma was right, you are what you eat."
He said the link with diabetes was "not surprising" because eating high GI foods inflates your blood glucose and insulin levels.
"You may literally 'wear out' your pancreas over time and eventually it may lead to type 2 diabetes in older age," Mr Barclay said.
The researchers were more surprised by the "strong relationship" between GI and cancer.
High GI foods cause constant spikes in blood glucose which increase insulin and a related substance called 'insulin-like growth factor one', both of which have been shown to increase the risk of developing cancer.
"Other research shows that a high GI diet tends to reduce 'good' HDL cholesterol levels and raise triglycerides levels; bad news for cardiovascular diseases," he said.
"And people with low HDL cholesterol and high triglyceride levels are more prone to gall stones."
The researchers said their findings support eating a low GI diet to maintain healthy weight and help avoid disease.
Caryl Nowson, a professor of nutrition and ageing at Deakin University in Melbourne, said because high GI foods were typically high in fat and sugar and low in fibre, they were also ready known to be linked with disease.
"This review is just a new way of breaking down dietary information we already have," Prof Nowson said.
She said while the benefits of eating according to GI rating had been proven, it was just one of many ways to structure a healthy diet.
"If you focus on having a classically balanced diet high in fibre and low in sugar, fat and refined foods you'll find you're eating relatively low GI anyway," Prof Nowson said.
©AAP 2008
