Eating white bread and sugary breakfast
cereals can increase the risk of diabetes, heart disease
and even cancer, 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 burned by the body quickly, leads to
a higher risk of common 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 gallstones 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.
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 [high-density lipoprotein] 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 gallstones."
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 already known to be linked with
disease.
"This review is just a new way of breaking down
dietary information we already have," Professor
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,"
Professor Nowson said. | 
