Don't bother forcing whole wheat pasta down your throat; white pasta is just as good for you, says Jennie Brand-Miller, one of the world's foremost authorities on the glycemic index.
White bread is, indeed, as wicked as everyone thinks it is -- but so are a lot of whole-grain breads and brown rice, said Brand-Miller, in Vancouver recently to promote the fourth edition of her book, The Low GI Handbook: Guide to the Long-term Health Benefits of Low GI Eating, and for meetings with a research client looking to market an edible-fibre product.
The glycemic index is a tool for measuring the impact of food carbohydrates on blood sugar.
Foods with a high-glycemic-index rating (70 and above) are digested quickly and cause blood-sugar levels to soar and ultimately crash, while low-glycemic-index (GI) foods (55 and below) are digested more slowly and produce small blood sugar fluctuations.
Eating low-GI foods has many health benefits including greater satiation -- good news for people looking to lose weight.
But knowing which foods have a low-GI rating is not always easy.
"A common misconception is that low-GI foods are always high in fibre, that they are the 'brown' version of foods, as in brown pasta or brown rice," said Brand-Miller, a University of Sydney human-nutrition professor who has specialized in GI and carbohydrate research for almost 30 years.
"Fibre content is not a guide to the glycemic index of a food," she said. "There are a lot of whole-grain breads that have a high GI. The simple reason is they've been cooked and processed, the particles are small, the starch is fully hydrated during processing and [digestive] enzymes can attack quite quickly. The only way you tell the GI of a food is to actually test it."
Brand-Miller's lab conducts rigorous tests to determine the glycemic rating of individual foods.
"There is nothing crude about the GI. It's probably the most precise measure we have in nutrition," she said.
"Most potatoes are high GI, most white rices, most breads whether brown or white will be high GI but, on the other hand, I can say most pasta will be low GI, as will most legumes such as lentils and chick peas. Even canned lentils and canned chick peas are still low GI," she said.
Strangely enough, Uncle Ben's brown rice has a low GI.
"They make a lot of their rices in a sachet. Two-minute rices. They've had to do a whole lot of research to come up with varieties of rice that don't go all soggy and sticky,' Brand-Miller said. "They've actually chosen varieties where the starch stays quite hard."
Be suspicious of anything that melts in your mouth.
"If you want a really quick, on-the-spot guide to the glycemic index, just hold the food in your mouth and see if it disappears quickly," she said.
"Compare a piece of white bread and white pasta. If you eat white bread, half the carbohydrates will be digested or dissolved before you swallow it, but the shape of that pasta will still be evident in your mouth after two minutes. It's not the pasta itself that makes you fat."
As for whole wheat pasta, it has a glycemic index of 40 compared to white pasta's 45.
"It's not really worth the trouble," Brand-Miller said.
Meanwhile, white bread has a glycemic index of 70, while some puffed, salty, low-fat snack foods come in at an astronomical 90.
"You may as well be eating pure glucose," she said.
"Blood-sugar levels or, more correctly, our blood-glucose levels, are linked to just about every disease process," she said.
"Whether it's diabetes or cardiovascular disease or cancer, or weight gain with time, blood glucose has something critical to do with it."
Brand-Miller said solid evidence shows a low-glycemic-index diet helps prevent Type 2 diabetes. It also appears to protect against cardiovascular disease.
"In North America, your lifetime risk of getting diabetes is one in three. A low-glycemic-index diet can reduce that risk by about 50 per cent -- or from 33-in-100 people, to 16."
As for heart disease, "the wrong sort of carbohydrate calories [such as those found in bread] are producing just as much harm as saturated fat calories," she said.
"We actually haven't moved forward in terms of dietary management of heart disease in the last 25 years," Brand-Miller said.
"People are still dying of heart disease which is related closely to what they eat. We might be helping people to survive a heart attack, but we're not actually reducing the rate of heart attack.
"The problem is these [refined] carbohydrate calories that have replaced saturated fat have been shown over and over again to have increased cardiovascular disease because, when your glucose levels get very high, you create oxidative stress and that is what causes inflammation -- and inflammation of the lining of the blood vessels is what creates the thickening of the blood vessels. That means blood vessels are less responsive and the heart has to work harder."
Australia has a not-for-profit glycemic-index symbol program run by the diabetes organization in that country. Foods with a low GI rating are permitted to make that claim and use the low GI symbol.
"I would really like to see that symbol become international," Brand-Miller said. "Juvenile diabetes organizations around the world could adopt it."
In general, most modern, starchy foods have a high-glycemic rating, while most fruit and vegetables, with the exception of potatoes, have a low rating. But it isn't as simple as that. Foods with more fat tend to have lower GI ratings, as do foods that contain acids.