Are all carbs bad for you?

The answer's no, ANDRÉ PICARD writes in the first of a series on the diet craze

By ANDRÉ PICARD

With reports from Avis Favaro, medical reporter at CTV News, and Jenny Wells, a CTV producer.

Tuesday, March 2, 2004 - Page A1

http://www.globeandmail.com/servlet...RBS02/TPHealth/

With three young children, his spouse working full-time, and shift work to juggle, Mark Stewart has a busy life. So there is little hesitation when it's his turn to prepare dinner: He gets the water boiling, cuts the vegetables for the sauce, and has a big batch of spaghetti on the table in no time.

"Pasta is definitely a staple in our family's diet," he says. "It's an easy meal to make; it's healthy, and we enjoy it a lot."

In this anti-carbohydrate era, when it has become gospel that carbs are the express lane to obesity, these are the words of a heretic: doubly so because he shuns red meat and more than half his diet consists of carbs including pasta, whole-wheat breads and fresh fruits and vegetables.

But Mr. Stewart, a Toronto firefighter, has many things that the Atkinsites, the South Beachers, the Zonies and followers of other trendy diets can only long for: a trim, buff body, boundless energy, good blood pressure and rock-bottom cholesterol.

What he has realized is that carbohydrates are not the monolithic evil they are made out to be: There are good carbs and bad carbs.

The good ones are those that break down slowly in the body and provide a steady source of energy. The bad ones give you a quick rush and leave you feeling hungry again not long after.

What he is doing, almost unwittingly, is choosing food based on its glycemic index, a measure of the speed at which food is digested and converted into glucose, the body's source of energy. It is a Canadian theory that has a devoted and growing following in scientific circles, and that is now entering the mainstream as a counterbalance to carbless mania.

GI has also spawned some of the hottest new entries in the diet book wars, with titles including The New Glucose Revolution, by University of Toronto professor Tom Wolever, and The GI Diet, by Rick Gallop, past president of the Heart and Stroke Foundation. What distinguishes GI from its competitors, however, is that it is more a scientific theory than a weight-loss fad.

"It's not a diet; it's a way of thinking of food," said David Jenkins, a world-renowned nutritional scientist and director of the Risk Factor Modification Centre at St. Michael's Hospital in Toronto.

He published the first research on the glycemic index in 1981, but, in his words, "it sank like a stone." Over the years, however, the evidence slowly accumulated as Dr. Jenkins and others published groundbreaking work on how dietary choices influenced rising rates of obesity, diabetes, heart disease and some forms of cancer.

Today, the GI approach is being hailed as the missing piece of the nutritional puzzle, the underlying explanation for why the high-carb, low-fat and carb-free approaches have all failed.

"This is emerging as one of the most promising, if not the most promising nutritional development ever," said Simin Liu, an assistant professor in the department of epidemiology at the Harvard School of Public Health.

The body converts all carbohydrates -- bread and sugar alike -- into sugar molecules that are burned or stored. The faster carbs are broken down by the digestive system, the quicker blood sugar goes up and the higher the GI of a given food. The GI value of pure glucose is set at 100, and every other food is ranked on a scale of 0 to 100 based on the actual effect on blood glucose levels.

Almonds rate a 0, apple juice 30, spaghetti 38, cheese pizza 60, Coca-Cola 63, a white bagel 72, a baked potato 85, and a fruit roll-up 99.

The blast of sugar that comes from high GI foods makes insulin levels go up and stresses the pancreas, our body's insulin factory. Insulin is a hormone that activates cells to absorb sugar in the form of glucose. This, in turn, leads to insulin resistance, a precursor of diabetes and heart disease.

"At least 25 per cent of the population is insulin-resistant, and half are overweight or obese," Dr. Liu said. "This indicates they can't handle the high glycemic load."

In modern times, we have adopted a diet of soft, chewy, processed foods that go down smoothly. We tend to think of these easily digestible foods as good, but in scientific terms, they are not. The body processes them quickly, demanding massive insulin production and leaving us hungry again only hours later.

Over time, this leads not only to unhealthy weight gain but to pancreatic burnout, a key contributor to many chronic diseases.

The glycemic index is the underlying rationale for limiting carbs in popular diets like Atkins, South Beach, the Zone and Sugar Busters, but Dr. Jenkins believes the idea has been perverted.

"To cut out carbs from the diet, that was sad," he said. "But they are revising their statements so that now they are not carbohydrate-exclusion diets but more selective carbohydrate diets."

In fact, most foods on the banned lists of these popular diets are high-GI foods. Low-GI carbs such as peas, beans and lentils are actually encouraged.

While there are now detailed lists of foods based on their glycemic index, Dr. Jenkins doesn't encourage tedious bean-counting. Common sense, he says, is a fairly good guide, and by that he means eating primarily unprocessed, fresh foods, including whole grains, nuts and lots of fruits and vegetables.

"I encourage people to revisit the foods which, over the last 100 years, we've thrown out of our diets: Try some pumpernickel bread, beans, peas, lentils; try a barley stew, or some oat bran muffins."

Jean Dumenil, a Quebec City cardiologist, tried treating patients with a low-GI diet and was amazed by the results.

Within a week, patients' cholesterol and triglycerides dropped sharply, and blood glucose levels remained steady and low. Even though the patients were allowed to eat as much as they wanted, their caloric intake also fell, even compared to an already healthy diet.

"The patients were eating 25 per cent less calories than they were eating on the American Heart Association diet. We were amazed by this," Dr. Dumenil said.

No one is claiming that GI is the magic formula for turning the obesity epidemic around.

But GI is helping us understand why many weight-control methods have failed. It is also proving a key element in understanding how to regulate blood sugar levels and control appetite.

First in a series.

Tomorrow: How breakfast is making today's kids fat.

Thursday: Labelling foods for the glycemic index.

Glycemic facts

A look at what the glycemic index is and the differences between a high and low glycemic meal.

What is the glycemic index?

The glycemic index is the measure of a food's natural or artificial sugar. Carbohydrate sugar, or glucose, is what our bodies use for energy, and our brains use for fuel.

What is the difference between a high and low glycemic meal?

High glycemic meals overwork the pancreas. The pancreas senses blood sugar and sends insulin to pack it away into muscle and fact cells.

If there is a surge or sugar, there is a surge of insulin. And if there is a surge of insulin, there is a suppression of glucagons. That's the hormone responsible for pulling sugar back out of muscles and fact cells to fuel the brain or give the body energy.

Impaired glucagons results in feelings of hunger. Overeating can result. In addition to weight gain, if repeated high glycemic meals are your habit, the repeated spikes of insulin in your bloodstream can create insulin resistance. That's a precursor to diabetes.

Low glycemic meals provide slowly released sugars into the bloodstream. So instead of spikes of insulin, a steady, moderate balance between insulin and glucagons allows for the steady, moderate metabolism of these sugars both into - and out of - their storage cells.

COMPILED BY JENNY WELLS, CTV NEWS