Dietary Experts Debate Carbohydrates

Aug 31, 003 -- Should people really care that they digest potatoes faster than carrots?

Macaroni faster than spaghetti? Rice Krispies faster than Special K? A greenish banana faster than a freckled one? A Snickers bar faster than a Twix?

Yes, say some of the country's top-tier nutritional experts. They are convinced that carbohydrates should be labeled good or bad, just the way fats are, and that some of the carbs Americans love most — velvety puddles of mashed potatoes, lighter-than-air white bread — are dietary evil, to be avoided like the nastiest artery-choking trans-fats.

No, contend other equally respected nutritional experts. Potatoes and other starchy standbys are perfectly respectable. A carb is a carb is a carb.

The debate involves an idea called the glycemic index. It is a way of rating how quickly carbohydrates are digested and rush into the bloodstream as sugar. Fast, in this case, is bad. In theory, a blast of sugar makes insulin levels go up, and this, strangely, leaves people quickly feeling hungry again.

The debate over whether every person who puts food in his mouth should know about this is fervid even for the field of dietary wisdom, where fierce opinions based on ironclad beliefs and sparse data are standard.

Despite its detractors, the idea seems to be gaining momentum, in part because it is offered as scientific underpinning by the authors of a variety of popular diet schemes, mostly of the low-carb variety. However, some painstakingly argue that the glycemic index is just as important for the carbohydrate-loving brown rice aficionado as it is for the most carbo-phobic, double-bacon-cheeseburger-hold-the-bun Atkins follower.

To believers, the glycemic index is a kind of nutritional Rosetta stone that explains much of what has gone wrong with the world's health and girth over the past two decades: Why diets so often fail. Why diabetes is becoming epidemic. Why mankind is growing so fat.

We overeat because we are hungry, the theory goes, and we are hungry because of what we have been told to eat, which is too much fast-burning food that plays havoc with metabolism by quickly raising blood sugar levels. All of that starch at the base of the food pyramid has had the unintended effect of making us ravenous.

"It's almost unethical to tell people to eat a low-fat, high-carbohydrate diet with no regard to glycemic index," says Janette Brand-Miller of the University of Sydney, one of the field's pioneers.

The idea has already entered the scientific mainstream in much of the world and is endorsed by the World Health Organization, but it remains deeply controversial in the United States. It is dismissed by some of the country's weightiest private health societies, including the American Heart Association and the American Diabetes Association.

To some of the skeptics, this is just another half-baked mishmash of dietary arm-waving, cobbled together to justify the high-fat, low-carb schemes that dietitians love to hate.

The fact that carbohydrates break down at different rates has been suspected for a long time. It is why diabetics (news - web sites) were once (but no longer) told to studiously avoid sweets, since presumably sugary foods would quickly turn into sugar in the blood stream. About 20 years ago, scientists came up with the glycemic index, or GI, as a way to compare this.

The body converts all carbohydrates — from starches to table sugar — 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 their GI.

The GI of at least 1,000 different foods has been measured, in the process knocking down many common-sense dietary beliefs. For instance, some complex carbohydrates are digested faster than the long demonized simple carbs. Foods such as white bread and some breakfast cereals break down in a flash, while some sweet things, like apples and pears, take their time.

In general, starchy foods like refined grain products and potatoes have a high GI — 50 percent higher than table sugar. Unprocessed grains, peas and beans have a moderate GI. Nonstarchy vegetables and most fruits are low.

While it seems reasonable that chewy, whole-grain bread is digested more slowly than a French baguette, some of the results are less obvious. For instance, overcooking can raise the GI. Ripe fruit is lower than green. A diced potato is lower than mashed, and thick linguini is lower than thin.

To make matters even more confusing, the glycemic index measures only the carbohydrate in food. Some vegetables, such as carrots, have quite high GIs, but they don't contain much carb, so they have little effect on blood sugar.

Therefore, some experts prefer to speak of food's glycemic load, which is its glycemic index multiplied by the amount of carb in a serving. Considered this way, a serving of carrots has a modest glycemic load of 3, compared with 26 for an unadorned baked potato.

Blood sugar levels may shoot twice as high after a high-GI meal as after a low one, and that unleashes metabolic havoc: The body responds with a surge of insulin, which prompts it to quickly store the sugar in muscle and fat cells. The high sugar also inhibits another hormone, glucagon, which ordinarily tells the body to burn its stored fuel.

Blood sugar plunges. So much is stored so fast that within two or three hours, levels may be lower than they were before the meal. Suddenly, the body needs more fuel. But because glucagon is still in short supply, the body does not tap into its fat supply for energy. The inevitable result? Hunger.

That, at least, is the theory. Experiments to prove this are difficult and time-consuming. Among those trying is Dr. David Ludwig of Boston's Children's Hospital, who has done several studies on overweight teenagers.

In one, he tested the idea that a high-GI breakfast makes people hungrier at lunch. A dozen obese boys were fed three different breakfasts, all with the same calories — a low-GI vegetable omelet and fruit, medium-GI steel-cut oats or high-GI instant oatmeal.

At noon, they could eat as much as they wanted. Those who started the day with instant oatmeal wolfed down nearly twice as much as those getting the veggie omelet.

Ludwig says overweight people do not need to starve themselves. On a low-GI diet, they can eat enough to feel satisfied and still lose weight.

In a pilot study, he tested this on 14 overweight adolescents. They were put on two different regimens — a standard low-cal, low-fat, high-carb diet and a low-GI plan that let them eat all they wanted. After one year, the low-GI volunteers had dropped seven pounds of pure fat. The others had put on four. Now he is repeating the study on 100 heavy teenagers.

Even such small experiments have been rare. Most support for the idea comes from big surveys that follow people's health and diets over time. Some of these show that those who consistently favor low-GI fare are less likely to become overweight or to get diabetes and heart disease.

The evidence is strong enough for authors of some popular diet books, who use the glycemic index as one of their primary rationales. "It's a new unifying concept that brings nutritional habits out of the dark ages and says it's all about the numbers," says Barry Sears, author of the Zone series of diet books. "It says diet does not have to be based on philosophy. It can be based on hard science."

Major U.S. health organizations are less impressed. Ludwig expects this to change, in part because paying attention to the glycemic index can help everyone choose healthier carbs, whether they go low-fat or high.

But that seems unlikely any time soon at the heart association. The head of its nutrition committee, Dr. Robert Eckel of the University of Colorado, says the theory that high-GI foods make people hungry is "ridiculous" and argues that a scientific case can be made for just the opposite.

Dietitians generally encourage a balanced, varied diet emphasizing unadulterated whole foods, and they cringe at a classification that puts ordinary baked potatoes and white rice on a taboo list.

"It's an artificial system of classifying foods as good and bad," says JoAnn Carson, a nutritionist at the University of Texas Southwestern Medical Center.

Others worry that the whole business is just too hard to keep straight.

"We are putting before the public an extraordinarily complicated message, which I don't think they will follow or be very happy with," says Dr. Xavier Pi-Sunyer of St. Luke's Roosevelt Hospital Center in New York City.

Not necessarily, responds Harvard's Dr. Walter Willett. "I do think this is an important concept for people to understand, but I don't think they need to worry about specific numbers."

His advice: Go light on the white bread, white rice, potatoes pasta and sugary foods.

EDITOR'S NOTE: Medical Editor Daniel Q. Haney is a special correspondent for The Associated Press.

Meditation Boosts Immune System

University of Wisconsin researchers found that people who did eight weeks of meditation training produced more antibodies to a flu vaccine. They also showed signs of increased activity in brain areas related to positive emotion than people who didn't meditate.

The study, which appears in the current issue of Psychosomatic Medicine, is the first to link meditation to changes in brain activity associated with positive feelings. It's also the first to demonstrate that meditation can affect immune function.

The study included 48 people. Half of them received weekly meditation training and were encouraged to meditate at home for an hour a day, six days a week, with the help of instructive audiotapes. All the people in the study received a flu vaccine.

The researchers recorded electrical activity in the left and front portions of the brains of the study participants. These areas of the brain become more active when a person experiences certain forms of positive emotion and reductions in anxiety.

Brain activity was measured at several points through the study as the subjects rested or wrote about positive and negative emotional experiences from their lives.

The researchers also tracked immune responses among the people in the study by measuring the level of antibodies produced by the flu vaccination.

The study found the people who did the meditation had more electrical activity in the targeted brain areas and also had higher levels of antibodies than those who didn't receive the meditation training.

"Our findings indicate that a short training program in mindful meditation has demonstrable effects on brain and immune function and underscores the need for additional research on the biological consequences of this intervention," researcher Richard J. Davidson says in a news release.

The Collateral Damage of Inflammatory Bowel Disease

That's what a new study from researchers at the Columbus Children's Research Institute (CCRI) and Columbus Children's Hospital found.

They also found gender differences in weight and body image contribute to these eating-behavior problems.

"Proper nutrition is important for all children, including the approximately nine out of every 100,000 kids affected by IBD," Laura Mackner, an assistant professor of pediatrics at Ohio State University School of Medicine and Public Health, says in a prepared statement.

"Once we determined that problematic eating behaviors were more prevalent among children with IBD than healthy children, we went a step further to determine who is more at risk for eating problems among children with IBD," Mackner says.

"Our research showed that for boys with IBD, lower weight was associated with eating behavior problems, but body image was not. For girls, it was just the opposite issue -- poor body image was related, but weight was not."

The study included 50 children with IBD and 32 healthy children between the ages of 11 and 17. The children and their parents completed different questionnaires. Parents were asked to identify how often eating behavior problems occurred. Children rated their body image.

"Problematic eating behaviors have been studied among children with other diseases like cystic fibrosis and juvenile rheumatoid arthritis. Until this study, there were no data related to eating behavior problems and IBD. Learning more about the eating behavior problems is the first step toward interventions aimed at improving these problems," Mackner says.

The study was presented at a recent meeting of the North American Society for Pediatric Gastroenterology, Hepatology and Nutrition.

Hidden Stress Underlies Heart Attacks, Study Shows

ORLANDO, Fla. (Reuters) Nov 11 - Stress you didn't even know you had could kill you, U.S. researchers reported on Tuesday.

They found people whose blood pressure rose during "mental stress" were six times more likely to have a heart attack or other severe heart event within six years than people who handled the stress more calmly.

And it was not stress that people knew they were feeling -- pulse was not affected and their volunteers usually had no idea their blood pressure was spiking, the researchers told a meeting of the American Heart Association in Orlando.

"How do you learn to manage something when you don't know you have it?" asked Diane Becker of Johns Hopkins University in Baltimore, who led the study.

The mental stress reaction trumped everything else. Other risk factors such as smoking, having high cholesterol, diabetes or being a man paled in comparison, the researchers found.

"People with hyper-reactive blood pressure to mental stress were more than six times as likely to have a coronary heart disease event," they said.

They tested 295 siblings who were under 60 but already had some signs of coronary artery disease. They tested this with an angiograph, which measures the thickness of an artery.

Many had not known they had early signs of heart disease.

They gave them a stress test during which they measured pulse and blood pressure, and then watched them for six years.

An "event" was defined as a heart attack, severe chest pain known as angina (news - web sites) or a 50 percent or more blockage of an artery.

Hyper-reactive people were those in the upper 25 percent of reaction, as defined by how much their blood pressure went up. The "hot" responders saw, on average, a 20 point rise in blood pressure during the stress test.

TEST THAT ANNOYS EVERYONE

The test was one that stresses most people, at least consciously, said Becker.

Words such as "red," "green" or "blue" are displayed on a computer screen. The background is in one color, the letters themselves are written in another, often a color not matching the word, and sometimes other distracting colors are thrown on the screen.

The colors and words change. "You are told to identify the color in the written word," Becker said. "It is very confusing. If you don't get it correct, it sends you a message that says 'wrong'," she added.

"The more you get right, the faster it goes, so you can never master it."

Becker said she could hear volunteers swearing at the screen as they took the test. Their pulse and blood pressure was monitored continuously.

Afterward, the volunteers rated how much stress they felt.

"There was no relationship between people's perception of stress and their actual mental stress," Becker said.

She believes the effect has to do with the sympathetic nervous system, which controls blood pressure and other nonconscious bodily functions. A hormone called catecholamine, which is related to adrenaline, may be the direct cause although she says more study is needed.

Becker hopes to identify the gene or genes responsible. Perhaps a blood test could be developed to warn those most at risk.

And while some studies have strongly linked hostility with heart disease, others have had mixed results.

Becker believes conscious stress and biological stress may be two different things.

"People's capacity to tell you that they are stressed is worth about nothing," she said. "We would see people with hideous responses who say they are fine."

Negative Emotions May Mean Trouble for Heart

NEW YORK (Reuters Health) Oct 24 - Adding to evidence that depression, anxiety and hostility can be hard on the heart, new research links negative emotions to a higher risk of coronary heart disease in men.

Among nearly 500 older men followed for three years, higher scores on a standard measure of negative emotions were tied to a higher risk of developing heart disease. The test gauged psychological factors like depressed mood, anxiousness, pessimism and distorted thought processes such as concentration problems.

For each one-point increase in these scores, heart disease risk climbed 6 percent, according to findings published in the American Journal of Cardiology.

Most importantly, the study's lead author said, men who harbored such emotions faced greater heart risks even when other key factors, like abdominal obesity, high blood pressure and insulin resistance, were taken into account.

This gives further evidence that negative emotions themselves have important effects on heart health, according to Dr. John F. Todaro, of Brown Medical School in Providence, Rhode Island.

He told Reuters Health there are several possible explanations for the connection. One has to do with heart rate variability, the normal fluctuations in a person's heart rate. People who are depressed or who have hostile personalities may have decreased heart rate variability, which puts stress on the system.

"The heart is working overtime," Todaro explained.

Another possibility has to do with inflammation in the cardiovascular system. Recent research suggests that depressed or hostile individuals have higher levels of inflammatory proteins and other "markers" in the blood, according to Todaro. It's widely believed that such continuous, system-wide inflammation plays an important role in coronary artery disease.

Todaro also pointed to a non-biological explanation: People with chronically negative feelings may be less likely to stick with medical advice or regimens that could prevent heart complications.

Another major question that remains unanswered is whether addressing emotional issues might prevent some cases of heart disease.

"If you treat negative emotions, what are the outcomes?" Todaro wondered.

Research into this area, he noted, has not yet been fruitful, but it is also in the very early stages.

SOURCE: American Journal of Cardiology, October 15, 2003.

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