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Low Carb, High Carb, Bad Carb: How Much is Best?

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Sept. 7, 2018 -- Carbohydrate confusion is rampant, and the latest research isn’t helping to clear it up.

Carbs have been vilified as the culprit behind weight gain in several trendy diets like Keto and Whole 30. But the headlines about one recent study were enough to unnerve even the most dedicated low-carb fan: '' ‘Low-Carb’ Diet May Up Odds for an Early Death'' was one of the scarier ones.

But another recent study by Harvard researchers found a higher chance of premature death in both low-carb eaters and high-carb eaters.

These conflicting findings point to a larger problem with carb research, experts say. Carbohydrate studies are plentiful, but agreement about the best way to eat carbs -- and how much of them we need on a daily basis -- is rare.

"The confusion is major at this stage," says Connie Diekman, director of university nutrition at Washington University in St. Louis and former president of the Academy of Nutrition and Dietetics. "People don't know what carbs are, how much they need."

So, what should you do about carbs -- go low, high, or stay in the middle? What's healthy and what’s moderate carbohydrate intake anyway? And which amount of carbs will help you lose weight and live longer? Or is that an impossible dream?

Low-Carb Diets

The newest study, presented at a meeting of European cardiologists in August, looked at a U.S. sample of nearly 25,000 people. It found that the low-carb eaters had a 32% higher chance of dying from any cause during a follow-up of over 6 years. The risk of death from heart disease, when looked at separately, was 51% higher, stroke, 50%, and cancer, 35%. They evaluated other studies to confirm their findings.

But experts not involved in the research took some issues with the study. It offered no clear-cut definition of low-carb; nor did the researchers have information about why people ate low-carb diets.

"You don't know if it's a select group of individuals who chose to go on a low-carb diet for health reasons," for instance, says Alice Lichtenstein, Gershoff professor of nutrition science and policy at Tufts University's Jean Mayer USDA Human Nutrition Research Center on Aging.

Another new study on carbohydrates from Harvard found that middle-of-the-roaders who kept their carbohydrate intake to 50% or 55% of total calories were the likeliest to live the longest. Those researchers evaluated dietary records completed by more than 15,000 U.S. adults, ages 45 to 64, between 1987 and 1989. During the 25-year follow-up, they found that the moderate carb eaters, staying at 50% to 55%, were less likely to die than both the low-carb eaters (in this study, less than 40%) and the high-carb eaters (in this study, more than 70%).

The researchers then combined their results with the results of seven other studies, including more than 432,000 people. They got the same results, finding moderate-carb eaters likely to live longer than low-carb or high-carb eaters.

In addition, they found that low-carb diets with protein and fat from animals, such as from beef, pork, and chicken, were linked with a higher risk of death than those that favored plant-derived protein and fat, such as from vegetables, nuts, peanut butter, and whole grains.

Previous studies have produced conflicting findings. Some have found that low-carb diets promote weight loss and can help heart health. But other studies have found that low-carb eating could boost the risk of heart disease, cancer, and earlier death.

Carbs Defined

While researchers continue to sort out exactly how many of our daily calories should come from carbs, experts say most of us could use a bit more information on carbohydrates, starting with: What exactly is a carb?

Some carbs occur naturally -- such as those in fruits, vegetables, milk, nuts, grains, seeds, and legumes. Other carbs are added to processed foods in the form of starch or extra sugars.

Sugar, the simplest carbohydrate form, is in fruits, vegetables, milk, and milk products. Starch is a complex carb found in grains, vegetables, and cooked dry beans and peas. Fiber, also a complex carbohydrate, is in fruits, vegetables, whole grains, and dry cooked beans and peas.

Our bodies convert carbohydrates into sugar or glucose as foods are digested. Glucose is a main source of fuel for our body, including the brain.

While carbs often get blamed for weight gain, they aren't all bad. Besides providing energy, carb-containing foods such as whole grains and dietary fiber can lower the chance of heart and blood vessel disease, according to experts at the Mayo Clinic. Fiber may also lower the risk of obesity and type 2 diabetes and help your digestion. Eating healthy carbs from fruits, vegetables, and whole grains is also linked with weight control.

"Carbohydrates are your body's energy [source], but what is important is which ones you choose and the quantity. That word moderation, which we all hate to hear, is important," says Diekman.

Defining Low, Moderate, High

Further confusing the issue is the definition of a low-carb diet. But most people term diets that allow 25% to 30% of calories from carbs as low-carb, says Stephen Phinney, MD, PhD, chief medical officer at Virta Health, which offers a very low-carb treatment to reverse diabetes.

So if you eat 2,000 calories a day, a diet of 25% carbs would mean eating 500 calories from carbs, or about 125 grams. The keto diet, as it's known, is even lower, with ketosis (the state at which your body is fueled mainly by fat and ketones) occurring when you eat 50 grams of carbohydrates a day or less.

Moderate, in general, is 45% to 65% of total calories from carbs.

And high is often defined as more than 70% of total calories from carbs.

The 'Party Line' On Carbs

The Dietary Guidelines for Americans recommends eating a moderate amount of carbs -- about 45% to 65% of your total daily calories. If you eat 2,000 calories a day, your carbs on this moderate plan should total about 900 to 1,300 calories, or about 225 to 325 grams a day. (A slice of whole wheat bread has 12 grams or more of carbs; a single 6-inch pancake, 30.)

Depending on which expert or which study you refer to, opinions differ about the benefits of low-carb versus higher-carb diets, and why moderation is the best course.

A low-carb diet can definitely benefit children with seizures, says Phinney, who’s a professor emeritus of medicine at the University of California, Davis. It can also help reverse type 2 diabetes. "This is dangerous to do on your own without expert medical supervision," he says, especially if people are being weaned from their diabetes medications.

Eating a small amount of carbs doubles the body's ability to burn fat during high-intensity exercise, Phinney says. Very lean and high-performing athletes, such as runners in 50- and 100-mile events, can run totally on body fat stores if they eat a very low-carb diet, improving performance, he says.

Phinney says he is not aware that the low-carb trend has gained traction among elite athletes who run shorter distances, such as the 26.2-mile marathon or the 13.1-mile half-marathon. But he has heard from many recreational runners who compete at these distances and shorter ones who follow the keto diet and find it improves their times. And he suspects the very low-carb diet may also be catching on with elite athletes besides runners.   

What about very low-carb eating for your average healthy person without seizure issues or diabetes? "I wouldn't advocate it for someone who doesn't have a tangible benefit," Phinney says.

If losing body fat is your aim, cutting dietary fat lowers body fat more than restricting carbs, according to a National Institutes of Health study. Kevin Hall, PhD, an NIH senior investigator and lead author, studied 19 men and women who were obese but free of diabetes. Before trying each of two diet types, they ate a diet of 50% of total calories from carbs, 35% from fat, and 15% from protein. Then they reduced total calories by 30% -- while on the low-carb plan they reduced carbs by 60%; while on the low-fat diet they reduced fat by 85%.

The reduced-fat diet was better than the reduced-carb diet at increasing fat burning, which led to body fat lossExperts agree that some carbs are better than others. Choose the least refined carbs -- think whole grains, brown rice -- says Lichtenstein.

Aim for the moderate range and don’t focus only on carbs. "You have to think about the whole diet,'' she says. The fat you eat should be healthy, such as from liquid vegetable oils. Protein should be lean. Within each category, choose the healthiest option, Lichtenstein says.

Follow these tips from Lichtenstein and Diekman to boost your diet's content of ''better'' carbs, fats, and protein:

  • Choose less-refined carbs -- whole wheat pasta over regular, whole grain hamburger buns over non-whole grain, Lichtenstein says. Grain foods such as pasta, whole grain cereals and breads, quinoa, lentils, and beans are also good fiber sources, Diekman says. Plus, they provide a good base for eating more vegetables.
  • Aim to get most of your carbs from fruits, vegetables, and grain foods, Diekman says, with the rest from dairy foods such as milk and yogurt.
  • For fats, choose liquid vegetable oils, nuts, and seeds, Lichtenstein says.
  • For protein, go for lean meats, nonfat dairy, and plant-based protein, Lichtenstein suggests.

Deciding how many of your daily calories should come from carbs isn't an easy decision, but one thing is sure: Although more research about the optimal balance of carbs is on the horizon, it may help you with your decision, or it could complicate it even more.

WebMD Article Reviewed by Brunilda Nazario, MD on September 07, 2018
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