Are Carbs the Enemy?
The debate over eating and diabetes
Learn More About Carbs
When it comes to diabetes, there may be no topic more fraught with controversy than carbohydrates. Sure, everyone agrees that the body uses carbs for energy in the form of glucose. But how much carbohydrate should people with diabetes really eat?
That question has divided researchers, doctors, dietitians—and people with diabetes themselves. Some insulin users in particular find that their blood glucose is far easier to control when they limit the carbs in their diet. Others think people with diabetes deserve to eat (and enjoy) the same healthy diet recommended for all Americans. All are deeply passionate on the subject. And, in a sense, they may all be right.
Today, most people with diabetes are encouraged to eat a balanced diet of lean meats and dairy, whole grains, healthy fats, and fruits and vegetables. This concept is backed by the American Diabetes Association (ADA) as well as the American Heart Association and American Dietetic Association, and it incorporates recommendations from agencies like the Department of Agriculture and the Department of Health and Human Services. While the ADA does not specify exact grams or percentages of calories from carbohydrate, the approach is generally moderate in carbs. According to Marion J. Franz, MS, RD, CDE, a registered dietitian and nutrition/health consultant in Minneapolis, studies have shown that people with diabetes generally get about 40 to 45 percent of their calories from carbs.
The moderate-carb approach stresses that grains should come in the form of whole grains instead of refined grains (like white flour), which have been stripped of important vitamins and minerals. Research has shown that eating a moderate-carb, high-fiber diet (like one that includes whole grains) may improve post-meal glucose levels and lower the risk for cardiovascular disease.
What's more, foods that contain carbohydrate also tend to contain a lot of other healthy things. Consider the four major categories of foods that have carbs: fruits, vegetables, grains, and dairy. Many of the individual foods in those categories are nutrition powerhouses. Legumes like lentils and black beans are chock-full of soluble fiber, which helps lower cholesterol levels. Veggies and fruits are a great low-calorie source of vitamins and minerals. Low-fat dairy products provide calcium and, in many cases, vitamin D.
Not only that, but carbs are an efficient source of energy. "Like gasoline powers a car, glucose powers your body," says Neal Barnard, MD, adjunct associate professor of medicine at the George Washington University School of Medicine and author of Dr. Neal Barnard's Program for Reversing Diabetes. "The idea that carbohydrate is a problem is, in my opinion, a mistaken one."
According to Franz, as long as people eat less or cover their carb intake with medications, they can keep blood glucose levels in check with a healthy diet. "What determines the blood glucose level," she says, is "certainly the amount of carbs you eat, but it's the balance between carbs and insulin."
What's more, she points out, the moderate diet is all about freedom. "If someone told me you have diabetes but you can't eat carbs, I'd be floored," says Franz. "I would cry out in alarm and say, 'But I deserve the right to eat healthfully, and I can keep my blood glucose in control by watching my portion sizes and, if necessary, taking medication.' "
Indeed, a lot of those newly diagnosed with diabetes are happy to find out that they can still have most of their favorite foods, in moderation—as long as they lower their blood glucose with medication and exercise. (People who control their diabetes without medication or who take oral drugs will need to watch how carbs affect their glucose levels and then work with their doctor to determine the right number of carbs and amount of medication needed to stay in good glucose control.) Gone are the days of "diabetic diets" that were meager and confining. Today, the idea is that people with diabetes can eat everything recommended to those without the disease. "If we look at what's important for all of us," says Franz, "it's important to eat healthy foods in the right portion sizes."
The Low-Carb Approach
When Richard Bernstein, MD, FACE, FACN, started eating a low-carbohydrate diet 40 years ago, he had heart disease and kidney disease, complications of uncontrolled type 1 diabetes. Bernstein says he cut the majority of carbs from his diet, and eventually his complications retreated.
Today, it wouldn't be an overstatement to say that Bernstein, author of Dr. Bernstein's Diabetes Solution: The Complete Guide to Achieving Normal Blood Sugars, has become low-carb's greatest cheerleader. Bernstein and others who back the low-carb diet say the best way to keep blood glucose levels low is to avoid raising them in the first place. As the body's fastest, easiest source of glucose, carbohydrates are the obvious target.
What's more, says Bernstein, counting carbs is an inexact science, even when food has a nutrition label. For restaurant meals and other unlabeled foods, he says, dosing insulin to match carbohydrates is a matter of even greater guesswork.
Instead, Bernstein advocates a higher-protein, higher-fat diet, and counsels patients in his medical practice on how to make it work. Their daily totals amount to about 20 to 30 grams of carbohydrate—usually less than 10 percent of the day's calories. (Some people who follow a lower-carb diet are less stringent, allowing 20 to 40 percent of their calories to come from carbs.)
"[In] the history of humanity, high-carbohydrate is new," Bernstein says. "It's an experiment that started in the 20th century." Replacing carbs with protein and fat is a smart alternative, says William Yancy, Jr., MD, MHS, a researcher at the Center for Health Services Research in Primary Care at Durham (N.C.) VA Medical Center and associate professor of medicine at Duke University Medical Center. "They all produce energy for the body. The body was designed this way. Just in case you didn't have one, you could use the other."
To match their carbohydrate intake, low-carb dieters cut their insulin doses. "The risk for hypoglycemia is brought about by a high-carbohydrate diet," says Bernstein. "You take industrial doses of insulin [to cover a large amount of carbs], you're certainly going to get hypoglycemia."
Critics say that the low-carb diet is hard to stick to over time. Any drop in A1C levels (average blood glucose over two to three months), they say, is a direct result of losing weight. But low-carb proponents counter that, even without weight loss, the low-carb diet can keep blood glucose levels in line. "Data would indicate that people with [type 2] diabetes, if the goal was glucose control, would be best off with a low-carb diet," says Mary Gannon, PhD, director of the Metabolic Research Laboratory at the Minneapolis VA Health Care System and associate professor in the Department of Medicine at the University of Minnesota.
In a 2004 study published in the journal Diabetes, Gannon found that men with type 2 diabetes had lower blood glucose levels after five weeks on a lower-carb diet (20 percent of calories from carbs) than they did on a higher-carb diet (55 percent of calories from carbs). A 2005 study by Yancy, published in the journal Nutrition & Metabolism, showed that when they ate fewer than 20 grams of carbohydrates per day, overweight people with type 2 diabetes improved their A1C enough that they were able to stop or decrease their diabetes medications. Another study, published in the Annals of Internal Medicine, found that eating fewer than 30 grams of carbs per day for a year improved A1C, lowered triglycerides, and raised HDL ("good") cholesterol more than a conventional diet. In all three studies, researchers saw improvements independent of weight loss.
The Fat Question
Both sides mostly agree that a low-carb approach will end up being high in fat, including saturated fat. What they don't agree on is whether that's a bad thing. According to low-carb proponents, the idea that saturated fat causes cardiovascular disease is misguided. "There's some misunderstanding about saturated fats," says Frank Nuttall, MD, PhD, chief of the Endocrinology, Metabolism & Nutrition Section at the Minneapolis VA Health Care System and professor of medicine at the University of Minnesota. "We really don't have good evidence that saturated fat causes coronary heart disease. It can raise cholesterol levels, but whether that's sufficient to raise the risk for coronary heart disease is not conclusive."
Yancy points to the long-term Nurses Health Study, which didn't find a link between saturated-fat consumption and heart disease. "Fat is something that we've demonized for 30 years now," he says. "People have realized the unsaturated fats are healthy. The new observational studies don't show saturated fat is bad."
Barnard, for one, disagrees. "I would never prescribe a low-carb diet for people with diabetes because they raise their risk for coronary artery disease," he says. And according to Alice Lichtenstein, a professor of nutrition at the Friedman School of Tufts University and director and senior scientist at the Cardiovascular Nutrition Laboratory in the school's Jean Mayer USDA Human Nutrition Research Center on Aging, people who eat more saturated fat have higher cholesterol levels and an increased risk for cardiovascular disease.
An important fact to consider, says Lichtenstein, an expert in fats, is a study's length. "When you're evaluating one diet over another," she says, "you've got to look at the period of time when they're losing weight as well as when their weight stabilizes." That is, while people may lower their cholesterol on a high-fat diet while losing weight, the same is not necessarily true when their weight stabilizes (which usually happens).
There may be another reason aside from concerns about heart disease to avoid fats: "When people don't eat carbohydrates, they eat fat, and they eat saturated fat," says Franz. "People have to eat something. . . . Eating a higher-saturated-fat diet contributes to insulin resistance." According to Barnard, fat buildup in the muscle cells correlates with insulin resistance. On the flip side, he says, eating a low-fat diet clears the buildup and improves insulin sensitivity.
The Right Way?
Part of the reason for the great carb divide is that science hasn't settled the debate. In addition to the research that demonstrates the success of a low-carb diet, there are also plenty of studies that show benefits of high-carb diets. Barnard's 2006 article in Diabetes Care, for instance, found improved cholesterol and decreased A1C in people on a vegan diet (consisting of no animal food or products, including dairy) that was a whopping 75 percent carbohydrate. Barnard supports a vegan diet because it beat out both low-carb and moderate diets when it came to heart health and glycemic control.
Another article from Diabetes Care, this one published in 2009, didn't find any difference between moderate-carb diets (45 percent of calories from carbs) and higher-carb diets (60 percent of calories from carbs) when it came to glucose control and cholesterol levels in people with type 2 diabetes.
But the real problem is that there's little long-term research on the subject. Plus, there are few studies on low-carb dieting for people with type 1 diabetes, who need insulin regardless of what diet they follow. "The physiology of the whole thing is very complex and not completely understood," says Franz. "How do you look at it long term?" Part of the problem is cost: Long-term studies are expensive to conduct. And it's difficult to consistently measure a large group of people's food intake over years or decades.
People with diabetes looking for a one-size-fits-all "right" way to eat are going to come up short. There probably is no one way to eat that works for everyone. For some, all but nixing carbs is the ideal way to normalize blood glucose levels. For others, eating a higher-carb diet and covering the carbs with insulin or oral medications wins. This is all part of the reason that the American Diabetes Association stresses that meal plans should be geared to fit each person's individual lifestyle.
So what should you do if you have diabetes and you're trying to eat healthfully? First of all, keep in mind that what works for someone else may not necessarily work for you—and vice versa. You may need to experiment a bit to see how different methods affect your blood glucose levels. Consider making an appointment with a registered dietitian, who can review your individual needs and circumstances and help you tailor a nutrition plan that's right for you. In the end, the best diet is the healthy one you're able to follow.