The Down Low on Low-Carb Diets

How to avoid the pitfalls and side effects of a low-carb weight loss plan.

From the WebMD Archives

You've cleaned out those pantry closets, gone food shopping, and made the commitment. It's official: you're on a low-carb diet!

But while the road to a slimmer new you may be paved with high-protein foods, if you're like most low-carbers it's likely you've also encountered a few potholes along the way.

"Any time you make a fundamental change in your diet your body is going to react -- and when it does you are bound to experience certain symptoms or problems," says Stephen Sondike, MD, director of the Nutrition, Exercise, and Weight Management Program (NEW) at Children's Hospital of Wisconsin.

When that change involves reducing carbs, he says, among the most common problems is constipation.

"One of the primary places where you are going to see metabolic changes on any kind of diet is in your gastrointestinal tract -- and that can include a change in bowel habits often experienced as constipation," says Sondike, who is also credited with conducting the first published, randomized clinical trial on low-carb diets. The reason, Sondike tells WebMD, is that most folks get whatever fiber they consume from high-carb foods such as bread and pasta. Cut those foods out, and your fiber intake can drop dramatically, while the risk of constipation rises.

"However, if you really follow a low-carb diet correctly, you will be replacing those starchy foods with low-carb, high-fiber vegetables -- which should help counter the constipation by providing as much, if not more fiber, than you had before," says Sondike.

Doctors say that eating up to five servings of low-carb vegetables daily -- foods such as broccoli, cauliflower, and lettuce -- can keep your bowels healthy without interfering with weight loss.

If it's still not doing the trick, Sondike says a fiber supplement -- such as Metameucil or FiberCon can help.

"The one thing I would not do is start taking laxatives -- adding more fiber to your diet is definitely a smarter and healthier way to deal with the problem," says Doris Pasteur, MD, director of the Nutrition Wellness program at Mt. Sinai Medical Center in New York City.

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A low-carb diet can help you lose weight because it turns on fat-burning processes, known as "dietary ketosis." These ketones are also thought to have an appetite suppressant effect.

However, Pasteur says that when large amounts of ketones are produced, your body can become quickly dehydrated -- another problem faced by those on a low-carb diet.

The solution: Drink more water.

"The lower your carb intake, the greater your risk of dehydration and subsequently the greater your need for water," says Pasteur. Most low-carb diet experts suggest drinking at least 2 quarts of water daily.

In addition to keeping you adequately hydrated -- which can also help alleviate constipation -- drinking lots of water can also help offset still another low-carb diet problem: bad breath. The ketones produced during the diet can lead to what is sometimes described as a fruity odor although it is often described as having an almost "chemical" odor similar to acetone or nail polish remover.

Now if you're thinking you'll just handle the problem by brushing and flossing a little more often, guess again. Since the breath odor is coming from metabolic changes and not necessarily a dental-related condition, traditional breath products are not likely to provide long-lasting relief. On the other hand drinking more water intake can do the trick.

"The water helps dilute the ketones in your system, and while that won't affect weight loss, it will help with the bad breath," says Sondike.

Low Carbs and Supplements

The lower your intake of carbohydrates, the greater your need for a vitamin supplement. That's the mantra that most doctors now recommend that everyone on a low-carb diet should never forget.

The reason? Any time you restrict your diet, particularly in terms of certain food groups, your nutrient levels can drop. But when your diet is low carb, experts say you may be in even greater need for certain key vitamins and minerals, particularly folic acid.

"If you're cutting out cereals, fruits, vegetables, fortified grains, then you are cutting out your major source of folic acid, a B vitamin that is not only important when you are pregnant, but important to everyone's overall health," says NYU nutritionist Samantha Heller.

What's more, says Heller, folic acid is key to controlling levels of homocysteine, an inflammatory factor linked to heart disease. If you're already at risk for cardiovascular problems, she says, dropping folic acid levels too low could put your health at serious risk.

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One way to protect yourself, she says, is to take a B vitamin supplement -- with at least 400 micrograms of folic acid daily.

"All of the B vitamins work together in a very complicated metabolic pathway and they need each other -- so if you are not going to get your source in foods, then a vitamin supplement is a must," says Heller.

Sondike agrees and says that, "Any time you are on a weight-loss diet you need a good multivitamin, regardless of whether you are limiting your carbohydrate intake or not," he says.

Although there has been some evidence that a low-carb diet can also take its toll on calcium levels, Sondike says that fortunately, this is usually only on a short-term basis.

"Your body will often shift metabolism when you do something different to it -- but it equalizes -- you see a rapid shift and a return to normal -- and the longer-term studies show normal results in this area," says Sondike. Still, he tells WebMD it's a "smart idea" to take a calcium supplement beginning at the start of your low-carb diet to safeguard against a possible deficiency. Tofu can also be a good source of calcium.

Another mineral you may want to supplement is potassium. While there is no concrete evidence that a dramatic potassium loss occurs on a low-carb regimen, Sondike says to ensure against problems he recommends patients use Morton's Light Salt -- a potassium chloride product that he says can add back any of this important mineral that's lost. Eating a few almonds is also a good way to supplement this mineral without adding carbs to your diet.

Finally, if you stick to your low-carb diet via the use of prepackaged foods, experts say read the label carefully to avoid ingredients that are notoriously responsible for gastrointestinal upsets, and especially excess gas. Among the worst offenders: sugar alcohol, found in sweeteners such as sorbitol.

"Anything above 10 grams or more of sorbitol at a time has been shown to cause gastrointestinal upset -- and some of these low-carb diet foods have as much as 30 grams a serving," says Heller. While it won't make you violently ill, she says, it can make you -- and those in the same room -- pretty uncomfortable.

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Sondike agrees and also cautions us to "read the labels."

"If a product is advertised as having 3 net carbs but the label says 35 grams of carbs, then it's likely that 32 grams are sugar alcohol -- and it's probably going to upset your stomach," says Sondike.

WebMD Feature

Sources

SOURCES: Stephen Sondike, MD, director, Nutrition, Exercise and Weight Management Program (NEW), Children's Hospital of Wisconsin, Milwaukee. Doris Pasteur, MD, director, Nutrition Wellness Program at Mt. Sinai Medical Center, New York City. Samantha Heller, MS, RD, nutritionist, NYU Medical Center, New York City.

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