How Low is Low Carb?

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Many agree: People with diabetes should eat a low-carb diet. Last week we looked at what “carbs” are. But what is meant by “low?” How much carbohydrate should you eat?

The Dietary Guidelines for Americans, 2010, (PDF) recommend that healthy people get 50–65% of their calories from carbohydrates. A study posted on the American Diabetes Association (ADA) Web site agrees. For a woman eating a below-average 2,000 calories a day, 50–65% would be 250–325 grams of carb a day.

The Dietary Guidelines call for “a balanced diet that includes six one-ounce (28.3 g) servings of grain foods each day.” This would mean 170 grams of carbohydrate from grains alone each day. And the average American diet includes many other carb sources.

Most men eat closer to 3,000 calories a day, so their numbers would be higher. Sixty percent of 3,000 would be 1,800 calories, equivalent to 450 grams of carbohydrate each day.

Anything less than the recommended range is sometimes considered “low-carb.” Most popular low-carb diets, like Atkins, South Beach, Zone, and Protein Power, are much lower, from 45% of calories down to 5%.

Many diabetes experts recommend somewhat lower carb intakes than ADA does. On our site, dietitian Jacquie Craig wrote, “Most people need between 30–75 grams of carbohydrate per meal and 15–30 grams for snacks.” So that sounds like between 120 and 300 grams a day.

Dr. Richard Bernstein, an MD with Type 1 diabetes and a long-time advocate of the low-carb approach to diabetes, suggests much lower intakes. He says eat 6 grams of carbs at breakfast, and snacks, 12 grams each at lunch and dinner. So that would be about 40 grams of carbs per day.

If 12 grams per meal sounds like a small amount, it is. It’s about the amount in an average slice of bread. And it provides only 48 calories — carbohydrates contain 4 calories per gram — which will not fuel a lot of work.

Even so, according to an article by diabetes educator Gary Scheiner, processing those 12 grams of carbs at lunch might require anywhere from half a unit of insulin to two units or more. If your body does not produce insulin, and none is injected, that one slice of bread can raise your blood glucose significantly, maybe from 5 to 50 points depending on the type of bread and your individual body.

According to Dr. Bernstein, injecting insulin doesn’t solve the problem very well, because it’s extremely difficult to match the peak of insulin action with the peak glucose level from the carbs you ate. That’s why he recommends very small amounts of carbs and very low doses of insulin.

How fast the carbs get into your system as glucose (indicated by the food’s glycemic index, or GI) may also play a role. If a food is slow enough (that is to say, has a low enough GI) and your body releases insulin slowly, it might be able to keep the numbers from going too high. People with diabetes don’t make enough insulin to cover a large dose of carbs, but might manage smaller servings OK.

Many low-carb diabetes advocates agree with Bernstein. Jenny Ruhl, keeper of the Web site Blood Sugar 101, recommends starting at 15 grams of carbs per meal. Other diets, like Atkins’, are even stricter. He recommended starting at 20 grams per day.

Ruhl says, “Adopting these very low carbohydrate limits will control your blood sugar very nicely. But over time, many people find that sticking to a diet this low in carbohydrate becomes impossible.”

So Ruhl and others recommend doing a lot of glucose monitoring at home. Try different foods, in different quantities, and see where your glucose is one hour and two hours after meals. You want to keep it below 140 milligrams per deciliter (mg/dl), because that’s where blood vessel and nerve damage seem to start. Write the results down.

But that’s not the end. Ruhl writes,

If a meal allows you to reach your blood sugar targets, try eating it again on a different day and test it again, possibly at a later time, to make sure that your good numbers weren’t just a result of slow digestion.

If your numbers go a little too high, she suggests trying smaller portions, and eliminating the questionable food if necessary. Because everybody is different, monitoring may be the only way to find out how much carbohydrate you can handle. And different types of carbs may affect you differently.

So, if carbs are the major energy source for most people, and you’re not supposed to eat them, what are you supposed to eat? Is it all meat and eggs from now on? What are the alternatives? The week after next, I’ll get more into what different carbs do differently, and how to know what’s best to eat. I might take next week for an amazing herbal treatment a reader notified us about.

In the meantime, here is a page that gives the precise carb content of almost any food you can think of.

Want to learn more about diabetes and low-carb diets? Read “Why I Low-Carb,” “What Does Low Carb Mean?” “Low-Carb Diabetes: What You Need to Know,” “More Evidence Supports Low-Carb Diet for Diabetes,” and “Low-Carb Diet May Cut Hunger, Food Cravings.”

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