Written by Franziska Spritzler, RD, CDE on June 3, 2017

Diabetes is a chronic disease that has reached epidemic proportions.

It currently affects over 400 million people worldwide (1).

Although diabetes is a complicated disease, maintaining good blood sugar control can greatly reduce the risk of complications (2, 3).

One of the ways to achieve better blood sugar levels is to follow a low-carb diet.

This article provides a detailed overview of low-carb diets for managing diabetes.

What is Diabetes, and What Role Does Food Play?

If you have diabetes, your body cannot process carbohydrates effectively.

Normally, when you eat carbs, they are broken down into small units of glucose, which end up as blood sugar.

When blood sugar levels go up, the pancreas responds by producing the hormone insulin. This hormone allows the blood sugar to enter cells.

In healthy people, blood sugar levels remain within a narrow range throughout the day. In diabetes, however, this system doesn't work the way it is supposed to.

This is a big problem, because having both too high and too low blood sugar levels can cause severe harm.

There are several types of diabetes, but the two most common ones are type 1 and type 2 diabetes. Both of these conditions can be diagnosed at any age.

In type 1 diabetes, an autoimmune process destroys the insulin-producing beta cells in the pancreas. Diabetics must inject insulin several times a day to ensure that glucose gets into the cells and stays at a healthy level in the bloodstream (4).

In type 2 diabetes, the beta cells at first produce enough insulin, but the body's cells are resistant to its action, so blood sugar remains high. To compensate, the pancreas produces more insulin, attempting to bring blood sugar down.

Over time, the beta cells lose their ability to produce enough insulin (5).

Of the three nutrients -- protein, carbs and fat -- carbs have the greatest impact on blood sugar control. This is because the body breaks them down into glucose.

Therefore, diabetics may need to take large dosages of insulin and/or diabetes medication when they eat a lot of carbohydrates

Can Low-Carb Diets Help Manage Diabetes?

Many studies support low-carb diets for the treatment of diabetes (6, 7, 8, 9, 10, 11).

In fact, prior to the discovery of insulin in 1921, very-low-carb diets were considered standard treatment for people with diabetes (12).

What's more, low-carb diets seem to work well in the long term, as long as patients adhere to the diet.

In one study, type 2 diabetics followed a low-carb diet for 6 months. Their diabetes remained well controlled more than 3 years later if they stuck to the diet (13).

Similarly, when people with type 1 diabetes followed a carb-restricted diet, those who followed the diet saw a significant improvement in blood sugar levels over a 4-year period (14)

What's the Optimal Carb Intake for Diabetics?

The ideal carb intake for diabetics is a somewhat controversial topic, even among those who support carb restriction.

Many studies found dramatic improvements in blood sugar levels, weight and other markers when carbs were restricted to 20 grams per day (7, 8).

Dr. Richard K. Bernstein, who has type 1 diabetes, has eaten 30 grams of carbs per day and documented excellent blood sugar control in his patients who follow the same regimen (15).

However, other research shows that more moderate carb restriction, such as 70–90 grams of total carbs, or 20% of calories from carbs, is also effective (13, 16).

The optimal amount of carbs may also vary by individual, since everyone has a unique response to carbs.

According to the American Diabetes Association (ADA), there’s no one-size-fits-all diet that works for everyone with diabetes. Personalized meal plans, which take into account your dietary preferences and metabolic goals, are best (17).

The ADA also recommends that individuals work with their health care team to determine the carb intake that’s right for them.

To figure out your ideal amount of carbs, you may want to measure your blood glucose with a meter before a meal and again 1 to 2 hours after eating.

As long as your blood sugar remains below 140 mg/dL (8 mmol/L), the point at which damage to nerves can occur, you can consume 6 grams, 10 grams or 25 grams of carbs per meal on a low-carb diet.

It all depends on your personal tolerance. Just remember that the general rule is the less carbs you eat, the less your blood sugar will rise.

And, rather than eliminating all carbs, a healthy low-carb diet should include nutrient-dense, high-fiber carb sources like vegetables, berries, nuts and seeds.

Which Carbs Raise Blood Sugar Levels?

Carbs in plant foods are made up of a combination of starch, sugar and fiber. Only the starch and sugar components raise blood sugar.

Fiber that is found naturally in foods, whether soluble or insoluble, does not break down into glucose in the body and does not raise blood sugar levels.

You can actually subtract the fiber from the total carb content, leaving you with the digestible or "net" carb content. For example, one cup of cauliflower contains 5 grams of carbs, 3 of which are fiber. Therefore, its net carb content is 2 grams.

Prebiotic fiber, such as inulin, has even been shown to improve fasting blood sugar and other health markers in type 2 diabetics (18).

Sugar alcohols such as maltitol, xylitol, erythritol and sorbitol are often used to sweeten sugar-free candy and other diet products.

Some of them, especially maltitol, can actually raise blood sugar levels in people with diabetes (19).

For this reason, the net carb count listed on a product's label may not be accurate if all of the carbs contributed by maltitol are subtracted from the total.

This carb counter may be a valuable resource. It provides data for hundreds of foods on total carbs, net carbs, fiber, protein and fat.

A Sample Day of Low-Carb Meals for Diabetics

Here is a sample menu with 15 grams or less of digestible carbs per meal. If your personal carb tolerance is higher or lower, you can adjust the serving sizes.

Breakfast: Eggs and Spinach

  • 3 eggs cooked in butter (1.5 grams of carbs).
  • 1 cup sautéed spinach (3 grams of carbs).
  • 1 cup blackberries (6 grams of carbs).
  • 1 cup coffee with cream and optional sugar-free sweetener.
  • Total digestible carbs: 10.5 grams.

Lunch: Cobb Salad

  • 3 oz (90 g) cooked chicken.
  • 1 oz (30 g) Roquefort cheese (1/2 gram of carbs).
  • 1 slice bacon.
  • 1/2 medium avocado (2 grams of carbs).
  • 1 cup chopped tomatoes (5 grams of carbs).
  • 1 cup shredded lettuce (1 gram of carbs).
  • Olive oil and vinegar.
  • 20 grams (2 small squares) 85% dark chocolate (4 grams of carbs).
  • 1 glass of iced tea with optional sugar-free sweetener.
  • Total digestible carbs: 12.5 grams.

Dinner: Salmon with Veggies

  • 4 oz grilled salmon.
  • 1/2 cup sautéed zucchini (3 grams of carbs).
  • 1 cup sautéed mushrooms (2 grams of carbs).
  • 1/2 cup sliced strawberries with whipped cream.
  • 1 oz chopped walnuts (6 grams of carbs).
  • 4 oz (120 g) red wine (3 grams of carbs).
  • Total digestible carbs: 14 grams.

Total digestible carbs for the day: 37 grams.