Diabetes is a chronic disease that has reached epidemic proportions.
It currently affects over 400 million people worldwide (1).
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.
Bottom Line: Diabetics are deficient in insulin, or resistant to its effects. When they eat carbs, their blood sugar can rise to potentially dangerous levels unless medication is taken.
Can Low-Carb Diets Help Manage Diabetes?
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).
Bottom Line: Research has shown that people with diabetes experience long-term improvements to blood sugar control while on a low-carb diet.
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.
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).
The optimal amount of carbs may also vary by individual, since everyone has a unique response to carbs. To figure out your ideal amount, 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.
Bottom Line: Carb intake between 20–90 grams per day has been shown to be effective at improving blood sugar control. However, it's best to test blood sugar before and after eating to find your personal carb limit.
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 (17).
Some of them, especially maltitol, can actually raise blood sugar levels in people with diabetes (18).
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.
Bottom Line: Starches and sugars raise blood sugar levels, but dietary fiber does not. The sugar alcohol maltitol may also raise blood sugar.
Foods to Eat and Foods to Avoid
It's best to focus on eating low-carb, high-quality whole foods.
It's also important to pay attention to your body's hunger and fullness cues, regardless of what you are eating.
Foods to Eat
You can eat the following low-carb foods until you're full, and you should make sure to get enough protein at each meal.
- Meat, poultry and seafood.
- Non-starchy vegetables (most vegetables except those listed below).
- Olive oil, coconut oil, butter, cream, sour cream and cream cheese.
Foods to Eat in Moderation
The following foods can be eaten in smaller quantities at meals, depending on your personal carb tolerance.
- Berries: 1 cup or less.
- Plain, Greek yogurt: 1 cup or less.
- Cottage cheese: 1/2 cup or less.
- Nuts and peanuts: 1–2 oz or 30–60 grams.
- Flaxseeds or chia seeds: 2 tablespoons.
- Dark chocolate (at least 85% cocoa): 30 grams or less.
- Winter squash (butternut, acorn, pumpkin, spaghetti and hubbard): 1 cup or less.
- Liquor: 1.5 oz or 50 grams.
- Dry red or white wine: 4 oz or 120 grams.
Reducing carbs usually lowers insulin levels, which causes the kidneys to release sodium and water (19).
Try to eat broth, olives or some other salty low-carb foods to make up for the lost sodium. Don't be afraid to add some salt to your meals.
However, if you have congestive heart failure, kidney disease or high blood pressure, talk to your doctor before increasing the amount of sodium in your diet.
Foods to Avoid
These foods are high in carbohydrates and can significantly raise blood sugar levels in diabetics:
- Bread, pasta, cereal, corn and other grains.
- Starchy vegetables like potatoes, sweet potatoes, yams and taro.
- Legumes, such as peas, lentils and beans (except green beans and snow peas).
- Fruit other than berries.
- Juice, soda, punch, sweetened tea, etc.
- Desserts, baked goods, candy, ice cream, etc.
Bottom Line: Stick to low-carb foods like meat, fish, eggs, seafood, non-starchy vegetables and healthy fats. Avoid foods that are high in carbs.
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.
Bottom Line: A meal plan to manage diabetes should space carbs evenly over three meals. Each meal should contain a balance of protein, healthy fats and a small amount of carbs, mostly from vegetables.
Talk to Your Doctor Before Changing Your Diet
When carbs are restricted, there is often a dramatic reduction in blood sugar.
For this reason, insulin and other medication dosages will usually need to be reduced. In some cases, they may need to be eliminated altogether.
One study reported that 17 of 21 subjects with type 2 diabetes were able to stop or reduce diabetes medication when carbs were limited to 20 grams a day (7).
In another study, type 1 diabetics consumed less than 90 grams of carbs each day. Their blood glucose control improved, and there were fewer incidences of low blood sugar because insulin dosages were significantly reduced (16).
If insulin and other medications are not adjusted for a low-carb diet, there is a high risk for dangerously low blood glucose levels, also known as hypoglycemia.
Therefore, it's important that people who take insulin or diabetes medication speak with their doctor before starting a low-carb diet.
Bottom Line: Most people will need to reduce their dosage of diabetes medication or insulin when following a low-carb diet. Failure to do so may result in dangerously low blood sugar levels.
Other Ways to Lower Blood Sugar Levels
In addition to following a low-carb diet, physical activity can also help control diabetes by improving insulin sensitivity.
A combination of resistance training and aerobic exercise is especially beneficial (20).
One recent observational study found that diabetics who slept 6.5 to 7.5 hours per night had better blood glucose control, compared to those who slept for less or more time (22).
Another key to good blood sugar control is stress management. Yoga, Qigong and meditation have been shown to lower blood sugar and insulin levels (23).
Bottom Line: In addition to following a low-carb diet, physical activity, quality sleep and stress management can further improve diabetes control.
Low-Carb Diets Are Effective Against Diabetes
Studies show that low-carb diets can effectively manage type 1 and type 2 diabetes.
Low-carb diets can improve blood sugar control, decrease medication needs and reduce your risk of diabetic complications.
Just remember to talk to your doctor before making any dietary changes, as your medication dosages may need to be adjusted.