More than 400 million people around the world are affected by the growing epidemic of diabetes. (1)
While a healthy body can efficiently break down dietary carbohydrates into tiny units of glucose that become blood sugar, this process doesn’t work properly for diabetics.
We’ll take a close look here at how low-carb diets can be used to manage blood sugar levels.
Diabetes 101: How Food Affects Blood Sugar
When blood sugar levels rise after eating the consumption of carbohydrates, insulin is produced by the pancreas. This hormone is necessary for blood sugar to be taken into cells and used to fuel body processes.
Blood sugar stays within a fairly narrow range during the day when everything works right; this is vital, since both low and elevated blood sugar levels can lead to serious harm.
The two most common types of diabetes are type 1 and type 2; people have been diagnosed with these disorders at all ages.
- Type 1 diabetes is characterized by an autoimmune process that destroys pancreatic beta cells that produce insulin; to facilitate glucose entering cells, type 1 diabetic patients inject insulin several times daily for blood sugar regulation. (3)
- Type 2 diabetic patients produce enough insulin at first, but cells grow resistant to the hormone, resulting in high blood sugar levels; the pancreas pumps out more insulin in an attempt to restore balance in the bloodstream, but eventually beta cells can’t keep up with the demand. (4)
Of the three macronutrients in food (carbohydrates, fats and proteins), carbs have the most significant impact on blood sugar levels.
When diabetic patients eat large quantities of carbohydrates, they may need to take bigger doses of diabetic medication or insulin to manage blood sugar.
Trials and Studies
Before the discovery of insulin in 1921, placing diabetic patients on a low carb diet was standard treatment for the disease. (9)
Those who follow the diet usually have good long-term results. In one study, type 2 diabetic patients following a low-carb diet were closely observed for six months, then re-evaluated three years later. Those who stuck with the plan had well-controlled blood sugar. (10)
Type 1 diabetic patients had similar results over a 4-year study period using a restricted carbohydrate diet. (11)
In some studies, dramatic improvements in both blood sugar levels and weight were noted by restricting carb intake to less than 20 grams daily. (12)
Other research indicates comparable results can be achieved by limiting carbs to 20% of dietary intake, or between 70 and 90 grams daily. (13)
Since everyone has a unique response to carbohydrates, the best way to pinpoint optimal carb amounts is measuring blood sugar levels an hour or two after meals.
Nerve damage begins to occur at 140 mg/dL (or mmol/L), so monitoring levels with a blood glucose meter can help patients determine optimal carbs for their bodies; some may need to keep carbs at 6 per meal, while others may be able to handle up to 25 or 30.
Carbohydrates and Food Choices
Fiber in plant foods is not broken down into glucose; sugar and starch content jacks up blood sugar.
Seeds, nuts, blueberries and vegetables are the preferred sources of carbohydrates because they are nutrient-dense and high in fiber.
When you’re looking at carb content of various foods, subtracting fiber carbs leaves a carb count that is called “net,” or “digestible” carbs.
For example, a cup of cauliflower delivers 5 carbs, but 3 are from fiber, so net carbs are only 2.
Inulin is a type of prebiotic fiber that has been shown to positively affect blood sugar levels and other health markers in diabetic patients. (14)
Be wary of sugar alcohols such as erithritol, mannitol and xylitol, which may be used to sweeten diet products like candy; these can raise blood sugar levels in diabetic patients.
For example, if carbs from mannitol are subtracted from total carb counts found on product labels, the result may be inaccurate. (15)
Also, fitness trackers may be a good resource for tracking intake.
These are examples of foods you can eat freely, some of which will also help make certain you’re getting plenty of protein:
- Eggs, meat, poultry and fish
- Cheese, avocados and olives
- Low-starch vegetables
- Quality fats and oils, such as coconut oil, olive oil, butter, cream cheese and sour cream
Depending on your level of carb tolerance, these foods can be eaten in smaller quantities:
- Starchy vegetables high in fiber, such as acorn, hubbard and butternut squash (a cup or less)
- Cottage cheese (½ cup) or Greek yogurt (1 cup)
- Berries (1 cup)
- Peanuts and nuts (1 to 2 ounces)
- Chia or flax seed (1 to 2 tablespoons)
- Dark chocolate at 85% cocoa (up to 30 grams)
- 5 ounces of liquor or 4 ounces of dry wine
Lowering carb intake will usually drop insulin levels, causing the kidneys to release both water and sodium. (16)
Low-carb foods that can help replace lost sodium include olives and broth, and adding a little salt to meals is fine unless you’re on a low-sodium diet as part of a plan for treating kidney disease, congestive heart failure or hypertension; in cases like these, consult your physician.
Foods such as these are higher in carbs and can raise blood sugar levels:
- Sweetened drinks like juice and soda; beer
- Fruit, except for berries
- Legumes, including beans, lentils and peas (greens beans and snow peas are exceptions)
- Yams, potatoes, sweet potatoes and taro
- Grains (including corn), bread, cereal and pasta
- Candy, deserts, baked goods, ice cream, etc.
If you take insulin or other medications to control diabetes, it’s vital to speak with your doctor before adopting a low-carb diet.
Blood sugar levels can fall dramatically in short periods of time when carb intake is reduced, and adjustments to medications may be necessary to prevent hypoglycemia, or dangerously low blood sugar levels.
Some patients have been able to stop taking medications altogether when following a low-carb diet. (17)
Other methods proven to help manage blood sugar levels include:
- Getting good quality sleep (18)
- Tegular resistance training and aerobic exercise (19)
- Reducing stress (20)
Many diabetics have had good results in dropping blood sugar levels by following a low-carb diet. Be sure to speak with your doctor before making dietary changes.
Summary: Restricting carbohydrates can be effective in reducing the risk of complications for patients with type 1 and type 2 diabetes; blood sugar levels may also be improved, and some patients are able to decrease or discontinue medications.