Low-carbohydrate diets are often so effective at controlling blood sugars that low blood sugar (hypoglycemia) becomes a serious risk for some diabetics. It’s rarely a problem for prediabetics. But people with diabetes using particular drugs could develop life-threatening hypoglycemia, particularly when switching to a reduced-calorie or low-carb style of eating.
CARBOHYDRATES AND BLOOD SUGAR
Never forget that carbohydrate consumption has a major effect on blood sugar (glucose) levels—often causing a rise—in many people with type 2 diabetes and prediabetes. Most folks with diabetes are taking medications to lower their glucose levels.
Remember that the main components of food—called macronutrients—are proteins, fats, and carbohydrates. Common carbohydrate sources are:
■ starchy vegetables (e.g., potatoes, corn, peas, beans)
■ milk products
■ sweetened beverages
■ other added sugars (e.g., table sugar, high fructose corn syrup, honey)
Low-carb and very-low-carb diets restrict the dieter’s carbohydrate consumption rather dramatically. The standard American diet, for instance, provides 250–300 grams of carbohydrate daily, or 50–60% of total energy (calories). A low-carb diet may provide in the range of 50–130 grams daily, or 10 to 25% of total calories. A very-low-carb diet provides under 50 grams of carb daily (under 10% of all calories), often starting at 20–30 grams. With very-low-carb diets, our bodies must use fats instead of carbohydrates as an energy source, and a result of this fat metabolism is the generation of ketone bodies in the bloodstream. So very-low-carb diets are often called ketogenic diets.
Many dietitians have been taught that you must eat at least 130 grams of carbohydrate daily to provide a rich, readily available source of energy—glucose, specifically—to your brain in particular, and other tissues. Millions of “low-carbers”—people with a low-carb way of eating—know that isn’t right, having proven it to themselves by experience. I personally lived on 30 grams (or less) daily for four months without problems with my brain or other organs. (Well, my wife might argue about the brain issue.) I felt fine and had plenty of energy.
In healthy people, prediabetics, and mild diabetics not treated with medication, carbohydrate restriction rarely causes low blood sugar problems. But in other diabetics, carbohydrate restriction can lead to serious, even life-threatening, symptoms of hypoglycemia.
DRUGS, DIET, AND HYPOGLYCEMIA
Traditional balanced diets for diabetics typically provide 50 to 60% of all calories as carbohydrates. Low-carb diets, remember, provide 25% or less of calories as carbohydrates. A diabetic trying to lose excess weight with a traditional balanced diet is told also to reduce total calories, which necessarily means lowering carbohydrate grams. So, hypoglycemia is also a potential problem for diabetics on these traditional reduced-calorie diets if they are taking particular diabetic medications.
Hypoglycemia, however, is an even greater risk for diabetics taking certain diabetic drugs while on a low-carb or very-low-carb diet. Serious, even life-threatening, symptoms of hypoglycemia may arise.
For diabetics taking certain diabetic drugs, carbohydrate restriction can lead to serious, even life-threatening, symptoms of hypoglycemia.
I hope I’ve made my point. This is dangerous territory. Review your diabetes drugs to see if they can cause hypoglycemia.
Steve Parker, M.D.