As someone with type 1 diabetes, you may be focused on the amount of carbs you eat to figure out how much insulin you need to pump into your body. But consider this: your after-meal blood sugars may be affected by more nutrients than carbs.

Growing evidence has shown that fat, protein, and the glycemic index of different foods may also have a significant impact on after-meal (postprandial) glucose levels, no longer singling out carbs as the sole culprit.

The research

Researchers searched through databases of studies to see the effects of protein, fat, and glycemic index on postprandial glucose control in people with type 1 diabetes. They also looked at how these people dosed after meals based on what they ate.

Led by Howard Wolpert, MD, director of the Insulin Pump and Continuous Glucose Monitoring Programs at Joslin Diabetes Center, the researchers analyzed different studies that kept the amount of carbohydrates in the meal consistent but varied the amounts of protein, fat, or glycemic index found in the food.

Fat and blood sugar

They looked at seven studies that examined the effect of dietary fat on postprandial blood sugar levels and found that adding fat to a participant's meal resulted in hyperglycemia, or high blood sugar levels, in the hours after a meal. Meals containing carbs and high levels of fat caused sustained late post-meal hyperglycemia hours after eating. This could be due to free fatty acids found in the fatty foods that directly induce insulin resistance.

Protein and blood sugar

The effects of protein were also examined in several studies, and they showed that adding protein to a test meal produced significant changes to post-meal blood sugar. High levels of protein intake led to increased glucose concentration in the blood in the after-meal period. When protein was the only thing consumed, blood sugar levels rose 100 minutes after the meal for protein loads greater than or equal to 75 grams. When protein was eaten with carbs, glucose levels rose three to four hours after the meal.

Glycemic index and blood sugar

Not surprisingly, the researchers found that meals high in glycemic index had higher blood sugar responses than meals low in glycemic index. But they also found that low glycemic index foods could cause early hypoglycemia, or low blood sugar levels, with each increase in glycemic index unit delaying hypoglycemia by one minute.

What to do with this information

The discoveries claim that high-fat/protein meals require more insulin than lower-fat/protein meals with the same carb content. Therefore, insulin doses may need to be measured based on overall fat, protein, and carb intake. After all, eating 35 grams of fat and 40 grams of protein can be like eating 20 grams of carbs without insulin, which greatly affects glucose levels. The results indicated that eating 50 grams of fat in a meal may even increase insulin requirements after the meal more than twofold.

These findings may change the way we measure postprandial insulin needs and dosages, according to the researchers.

“These studies have important implications for clinical practice and patient education and point to the need for research focused on the development of new insulin dosing algorithms based on meal composition rather than on carbohydrate content alone,” Dr. Wolpert and his colleagues wrote.

Furthermore, the researchers found that prandial insulin taken 15 to 20 minutes before a meal with fat and protein amounts factored in may be more effective in controlling postprandial blood sugar levels in those with type 1 diabetes.

If your blood sugars are off and you can’t seem to get that hyperglycemia down, talk to your doctor about factoring in your fat and protein intake for perhaps a more accurate perspective of your insulin needs.