Nutritional Pearls: Fighting Insulin Resistance
Bob is a 46-year-old overweight man concerned about his risk of developing diabetes. The disease runs in his family, and Bob has already begun showing signs of prediabetes. He asks if there are any lifestyle changes he can make to help prevent the development of the disease.
How do you advise your patient?
(Answer and discussion on next page)
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Answer: a Mediterranean-like diet, high in fruits and vegetables and low in grilled meats and processed foods, is best for patients with prediabetes and type 2 diabetes.
Advanced Glycation End Products
Advanced glycation end products (AGEs) are oxidants formed when sugars chemically react with proteins. A typical Western diet tends to be high in AGEs, as they appear not only in foods that are cooked at a high temperature (such as meats that are roasted, fried, or grilled), but also in highly processed baked goods (think white breads), foods that contain trans fats, beer (sorry), and roasted coffee beans (even more sorry).
High levels of AGEs in the body have been shown to contribute to poor insulin sensitivity (or insulin resistance), in which the body does not use its natural insulin as effectively as it should. Decreased insulin sensitivity is one of the symptoms of prediabetes. Often, insulin sensitivity can be improved with weight loss and exercise, but not always, so researchers are interested in other ways to help improve insulin sensitivity. Studies in rats have suggested that a diet low in AGEs might help improve insulin sensitivity, but while rats are similar to people, they are not people. Studies in humans are always needed to confirm animal studies.
The Research
Fortunately, a team in Australia designed a study in humans to assess this very question. Twenty otherwise clinically healthy but overweight or obese men and women participated in this very well-designed feeding study. For 2 weeks, the participants followed a diet that was low in AGEs or high in AGEs. After a 4-week washout period, the participants then switched diets (from high-AGE to low-AGE, or vice versa) and followed that diet for an additional 2 weeks. The authors were careful to customize both types of diets for each participant to provide the same number of calories and the same proportion of macronutrients regardless of the level of AGEs they were consuming. Furthermore, all of the food consumed for the 2 diets was provided by the researchers, including all meals, snacks, and even beverages.
At the start and end of each diet period, the participants underwent a glucose tolerance test as well as provided urine samples, which allowed the authors to verify the amount of AGEs each participant had consumed. While the high-AGE diet did not appear to significantly affect the participants' insulin sensitivity—possibly because their usual diet was already higher in AGEs—the low-AGE diet significantly improved the participants' insulin sensitivity, meaning their body’s ability to utilize insulin and manage their blood glucose improved.
What’s the “Take-Home”?
The authors note that this study included people who were overweight or obese but neither prediabetic or diabetic. Concluding that those who are diabetic should follow a low-AGE diet would be leaping to conclusions on a par with believing that if A = B and B = C, then A = Z. That said, eating less grilled meats, avoiding highly processed foods like white bread in favor of whole grains, and consuming more vegetables and fruits (good sources of antioxidants) is a feature of a Mediterranean-style diet, which we know is the best diet for type 2 diabetics.
Reference:
de Courten B, de Courten MPJ, Soldatos G, et al. Diet low in advanced glycation end products increases insulin sensitivity in healthy overweight individuals: a double-blind, randomized, crossover trial. Am J Clin Nutr. 2016;103(6):1426-1433.