Low-Heat Cooking May Reduce Insulin Resistance

Miriam E. Tucker

August 22, 2013

Low-temperature cooking reduced insulin resistance among overweight women, a 4-week study found.

The results were published online August 19 in Diabetes Care by Alicja B. Mark, PhD, from the department of nutrition, exercise and sports, faculty of science, University of Copenhagen, Denmark, and colleagues.

Cooking at high temperature — such as with baking, roasting and frying — induces formation of advanced glycation end products (AGEs), which are associated with inflammation and believed to impair glucose metabolism in patients with type 2 diabetes. Common high-AGE foods include bakery products, cooked meat, and roasted coffee.

The study investigated the effects of consuming foods cooked at high temperature (high-AGE) or low temperature (low-AGE) on the development of markers of insulin resistance among 74 overweight women (body mass index [BMI] 25–40 kg/m2) aged 20 to 50 years. The effect of adding fructose to the diet was also investigated, since fructose is an important reactant for several AGE precursors and could therefore ramp up endogenous AGE formation, Dr. Mark and colleagues explain.

Patients randomized to a high-AGE diet were instructed to fry, bake, roast, or grill their food; eat bread with the crust; and choose other high-AGE foods from a list. The low-AGE group was told to boil or steam their food, eat bread without the crust, and choose lower-AGE foods from a list. They were also randomized to supplements of either fructose or glucose.

At 4 weeks, no effect was seen from the fructose or glucose on insulin resistance, as assessed by the homeostasis model assessment of insulin resistance (HOMA-IR) and the calculated insulin sensitivity index (ISI) or on any secondary measures.

But the AGE content of the diet did make a difference. Weight, BMI, and waist circumference all decreased in both the high- and low-AGE groups (P < .05), but to a greater degree among those in the low-AGE group compared with the high-AGE group (P < .02).

Overall, the low-AGE group consumed about 15% more protein, 10% more carbohydrates, and 22% less fat than did the high-AGE group (all P < .05).

Measurement of dietary and urinary AGE concentrations showed that the estimated mean intake was significantly higher in the high-AGE group compared with the low-AGE group and that the mean daily urinary AGE excretion decreased significantly after the intervention in the low- but not the high-AGE group.

Compared with the women consuming the low-AGE diet, those on the high-AGE diet showed increased levels of fasting insulin and HOMA-IR (P < .001) and decreased ISI (P = .04). These effects remained significant after adjustment for age, change in weight, and change in waist circumference (both P = .001). Adjustment for dietary intake of macronutrients also did not affect the results, Dr. Mark and colleagues note.

Fasting and 2-hour glucose levels did not change significantly with the dietary interventions, and plasma lipids, total glucagonlike peptide-1, and skin autofluorescence — a reflection of accumulated AGEs — did not differ between groups.

Although the authors acknowledge several limitations of their study, including the possible influence of change in body weight despite attempts to adjust for it and the lack of control over compliance with the actual meal plan, they nonetheless conclude, "Low-temperature cooking methods with limited formation of AGEs may decrease the risk of developing insulin resistance, either by decreasing dietary fat intake or by restricting dietary AGE content."

This study was part of the research program UNIK: Food, Fitness & Pharma for Health and Disease, supported by the Danish Ministry of Science, Technology, and Innovation. The authors have reported no relevant financial relationships.

Diabetes Care . Published online August 19, 2013. Abstract


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