Insulin resistance is characterized by specific changes of the composition of fatty acids in the serum lipids and in the skeletal muscle membranes. Impaired insulin sensitivity is associated with high proportions of palmitic (16:0) acid and low levels of linoleic (18:2 n‐6) acid in serum. In addition, there are apparent changes of the fatty acid desaturase activities, suggesting an increased activity of the Δ9 and Δ6 desaturases and a decreased activity of the Δ5 desaturase. The activity of the fatty acid desaturases is regulated by long‐chain polyunsaturated fatty acids and insulin and is probably also dependent on the degree of physical activity. A high ratio between arachidonic (20:4 n‐6) and dihomo‐gamma linolenic (20:3 n‐6) acid, as a measure of Δ5 desaturase activity, in the skeletal muscle phospholipids has been related to good insulin sensitivity. Available knowledge seems to indicate that the degree of saturation of the body lipids, and especially the proportion of palmitic acid in the lipid membranes, may be critical for insulin sensitivity. The strong relationships between the Δ5 desaturase activity, a high content of long‐chain polyunsaturated fatty acids in the skeletal muscle, and insulin sensitivity may be due to parallel effects of diet and/or physical activity on the fatty acid composition and on insulin sensitivity.

High intakes of whole grain foods are inversely related to the incidence of coronary heart diseases and type 2 diabetes, but the mechanisms remain unclear. Our study aimed to evaluate the effects of a diet rich in whole grains compared with a diet containing the same amount of refined grains on insulin sensitivity and markers of lipid peroxidation and inflammation. In a randomized crossover study, 22 women and 8 men (BMI 28 +/- 2) were given either whole-grain or refined-grain products (3 bread slices, 2 crisp bread slices, 1 portion muesli, and 1 portion pasta) to include in their habitual daily diet for two 6-wk periods. Peripheral insulin sensitivity was determined by euglycemic hyperinsulinemic clamp tests. 8-Iso-prostaglandin F(2alpha) (8-iso PGF(2alpha)), an F(2)-isoprostane, was measured in the urine as a marker of lipid peroxidation, and highly sensitive C-reactive protein and IL-6 were analyzed in plasma as markers of inflammation. Peripheral insulin sensitivity [mg glucose . kg body wt(-1) . min(-1) per unit plasma insulin (mU/L) x 100] did not improve when subjects consumed whole-grain products (6.8 +/- 3.0 at baseline and 6.5 +/- 2.7 after 6 wk) or refined products (6.4 +/- 2.9 and 6.9 +/- 3.2, respectively) and there were no differences between the 2 periods. Whole-grain consumption also did not affect 8-iso-PGF(2alpha) in urine, IL-6 and C-reactive protein in plasma, blood pressure, or serum lipid concentrations. In conclusion, substitution of whole grains (mainly based on milled wheat) for refined-grain products in the habitual daily diet of healthy moderately overweight adults for 6-wk did not affect insulin sensitivity or markers of lipid peroxidation and inflammation.

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Plasma AR concentrations are correlated with intake assessed by food records, which suggests that ARs are selective nutritional biomarkers for the intake of whole-grain wheat and rye.

The fatty acid composition of skeletal muscle lipids reflects the fatty acid composition of the diet in healthy men and women.