Almonds and health risk factors - Carbohydrate Metabolism and Diabetes

Nutrition Research Newsletter,  Dec, 2002  by Jennifer C. Lovejoy,  Marlene M. Most,  Michael Lefevre

• E-mail
• Print
• Link

There is controversy regarding the relative health benefits of high-carbohydrate diets compared with diets high in monounsaturated fat (MUFA). High-fat diets have been associated with the worsening of insulin sensitivity in many clinical studies of non-diabetic persons. In patients with established diabetes, high-fat diets increase fasting and postprandial glucose and insulin concentrations, whereas adherence to a low-fat diet improves glucose tolerance over five years in persons with impaired glucose tolerance.

Nuts are high in MUFA, fiber and micronutrients and have been shown to have beneficial effects on cardiovascular risk. Although studies suggest that nuts can reduce heart disease risk in healthy persons, the effect of nuts on insulin resistance and in patients with type 2 diabetes have not been well studied. A recent study assessed the effects of an almond-enriched diet on insulin sensitivity and lipids in patients with normoglycemia or type 2 diabetes. The study also performed a direct comparison of almonds with other dietary sources of MUFAs to test the hypothesis that an increased nut consumption produces greater benefits than do high-MUFA oils on serum lipids and lipoproteins and glycemia in patients with type 2 diabetes.

Two studies were conducted. In study 1, 10 healthy men and 10 premenopausal women received 100 g almonds/ day for four weeks after a baseline assessment of lab values. Study 2 was a randomized crossover study that compared four diets in 30 volunteers with type 2 diabetes: (1) high fat, high-almond (HFA: 37% total fat, 10% from almonds); (2) low-fat, high-almond (LFA; 25% total fat, 10% from almonds); (3)high-fat control (HFC; 37% total fat, 10% from olive or canola oil); and (4) low-fat control (LFC; 25% total fat, 10% from olive or canola oil). After each four-week diet, total cholesterol, HDL cholesterol, triacylglycerols, and oral glucose tolerance were measured.

In study 1, almond consumption did not change insulin sensitivity significantly, although body weight increased and total- and LDL cholesterol decreased by 21% and 29%, respectively. Despite the slight increase in weight, total energy intake only increased slightly, but not significantly. In addition, the ratio of total to HDL cholesterol and of LDL to HDL cholesterol decreased after almond supplementation. In study 2, total cholesterol was lowest with the HFA diet. Lipid and lipoprotein concentrations during all experimental diets were lower than those at the time of enrollment, suggesting that all experimental diets were lower in total and saturated fat or both than were the subjects' usual diets. HDL cholesterol was significantly lower with the almond diets. No main effect of fat source (almond compared with oil) or fat level (high fat compared with low fat) on any glucose or insulin index was observed.

In healthy adults (study 1), it appears that the increase in nut consumption did not substantially influence insulin sensitivity. However, body weight increased significantly after four weeks of supplementation with almonds, which may have masked or reduced changes in insulin sensitivity. In the diabetic subjects, there was a significant decrease in HDL cholesterol in patients with type 2 diabetes who consumed almond-enriched diets, but there was no effect on the ratio of LDL to HDL cholesterol or of total to HDL cholesterol from the dietary fat source, implying that the effects of almonds on lipids are similar to those induced by high-MUFA oils. Nevertheless, the changes in serum lipids induced by adding almonds to the diet were greater than those predicted by the change in fatty acid composition of the diet, suggesting that fiber or some other component of almonds may modulate these effects.

Jennifer C. Lovejoy, Marlene M. Most, Michael Lefevre, et al., Effects of diets enriched in almonds on insulin action and serum lipids in adults with normal glucose tolerance or type 2 diabetes, Am J Clin Nutr 76(5): 1000-1006 (November 2002) [Address reprint requests to JC Lovejoy, Pennington Biomedical Research Center, 6400 Perkins Road, Baton Rouge, LA 70808. E-mail:lovejoj@pbrc.edu]

COPYRIGHT 2002 Frost & Sullivan
COPYRIGHT 2003 Gale Group