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Nuts, Nuts, and More Nuts Lower A1c and Cardiovascular Disease

Sep 8, 2018
 

New study shows that nut intake may improve glycemic control and reduce risk of cardiovascular disease in people who have type 2 diabetes.

For patients with type 2 diabetes, maintaining a diet low in carbohydrates is arguably the most important factor when it comes to managing glucose and overall health. A few studies have examined the effects of replacing a carbohydrate-rich diet with a diet rich in monounsaturated fatty acids on glucose levels and cardiovascular disease risk reduction.

David Jenkins et al. sought to examine the glycemic and cardiovascular effects of a diet consisting of mixed nuts versus whole-wheat muffins as the primary source of energy in patients with type 2 diabetes. Primary data was collected by the investigators from a 3-month study completed in 2008 that had failed to adjust for repeated measures. The investigators of this new study corrected those statistical errors and presented new data of interest, including clotting factors and LDL particle size.

Enrolled into the study were 117 men and postmenopausal women with type 2 diabetes on non-insulin glucose lowering agents. Participants were eligible if they had baseline HbA1c values between 6.5% and 8% and were randomized into one of three diet groups: A full-dose nut diet, a full-dose muffin diet, or a half-dose nut and half-dose muffin diet, with all three diets providing equivalent amounts of energy per serving (477 per 2000 kcal, 471 per 2000 kcal, and 474 per 2,000 kcal, respectively). The nuts consisted of raw almonds, pistachios, walnuts, pecans, hazelnuts, peanuts, cashews, and macadamias in equal quantities by weight. The muffins were whole-wheat and sweetened only with apple concentrate. All three diets had similar protein content. Throughout the course of the study, participants did not alter their existing glucose-lowering medication regimen.

Data from 108 participants were included in the post-intervention results. Of the three diets, the full-dose nut diet reduced HbA1c by an average of 0.19% [95% CI −0.35%, −0.02%]), (p = 0.026) and provided a 9.2% greater total energy intake from monounsaturated fat (95% CI 7.1, 11.3) compared with the full-dose muffin diet. Total cholesterol was also significantly reduced in the full-dose nut group compared with the full-dose muffin group (−0.25 mmol/l; p = 0.022). Compared with the full-dose muffin diet, a significant change in ApoB of 0.09 g/l in patients on the full-dose nut diet was observed ([95% CI −0.17, −0.003]; p = 0.039).

LDL particle size was observed as a secondary outcome, with a significant reduction observed in the full dose nut group compared with the full-dose muffin group. No treatment differences were noted in majority of clotting factors examined (factors VII, VIII, fibrinogen, or PAI-1) and no significant weight change was noted with any of the treatment groups.

Overall, this study demonstrated that a mixed nut diet rich in monounsaturated fatty acids lowered HbA1c, LDL cholesterol, and ApoB levels as compared with a whole-wheat carbohydrate diet in patients with type 2 diabetes. While a reduction in HbA1c of 0.19% may seem relatively small, the FDA recognizes a reduction in HbA1c of 0.4% to be therapeutically significant, indicating that simply changing a small component of one’s diet over a short period of time can improve glucose levels by half the significant amount. These results further emphasize the importance of a lower carbohydrate diet as an important factor in patients who have type 2 diabetes wishing to improve clinical outcomes and quality of life when medication alone is unable to achieve glycemic goals. These results also further support previous studies examining additional forms of MUFAs on reduction of CVD in high-risk patients outside of those with type 2 diabetes, such as those with a history of atrial fibrillation and stroke.

Practice Pearls:

  • Exchanging carbohydrate intake for energy in the form of monounsaturated fats can improve glucose levels and reduce CVD risk in patients with type 2 diabetes.
  • A nut-rich diet high in monounsaturated fatty acids is not associated with an increase in body weight compared with a diet rich in whole-wheat carbohydrates despite the high lipid content of the nuts.
  • Nut-rich diets reduce the glycemic load when added to a meal in replacement of carbohydrates and may delay both gastric emptying and the rate of small intestinal absorption, leading to a steadier postprandial glycemic response.

Reference:

Jenkins, David J.A., et al. (2018). Nuts as a Replacement for Carbohydrates in the Diabetic Diet: a Reanalysis of a Randomised Controlled Trial. Diabetologia, 61(8), 1734–1747. PubMed, doi:10.1007/s00125-018-4628-9.

Clarke Powell, Pharm.D. Candidate 2019, LECOM School of Pharmacy