Premeal almonds reduce insulin levels, improve glycaemic control in prediabetes

Consumption of almonds 30 min before each major meal can help lower postprandial hyperglycaemia (PPHG), insulin, C-peptide levels, and glucagon levels, as well as improve glucose variability and glycaemic control on continuous glucose monitoring system (CGMS) in individuals with prediabetes, a recent study in India has shown.

“Adopting such strategies to manage hyperglycaemia, especially in a prediabetes state can be helpful in delaying or controlling conversion to diabetes or even help reversal to normal glucose regulation,” the researchers said.

“This is even more important in the case of the Asian Indian population, where the prevalence of diabetes is increasing at an alarming pace every year, and PPHG is a prevalent abnormality in the blood glucose profile,” they added.

This study has two phases. The first phase was an oral glucose tolerance test (OGTT)-based crossover randomized control study, in which the effect of a single premeal almond load (20 g) taken before OGTT was assessed (n=60, 30 each period).

The second phase was a CGMS-based, free-living, open-label, crossover randomized control trial, which was conducted for 3 days and included premeal almond load before three major meals. The researchers compared control and premeal almond load diets for glycaemic control (n=60, 30 in each period).

In the OGTT-based study, participants on almond load diet had significantly lower overall area under the curve (AUC) for blood glucose, serum insulin, C-peptide, and plasma glucagon post-75 g oral glucose than those who had the control diet (p<0.001). [Eur J Clin Nutr 2023;77:586-595]

The almond diet also led to a significantly lower PPHG (18.05 percent in AUC on OGTT, 24.8 percent at 1-hour, 28.9 percent at 2-hour OGTT, and 10.07 percent during CGMS). The second phase of the study demonstrated significantly better 24-glucose variability with premeal almond load.

Daily glycaemic control significantly improved the mean 24-hour blood glucose concentration, time spent above 7.8 mmol/L of blood glucose, alongside the corresponding AUC values. Additionally, premeal almond load led to a significant decrease in overall hyperglycaemia, PPHG, peak 24-hour glycaemia, and minimum glucose level during night.

These findings were consistent with those from earlier studies, in which postprandial blood glucose concentrations decreased by 9‒20 percent in healthy individuals and by 7‒30 percent in those with prediabetes and type 2 diabetes. [J Nutr 2006;136:2987-2992; Metabolism 2007;56:400-404; Nutr Metab (Lond) 2011;8:6; Nutr Metab Cardiovasc Dis 2011;21:S34-39; Metabolism 2011;60:1312-1317]

Mechanism

“It is difficult to comment on the exact mechanism of action of preloading almonds,” the researchers said. “The following have been researched and discussed.”

First, premeal almond load stimulates the release of stored insulin 30 minutes earlier than that stimulated by a 75-g oral glucose load. This is described as priming the “pancreatic pump.” [J Am Board Fam Med 2016;29:759-766]

Second, the fibre content of almonds increases the viscosity of intestinal contents, thus delaying glucose diffusion. Its fat content also slows gastric emptying time, which then delays glucose absorption. [Eur J Clin Nutr 2013;67:1205-1214]

Third, almonds are rich in zinc and magnesium, which stimulate the tyrosine kinase receptor in adipose tissues, thus improving insulin sensitivity. Fourth, almonds contain high amounts of monounsaturated fatty acids, which can also increase insulin sensitivity. Finally, these nuts can reduce hunger. [J Nutr Biochem 2009;20:399-417; Int J Obes Relat Metab Disord 2000;24:1167-1175]

“These mechanisms may be operative in combination to reduce PPHG,” the researchers said.