Characterization of the post-prandial insulinemic response and low glycaemic index of a soy beverage.

Jose Ce Serrano,Meritxell Martín-Gari,Manuel Portero-Otín,Anna Cassanye,Ana Belen Granado-Serrano,Harald Staiger

doi:10.1371/journal.pone.0182762

Abstract

Soybean is recognized as rich source of bioactive compounds for the improvement of glucose homeostasis. However, the post-prandial mechanisms of action have not been extensively described. The aim of this study is to determine the changes in glucose homeostasis and related factors after acute intake of a soy beverage. Twenty-nine subjects (15 women and 14 men, with an average age of 19.5 ± 1.2) ingested 500 mL of water, glucose (20.5 g/500 mL) and soy beverage (20 g of carbohydrate) in three separate sessions. Capillary blood glucose was monitored every 15 min until 120 min post-prandial, and blood samples were collected at baseline and after 60 min for insulin, incretin, free amino acids, antioxidant capacity and inflammation marker analysis. The increase in capillary glucose after soy-beverage intake was negligible. This is explained in part by an increase in 83% in insulin levels than induced with glucose alone, which is mainly mediated by a low insulin degradation ratio (determined by c-peptide ratio), incretins and likely also by the modulation of the antioxidant environment. No associations were observed between the insulin levels and soy amino acid uptake. It could be concluded that the acute low glycaemic response of a soy beverage may involves a relationship between incretin and insulin secretion and insulin degradation.

Highlights

Over the last decades, scientific evidence of the impact of soy foods and supplements has grown considerably, and in most countries there is broad social acceptance of their health benefits and, in some cases, therapeutic role in glucose and insulin management
The soy beverage tested in this study performed an estimated glycaemic index of 43% (Fig 1), making it a low glycaemic index food
The soy beverage tested in this study induces low post-prandial glycaemia that could be explained by three main mechanisms: 1) a reduction in the absorption of digestible carbohydrates; 2) an increase in insulin secretion or a reduction in its degradation; and 3) systemic uptake of the absorbed glucose

Summary

Introduction

Scientific evidence of the impact of soy foods and supplements has grown considerably, and in most countries there is broad social acceptance of their health benefits and, in some cases, therapeutic role in glucose and insulin management. Soybean is a rich source of vegetable proteins, complex carbohydrates, polyunsaturated fat, soluble fibres and isoflavones that may be beneficial in the prevention of insulin resistance. With regard to the effects of soy foods on glucose homeostasis, several studies have shown that soy products and foods significantly improve glycaemic control [1]. In vitro studies suggest that the α-glycosidase and tyrosine kinase inhibitory properties of soy isoflavones may inhibit intestinal glucose uptake [2,3]. Human studies have indicated that soy protein or isoflavones may improve glycaemic control and increase insulin sensitivity, lowering the risk of diabetes [4,5].

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