Slow digestible starch in native pea starch lowers glycemic response with no adverse effects on gastrointestinal symptoms in healthy adults

INTRODUCTION

Since 1990, there has been a dramatic increase in the global prevalence of diabetes. Most of the cases nowadays are related to Type 2 diabetes (1). Although there are several factors that influence the development of type 2 diabetes, including both genetic and environmental, it is evident that the most influential effects are through lifestyle and behavioral influences commonly associated with urbanization, junk food or lower fiber intake through the diet (2).

In this context, high glycemic index (GI) carbohydrate consumption becomes problematic  because they are rapidly digested in the small intestine. As a consequence, post prandial blood glucose concentrations rise rapidly to high levels inducing a strong pancreatic insulin response that when repeated over multiple meals, days, and years contributes to the onset of glucose intolerance, followed by insulin resistance and the associated increase in circulating insulin levels and finally the onset of type 2 diabetes. As carbohydrates are the main contributors to the daily energy requirements of a balanced diet (3), reducing their glycemic impact ought  to be considered as a way of preventing and reducing prevalence  of type 2 diabetes.

In 1992, Englyst proposed a new carbohydrate classification according to their in vitro digestibility. The in vitro methodology allowed researchers to classify carbohydrates, especially starch, into three categories according to their ability to deliver glucose through the action of digestive enzymes: rapidly digestible starch (RDS), slow digestible starch (SDS) and resistant starch (RS) fractions (4).

Pea (Pisum sativum L.) is one of the most widespread and most cultivated annual legume crops in temperate regions as it is an excellent source of protein (15-30% Dry Matter), starch (50% Dry Matter) and micronutrients (zinc, iron and vitamins). It has a high amylose content, which is associated with slow digestibility pattern (5)(6).

MATERIALS AND METHODS

Objective

The objective of the present  study is to test if the native pea starch could be used to propose recipes with claims based on slow digestibility and low GI.

Carbohydrates

Native pea starch (Pea Starch LN30), Anhydrous glucose and Maltodextrin Glucidex®IT19

In vitro testing by Englyst method

The starch profile of pea starch LN30 and Glucidex®IT19 maltodextrin was determined according to an adaptation of the Englyst methodology, with slight modifications. This procedure allows to measure different fractions of starch: RDS (Rapidly Digestible Starch), SDS (Slowly Digestible Starch) and RS (Resistant Starch) following enzymatic digestion.

In vivo Glycemic index testing

A non-blind, repeat measure, crossover design trial was used to study the glycemic index of Pea Starch LN30, Glucidex®IT19 Maltodextrin, a pea starch powder mix recipe and a maltodextrin powder mix recipe against a reference of glucose.  The participants acted as their own controls and they were randomly assigned to test each product against the reference glucose using a pseudo-random number generator.

Healthy volunteers: n=16 UK

RESULTS

In vitro testing by Englyst method

The amount of RDS, SDS and RS in Pea Starch LN30 were 16%, 30% and 54%, respectively while Glucidex®IT19 Maltodextrin showed higher RDS content (93%) and much lower SDS (1%) and RS (6%).

Table 1: Starch profile of native Pea Starch LN30, Glucidex®IT19 Maltodextrin, pea starch based powder mix recipe and maltodextrin based powder mix recipe.

In vivo Glycemic index testing

There was a significant difference (p<0.05) in the change in blood glucose between Pea Starch LN30 and Glucidex®IT19 Maltodextrin at 15, 30, 45, 90, 120, 150 and 180 minutes after consumption. The glucose response after Pea Starch LN30 was significantly lower (p<0.05) at 15 (-1.3mmol/l), 30 (-2.5mmol/l) and 45 min (-1.7mmol/l) compared to Glucidex®IT19 Maltodextrin.

SEM, standard error of the mean

Gastrointestinal Symptoms

There was no significant difference (p>0.05) in mean scores for well-being and gastrointestinal symptoms after consumption of Pea Starch LN30 and Glucidex®IT19 Maltodextrin or between the two recipes.

DISCUSSION

This study shows that the native pea starch contains 30% SDS and 54% RS according to the in vitro testing by Englyst method. This implies a high dietary fibre content in pea starch as RS is known to act as dietary fibre. However, when determined with the current  consensual resistant starch AOAC 2002.02 methodology, (7) the dietary fibre content (represented by type 2 resistant starch) of the native pea starch (8) was determined as 11%. With the 11% resistant starch considered as dietary fibre, meaning the starch fraction that is not at all digested in the upper part of the small intestine, the slowly digested fraction of the pea starch can be estimated to be 73% (100 - 11% RS - 16% RDS). This explains the very weak postprandial glycemic response which might consequently trigger a very weak insulin response.

The glycemic response result reflects the slow digestion feature of native pea starch leading to a very limited increase in blood glucose, with less than 0.5 mM/L increment.

In this study, the pea starch-based recipe elicited an attenuated glycemic response compared to the maltodextrin-based recipe. This effect may be attributed to the low RDS content and high RS and SDS contents of pea starch identified during in vitro digestion.

In this study, there were no differences in the gastrointestinal symptoms following pea starch product compared to the maltodextrin product.

CONCLUSIONS

In conclusion, this study has demonstrated the presence of high SDS content in pea starch, which reduced postprandial glycemic response compared to maltodextrin, which is a rapidly digested carbohydrate. Irrespective of the high levels of SDS, the pea starch recipe did not induce any negative gastrointestinal symptoms. Pea starch may therefore prove to be a beneficial ingredient in developing food products for improving glycemic control without undesirable side effects.

LIST OF REFERENCES

(1): Lin X, Xu Y, Pan X, et al. Global, regional, and national burden and trend of diabetes in 195 countries and territories: an analysis from 1990 to 2025. Scientific Reports. 2020;10(1):14790. doi:10.1038/s41598-020-71908-9

(2): Magkos F, Hjorth MF, Astrup A. Diet and exercise in the prevention and treatment of type 2 diabetes mellitus. Nature Reviews Endocrinology. 2020;16(10):545-555. doi:10.1038/s41574-020-0381-5

(3): Buyken AE, Mela DJ, Dussort P, et al. Dietary carbohydrates: a review of international recommendations and the methods used to derive them. European Journal of Clinical Nutrition. 2018;72(12):1625-1643. doi:10.1038/s41430-017-0035-4

(4): Englyst HN, Kingman SM, Cummings JH. Classification and measurement of nutritionally important starch fractions. Eur J Clin Nutr. 1992;46 Suppl 2:S33-50.

(5): Robinson GHJ, Balk J, Domoney C. Improving pulse crops as a source of protein, starch and micronutrients. Nutr Bull. 2019;44(3):202-215. doi:10.1111/nbu.12399

(6): Dahl WJ, Foster LM, Tyler RT. Review of the health benefits of peas (Pisum sativum L.). Br J Nutr. 2012;108 Suppl 1:S3-10. doi:10.1017/S0007114512000852

(7): McCleary BV, McNally M, Rossiter P, et al. Measurement of Resistant Starch by Enzymatic Digestion in Starch and Selected Plant Materials: Collaborative Study. Journal of AOAC INTERNATIONAL. 2002;85(5):1103-1111. doi:10.1093/jaoac/85.5.1103

(8): Birt DF, Boylston T, Hendrich S, et al. Resistant Starch: Promise for Improving Human Health12. Adv Nutr. 2013;4(6):587-601. doi:10.3945/an.113.004325

DISCLAIMER

This informative, scientific and technical data relates to ingredient not intended to be delivered as such to the final consumer and is only addressed to Food Business or Health Care professionals for pedagogic information purpose.

® Registered trademark of Roquette Frères - © Roquette Frères S.A.