Br J Nutr. 2015 Jun 28;113(12):1931-9. doi: 10.1017/S0007114515001270.

Postprandial glycaemic response: how is it influenced by characteristics of cereal products?

 

Alexandra Meynier1*, Aurélie Goux1, Fiona Atkinson2, Olivier Brack3 and Sophie Vinoy1

1Nutrition Department, Mondelez International R&D, 6 Rue René Razel – Bâtiment K, 91400 Saclay, France

2Human Nutrition Unit, School of Molecular Bioscience, University of Sydney, Sydney, NSW 2006, Australia

3Statistique Industrielle KHI2 Consulting (KSIC), Esches, France

 

Abstract

Cereal products exhibit a wide range of glycaemic indexes (GI), but the interaction of their different nutrients and starch digestibility on blood glucose response is not well known. The objective of this analysis was to evaluate how cereal product characteristics can contribute to GI and insulinaemic index and to the parameters describing glycaemic or insulinaemic responses (incremental AUC, maximum concentration and Δpeak). Moreover, interactions between the different cereal products characteristics and glycaemic response parameters were assessed for the first time. Relationships between the cereal products characteristics and the glycaemic response were analysed by partial least square regressions, followed by modelling. A database including 190 cereal products tested by the usual GI methodology was used. The model on glycaemic responses showed that slowly digestible starch (SDS), rapidly digestible starch (RDS) and fat and fibres, and several interactions involving them, significantly explain GI by 53% and Δpeak of glycaemia by 60 %. Fat and fibres had important contributions to glycaemic response at low and medium SDS contents in cereal products, but this effect disappears at high SDS levels. We showed also for the first time that glycaemic response parameters are dependent on interactions between starch digestibility (interaction between SDS and RDS) and nutritional composition (interaction between fat and fibres) of the cereal products. We also demonstrated the non-linear effect of fat and fibres (significant effect of their quadratic terms). Hence, optimising both the formula and the manufacturing process of cereal products can improve glucose metabolism, which is recognised as strongly influential on human health.

KEYWORDS: Cereal product; Glucose metabolism; Insulin; Starch digestibility

PMID : 25998901

 

Supplement

Postprandial glycemia has been implicated in the etiology of chronic metabolic diseases like obesity, type 2 diabetes and cardiovascular diseases. The concept of glycemic index (GI) developed by Jenkins et al (1981)(1) allows a ranking of food products according to the glycemic response they induce. Starch is one of the most important glycemic carbohydrates (CHO) in cereal products. However, intrinsic properties of starch (gelatinization, amylose/amylopectin ratio etc.) and macronutrients present in the food influence the rate of digestibility of starch. Starch digestibility can be evaluated in vitro using the method developed by Englyst et al. (1996)(2) which classifies starch into three fraction: rapidly digestible starch (RDS), slowly digestible starch (SDS) and resistant starch (RS). Several studies have already studied the impact of food physic-chemical characteristics on the glycemic index of food products. However, either they studied few products or few categories of products and none of them evaluated the effect of interactions between starch digestibility and nutritional composition of the foods on their glycemic index.

Our aim was thus to test the influence of CHO digestibility and the nutritional characteristics of a large sample of different categories of processed cereal-based foods on GI, II and on various parameters of glycemic and insulinemic response curves. The originality of this work was to evaluate the interactions among the different parameters in cereal-based foods; to discuss the physiological relevance of glycemic and insulinemic descriptors.

For this, we analyzed a database including 190 cereal-products including extruded cereals, dried bakery products and crackers, soft bakery products and biscuits. The cereal products displayed GI values ranging between 17 and 94. We evaluated the impact of nutritional composition parameters (Fat, proteins, fibers, glycemic CHOs) and starch digestibility parameters (RDS, SDS and RS) of the glycemic index, iAUC (0-120) glycemia , Cmax glycemia and Δpeak glycemia (difference between Cmax glycemia and baseline value of glycemia). We also investigated the effect of the different interactions between these parameters. The same analyses were performed on insulinemia parameters but a strong impact of the laboratory where the analyses were performed was detected. Therefore, it was not possible to conclude on these parameters.

The model explaining the best the glycemic response (48.9%) included four factors (SDS, fat, RDS and fibers) and four interactions (fibres², SDS x RDS, fat x fibres, fat²).

 

Table 1. Factors significantly influencing glycemic response parameters (glycemic index, incremental area under the blood glucose response curve, Δpeak of glycemic response and maximum concentration of blood glucose)AM tab1

 

 

SDS contributed the most to the model developed (17.4 %), followed by the quadratic effect of fibers and fat. The GI and Δpeak g are the glycemic response parameters that are best explained by the model (52.9 % and 60.1 %, respectively).

 

 

AM FIG1A

 

AM FIG1B

Figure 1. Impact of fat and fibres on (A) glycaemic index (GI) and (B) Δpeak of glycemic response (Δpeak glycemia) values clusterised as low, medium and high levels of slowly digestible starch (g/portion) in the cereal products.

 

 

For identical fat and fibres contents in the cereal products, GI is higher with low SDS content (range 80–50). With low and medium SDS contents in the products, increased fat and fibres lowers the GI value (from 80 to 40 and from 70 to 20, respectively), indicating that fat and fibres are important contributors to GI. With high SDS content (13 g/portion), the contributions of fibres and fat to GI are limited (the GI values do not fluctuate much, ranging from 40 to 60).

Similar contributions of SDS, fat and fibres are observed on Δpeak glycemia.

 

AM FIG2

Fig. 2. Example of prediction profiler showing fibre content effect on glycemic index (GI) at different fat levels and at a medium level of slowly digestible starch (8.5 g/portion). Ordinates correspond to the predicted GI values. Fat levels correspond to minimum (0·5 g/portion), medium (9·3 g/portion) and maximum (18·1 g/portion) fat contents of products present in the database.

 

GI decreases when the fibre content of the product portion increases. This effect is the strongest when the fat content of cereal products is low. The effect of fibres is reduced as the fat content increases until being lost with the highest fat content (about 18 g/portion).

The results obtained in the present study confirm the major impact of SDS on the glycemic index and glycemic response parameters of processed cereal food products, with the biscuit category displaying the highest SDS contents eliciting the lowest GI values. We also confirmed the impact of fat and fiber content which reduce the glycemic response following the ingestion of the cereal products.

Finally, this is one of the first studies investigating the effect of nutritional composition and starch digestibility parameters on different categories of cereal products and an important number of products. This is also the first time the interaction between the nutritional composition and starch digestibility parameters was investigated on the glycemic response induced by the consumption of processed cereal products.

 

References:

  1. Jenkins DJ, Wolever TM, Taylor RH et al. (1981) Glycemic index of foods: a physiological basis for carbohydrate exchange. 1981/03/01, 362-6.
  2. Englyst HN, Veenstra J, Hudson GJ (1996) Measurement of rapidly available glucose (RAG) in plant foods: a potential in vitro predictor of the glycaemic response. British Journal of Nutrition 75, 327-37.

 

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