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NutrInsight • Slow-release carbohydrates: Growing evidence on metabolic responses and public health interest

1.4 Glycemic responses are significantly influenced by
the SDS content of cereal foods

Given the potential for preserving SDS content by limiting starch gelatinization during food processing, it is
important to understand the physiological impact of SDS content.

Interest in using high SDS foods to control the postprandial glycemic response

Several randomized controlled trials in humans have investigated the physiological effects of consuming
cereal products with a high SDS content or nearly no SDS as part of a small meal. These clinical studies
showed that a high SDS content in cereal foods induces a reduced glycemic response, without exacerbating
the insulinemic response [Vinoy et al., 2013; Péronnet et al., 2015; Nazare et al., 2010]. Some of these studies
also assessed overall postprandial carbohydrate metabolism using a sophisticated isotopic method. This
method, as well as the results obtained, were presented by Prof. Martine Laville during the symposium,
and are detailed in the next chapter. The following sections focus on interesting results obtained using the
glycemic index (GI) as an in vivo marker to assess the metabolic impact of individual foods.

Impact of processing on the glycemic index of cereal foods

The GI classifies foods according to their impact on postprandial glycemia compared to a reference food.
The portion sizes of the test foods and the reference food are defined in order to provide the same amount
of available carbohydrates. The GI has often been used in research. For example, Englyst and coworkers
investigated how the GI is related to the relationship between SDS and the starch gelatinization index
previously described in this chapter [Englyst et al., 2003]. Using three groups of cereal products (breakfast
cereals, bakery products and crackers, and biscuits), this study showed that the biscuits group, which had
the highest mean SDS content due to a low level of starch gelatinization during food processing, also had
the lowest mean GI value (see Figure 3).

The impact of food processing on the postprandial glycemic response was also shown in a recent systematic
review analyzing the GI of wholegrain oat products. This study suggests that a smaller particle size and
increased starch gelatinization increase GI [Tosh et al., 2015].

Therefore, food processing influences the GI of cereal foods. However, as starch is not the only compound
found in processed cereal foods, it is important to also study the effect of other food components on the
glycemic response.

SDS is the major contributor to the glycemic response to cereal foods

The influence of nutritional composition and starch digestibility characteristics on the glycemic response
to cereal products was evaluated in a recent study [Meynier et al., 2015]. The originality of this study is that
it was the first to assess the contribution of both the interactions between different components and their
individual effects, using a large dataset of 190 cereal products that were tested using typical GI methodology.
Out of all the components and interactions tested, SDS was the major contributing factor to the glycemic
response, which confirms results that were previously obtained using smaller numbers of cereal products
[Englyst et al., 2003; Garsetti et al., 2005].

Meynier and coworkers also showed that 53% of GI variability is explained by a model involving SDS, RDS,
fat, fiber, and several interactions between these components. As Figure 4 shows, fat and fiber contribute
significantly to the GI at low and medium SDS contents, but their contributions are limited in foods with a
high SDS content. Indeed, in the high SDS content cluster, the decrease in GI fluctuates only from 60 to 40
when the fat and fiber contents increased, whereas it decreases from 70 to 20 and from 80 to 40 when fat
and fiber increased in the medium and low SDS content clusters, respectively (see Figure 4).

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