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

1 SLOWLY DIGESTIBLE STARCH: DEFINITION,

SOURCES, AND RECOGNIZED INTEREST
IN ITS EFFECT ON THE GLYCEMIC RESPONSE

Dr. Sophie Vinoy, Nutrition Research Group Leader at Mondele-z International R&D,
Saclay, France

According to nutritional recommendations, starch should be the major component of the diet. Due to several
factors, such as the botanical origin of the starch or food processing conditions, the digestibility of starch can
differ widely, from rapid digestibility to complete indigestibility. After briefly discussing these points, Dr. Sophie
Vinoy, nutrition researcher at Mondele-z International, presented a validated method for in vitro quantification
of the fraction of starch that is digested slowly in the small intestine, called Slowly Digestible Starch (SDS).
During the symposium, the relationship between the SDS content and the extent of starch gelatinization in
processed cereal foods was detailed, as well as the in vivo impact of SDS content on the postprandial glycemic
and insulinemic responses.

1.1 Starch, a key carbohydrate for human nutrition

International and national official institutions (FAO, WHO, US Department of Health and Human Services (HHS),
and the USDA) recommend that carbohydrates constitute 45% to 55% of daily energy intake [FAO & WHO,
1998; HHS & USDA, 2015], with the majority of dietary carbohydrates coming from starch. The importance of
this dietary component can be highlighted by a simple calculation based on recently published limits for free
sugar intake [WHO, 2015] and an energy need of 2000 kcal per day. According to this estimation, the quantity
of starch consumed on a daily basis should be approximately 130 g to 200 g. This is in agreement with national
food-based dietary guidelines that rank cereal foods, which are the major source of starch intake, as the basis
of the diet [The Chinese Food Guide Pagoda; Eatwell Guide; MyPlate].
As starch is the major component of our daily diet, it is important to investigate its digestibility.

1.2 Starch has different digestibility properties

There is not one starch

Starch is composed of two large glucose polymers: amylose and amylopectin. Amylose has a linear structure
comprised of glucose units linked by a-1,4 bonds. Amylopectin has a branched structure, with a-1,6-linked
glucose units at the branch point and a-1,4 bonds in the linear regions [Bornet, 1993]. As a result of their
different structures, these two molecules are not digested in the same way in the small intestine and specific
enzymes are required to digest the a-1,6-glycosidic bonds in amylopectin [Ao et al., 2007].

In plants, amylose and amylopectin are organized in concentric layers of alternate crystalline and amorphous
regions, which form a granule. The structural characteristics of starch granules, such as granule size and the
unit-chain length distribution of amylopectin, vary with the botanical origin of the starch, and modulate their
enzyme digestibility [Srichuwong et al., 2005]. For example, among 15 starches selected from different botanical

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