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

2 NMECFLEEFIWCNEHICLCYTAASNELMIOESFVEMRSIDSLGEOOINNWFCG-AERECOEVTLNIIEDOTAENHSNEEOCPCFEHAPRYOSBLIOYOHPLHYODEGRNICAOATLLESS:

FROM CEREAL FOODS

Prof. Martine Laville, Professor of Nutrition, Medical School, Lyon 1 University,
France

Slowly Digestible Starch (SDS) is a starch fraction of interest that, when present at high levels in starchy
foods, decreases the postprandial glycemic response. But how does SDS modulate the glycemic response?
Prof. Martine Laville from the Rhône-Alpes Research Center for Human Nutrition (CRNH Rhône-Alpes, France)
detailed the clinical evidence regarding the acute physiological effects of SDS, and particularly the results
obtained using a method that enables investigation of the metabolic fate of ingested carbohydrates (from
absorption to uptake). This technique has proven that the starch fraction identified as SDS is relevant in humans.
She also presented some promising findings suggesting that preserving a high SDS content in starchy foods
may have beneficial effects to human health.

2.1 Modulation of postprandial glycemia:
interest and nutritional factors involved

In healthy subjects, the blood glucose concentration is maintained within a narrow range (4-10 mmol/l), despite
an intermittent supply of glucose from the diet (exogenous glucose). This is possible due to tight hormonal
regulation of glucose uptake by tissues and hepatic glucose production. This regulation, which is responsible
for maintaining glucose homeostasis, is impaired in diabetic subjects, leading to hyperglycemia which, when
prolonged, can lead to several health complications.

Postprandial glycemic excursions (and related insulinemic and lipidemic excursions) have been highlighted
in the genesis of chronic metabolic diseases [Blaak et al., 2012], which has led to interest in nutritional
interventions that could help limit these postprandial events.

Since the introduction of the GI concept in the 1980s, numerous studies have investigated the effects of a low
GI diet. Although there is evidence in the literature of the positive health effects of a low GI diet in diabetic
and glucose-intolerant subjects, the positive health effects of a low GI diet in healthy subjects remain to be
determined. One potential explanation for the discrepancies observed between these studies is that the
GI of foods can be decreased by different nutritional factors, including the type and quality of the ingested
carbohydrates and the quantity of other nutrients (fat and protein) [Vinoy et al., in press]. Depending on the
factor(s) involved, the impact on gastrointestinal and hormonal factors that interact with the blood glucose
response (such as gastric emptying, intestinal absorption, microbiota, insulin, glucagon, and gut hormones)
differs.

The slow digestibility of starch, as characterized by the SDS content, is one nutritional factor able to decrease
the glycemic response. To better understand the mechanisms involved, the impact of SDS on intestinal
absorption has been investigated, in addition to the metabolic aspects. This has been made possible due to a
sophisticated tracking method that uses stable glucose isotopes.

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