Inhibitory effect of black tea, lemon juice, and other beverages on salivary and pancreatic amylases: What impact on bread starch digestion? A dynamic in vitro study

Abstract

Certain food properties (ex.: pH, polyphenolic composition) can inhibit digestive amylases and thereby slow down starch digestion. Our aim was twofold. (1) To determine the impact of 21 beverages and condiments (coffees, teas, wines, vinegars and lemon juice) on salivary and pancreatic amylolysis: inhibition ranged from 10% to 100% in our experimental conditions. (2) To investigate the effect of one black tea and lemon juice (selected for their strong inhibitory capacity) on starch hydrolysis during dynamic oro-gastro-intestinal digestion of bread. Compared to water (control), the effect of black tea was limited to a ≈20% reduction of released oligosaccharides during the intestinal phase. Lemon juice had a remarkable effect, completely interrupting gastric amylolysis by salivary amylase via a preliminary acidification of gastric contents. These results provide a strong biochemical rationale for the development of dietary strategies to improve the glycaemic impact of starch-rich meals which could be tested in vivo.

Glycemic response, satiety, gastric secretions and emptying after bread consumption with water, tea or lemon juice: a randomized crossover intervention using MRI

“…The common denominators of the meals resulting in lower postprandial glycemia in these 18 independent studies were the main glucose source (starch) and the overall lower pH of the meal. Previously, we provided evidence that the lower glycemia could, at least in part, be explained by a premature interruption of starch digestion in the stomach [5,15]. Conversely, a reduced and/ or delayed gastric emptying with acidic meals has also been identified as another candidate explanation [21], since gastric emptying rates influence the rate of nutrient absorption into the blood stream.…”

“…The exploitation of this knowledge to slow down starch digestion has also been the subject of some of our previous work. Particularly, we have examined routes of HSA inactivation during gastric digestion in vitro and observed promising results via either an increase in acidity or polyphenol content [5,15]. A growing body of evidence from randomized, controlled, crossover trials reinforces the viability of lowering postprandial glycemic responses to starchy foods by 20-50% with increased meal acidity.…”

Mathematical modelling of food hydrolysis during in vitro digestion: From single nutrient to complex foods in static and dynamic conditions

“…In static in vitro digestion protocols, however, the oral phase is often ignored or only performed to break down solid foods into small-sized particles with no addition of salivary α-amylase. This is justified by the short duration of the oral phase and by the widespread use of a gastric pH of 3.0 or below, which irreversibly inactivates human salivary α-amylase (Bernfeld et al, 1948;Freitas & Le Feunteun, 2019). Although some studies have suggested that an oral digestion step should be included in static in vitro digestion protocols as it modifies starch digestion kinetics in the intestinal phase (Tamura et al, 2017), others did not observe any modification (Woolnough et al, 2010).…”

“…Figure 2A provides an example of a data set for all enzymes generally included in an in vitro gastric digestion experiment (Brodkorb et al, 2019;Mulet-Cabero et al, 2020). The maximum activity of human salivary amylase is around pH 6-7, and gradually decreases until it is totally inactivated around pH 3.0-3.5 (Bernfeld et al, 1948;Freitas et al, 2018;Freitas & Le Feunteun, 2019). The activity of porcine pepsin is generally negligible for pH above 5 and has its maximum around pH 2 .…”

Anti‐hyperglycaemic effects of Burdock (Arctium lappa L.) leaf flavonoids through inhibiting α‐amylase and α‐glucosidase

“…Hyperglycaemia can be improved by controlling blood glucose levels within the normal range; therefore, reducing postprandial blood glucose is key to reducing harm. Starchy foods are a leading source of exogenous glucose and play a crucial role in postprandial blood glucose (Freitas & Le Feunteun, 2019). An effective management approach to achieve a lower glycaemic response to starchy foods is by decreasing starch hydrolysis or glucose absorption which may be achieved by inhibiting activities of α‐A and α‐G activities which cause a delayed absorption of glucose during digestion (Sun & Miao, 2020).…”