The inhibition of enzymes that hydrolyze starch during digestion could constitute an opportunity to slow down the release, and ultimately the uptake, of starch-derived glucose. Simple dietary approaches consisting in pairing starch-rich foods with beverages that have the capacity to inhibit such enzymes could be an effective and easily implementable strategy. The objective of this work was to test the impact of black tea and lemon juice on the glycemic response to bread and subsequent energy intake in healthy adults.
A randomized crossover study was conducted with equal portions of bread (100 g) and 250 ml of water, black tea or lemon juice. Capillary blood glucose concentrations were monitored during 180 min using the finger-prick method. Ad libitum energy intake was assessed 3 h later.
Tea had no effect on the glycemic response. Lemon juice significantly lowered the mean blood glucose concentration peak by 30% (p < 0.01) and delayed it more than 35 min (78 vs. 41 min with water, p < 0.0001). None of the tested beverages had an effect on ad libitum energy intake.
These results are in agreement with previous in vitro studies showing that lowering the pH of a meal can slow down starch digestion through premature inhibition of salivary α-amylase. Furthermore, the effect of lemon juice was similar to what has been repeatedly observed with vinegar and other acidic foods. Including acidic beverages or foods in starchy meals thus appears to be a simple and effective strategy to reduce their glycemic impact.
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Area under the curve
Body mass index
Human salivary α-amylase
Visual analogue scale
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We thank the participants for their significant contribution. We thank Anders Sjödin and Thea Toft Hansen (University of Copenhagen) for their help during the preparation of this study. We thank Claire Gaudichon (AgroParisTech), Furio Brighenti (University of Parma), Luca Marciani (University of Nottingham) and Valérie Micard (Montpellier Supagro) for helpful discussions. We thank David Forest for technical help. We thank Amira Halabi and Ousmane Suwareh (INRAE) for their help using R software for statistical analysis. We thank Pascal Bonnarme, head of the GMPA research unit, and Isabelle Souchon and Anne Saint-Eve, team leaders, for their valuable support and technical help.
Daniela Freitas acknowledges funding from an IDEX Paris-Saclay doctoral grant. This research did not receive any other specific grant from funding agencies in the public, commercial or not-for-profit sectors.
Conflict of interest
The authors report no conflict of interest.
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Freitas, D., Boué, F., Benallaoua, M. et al. Lemon juice, but not tea, reduces the glycemic response to bread in healthy volunteers: a randomized crossover trial. Eur J Nutr 60, 113–122 (2021). https://doi.org/10.1007/s00394-020-02228-x
- Glycemic index
- Salivary α-amylase