Public Thesis defense - LIBST

Influence of dietary proteins on relevant aspects of carotenoid bioavailability by Mohammed IDDIR

Pour l’obtention du grade de Docteur en sciences agronomiques et ingénierie biologique

Carotenoids are secondary plant metabolites with antioxidant and anti-inflammatory properties. Some can be converted into vitamin-A. Their dietary intake and tissue concentrations have been related to the reduced incidence of several chronic diseases. Due to their low water solubility requiring emulsification prior to absorption, carotenoids are of low and varying bioavailability. While dietary fiber, lipids, and minerals were shown to influence the solubilization of carotenoids, a prerequisite for their bioavailability, the interactions between proteins and carotenoids during gastro-intestinal (GI) digestion have, to our knowledge, never been studied systematically.

The purpose of the PhD thesis was thus to study interactions of carotenoids and frequently consumed proteins during digestion that could impact aspects of carotenoid bioavailability. Preceding a confirmatory human trial, in vitro studies were conducted, by means of GI digestion coupled to Caco-2 cellular uptake models to investigate bioaccessibility and cellular uptake, respectively.

When investigating effects of whey and soy protein isolates (WPI, SPI), gelatin and sodium caseinate on individual carotenoids, carotene bioaccessibility increased by almost 2-fold, while xanthophylls were reduced in their bioaccessibility to about half. Similarly, for real food matrices, bioaccessibility and uptake were more enhanced for apolar carotenes vs. xanthophylls. In the human trial, WPI improved by about 1/3 the bioavailability of carotenoids from the tomato/carrot juice, while SPI had a borderline negative effect, confirming in vitro results.

These findings may aid consumers in choosing meal compositions, especially persons relying on carotenoids for meeting vitamin A requirements, such as vegetarians, or those living in areas with low available pre-formed vitamin A. The results may also be interesting for food/supplement producers, offering insights into formulations that assure high carotenoid bioavailability.

Jury members :

• Prof. Yvan Larondelle (UCLouvain), supervisor
• Prof. Torsten Bohn (Luxembourg Institute of Health, Luxembourg), supervisor
• Prof. Isabelle Donnay (UCLouvain), chairperson
• Prof. Cathy Debier (UCLouvain), secretary
• Prof. Cédric Guignard (Luxembourg Institute of Science and Technology, Luxembourg)
• Prof. Antonio Cilla (University of Valencia, Spain)
• Prof. Susanne Baldermann (University of Bayreuth, Germany)

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