Does protein intake improve the bioavailability of carotenoids?

2019 - 05 - 13

LIH launches CAROPROT, a new study in nutrition research with healthy volunteers. It will be investigated how our body could better absorb carotenoids, plant pigments that are thought to be very beneficial for health.

Carotenoids are organic compounds that belong to the chemical family of terpenoids. These plant pigments are responsible for the red, orange and yellow colouring of many fruits and vegetables such as tomatoes, carrots and maize, but are also contained in leafy vegetables such as spinach or kale. Carotenoids, like beta-carotene for example, are precursors by which the body can produce vitamin A. Many studies suggest that carotenoids have further positive health effects. Their consumption has been associated with a reduced incidence of developing several chronic diseases, such as diabetes, cardiovascular diseases, certain eye diseases and some types of cancer.

Limited absorption of carotenoids Carotenoids are absorbed by intestinal cells during digestion, and then transported via the bloodstream to organs and tissues. The absorption of carotenoids is however incomplete. Their bioavailability is not optimal as these molecules are very lipophilic and thus not soluble in water. Their assimilation therefore depends on their chemical properties but also on the surrounding environment, in particular on the composition of the food ingested simultaneously during a meal. It is interesting to study how certain food combinations could positively influence the bioavailability of carotenoids.

Carotenoids and proteins – CAROPROT

In the new research project led by Dr Torsten Bohn at LIH’s Department of Population Health, researchers will study how proteins could change and maybe improve the solubilisation and absorption of carotenoids. Indeed, proteins were shown to be effective emulsifiers, having both hydrophobic and hydrophilic parts in their molecular structure. To date, the effect of protein-carotenoid interaction during digestion, absorption and biodistribution on carotenoid bioavailability has never been studied in detail.

The CAROPROT study aims to fill this knowledge gap and may provide indications for a diet with optimised carotenoid absorption. This would be particularly beneficial for people who do not consume enough vitamin A from meat, such as vegetarians and vegans’, explains Dr Bohn. ‘The main objective of this study on human subjects will be to evaluate the influence of the simultaneous consumption of two different selected protein sources on the bioavailability of food carotenoids’, adds Mohammed Iddir, PhD candidate in Dr Bohn’s group.

Healthy participants wanted

For the CAROPROT study, the research team is seeking healthy male volunteers that will be subjected to a controlled diet for nearly a month. Various tests will be conducted on these subjects and biological samples will be taken for laboratory analysis. In total, 24 men from Luxembourg and the surrounding regions, aged between 20 and 50 years, shall to be included in the study. Exclusion criteria are obesity, smoking, frequent alcohol consumption, vegan diet, certain allergies, intake of food supplements and continuous medical treatment. Women cannot be included in the study due to a possible impact of the menstrual cycle on the measured parameters.

The procedure consists of three clinical visits at the LIH premises in Strassen of approximately 11 hours each. During these visits, a breakfast rich in carotenoids will be given, blood samples will be taken at different time-points and a medical check-up will be conducted. For some subjects, faecal samples will be collected as well. Participants will be required to follow a diet low in carotenoid-rich fruit and vegetables for four weeks. Participation will be compensated with 300 euros at the end of the study. The medical check-up is for free and the results will be communicated to the participants.

Funding and collaboration

The CAROPROT project is supported by a CORE grant (C16/BM/11320230) from the National Research Fund (FNR). The Luxembourg National Committee for Research Ethics (CNER) approved the experimental protocol (201710/04). The study will be conducted in close collaboration between two units of LIH’s Department of Population Health: the Epidemiology and Public Health Research Unit and the Clinical and Epidemiological Investigation Centre. The Luxembourg Institute of Science and Technology (LIST) is also a partner in this study, in part responsible for analytical measurements. In addition, Laboratoires Réunis will be involved by determining certain parameters such as eligibility markers in blood samples.

Interested in taking part in the study to contribute to nutrition research?
Please contact: Guilherme Marques, (+352) 26 970 821,

Questions about the CAROPROT study?
Please contact: Dr Torsten Bohn, (+352) 26 970 394,