During the winter period, vitamin D deficiency is a common problem in the northern part of the world, affecting up to 1 billion people. There is every indication that vitamin D has a substantial impact on our health. One way of ensuring that we take up sufficient vitamin D is to fortify foods with the vitamin, which is mainly produced in our skin when exposed to sunlight.

However, vitamin D fortification is complicated as the vitamin is fat-soluble and prone to degradation in foods.   

Within the framework of the DFORT project, funded by Innovation Fund Denmark with an amount of 13 million DKK, researchers from Aarhus University cooperate with a number of Danish and international partners to improve vitamin D availability.   

How to bind vitamin D in the stomach?

The researcher have used model systems to study how selected milk proteins are able to form vitamin D complexes and thus protect the vitamin against degradation long enough to ensure that vitamin D is absorbed into our digestive system.

Professor Daniel Otzen from the iNANO Centre at Aarhus University explains:

  - Our hypothesis was that a complex consisting of the milk protein ?-lactalbumin and a fatty acid might form a protective membrane around the vitamin. However, these complexes quickly disintegrated because of the acidic stomach environment. We then discovered that the pure protein, ?-lactalbumin, is able to bind vitamin D – very efficiently. It is a flexible protein which quickly looses its structure and thus forms a larger surface on which to bind the vitamin. This was a bit of an eye-opener.   

The ?-lactalbumin whey protein is a natural component in milk, and occurs in large quantities. Usually, another whey protein, ?-lactoglobulin, is used to bind vitamin D in fortified milk products. However, in this case ?-lactalbumin demonstrated the best effect at a low pH value, i.e. in an acidic environment.   

Increased vitamin uptake

Next, Project Leader Trine Kastrup Dalsgaard, Department of Food Science, studied the stability of vitamin D3 in food systems.

It has been demonstrated that milk and juice are able to significantly improve solubility and stability of vitamin D3, but that milk may provide further protection of the vitamin. At Department of Food Science and Department of Clinical Medicine, a long-term intervention study – in rats and in humans – is currently planned in order to study vitamin bioavailability and the effect of complex formation using milk proteins.

- It is hypothesized that protein-bound vitamin D will degrade less than normally in the acidic stomach environment resulting in increased vitamin uptake. This will allow an increased vitamin uptake and help reduce uptake rate as well as the utilization of the vitamin, Trine Kastrup Dalsgaard says.

Further information

Partners in this interdisciplinary project include researchers from Aarhus University Hospital, iNANO and Departments of Food Science and Clinical Medicine at Aarhus University, Leida University in Spain, Groningen University in the Netherlands as well as the companies Arla Foods Amba, Arla Foods Ingredients, DSM and Rynkeby. The project ends by 30 August 2020.    
 

Contact
Project leader Trine Kastrup Dalsgaard
Department of Food Science, AU 
Mail: trine.dalsgaard@food.au.dk
Phone +45 8715 7998