Background
Vitamin D3 is involved in a large number of physiological processes from bone formation and reproduction to modulating the immune system. There are two sources of vitamin D3 in cattle and other mammals:
-Synthetic vitamin D3 supplied in the feed.
- Natural vitamin D3, which is synthesised in the skin during exposure to sunlight or UV light.
From a physical and chemical point of view, vitamin D3 from the two sources is indistinguishable; however, from a physiological perspective it seems to be an entirely different matter. But - how on earth does the body go about distinguishing two completely identical molecules from each other, and even discriminate so heavily against one of the forms (the synthetic) that it is highly toxic in the body and can be easily overdosed in contrast to the natural form?
This is the question which this project attempts to answer before a much-needed revision of the existing recommendations for vitamin D3 supplementation of cattle and other livestock can be implemented. A revision, which ultimately may lead to the conclusion that vitamin D3 should not be provided through the diet, but should be provided through exposure to natural or artificial sunlight (UV light). An insight which could turn the management of livestock vitamin supply inside out in both conventional and organic farms.
Project period
February 1st 2013 - January 31st 2016.
Poster: Vitamin D2 and Vitamin D3
Poster: Vitamin A and Vitamin E -EAAP 2014
Abstract: Vitamin A and E circulate in different cattle plasma fractions
Hypotheses
Securing a sufficient vitamin D3 (D3) status of dairy cattle is particularly important in human health, because dairy products are an important source of dietary D3 in human nutrition. There are two sources of D3 in cattle and other mammals including humans: endogenous D3 produced in the skin during exposure to sunlight or UV light and synthetic dietary D3 absorbed from the gut. Vitamin D3 from the two sources are chemically similar but act very different in the organism i.e. dietary D3 from supplements is highly toxic, while it is impossible to be D3 intoxicated by sunlight. In this project it is hypothesised, that synthetic dietary D3 uses a different plasma transport mechanism than endogenous D3, and that this prevents dietary D3 from feedback regulating the synthesis of transport proteins and enzymes involved in D3 metabolism, thereby causing the severe toxicity of synthetic D3.
Implications and perspectives
Understanding the physiology behind the difference between endogenous and dietary synthetic D3 holds the key to developing safe D3 supplements in the feed-, food-, and medical industry. However, research on the physiology behind an effective and safe utilisation of synthetic D3 additives in comparison to UV light or sunlight is seriously lacking. It appears from experience that, for the time being, endogenous sources of D3 are the better choice for safely providing dairy cattle high enough levels of D3 to secure the nutritional value of dairy products, since dietary D3 is toxic in the necessary doses. Natural sources of D3 are of particular interest in organic husbandry since it builds on a sustainable approach to agriculture and consumers demand organic milk, meat etc. produced without synthetic additives.
Time schedule
The project runs for 36 months and includes establishing the mechanisms behind plasma transport of D3 from endogenous and synthetic dietary sources both when they are present in plasma one by one and simultaneously, by using vitamin D2 as a substitute for synthetic dietary D3.
| 2013 | 2014 | 2015 | |||||||||
Q1 | Q2 | Q3 | Q4 | Q1 | Q2 | Q3 | Q4 | Q1 | Q2 | Q3 | Q4 | |
Part 1 Plasma transport of natural D3 |
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Part 2 Plasma transport of synthetic D3 |
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Part 3 Validation of D2 as substitute for D3 | x | x | x |
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Part 4 Distinction between synthetic D3 and natural D3 |
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