When nature knows best

Projektets formål og baggrund

Vitamin D3 er involveret i en lang række fysiologiske processer fra knogledannelse og reproduktion til immunforsvarets funktion. Der findes to kilder til forsyning med vitamin D3 hos kvæg og andre pattedyr:
- Syntetisk vitamin D3, som tildeles i foderet gennem vitamintilskud.
- Naturligt vitamin D3, som produceres i huden ved bestråling med sollys eller UV-lys.

Set fra en fysisk-kemisk vinkel er de to typer vitamin D3 fuldstændig ens, men set fra en fysiologisk vinkel er det tilsyneladende en helt anden sag. Men hvordan i alverden bærer kroppen sig ad med at skelne to fuldstændig ens molekyler fra hinanden og tilmed diskriminere så stærkt mod den ene (syntetiske) form, at det er stærkt toksisk i organismen og meget let kan overdoseres i modsætning til den naturlige form?

Det er et spørgsmål, som dette projekt forsøger at besvare, inden en tiltrængt revidering af de eksisterende fodernormer for vitamin D3-tildeling til kvæg og andre husdyr kan gennemføres. En revidering som i yderste konsekvens kan føre til den konklusion, at vitamin D3 slet ikke bør tildeles via foderet, men bør skaffes gennem bestråling med naturligt eller kunstigt sollys (UV-lys). En erkendelse som kunne vende husdyrbrugets management af dyrenes vitaminforsyning på hovedet hos både konventionelle og økologiske bedrifter.

Projektperiode og offentliggørelse
Projektet starter Februar 2013 og afsluttes januar 2016. Projektets resultater, som forventes at foreligge ved projektets afslutning, offentliggøres på ANIS hjemmeside, ved nationale kongresser, i nationale og internationale fagtidsskrifter.

 

Project description

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.

 

  • Endogenous and dietary D3 uses different transport mechanisms in plasma.
  • Failure of binding dietary D3 to designated D3 transport proteins used by endogenous D3 in plasma causes the severe toxicity of synthetic dietary D3 due to failing feedback regulation of transport proteins and liver based enzymes involved in D3 metabolism.

 

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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x

 

 

 

 

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x

 

 

Part 2

Plasma transport of synthetic D3

 

 

 

 

x

x

 

 

x

x

 

 

Part 3

Validation of D2 as substitute for D3

x

x

x

 

 

 

 

 

 

 

x

 

Part 4

Distinction between synthetic D3 and natural D3

 

 

 

 

 

 

x

x

 

 

x

x