For immediate release
16 September 2004

Vitamin D briefing - a summary

Press briefing given by Dr Birgit Teucher at the Science Media Centre in London on Thursday 16th September, in collaboration with:

• Graham Bentham - Professor of Environmental Sciences at the University of East Anglia
• Professor Brian Wharton - Institute of Child Health, London
• Dr Barbara Boucher - Honorary senior lecturer at Barts & the London Queen Mary School of Medicine and Dentistry
  

Health functions

Bone health

The role of vitamin D has traditionally been thought to be limited to calcium and phosphate homeostasis, and associated maintenance of bone health, i.e. prevention of rickets (or osteomalacia - adult equivalent of rickets) and its contribution to reducing the risk osteoporosis (or loss of bone mass).

Newly proposed health functions

• Since the 1980's it has become increasingly apparent that vitamin D may have important roles beyond its effects on bone.
• A wealth of epidemiological literature provides circumstantial evidence that chronic vitamin D insufficiency may be associated with an increased risk of various diseases including muscle weakness, hypertension, autoimmune disease such as multiple sclerosis and type 1 diabetes, cardiovascular disease, and certain types of cancer (e.g. colorectal cancer, prostate cancer, breast cancer).
• We do not know how much vitamin D is required for these health benefits.
• The newly proposed biological roles for vitamin D are supported by molecular data confirming that many tissues other than bone have vitamin D receptors and most importantly that many of these tissues can produce the biologically active form of vitamin D.

Some references

VanAmerongen BM, Dijkstra CD, Lips P and Polman CH (2004) Multiple sclerosis and vitamin D: an update. European Journal of Clinical Research 58, 1095-1109.

Holick FM (2003) Vitamin D: A millennium perspective. Journal of Cellular Biochemistry 88, 296-307.

Vieth R (2004) Why the optimal requirement for vitamin D3 is probably much higher than what is officially recommended for adults. Journal of Steroid Biochemistry and Molecular Biology 89-90, 575-579.

Vitamin D status of UK adults

• Progress in vitamin D research suggests that the traditionally used cut-off to determine vitamin D deficiency is now considered out of date by many scientists. Even at this level approx. 24% of adults aged 19 to 64 are classified as vitamin D deficient in winter according to the most recent National Diet and Nutrition Survey.
• Clinical evidence supports a doubling of this cut-off level to ensure optimal bone health and a reduced risk of osteoporosis. At this level, approx. half of the UK population would be classed as vitamin D deficient during the winter months.
• The proposed target level in relation to the newly defined actions of vitamin D would mean that almost all British people are deficient, especially during winter.
• Lifestyle may play an important role in determining an individual's vitamin D status. The dominance of indoor activities may contribute to the high prevalence of low vitamin D status among young adults. There is also evidence to suggest that increased body fat may reduce the bioavailability of vitamin D.

The role of diet

• Fatty fish, cod liver oil and egg yolk are good sources of vitamin D. Fortified foods such as breakfast cereals and margarine add to the total UK vitamin D intake.
  
• If the US "adequate intake" level for vitamin D was applied in the UK, 90% of the UK adult population would fall short.
  
• There is no UK recommended intake level for 19-64 year old adults.

Future research

A wealth of evidence suggests that current guidelines for vitamin D should be revised, but more information is required before this can be done.

• For most of the new functions we need more research to elucidate the mechanisms of disease prevention
• Clinical trials are needed to identify target levels for vitamin D (status) that are commensurate with optimal health.
• There is limited knowledge about the bioavailability of different sources and forms of vitamin D.
• Once new target levels have been identified, these need to be translated into food fortification policies and programmes to improve dietary intake of vitamin D.
• There is a need for international standardization of vitamin D measurements.

Some references

Hollis B (2004) Editorial: The determination of circulating 25-hydroxyvitamin D: no easy task. Journal of Clinical Endocrinology and Metabolism 89, 3149-3151.

Further background

Vitamin D deficiency and children:
www.sacn.gov.uk/pdfs/smcn_03_02.pdf "In Cincinnati 20 minutes a day out of doors with exposed hand and face were enough to maintain satisfactory vitamin D levels in older infants".

FSA 2002 review of vitamin D:
www.food.gov.uk/multimedia/pdfs/evm-00-11r.pdf

EU research project on vitamin D food fortification:
www.optiford.org

US factsheet on vitamin D, including food sources:
http://ods.od.nih.gov/factsheets/vitamind.asp

www.bbc.co.uk/science/hottopics/sunshine/benefits.shtml

Please contact Zoe Dunford for more information, and an interview with an IFR scientist on this subject: 01603 255111 / zoe.dunford@ifr.ac.uk

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