Current Controversies in Vitamin D Dr. Susan Lanham-New
Head, Nutritional Sciences Division University of Surrey FFL eSeminar A-level and Advanced Hi...
Current Controversies in Vitamin D Dr. Susan Lanham-New
Head, Nutritional Sciences Division University of Surrey FFL eSeminar A-level and Advanced Higher teachers and students Wednesday 6th October 2010
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FFL eSeminar A-level and Advanced higher London 06/10/2010 Outline of Presentation What is vitamin D? – Nutrient or pro-hormone? – Dietary sources Importance of UVB exposure – Helpful guide re your ‘shadow’ Vitamin D recommendations Results of FSA funded University of Surrey D-FINES study Problem of vitamin D ‘insufficiency’ in UK – What is the optimal cut-off for vitamin D? Safe tolerable upper limit of vitamin D – Toxicity issues
• Importance of the Vitamin D receptor • Rank Forum on Vitamin D & other key vitamin D papers
Vitamin D Headlines Vitamin D has been recently heralded as the wonder vitamin
Vitamin D Sources
Vitamin D is a fat soluble vitamin. Sources: Diet (oily fish, cod liver, margarine, butter, milk, fortified cereals, eggs, supplements) Sun light (UVB, 290315 nm)
Vitamin D Function: maintain serum calcium Kidney reabsorption of calcium
1,25OH2D Intestinal absorption of calcium
Bone resorption of calcium
Conflicting international recommendations….. UK DoH 1998 = No recommended μg/day (sun); US 1997 = 5 μg/day adults; 10/15 μg/day elderly
Vitamin D Requirements Age group
DRI
RNI
(Institute of Medicine, 1997)
(Department of Health, 1991)
0-6 months
5 μg (200 IU)
8.5 μg (340 IU)
7 mo - 3 y
5 μg (200 IU)
7 μg (280 IU)
4 - 50 years
5 μg (200 IU)
0 μg
51 - 64 years
10 μg (400 IU)
0 μg
65 – 70 years
10 μg (400 IU)
10 μg (400 IU)
71 + years
15 μg (600 IU)
10 μg (400 IU)
COMA reports 1991/1998
SACN Position statement on Vitamin D 2007
Vitamin D Deficiency
Vitamin D deficiency causes: Rickets in children. Osteomalacia in adolescents and adults. Secondary hyperparathyroidism.
Commonly used cut off; 12 ng/ml (25OH)D
Vitamin D People at risk
People at risk: Living in high latitude Ethnicity (darker skin) Limited outdoor activity Exclusively breast-fed infants Aging Veiling
FSA NO5 Call Title: Interaction between diet and sunlight exposure on vitamin D status (25OHD) and functional markers of calcium metabolism and bone health in Asian and Caucasian women living in Southern England Applicants: Lanham-New SA (Surrey) and Berry JL (Manchester) Duration Start: 1st November 2005 for 48 months
D-FINES Study
Vitamin D, Food Intake, Nutrition and Exposure to Sunlight in Southern England
Background Questions which we were trying to address and why these are important for the RNI •
There is evidence in the literature (NDNS surveys and 1958 British Cohort) of low 25OHD status but there is little data on the consistent effect of season on 25OHD in Caucasians and no data on Asian populations
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We know that vitamin D is derived from two sources: - Skin (endogenous) - Diet (exogenous)
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We don’t know what the relative significance of both dietary sources and sunlight exposure on vitamin D status is
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This is a key question as the current RNI for the 4-64 year old population is based on the assumption that individuals get enough UVB exposure for vitamin D manufacture
Vitamin D intake & status in Elderly British Men and Women Free-living elderly 97% of participants had intakes below the RNI 8% of participants had low blood levels of 25-OHD RNI Institutionalised 99% of participants had intakes below the RNI 37% of participants had low blood levels of 25-OH National Diet & Nutrition Survey: people aged 65 years and over. HMSO 1998.
