Vitamin D: evidence of insufficiency and effectiveness of dietary supplementation

1
Vitamin D evidence of insufficiency and
effectiveness of dietary supplementation

• Julie Wallace
• Northern Ireland Centre for Food and Health

2
Vitamin D

• A fat soluble vitamin found in two forms
• Vitamin D2 synthesised in plants
• Vitamin D3 synthesised in animals
• Two main forms in humans
• 25(OH)D3 (status measure)
• 1,25(OH)2D3 (active hormonal form)
• Functions
• 1,25(OH)2D3 stimulates Ca absorption and
  mobilization, via parathyroid hormone
• Classical role in bone mineralisation
• Non-skeletal effects immunoregulatory effects,
  regulation of glucose metabolism, cancer
  prevention etc.

biologically inactive
3
Vitamin D status

• Cut-off for vitamin D status not clearly defined.
  
• A plasma concentration of lt25 nmol/L of 25(OH)D
  denotes deficiency based on prevention of rickets
  and osteomalacia1
• In terms of vitamin D sufficiency, concentrations
  up to 80 nmol/L have been suggested for optimal
  bone health2
• However, concentrations up to 100 nmol/L are also
  proposed, albeit more speculatively3

4
Vitamin D -sources

• Primary source
• Synthesis in the skin following exposure to UVB
  irradiation from the sun
• BUT
• Synthesis is limited
• Sunscreen use
• Cloudy day no UV penetration
• From Oct-Mar UV light is of insufficient
  intensity for synthesis
• Synthesise vitamin D in the summer and store for
  the winter?

5
Summer 2008 in Northern Ireland!
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Vitamin D -sources

• With insufficient sun exposure for synthesis,
  vitamin D becomes an essential nutrient
• Currently no recommended intake for UK adults
  only vulnerable groups
• Available in the diet
• fish oils,
• liver,
• egg yolks,
• fortified foods only very limited sources
• Is there evidence of sub-optimal status in the UK?

7
Evidence of impaired statusin the UK and Ireland

• At risk groups
• 94 of Asian women had serum 25(OH)D ltor37.5
  nmol/l4
• 37.2 of the elderly Irish women, with inadequate
  vitamin D status in wintertime5
• 24 of inner-city children classified as
  deficient6
• Among pregnant women, 64 of Middle-Eastern women
  and 13 of Caucasian women deficient7
• General population
• 15 of UK adults deficient8
• 23 of adults in the low income survey deficient9

8
And in Northern Ireland?

• Clinical studies
• A high prevalence of vitamin D inadequacy in
  elderly patients, higher in patients with a hip
  fracture10
• 13 of fibromyalgia patients classified as
  vitamin D deficient11
• 14 of men with forearm fracture vitamin D
  deficient12

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Recent research within NICHE

• Status in adolescents
• Status and supplementation in young adults aged
  20-30 years
• Investigation of the contribution of sunlight and
  diet to vitamin D status in adults aged 20-40
  years

10
Vitamin D status in adolescents the Northern
Ireland Young Hearts 2000 cohort.

• YH2000 - a cross-sectional study of a
  representative sample of adolescents, aged 12 and
  15 years
• Subjects provided a blood sample
• vitamin D, PTH and bone turnover markers
• Data collected on
• pubertal status and anthropometry
• Bone Mineral Density (BMD)
• physical activity
• food intakes.
• n1015
• Collaboration between UU, QUB and UCC funded by
  the Higher Education Authority

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YH2000 vitamin D status

• Intakes of vitamin D were low (median lt2 µg/d)
• Overall, 36 were vitamin D insufficient (25(OH)D
  lt50nmol/l)
• Insufficiency was more common in individuals
  sampled in wintertime
• Insufficiency in wintertime was more prevalent
  among girls 55 versus 38

Hill et al British Journal of Nutrition 2008 99
1061-7
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YH2000 vitamin D insufficiency has implications
for bone health among girls living in Northern
Ireland

• Girls with low vitamin D status had higher PTH
  and bone
• turnover markers than did those with high
  vitamin D status.

Cashman et al, American Journal of Clinical
Nutrition 2008 87 103944.
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Status and supplementation in young adults aged
20-30 years
Recruit healthy adults (18-30 yrs)
January
Baseline blood sample
8 weeks
March
Post-supplementation blood sample
Vitamin D status
Calcium PTH concentrations
Bone turnover markers
Immune function measurements
14
Vitamin D insufficiency is evident among young
adults in Northern Ireland in winter. Status is
improved following supplementation with 15µg of
vitamin D3

Barnes et al, European Journal of Clinical
Nutrition 2006 60 727-733
15
Dietary requirements for vitamin D An
investigation of the relative significance of
dietary intake and sunlight on vitamin D status.

• Project in collaboration with UCC and funded by
  the Food Standards Agency

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240 adults (20-40yrs) 120 at UU and 120 at
UCC
May/June
Sunshine exposure diary/questionnaire
Polysulphone badges
July
BASELINE
October/Nov
Repeat with 65-85 year old adults
15µg D?
10µg D3
5µg D?
placebo
6 months
March
POST SUPPLEMENTATION
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Results from the 20-40yr old volunteers
18
Dietary vitamin D intake, sunshine exposure and
vitamin D status at baseline and
post-intervention.
Values represent medians (IQR). Repeated measures
ANOVA was used to test the treatment X time
interaction for serum 25(OH)D (P0.0001).
Different superscript letters represent
significant (Plt0.05) differences among groups.
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Dietary requirement to prevent deficiency

• Question What is the dietary vitamin D intake
  required
• during wintertime to prevent deficiency ie
  maintain
• 25(OH)D gt25nmol/L (accounting for the impact of
• sun exposure)?
• Answer
• To keep 25(OH)D gt25nmol/l in 97.5 of the
  population,
• recommended intake (RDA) should be set at
• 9ug/d.
• Accounting for sun exposure, the RDA was
  estimated as
• 7µg/d in sun seekers
• and
• 12µg/d in sun avoiders
• Higher than current intakes

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Dietary requirement for sufficiency
Question What is the dietary vitamin D intake
required during wintertime to prevent deficiency
ie maintain serum 25(OH)D above 50nmol/L
(accounting for the impact of sun
exposure)? Answer To keep 25(OH)D gt50nmol/l in
97.5 of the population, recommended intake
(RDA) should be set at 28ug/d. Accounting for
sun exposure, the RDA was estimated as 26µg/d in
sun seekers and 32µg/d in sun
avoiders Considerably higher than current intakes
Cashman et al American Journal of Clinical
Nutrition in press
21
To summarise

• Should we be concerned about vitamin D in
  Northern Ireland?
• Vitamin D has the potential to impact on many
  diseases, not just on bone health
• Status in Northern Ireland is low among healthy
  adults and adolescents in wintertime
• Extensive evidence of insufficiency and also data
  highlighting deficiency
• Increased dietary vitamin D can improve
  wintertime status but at intakes that are
  unlikely to be achieved with food based dietary
  strategies alone

YES!
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Acknowledgements

• University College Cork
• Professor Kevin Cashman
• Dr Mairead Kiely
• Dr Tom Hill
• Queens University Belfast
• Professor Liam Murray
• University College Dublin
• Professor Colin Boreham
• Altnagelvin Area Hospital
• Dr William Dickey
• Dr John McCarthy

• University of Ulster
• Professor Sean Strain
• Dr Maxine Bonham
• Dr Emeir Duffy
• Dr Pamela Magee
• Dr Geraldine Horigan
• Dr Maria Barnes
• Ms Kirsty Forsythe
• Ms Clare Griffin
• Mr Douglas Dalrymple
• Alberta Cancer Board
• Dr Paula Robson

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References

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• Yu et al, Clin Endocrinol (Oxf). 2008
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• Nelson et al 2007 Low Income Diet and Nutrititon
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