Vitamin D deficiency Prevalence and health implications for the South Asian community in New Zealand

Vitamin D deficiency

     Prevalence and health
implications for the South Asian
  community in New Zealand
          Pamela von Hurst PhD
 Institute of Food, Nutrition and Human Health
        Massey University, Albany

Overview
 What is vitamin D?
 Vitamin D and health
 The Surya Study
 Health implications for South Asian people

History
 Cod-liver oil and sunshine
  found to prevent rickets
  (c.1913)
 Vitamin D isolated and
  identified c.1940
 Active metabolite calcitriol
  discovered in 1963
 Vitamin D subsequently
  established as important
  nutrient for bone health

Sources and metabolism

   Dietary sources of vitamin D are
    minimal
    – Restricted to oily fish and fish oils, some
      fortified foods

   Main source is endogenously produced
    in skin exposed to UVB radiation
   Supplements available by prescription
    or over-the-counter

Vitamin D and health
   Bone health
    – Absorption of dietary calcium in small
      intestine
    – Reabsorption of calcium in the kidney
    – Controls balance between bone breakdown
      (resorption) and mineralisation

   Muscle strength and function

Vitamin D deficiency and bone

   Infantile rickets
    – Exclusively breast-fed infants at risk
    – Re-emerging in New Zealand and Australia
    – Increased risk of infection co-exists

   Osteomalacia in adolescents and adults
    – Idiopathic bone pain
    – Soft bones prone to bowing
    – Kyphosis and scoliosis

   Osteoporosis
    – Loss of fully mineralised bone
    – Associated with loss of oestrogen at
      menopause
    – Asymptomatic until fracture
    – Spine loses bone earlier than hip

Other diseases
   A number of different cancers under
    investigation
   Strong evidence for cardiovascular disease
    and hypertension
   Auto-immune diseases: type 1 diabetes,
    multiple sclerosis, rheumatoid arthritis
   Associations with insulin secretion, glucose
    handling and type 2 diabetes

Vitamin D deficiency in pregnancy

   Low levels in mother during pregnancy
    shown to have derogatory effect on long
    term health of child:
    – Bone health (Javaid, 2006)
    – Development of type 1 diabetes   (Hyponnen, 2001)

The Surya Study
            Aim: to investigate the effect of improved vitamin D
            status on insulin resistance and bone turnover

   A randomised, placebo controlled, double-blind intervention trial
    with vitamin D supplementation in South Asian women who were
    insulin resistant (HOMA-IR > 1.93) and vitamin D deficient (serum
    25(OH)D < 50 nmol/L).
   Subjects were given either 4000 IU (100 g) per day vitamin D3
    (n=42) or placebo (n=39) for 6 months
   Outcome measures included fasting glucose, insulin, C-peptide,
    PTH, 25(OH)D, bone markers, lipids and inflammatory markers.

Key findings – screening group
   235 South Asian women living in Auckland were
    screened for participation in the trial
   Over 45% were insulin resistant (HOMA-IR >
    1.93), but were not obese
   Post-menopausal women had low BMD in
    lumbar spine compared to the general
    population (age and gender matched)
   Young women (20 – 29 years) low BMD, low
    dietary calcium, low serum 25(OH)D
    – Current study investigating this further

Vitamin D status and Seasonal
                    variation
                                           Median 27.5 nmol/L
45%                                                                              50

40%                                                                              45

                                                                                 40
35%

                                                                                 35

                                                       Serum 25(OH)D3 (nmol/L)
30%

                                                                                 30
25%
               43%                                                               25
20%

15%
       Bone health                                                               20

      compromised
                                                                                 15

10%
                                                                                 10

 5%
                                                                                 5

 0%                                                                              0
      Severe      Moderate     Mild         Adequate                                     Summer         Autumn            Winter            Spring

                                                                                      Summer (n=76)              33.5 (25.6, 46.2) nmol/L
15%    Severe deficiency      50 nmol/L

Key findings of the trial
       Vitamin D supplementation does reduce
        insulin resistance when:
    –     Subject is vitamin D deficient and insulin resistant
    –     Supplementation is sufficient to increase serum 25(OH)D to
          80 nmol/L or above
    –     This level of adequacy is maintained for a period of time
          exceeding 3 months

       Markers of bone turnover were reduced with
        vitamin D supplementation in post-
        menopausal women

Implications for health in the
        South Asian community

   Increasing prevalence of osteoporosis and
    reduced quality of life in older age
   Increased incidence of rickets and infectious
    diseases in infants and children
   High levels of type 2 diabetes and CVD already
    present in South Asian population
    – vitamin D deficiency could be partially responsible for
      this situation

Recommendations?
   Supplementation
    – Prescription dose vitamin D3 50,000 IU
      (1.25mg) per month
    – Over the counter 1000 IU per day largest
      dose
   Sun exposure
    – Fear of skin cancer
    – Ineffective recommendations available

Conclusions

1.   South Asian women living in NZ are at
     high risk of vitamin D deficiency
2.   This will potentially impact negatively
     on their long term health, especially
     bone and metabolic conditions
3.   Vitamin D deficient mothers will
     produce vitamin D deficient children
4.   Realistic messages about sun exposure
     and/or use of supplements are required

Acknowledgements
 The Surya study was funded by NZ Lotteries Health Fund
 Supplements were donated by Blackmores Australia
 Clinical space was kindly provided by Mount Roskill
  Medical Centre

The 235 wonderful women from the Auckland South Asian
 communities who volunteered to participate in the study