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Vitamin D: who needs it?

Evidence that low vitamin D blood levels do not predict osteoporosis

In South Africa, with comparable sunlight exposure to Australia, dark skinned people were less likely to have osteoporosis. Similar findings were reported from the UK and USA, comparing dark skinned and light skinned healthy adults. 

S Afr Med J. 1994 Jun;84(6):328-32. Risk factors for the development of osteoporosis in a South African population. A prospective analysis.Blaauw R, Albertse EC, Beneke T, Lombard CJ, Laubscher R, Hough FS.

Ann Hum Biol. 1999 May-Jun;26(3):229-42.An investigation of ethnic differences in bone mineral, hip axis length, calcium metabolism and bone turnover between West African and Caucasian adults living in the United Kingdom. Dibba B, Prentice A, Laskey MA, Stirling DM, Cole TJ.

J Bone Miner Res. 2004 Apr;19(4):560-5. Epub 2004 Jan 5.Comparison of cross-sectional geometry of the proximal femur in white and black women from Detroit and Johannesburg. Nelson DA, Pettifor JM, Barondess DA, Cody DD, Uusi-Rasi K, Beck TJ.

In the Middle East, studies in Saudi Arabia, Lebanon and Kuwait found low vitamin D levels but highly variable rates of osteoporosis, linked more to nutritional problems than to vitamin D levels. In these regions, both man and women dress to protect their skin from the sun and women in particular have very little sun expose and are measurably vitamin D deficient. However the rates of osteoporosis are vary greatly across the region. As in counties with high sun exposure, more than 70% of this population was affected by Vitamin D insufficiency , as defined by European test levels.The prevalence of osteoporosis in the Saudi Arab population was high in women and low in men when using the US/European data reference. Data from Kuwait showed no difference compared with Caucasian normative values.

J Musculoskelet Neuronal Interact 2007; 7(2):131-143 Middle East and North Africa consensus on osteoporosis G. Maalouf1, M.H. Gannagé-Yared1 et al 

  

Rickets in Australia

Although recent headlines in the media in reported that ‘Alarmingly, doctors are now treating rickets in Australian children. The condition, which affects growing bones and is linked to vitamin D deficiency, was thought to have died out in the industrial revolution’. 

The reported study actually found that the children identified with rickets and severe vitamin D deficiency were not typical of the general Australian population and their condition could not be ascribed to use of sunscreen or sedentary lifestyles. They were more likely to have had nutritional deficiency during infancy. “Most children were born in Africa (252; 63%) and 75% of children were refugees”.

(Incidence of vitamin D deficiency rickets among Australian children: an Australian Paediatric Surveillance Unit study. Craig F Munns, Peter J Simm, Christine P Rodda, Sarah P Garnett, Margaret R Zacharin, Leanne M Ward, Janet Geddes, Sarah Cherian, Yvonne Zurynski and Christopher T Cowell, on behalf of the APSU Vitamin D Study Group, Med J Aust 2012; 196 (7): 466-468.)

 

Testing for vitamin D

Lack of accuracy in estimating dietary intake and skin synthesis

'The unique problem of estimating total intake of a substance that can be provided in the diet or made in the skin by exposure to sunlight makes it difficult to estimate adequate total intakes of vitamin D for the general population. Accurate food composition data are not available for vitamin D, accentuating the difficulty for estimating dietary intakes.'

'Skin synthesis is equally difficult to estimate, being affected by such imponderables as age, season, latitude, time of day, skin exposure, sun screen use, etc. In vitamin D - replete individuals, estimates of skin synthesis are put at around 10 µg /day (24, 41), with total intakes estimated at 15 µg/day '.

Evidence used for estimating recommended vitamin D intake, Federal Agriculture Organisation, USA, Human Nutrition Guidelines

http://www.fao.org/docrep/004/Y2809E/y2809e0e.htm

  

Obesity, race and BMI risks

People with higher BMI have lower Vitamin D levels, but no increased risk of osteoporosis.

•Asian and Caucasian women have osteoporosis more often than Black women, due to the difference in the thickness of their bones. 

•The average calcium intake among Asian women has been observed to be about half that of Western population groups. 

•Asian women have fractures of the spine or vertebrae more often than Caucasians. 

•Slender women have less bone mass than heavy or obese women. 

University of Washington Womans health site http://depts.washington.edu/uwcoe/index.html

Most at risk populations are older Chinese and Caucasian women with low BMI 

Bone. 2005 Jun;36(6):987-98. Structural and biomechanical basis of racial and sex differences in vertebral fragility in Chinese and Caucasians.

Duan Y, Wang XF, Evans A, Seeman E.

  

 

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