Blacks living in urban area vs rural have less vitamin D if older than 50 – Oct 2011

Urbanization of black South African women may increase risk of low bone mass due to low vitamin D status, low calcium intake, and high bone turnover

Nutrition Research
Volume 31, Issue 10, October 2011, Pages 748-758 doi:10.1016/j.nutres.2011.09.012
Marlena C. Krugera, ,, Iolanthé M. Krugerb, Edelweiss Wentzel-Viljoenc, Annamarie Krugerb
a Institute of Food, Nutrition and Human Health, Massey University, Palmerston North 4442, New Zealand
b Africa Unit for Transdisciplinary Health Research (AUTHeR), Faculty of Health Sciences, North-West University, Potchefstroom Campus, South Africa
c TReNDS, Centre of Excellence for Nutrition (CEN), Faculty of Health Sciences, North-West University, Potchefstroom Campus, South Africa
Received 14 June 2011; revised 19 September 2011; Accepted 19 September 2011. Available online 7 November 2011.

Globally, rural to urban migration is accompanied by changes in dietary patterns and lifestyle that have serious health implications, including development of low bone mass. We hypothesized that serum 25 (OH) vitamin D3 (25[OH]D3) levels will be lower, bone turnover higher, and nutrition inadequate in urban postmenopausal black women, increasing risk for low bone mass.

We aimed to assess the prevalence of risk factors for low bone mass in 1261 black women from rural and urban areas in the North West Province of South Africa (Prospective Urban and Rural Epidemiology–South Africa project). Fasting blood samples were taken; and participants were interviewed to complete questionnaires on self-reported diseases, fractures, and dietary intakes. Bone health markers were assessed in a subgroup of 658 women older than 45 years.
Specific lifestyle risk factors identified were

  • inactivity,
  • smoking,
  • injectable progestin contraception use
  • high alcohol consumption

Dietary risk factors identified were low calcium and high animal protein, phosphorous, and sodium intakes.

The 25(OH)D3 and C-terminal telopeptide (CTX) levels were significantly higher in the rural vs the urban women older than 50 years. Parathyroid hormone (PTH) levels increased with age in both groups. The 25(OH)D levels were inversely correlated with CTX and PTH in rural women. In urban women, PTH and CTX were correlated while dietary calcium was inversely correlated with CTX and PTH with 25(OH)D3. The combination of low dietary calcium (<230 mg/d), marginally insufficient 25(OH)D3 status, and raised PTH may result in increased bone resorption. Further research is required to assess bone health and fracture risk in black African women.

Abbreviations: 25(OH)D3, 25 dihydroxyvitamin D3; BMD, bone mineral density; BMI, body mass index; CDT, carbohydrate-deficient transferrin; CTX, C-telopeptides of type I collagen; GGT, ?-glutamyl transferase; HIV, human immunodeficiency virus; PTH, parathyroid hormone; PURE, Prospective Urban and Rural Epidemiology study

Summary of data from the study

Age Rural ng Urban ng
<50 30.8 31.0
50-59 30.1 26.9
60-69 30.1 26.1
70+ 26.0 25.8

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Candidate reasons for decrease of vitamin D in urban area include:

  • Air pollution/haze reduces the UVB needed to make vitamin D
  • Different clothing standards urban/rural- dress length, shoes, etc.
  • Not go outdoors as much in urban area (feel less safe, availability of air conditioning, lack of garden)
  • Not as good nutrition (including artificial fertilizers which do not provide Magnesium in the greens)
  • Older black women in urban areas might not make their skin as shinny as rural women - which results in less vitamin D uptake

See also VitaminDWiki

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