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Chinese have very low vitamin D - July 2013

A glimpse of vitamin D status in Mainland China

Nutrition Volume 29, Issues 7–8, July–August 2013, Pages 953–957
  • DSM Nutritional Products, Human Nutrition and Health, Beijing, China and Kaiseraugst, Switzerland

Abstract

As an essential dietary micronutrient, vitamin D plays a pivotal role in promoting calcium absorption in the intestine and maintaining a healthy skeletal system throughout life. Beyond bone health, an emerging volume of scientific studies shows that vitamin D also may provide cardiovascular, metabolic, and immunologic benefits and reduce mortality. To our knowledge, in mainland China no national surveys have been conducted to date to depict the overall vitamin D status in the population. Therefore, the purpose of this contribution was to provide the best possible evaluation of vitamin D deficiency/insufficiency in China by reviewing publications that measured plasma/serum 25-hydroxyvitamin-D (25OHD) levels in various age groups and in different areas of China from January 2000 to June 2012. From these investigations conducted throughout the country and from newborns to adults to the elderly, it has been found that vitamin D deficiency/insufficiency is prevalent in the Chinese population in almost all age groups and areas if individuals are not taking vitamin D–fortified products/supplements or are lacking sufficient sunshine exposure. Some studies showed severe deficiency (25OHD <25 nmol/L) in Nanjing (north latitude 31) during the winter months and in Beijing (north latitude 40) in the fall. This unoptimistic situation represents a significant but modifiable public health risk that deserves greater attention and more efficient and timely management.

Keywords

  • Blood;
  • 25-Hydroxyvitamin D;
  • Bone;
  • Nutrient deficiency;
  • Nutritional status;
  • Population;
  • Public health

Introduction

Vitamin D is an essential dietary micronutrient because it plays a pivotal role in aiding intestinal absorption of calcium and phosphorus, therefore, exerting a favorable effect on bone mineralization and musculoskeletal health. Other than the classical effects of vitamin D on calcium and phosphorus metabolism and on bone health and muscle strength, an emerging volume of scientific studies also shows that vitamin D deficiency/insufficiency may increase the risks for developing non-skeletal disorders such as cardiovascular disease, type 2 diabetes, autoimmune disease, selected cancers, high blood pressure, depression, and overall mortality 1 and 2.

In Mainland China, there has, to our knowledge, been no systematic national survey to depict the landscape of vitamin D deficiency, insufficiency, and adequacy. However, research interests in the topic developed and continued to mount over the past decade(s), and as a result, circulating vitamin D status has been examined in various populations and regions.

The purpose of this contribution is to provide best possible overview from these studies that measured circulating 25-hydroxyvitamin-D (25OHD) levels in Mainland China. Serum or plasma 25(OH)D concentration is widely accepted as the best biomarker to define vitamin D status, because it reflects both the endogenous vitamin D photosynthesis by skin in response to sun exposure and vitamin D ingestion via digestive track from dietary sources 3. To this end, peer-reviewed original English publications from January 2000 to November 2012, which examined 25(OH)D values, were retrieved from databases and analyzed. Studies were not included when the number of participants was less than 30 and when they had known overt vitamin D intake. A deficient vitamin D level is defined as being 25(OH)D <25 nmol/L; insufficient <50 nmol/L; desirable >75 nmol/L (as recommended by International Osteoporosis Foundation IOF, the Endocrine Society, and many scientists in the field) 4. Therefore, levels between 50 nmol/L and 75 nmol/L were defined as inadequate (although they are defined as adequate by the Institute of Medicine). These cut-off points are also in line with the recently published global vitamin D status map by the IOF 5 (http://www.iofbonehealth.org/facts-and-statistics/vitamin-d-studies-map).

Vitamin D status in the youth

As shown in Table 16, 7, 8, 9, 10, 11 and 12, vitamin D deficiency was phenomenal in the youth. There was no group with desirable 25(OH)D levels and as many as 40% to 90% had blood 25(OH)D levels lower than 50 nmol/L. A study in Beijing showed even worse vitamin D status: More than 40% of school-aged girls had 25(OH)D levels below 12.5 nmol/L in January. This significant vitamin D deficiency remained in 5% to 9% of them even in September and October 9.

Table 1. Vitamin D status in the youth

Publication Age (yrs) Number Place Latitude (north) Season D Use Assay method 25-OH-D (nmol/l) Deficiency (%)
<12.5 <25 <37.5 <50 <75 <80
Wang J. 2010 Newborn 77 (MF) Chengdu 30 Sept Unknown Enzyme immunoassay 41.0 ± 18.9     44.2     96.1
Song S. 2012 Newborn 58 (MF) Beijing 40 Apr-May No ELISA 27.9 ± 1.6*   46.6   93.2 100  
Zhu Z. 2012 6-11 1440 (MF) Hangzhou 30 All Unknown ELISA 56.1 ± 19.9   2.0   40.3 88.3  
  12-16 183 (MF) Hangzhou 30 All Unknown ELISA 52.1 ± 17.0   3.3   46.4 89.6  
Du X. 2001 12.7 108 (F) Beijing 40 Jan Unknown Competitive protein assay 13.9 ± 9.6 42.5          
          Sept-Oct Unknown Competitive protein assay 30.2 ± 11.9 5.1          
  13.0 57 (F) Beijing 40 Jan Unknown Competitive protein assay 12.7 ± 5.9 49.6          
          Sept-Oct Unknown Competitive protein assay 24.7 ± 10.6 6.6          
  13.2 64 (F) Beijing 40 Jan Unknown Competitive protein assay 12.8 ± 6.7 45.1          
          Sept-Oct Unknown Competitive protein assay 23.8 ± 8.7 9.2          
Foo L. 2009 15.0 301 (F) Beijing 40 Mar-Apr No RIA 34.0   32.8 68.4 89.2    
Arguelles L. 2009 16.4 226 (FM) Anqing 31 All Unknown HPLC 45.0 ± 23.5           90.3

M, male; F, female; All, the blood samples were collected in all seasonsThe 25-OH-D values are expressed in mean ± SD (or mean ± SE when with *) or median, and are converted if not in nmol/l. Different deficiency/insufficiency cutoffs and rates were provided by investigators

Poor vitamin D status was not seen in participants taking vitamin D–fortified products or supplementation (Table 2A) 8 and 13, unequivocally suggesting that vitamin D supplementation improved 25(OH)D status. Additionally, exposure to sunshine, thus allowing individuals to receive ultraviolet B (UVB), in the summer months improved 25(OH)D status in the same children who were previously deficient (Table 2B) 14. Consequently, clinical rickets declined from 41.6% to 17%.

Table 2. Vitamin D status can be improved in children

A. Effect of supplementation
Publication Age (yrs) Number Place Latitude (north) Season D Use Assay method 25-OH-D (nmol/l) Deficiency (%)
<25 <50 <75
Zhu Z. 2012 0–1 2116 (MF) Hangzhou 30 All Yes ELISA 98.7 ± 47.1 0.4 5.4 33.6
  2–5 2269 (MF) Hangzhou 30 All Yes ELISA 69.6 ± 30.4 1.1 21.9 68.6
Liang GY. 2011 0–10 76 (MF) Nanjing 32 Nov-Mar Yes EIA 80.5 ± 29.3 1.3 10.5  
  0–10 66 (MF) Nanjing 32 Nov-Mar Yes EIA 65.7 ± 32.3* 16.7 30.8  
B. Effect of sunshine exposure
Publication Age (month) Number Place Latitude (north)/Elevation(meter) Season D Use Assay method 25-OH-D (nmol/l) Deficiency (%)
<12.5 <30 <50
Strand MA. 2009 18.2 177 (MF) Yuci 37/797 Apr Unknown Radioimmunoassy 34.5 ± 74.3 33.5 65.3 84.3
  23.3 172 (MF) Yuci 37/797 Sept 4.2% Radioimmunoassy 127.8 ± 143.5 0 2.9 8.1

For footnote: please see Table 1

∗With respiratory infection.

Vitamin D status in adults

A larger percentage of adults had blood 25(OH)D levels below 50 nmol/L (Table 3) 6, 7, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26 and 27. The best 25(OH)D levels (67.2 nmol/L) in adult groups were reported in Jinan 22; whereas the worst (<25 nmol/L) was found in pregnant women in Nanjing and pregnant women with gestational diabetes mellitus in Beijing 15 and 20.

Table 3. Vitamin D status in adults

Publication Age (yrs) Number Place Latitude (north) Season D Use Assay method 25-OH-D (nmol/l) Deficiency (%)
<25 <50 <75 <80
Jiang L. 2012 26.3 78 (F) Nanjing 31 Winter 99 IU ELISA 22.6 ± 12.7 65.8 96.1    
  27.7 78 (F) Nanjing 31 Summer 117 IU ELISA 31.8 ± 9.2 22.4 94.7    
Woo J. 2008 26.9 220 (F) Beijing 40 Feb-May No Radio-immunoassay 29 40 94    
  27.9 221 (F) Hong Kong 22 Feb-May No Radio-immunoassay 34 18 92    
Shao H. 2012 26.8 130 (F) Shanghai 31 Jul-Dec No Chemiluminescence 30.2        
  27.3 139 (F) Shanghai 31 Jul-Dec No Chemiluminescence 29.7        
Wang J. 2010 End preganacy 77 (F) Chengdu 30 Sept Unknown Enzyme immunoassay 36.0 ± 18.9       97.4
Tao M. 2012 28.1 1695 (F) Shanghai 31 All No Chemiluminescence 43.9 ± 28.6   69.0 91.0  
Yang B. 2012 29.4 41 (M) Xi’an 34 All Unknown ELISA 52.5 ± 15.9        
  30.3 314 (M) Xi’an 34 All Unknown ELISA 53.3 ± 14.5        
  30.5 195 (M) Xi’an 34 All Unknown ELISA 54.1 ± 14.3        
Song S. 2012 29.9 70 (F) Beijing 40 Apr-May No ELISA 28.6 ± 1.4 54.3 90.2 100  
Yan L. 2000 30.9 48 (F) Shenyang 42 Apr-May No Radio-immunoassay 40.7 ± 14.1 13.0      
  31.1 48 (M) Shenyang 42 Mar-May No Radio-immunoassay 31.4 ± 10.4 29.0      
Wang O. 2012 31.0 200 (F) Beijing 40 All Unknown ELISA 25.9        
  32.0 200 (F) Beijing 40 All Unknown ELISA 22.4 53.8 96.3    
Lu H. 2012 43.0 2588 (MF) Shanghai 31 Feb-Mar No Chemiluminescence 52.2   30 (M)
46 (F)
84 (M)
89 (F)
 
Yin X. 2012 49.4 601 (MF) Jinan 37 Nov-Dec No RIA 67.2 ± 25.3   28.6 66  
Lin S. 2012 56.5 1101 (MF) Linxian 36 Spring No Enzyme immunoassay 31.7        
Li L. 2012 Adults 1420 (MF) Dali 25 Mar-May No RIA 54.9        
Ren C. 2012 Adults 197 (MF) Guangzhou 23 All No ELISA 48.9 ± 23.7§   57.9 91.9  
Huang Y. 2012 Adults 49 (F) Shanghai 31 Jan-Apr No Chemiluminescence 29.4        

Footnote: please see Table 1The elevation in Dali is 2007 meters

∗The data from Hong Kong were used for head-to-head comparison with Beijing.

†Pragnancy.

‡Pragnancy with gestational diabetes.

§Gastric cancer.

Surprisingly, in women of childbearing age, a lower 25(OH)D level also was found in lower latitude regions (29 nmol/L in Beijing versus 34 nmol/L in Hong Kong where the latitude is 22 north) 18.

Vitamin D status in the elderly

The elderly are fourfold less efficient in cutaneous vitamin D photosynthesis than youth 28 and 29 and are particularly vulnerable to bone fracture or mobility disorders. The 25(OH)D status was alarming in the fast-growing aging Chinese population (Table 4) 17, 30, 31, 32, 33, 34, 35 and 36. There was no any study showing average 25(OH)D above 50 nmol/L. In two large-scale investigations in Beijing and Shanghai, as high as 70% to 90% of the participants had blood 25(OH)D levels below 50 nmol/L 30 and 35. In 1460 elderly urban Shanghai residents, only 3.9% had plasma 25(OH)D levels >75 nmol/L 31. Oral cholecalciferol (vitamin D3) at 925 IU/d, raised serum 25(OH)D from 40 nmol/L to 50 nmol/L in 3 mo in 45 postmenopausal women 34.

Table 4. Vitamin D status in the elderly

Publication Age (yrs) Number Place Latitude (north) Season D Use Assay method 25-OH-D (nmol/l) Deficiency (%)
<25 <50 <75
Lu L. 2009 50-70 3262 (MF) Shanghai
Beijing
31
40
Apr-Jun Unknown Radio-immunoassay 40.4   69.2  
Dorjgochoo T. 2012 61 1460 (MF) Shanghai 31 All Unknown chemiluminescence 34.7     96.1
Kruger M. 2012 61.5 32 (F) Beijing 40 Feb-May No Chemiluminescence 33.1 ± 15.5      
  62.7 31 (F) Beijing 40 Feb-May No Chemiluminescence 29.3 ± 12.0      
Zhou X. 2012 62.1 181 (MF) Beijing 40 All No ELISA 35.8 ± 12.4 20.4 86.1 100
  63.6 193 (MF) Beijing 40 All No ELISA 32.1 ± 10.8* 21.2 94.3 100
Zhang H. 2012 63.8 100 (F) Shanghai 31 Dec-Mar <600IU Chemiluminescence 42.0 ± 13.5      
Zhao J. 2011 64.1 1724 (F) Beijing 40 Unknown Unknown Chemiluminescence 33.0 ± 13.5   89.7 99.4
Yan L. 2003 65.2 110 (F) Shenyang 42 Feb-Apr 14.5% Radio-immunoassay 30.9 ± 13.5 39.1    
  67.9 108 (M) Shenyang 42 Feb-Apr 9.3% Radio-immunoassay 27.1 ± 11.5 52.8    
Yan L. 2000 66.9 48 (F) Shenyang 42 Apr-May No Radio-immunoassay 42.9 ± 21.2 15.0    
  68.9 50 (M) Shenyang 42 Mar-May No Radio-immunoassay 28.4 ± 12.5 48.0    

Footnote: please see Table 1

∗With COPD.

Discussion

The data presented in this contribution are likely epitomic for the nation because the investigations were conducted in the east part of Hu’s line (Fig. 1), which has been with <40% of the land and >90% of the population since 1930s 37. In the global map of vitamin D deficiency/insufficiency 3 and 38, these data from China would stand for a sizable geographic area and the largest population.

Full-size image (93 K)

Fig. 1. Distribution of studies. In some places like Beijing and Shanghai, multiple studies were conducted. The original blank map is from http://en.wikipedia.org/wiki/File:China_edcp_relief_location_map.jpg#file. The map is licensed under Creative Commons ShareAlike 3.0 http://creativecommons.org/licenses/by-sa/3.0/deed.en.

Vitamin D deficiency/insufficiency in China might have been caused by multiple factors, some of which are unique and worthy of being recognized. First, with the rapid transformation from an agrarian to an industrialized society, the urban proportion of population increased from 33% in 2000 to 50% in 2013 (the fifth and sixth National Population Survey http://www.stats.gov.cn). Accordingly, the number of people engaged in an outdoor profession with sun exposure has dramatically decreased. Second, due to air pollution accompanied by industrialization and urbanization, people were discouraged from spending time outdoors and UVB was prevented from penetrating the atmosphere; Third, the preference for lighter skin color (fair skin) in the society remains unchanged, leading to popular use of hats, umbrellas, and sunscreens when outdoors. UVB radiation–related skin carcinomas also are increasingly a concern. Fourth, despite massive and successful improvements in macronutrient intakes in the Chinese population, micronutrient intake did improve in parallel 39. In fact, natural food rich in vitamin D in the Chinese diet remain scarce, and food and beverages fortified with vitamin D are limited in the market.

Over the past several decades, the life span and life expectancy of the Chinese people has increased significantly, which brought the consequences of vitamin D deficiency, like osteoporosis and bone fracture, into greater prominence 40. Accompanied by poor 25(OH)D status, a bone mineral density (BMD) survey with dual-energy X ray absorptiometry (DXA) in 10 Chinese cities estimated that the proportion of osteoporosis in men and women over age 50 y was 10.4% and 31.2%, respectively 41. Furthermore, the incidence of hip fracture in Beijing in the period 2002 to 2006 escaladed much more rapidly compared with 1990 to 1992 42. Vitamin D deficiency increases the risk for both osteoporosis and falls 43 and 44, which are the two major risks for bone fracture.

In summary, from published investigations in Mainland China since the year 2000, vitamin D deficiency/insufficiency was found to be widely prevalent, which constitutes a significant but modifiable public health risk that deserves greater awareness and more efficient and timely management. To attain a desirable vitamin D status at the population level, it requires multiple approaches (e.g., promotion of a healthy lifestyle, implementation of recommended daily intake, development of voluntary and mandatory fortification programs, and regulation establishment and reinforcement).

(References are in PDF at the bottom of this page)

See also VitaminDWiki

NONE of the pregnant Beijing women had adequate levels of vitamin D – April 2013

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