51
|
Heijboer AC, Oosterwerff M, Schroten NF, Eekhoff EMW, Chel VGM, de Boer RA, Blankenstein MA, Lips P. Vitamin D supplementation and testosterone concentrations in male human subjects. Clin Endocrinol (Oxf) 2015; 83:105-10. [PMID: 25557316 DOI: 10.1111/cen.12711] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/24/2014] [Revised: 11/26/2014] [Accepted: 12/19/2014] [Indexed: 01/07/2023]
Abstract
OBJECTIVE A possible association between serum 25-hydroxyvitamin D and testosterone levels has been reported; however, contradictory results have emerged. DESIGN To investigate a causal link between vitamin D and testosterone status, we studied the effect of vitamin D supplementation on serum testosterone concentrations in three independent intervention studies including male patients with heart failure (study 1), male nursing home residents (study 2) and male non-Western immigrants in the Netherlands (study 3). METHODS In study 1, 92 subjects were randomized to either vitamin D (2000 IU cholecalciferol daily) or control. Blood was drawn at baseline, after 3 and 6 weeks. In study 2, 49 vitamin D deficient subjects received either vitamin D (600 IU daily) or placebo. Blood was drawn at baseline, after 8 and 16 weeks. In study 3, 43 vitamin D deficient subjects received either vitamin D (1200 IU daily) or placebo. Blood was drawn at baseline, after 8 and 16 weeks. Serum 25-hydroxyvitamin D levels were measured using LC-MS/MS or radioimmunoassay. Testosterone levels were measured using a 2nd generation immunoassay. RESULTS Serum 25-hydroxyvitamin D levels significantly increased in all treatment groups (median increase of 27, 30 and 36 nmol/l in studies 1, 2 3, respectively) but not in the control groups. The documented increase in 25-hydroxyvitamin D levels, however, did not affect mean testosterone concentrations at the end of the study (median increase of 0, 0.5 and 0 nmol/l in studies 1, 2 and 3, respectively). CONCLUSIONS In this post hoc analysis of three small clinical trials of limited duration in men with normal baseline testosterone concentrations, vitamin D supplementation was not associated with an increase in circulating testosterone concentrations.
Collapse
Affiliation(s)
- Annemieke C Heijboer
- Department of Clinical Chemistry, VU University Medical Center, Amsterdam, the Netherlands
| | - Mirjam Oosterwerff
- Department of Internal Medicine, VU University Medical Center, Amsterdam, the Netherlands
| | - Nicolas F Schroten
- Department of Cardiology, University of Groningen, University Medical Center Groningen, Groningen, the Netherlands
| | - Elisabeth M W Eekhoff
- Department of Internal Medicine, VU University Medical Center, Amsterdam, the Netherlands
| | - Victor G M Chel
- Overduin Katwijk, Katwijk, the Netherlands
- Department of Public Health and Primary Care, Leiden University Medical Center, Leiden, the Netherlands
| | - Rudolf A de Boer
- Department of Cardiology, University of Groningen, University Medical Center Groningen, Groningen, the Netherlands
| | - Marinus A Blankenstein
- Department of Clinical Chemistry, VU University Medical Center, Amsterdam, the Netherlands
| | - Paul Lips
- Department of Internal Medicine, VU University Medical Center, Amsterdam, the Netherlands
| |
Collapse
|
52
|
Dabrowski FA, Grzechocinska B, Wielgos M. The role of vitamin D in reproductive health--a Trojan Horse or the Golden Fleece? Nutrients 2015; 7:4139-53. [PMID: 26035242 PMCID: PMC4488777 DOI: 10.3390/nu7064139] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2015] [Revised: 05/16/2015] [Accepted: 05/19/2015] [Indexed: 12/19/2022] Open
Abstract
In the last decade, vitamin D was in the spotlight in many fields of research. Despite numerous publications, its influence on reproductive health remains ambiguous. This paper presents an up-to-date review of current knowledge concerning the role of cholecalciferol in human reproduction. It covers various infertility issues, such as polycystic ovary syndrome, endometriosis, myoma-induced infertility, male infertility, premature ovary failure and in vitro fertilization techniques. Vitamin D deficiency, defined as serum concentration of 25-hydroxycalciferol of less than 50 nmol/L, is commonly noted more frequently than only in fertility clinic patients. It is a global trend that is observed in all age groups. The results of original publications dated up to 2015 have been summarized and discussed in a critical manner. Most experts agree that vitamin D supplementation is a necessity, particularly in women suffering from obesity, insulin resistance or small ovarian reserve, as well as in men with oligo- and asthenozoospermia if serum concentration should fall below 50 nmol/L (normal range up to 125 nmol/L). High concentration of vitamin D and its metabolites in decidua during the 1st trimester suggests its important role in the implantation process and a local immunological embryo-protection. On the other hand, evidence-based research did not prove a significant difference so far in ovulation stimulation or embryo development depending on vitamin D level. In one of the publications, it was also found that vitamin D binding protein (VDBP) has a molecular similarity to anti-sperm antibodies, and another one concluded that both low (<50 nmol/L) and high (>125 nmol/L) concentration of vitamin D are associated with decreased number and quality of spermatozoa in semen. Vitamin D is definitely not a Trojan Horse in reproductive health, since there were no adverse effects reported for vitamin D intake of up to 10,000 IU/day, but to proclaim it the Golden Fleece, more evidence is needed.
Collapse
Affiliation(s)
- Filip A Dabrowski
- Department of Obstetrics and Gynecology, Faculty of Medicine, Medical University of Warsaw, Starynkiewicza Sq. 1/3, 02-015 Warsaw, Poland.
| | - Barbara Grzechocinska
- Department of Obstetrics and Gynecology, Faculty of Medicine, Medical University of Warsaw, Starynkiewicza Sq. 1/3, 02-015 Warsaw, Poland.
| | - Miroslaw Wielgos
- Department of Obstetrics and Gynecology, Faculty of Medicine, Medical University of Warsaw, Starynkiewicza Sq. 1/3, 02-015 Warsaw, Poland.
| |
Collapse
|
53
|
Fong JP, Lee FJ, Lu IS, Uang SN, Lee CC. Relationship between urinary concentrations of di(2-ethylhexyl) phthalate (DEHP) metabolites and reproductive hormones in polyvinyl chloride production workers. Occup Environ Med 2015; 72:346-53. [DOI: 10.1136/oemed-2014-102532] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2014] [Accepted: 01/15/2015] [Indexed: 11/03/2022]
|
54
|
Li XP, Zeng S, Wang M, Wu XP, Liao EY. Relationships between serum omentin-1, body fat mass and bone mineral density in healthy Chinese male adults in Changsha area. J Endocrinol Invest 2014; 37:991-1000. [PMID: 25097104 DOI: 10.1007/s40618-014-0140-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/04/2014] [Accepted: 07/15/2014] [Indexed: 02/02/2023]
Abstract
PURPOSE The present study is firstly designed to identify the relationship between serum omentin-1 concentration, body fat mass and bone mineral density in healthy Chinese male adults in Changsha city. METHODS A total of 219 (20-80 years old) healthy subjects were enrolled in this cross-sectional study. Serum omentin-1, adiponectin, leptin, resistin and bone turn over biochemical markers were measured with enzyme-linked immunosorbent assay. Bone mineral density (BMD) and fat body composition were determined using dual-energy-X-ray absorptiometry. RESULTS Serum omentin-1 levels in the overweight subjects were significantly lower than those of the subjects with normal weight (p < 0.05). Omentin-1 was negatively correlated with weight (r = -0.418), body mass index (BMI, r = -0.419), waist circumference (r = -0.402), waist-to-hip ratio (WHR, r = -0.355), fat body mass (FBM, r = -0.430), fat % (r = -0.408), trunk fat (-0.431). However, after controlling for age, BMI and FBM, no significant correlation was noticed between omentin-1 and BMD at different skeletal sites. Pearson's correlation coefficients and partial correlation coefficients after adjustment showed no significant correlations between omentin-1 and bone turn over biochemical markers, including bone-specific alkaline phosphatase and bone cross-linked N-terminal telopeptides of type I collagen. Multiple line stepwise regression analysis revealed that FBM, WHR, adiponectin were important variables affecting omentin-1. Moreover, lean tissue mass was the most important factor affecting BMD and explained 10.5-14.7 % of the variance. Omentin-1, leptin and resistin were not the predictors of BMD. CONCLUSIONS Serum omentin-1 was negatively correlated with FBM and BMI in healthy Chinese male adults, It was not significantly correlated with bone turnover biochemical markers. Omentin-1 may exert ambiguous effects on BMD, which maybe caused by the complex interactions among adipokines, hormonal activity, and body composition and bone metabolism.
Collapse
Affiliation(s)
- X P Li
- Department of Clinical Laboratory, The Second Xiangya Hospital of Central South University, No. 139, Middle Renmin Road, Changsha, 410011, China
| | | | | | | | | |
Collapse
|
55
|
Traish AM. Adverse health effects of testosterone deficiency (TD) in men. Steroids 2014; 88:106-16. [PMID: 24942084 DOI: 10.1016/j.steroids.2014.05.010] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/09/2014] [Revised: 05/05/2014] [Accepted: 05/21/2014] [Indexed: 12/20/2022]
Abstract
Testosterone and its metabolite, 5α-dihydrotestosterone are critical metabolic and vascular hormones, which regulate a host of biochemical pathways including carbohydrate, lipid and protein metabolism and modulate vascular function. Testosterone deficiency (TD) is a well-recognized medical condition with important health implications. TD is associated with a number of co-morbidities including increased body weight, adiposity and increased waist circumference, insulin resistance (IR) and type 2 diabetes mellitus (T2DM), hypertension, inflammation, atherosclerosis and cardiovascular disease, erectile dysfunction (ED) and increased incidence of mortality. In this review, we summarize the data in the literature on the prevalence of TD and its association with the various co-morbidities and suggest that T therapy is necessary to improve health outcomes in men with TD.
Collapse
|
56
|
Lee HS, Kim YJ, Shim YS, Jeong HR, Kwon E, Hwang JS. Associations between serum vitamin D levels and precocious puberty in girls. Ann Pediatr Endocrinol Metab 2014; 19:91-5. [PMID: 25077092 PMCID: PMC4114046 DOI: 10.6065/apem.2014.19.2.91] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/10/2014] [Revised: 06/24/2014] [Accepted: 06/30/2014] [Indexed: 01/22/2023] Open
Abstract
PURPOSE Vitamin D deficiency has been linked to chronic diseases, such as diabetes mellitus, obesity and autoimmune disease. However, data on the vitamin D status and its association with precocious puberty in girls are limited. We aimed to investigate the association between serum 25-hydroxyvitamin D (25OHD) and precocious puberty in girls. METHODS A total of 60 girls with central precocious puberty (CPP) and 30 control girls were enrolled. Anthropometric measurement and serum level of 25OHD were estimated for all subjects. RESULTS There was a significant difference in the mean serum 25OHD concentration between the precocious puberty group and the control group (17.1±4.5 ng/mL vs. 21.2±5.0 ng/mL, P<0.05). Forty-two of the 60 girls with CPP (70%) had vitamin D deficiency (defined as serum 25OHD<20 ng/mL) and 18 (30%) had vitamin D insufficiency. Of the 30 girls in the control group, vitamin D deficiency was seen in 13 subjects (43.3%), 15 subjects (50%) had vitamin D insufficiency, and 2 subjects (6.7%) had sufficient serum vitamin D (defined as serum 25OHD>30 ng/mL). Vitamin D deficient girls had a significantly higher odds ratio (OR, 3.05; 95% CI, 1.22-7.57, P=0.021). CONCLUSION These results showed that vitamin D levels may be associated with precocious puberty. Further studies are required to establish the potential effect of vitamin D status on puberty.
Collapse
Affiliation(s)
- Hae Sang Lee
- Department of Pediatrics, Ajou University Hospital, Ajou University School of Medicine, Suwon, Korea
| | - You Jin Kim
- Department of Pediatrics, Ajou University Hospital, Ajou University School of Medicine, Suwon, Korea
| | - Young Seok Shim
- Department of Pediatrics, Ajou University Hospital, Ajou University School of Medicine, Suwon, Korea
| | - Hwal Rim Jeong
- Department of Pediatrics, Ajou University Hospital, Ajou University School of Medicine, Suwon, Korea
| | - Eunbyul Kwon
- Department of Pediatrics, Ajou University Hospital, Ajou University School of Medicine, Suwon, Korea
| | - Jin Soon Hwang
- Department of Pediatrics, Ajou University Hospital, Ajou University School of Medicine, Suwon, Korea
| |
Collapse
|
57
|
Vanni VS, Vigano' P, Somigliana E, Papaleo E, Paffoni A, Pagliardini L, Candiani M. Vitamin D and assisted reproduction technologies: current concepts. Reprod Biol Endocrinol 2014; 12:47. [PMID: 24884987 PMCID: PMC4082488 DOI: 10.1186/1477-7827-12-47] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/14/2014] [Accepted: 05/10/2014] [Indexed: 12/02/2022] Open
Abstract
Accumulating evidence from animal and human studies suggests that vitamin D is involved in many functions of the human reproductive system in both genders, but no comprehensive analysis of the potential relationship between vitamin D status and Assisted Reproduction Technologies (ART) outcomes is currently available. On this basis, the purpose of this systematic review and meta-analysis was to perform an in-depth evaluation of clinical studies assessing whether vitamin D status of patients undergoing ART could be related to cycle outcome variables. This issue is of interest considering that vitamin D deficiency is easily amenable to correction and oral vitamin D supplementation is cheap and without significant side effects. Surprisingly, no studies are currently available assessing vitamin D status among male partners of couples undergoing ART, while seven studies on vitamin D status of women undergoing controlled ovarian hyperstimulation (COH) for ART were found and included in the review. Results show that vitamin D deficiency is highly prevalent among women undergoing COH, ranging from 21% to 31% across studies conducted in Western countries and reaching 75-99% in Iranian studies. Data on vitamin D deficiency (25-hydroxyvitamin D serum levels <20 ng/ml) in relation to ART outcomes could be extracted from three studies and included in the meta-analysis, yielding a common risk ratio (RR) of 0.89 (95% CI 0.53-1.49) and showing a lower but not statistically significant likelihood of clinical pregnancy for vitamin-D-deficient women compared with vitamin-D-sufficient patients. In conclusion, there is insufficient evidence to support the routine assessment of vitamin D status to predict the clinical pregnancy rate in couples undergoing ART. The partly conflicting results of the available studies, potentially explaining the lack of statistical significance for a negative influence of vitamin D deficiency on clinical pregnancy rate, are likely secondary to confounders and insufficient sample size, and further larger cohort and randomised controlled studies are required.
Collapse
Affiliation(s)
- Valeria S Vanni
- Department Obstetrics and Gynecology, San Raffaele Scientific Institute, Via Olgettina 60, 20136 Milano, Italy
| | - Paola Vigano'
- Department Obstetrics and Gynecology, San Raffaele Scientific Institute, Via Olgettina 60, 20136 Milano, Italy
| | - Edgardo Somigliana
- Department Obstetrics and Gynecology, Fondazione Cà Granda, Ospedale Maggiore Policlinico, Via Commenda 12, 20122 Milano, Italy
| | - Enrico Papaleo
- Department Obstetrics and Gynecology, San Raffaele Scientific Institute, Via Olgettina 60, 20136 Milano, Italy
| | - Alessio Paffoni
- Department Obstetrics and Gynecology, Fondazione Cà Granda, Ospedale Maggiore Policlinico, Via Commenda 12, 20122 Milano, Italy
| | - Luca Pagliardini
- Department Obstetrics and Gynecology, San Raffaele Scientific Institute, Via Olgettina 60, 20136 Milano, Italy
| | - Massimo Candiani
- Università Vita-Salute, San Raffaele Scientific Institute, Via Olgettina 58, 20132 Milano, Italy
| |
Collapse
|
58
|
Abstract
Vitamin D is a versatile signalling molecule with a well-established role in the regulation of calcium homeostasis and bone health. The spectrum of vitamin D target organs has expanded and the reproductive role of vitamin D is highlighted by expression of the vitamin D receptor (VDR) and enzymes that metabolize vitamin D in testis, male reproductive tract and human spermatozoa. The expression levels of VDR and CYP24A1 in human spermatozoa serve as positive predictive markers of semen quality, and VDR mediates a nongenomic increase in intracellular calcium concentration that induces sperm motility. Interestingly, functional animal models show that vitamin D is important for estrogen signalling and sperm motility, while cross-sectional studies support the positive association between serum 25-hydroxyvitamin D level and sperm motility in both fertile and infertile men. Expression of VDR and enzymes that metabolize vitamin D in fetal testis indicates a yet unknown role during development, which may be extrapolated from invasive testicular germ cell tumours where 1α,25-dihydroxyvitamin D induces a mesodermal differentiation of the pluripotent testicular cancer cells. Taken together, vitamin D signalling has a positive effect on semen quality, increases estrogen responsiveness and differentiates germ cell tumours. Future studies are needed to determine when 1α,25-dihydroxyvitamin D acts in a paracrine manner and whether systemic changes, which are subject to pharmacological modulation, could influence male reproductive function.
Collapse
Affiliation(s)
- Martin Blomberg Jensen
- University Department of Growth and Reproduction, Rigshospitalet, Section 5064, Blegdamsvej 9, 2100 Copenhagen, Denmark
| |
Collapse
|
59
|
Bone mineral density and response to treatment in men younger than 50 years with testosterone deficiency and sexual dysfunction or infertility. J Urol 2013; 191:1072-6. [PMID: 24161998 DOI: 10.1016/j.juro.2013.10.070] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/18/2013] [Indexed: 11/23/2022]
Abstract
PURPOSE Testosterone deficiency is a known risk factor for osteopenia and osteoporosis in older men. Less is known about the impact of testosterone deficiency on bone mineral density in younger men. MATERIALS AND METHODS We retrospectively reviewed the charts at an andrology/infertility clinic and identified 399 men younger than 50 years who underwent baseline dual energy x-ray absorptiometry and had total testosterone less than 350 ng/dl or free testosterone less than 1.5 ng/dl. Additional analysis was done in a subgroup of 75 men (18.8%) in whom dual energy x-ray absorptiometry was repeated after treatment at a mean ± SD of 30.4 ± 16.2 months. The determination of osteoporosis or osteopenia was based on T-scores (osteopenia less than -1.0 and osteoporosis less than -2.5) of the lumbar spine and left hip. RESULTS Of all 399 men 141 (35.3%) had bone mineral density consistent with osteopenia at the lumbar spine (137) and/or the total hip (19). In 11 men (2.75%) bone mineral density was consistent with osteoporosis at the lumbar spine. On multivariate analysis higher body mass index was independently associated with increased bone mineral density at the spine (p <0.0001) as well as the hip (p <0.001). Testosterone treatment in 43 men increased spine bone mineral density (p <0.001). Significant decreases in spine bone mineral density developed in 21 men treated with clomiphene citrate or anastrazole (p = 0.003). No significant change was noted in hip bone mineral density for any treatment. CONCLUSIONS More than a third of men younger than 50 years with testosterone deficiency and infertility or sexual dysfunction had decreased bone mineral density. Testosterone treatment increased bone mineral density while estrogen modulators such as clomiphene citrate or aromatase inhibitors decreased bone mineral density. These results suggest that dual energy x-ray absorptiometry may be warranted in young men with testosterone deficiency.
Collapse
|
60
|
Blomberg Jensen M, Lieben L, Nielsen JE, Willems A, Jørgensen A, Juul A, Toppari J, Carmeliet G, Rajpert-De Meyts E. Characterization of the testicular, epididymal and endocrine phenotypes in the Leuven Vdr-deficient mouse model: targeting estrogen signalling. Mol Cell Endocrinol 2013; 377:93-102. [PMID: 23850520 DOI: 10.1016/j.mce.2013.06.036] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/14/2013] [Revised: 06/12/2013] [Accepted: 06/30/2013] [Indexed: 12/21/2022]
Abstract
Vitamin D is a key factor for calcium and bone homeostasis, but signalling through the vitamin D receptor (VDR) seems also to be important for testicular function. To test the functional role of vitamin D signalling we examined the male reproductive system of the Leuven Vdr-ablated (Vdr(-/-)) mice, previously established as a model for hereditary vitamin D-resistant rickets. We investigated reproductive hormones, changes in gene expression and histological phenotype of eleven Vdr(-/-), eight Vdr(+/-) and nine Vdr(+/+) mice. Testicular and epididymal histology were grossly normal in Vdr(-/-) mice. Accordingly, no differences were found in serum concentrations of testosterone, estradiol, LH, and FSH or testicular expression of Cyp19a1, Ersα, Cyp17a1, Star, Insl3, Inhbb, and Amh. However, a significantly lower ERβ expression was found in testis of Vdr(+/-) and Vdr(-/-) mice, conversely epididymal expressions of ERα and the estrogen-target gene Aqp9 were higher. In conclusion, vitamin D seems dispensable for murine spermatogenesis and sex hormone production, but aberrant estrogen-signalling may elicit some of the VDR-mediated effects on male reproduction.
Collapse
|
61
|
Zhang W, Stoecklin E, Eggersdorfer M. A glimpse of vitamin D status in Mainland China. Nutrition 2013; 29:953-7. [PMID: 23594582 DOI: 10.1016/j.nut.2013.01.010] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2012] [Revised: 01/07/2013] [Accepted: 01/11/2013] [Indexed: 12/27/2022]
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 (25[OH]D) 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 (25[OH]D <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.
Collapse
Affiliation(s)
- Weiguo Zhang
- DSM Nutritional Products, Human Nutrition and Health, Beijing, China and Kaiseraugst, Switzerland.
| | | | | |
Collapse
|