Vitamin D status and determinants of deficiency in non-supplemented athletes during the winter months in Tunisia.

Original VitaminPaper D status in athletes DOI: 10.5604/20831862.1163690 Biol. Sport 2015;32:281-287 Vitamin D status and determinants of deficiency in non-supplemented athletes during the winter months in Tunisia AUTHORS: Sghaier-Ayadi A1,2, Feki M2, Bezrati-Ben Ayed I1, Abene O1, Ben Fredj MK2, Kaabachi K2, Chaouachi A1,3 1 Tunisian Research Laboratory ‘’Sport Performance Optimisation’’, National Center of Medicine and Science in Sports, Tunis, Tunisia 2 Laboratory of Biochemistry, Rabta Hospital, Faculty of Medicine of Tunis, El Manar University, Tunis, Tunisia 3 AUT University, Sports Performance Research Institute New Zealand, Auckland, New Zealand ABSTRACT: Recent reports suggest that hypovitaminosis D in athletes is as common as in the general population. This study was devised to examine vitamin D status and determinants of deficiency in athletes living in a sunny country (Tunisia). One hundred and fifty national elite athletes, training outdoors (n=83) or indoors (n=67), were enrolled from January to February 2012. Plasma 25-hydroxyvitamin D was measured by radioimmunoassay. Concentrations were between 50 and 75 nmol · l-1 in 21.3% of participants, between 25 and 50 nmol · l-1 in 55.3% of participants and <25 nmol · l-1 in 14.7% of participants. The concentrations were significantly lower in indoor athletes than outdoor athletes (36.2±19.0 nmol · l-1 vs. 49.1±19.2 nmol · l-1; p<0.001). In multivariate analysis, vitamin D deficiency (25-hydroxyvitamin D <50 nmol · l-1) was associated with indoor sports [multi-adjusted odds ratio (95% confidence interval), 5.03 (1.64-15.4); p=0.005], female gender [3.72 (1.44-9.65); p=0.007] and age < 18 years [2.40 (1.01-5.85); p=0.05]. Athletes living in sunrich environments are exposed to a high risk of vitamin D inadequacy. Given the importance of vitamin D in health and athletic ability, targeting sufficient levels of plasma 25-hydroxyvitamin D in athletes is well justified. CITATION: Sghaier-Ayadi A, Feki M, Bezrati-Ben Ayed I et al. Vitamin D status and determinants of deficiency in non-supplemented athletes during the winter months in Tunisia. Biol Sport. 2015;32(4):281–287. Received: 2015-01-02; Reviewed: 2015-02-16; Re-submitted: 2015-03-30; Accepted: 2015-03-31; Published: 2015-08-04. Corresponding author: Anis Chaouachi Tunisian Research Laboratory ‘’Sports Performance Optimisation’’ National Center of Medicine and Science in Sports (CNMSS) Bp263, Ave Med Ali Akid, 1004 El Menzah, Tunis, Tunisa Tel: +216 21 17 69 40 Fax: +216 71 70 97 89 E-mail: Key words: cholecalciferol hypovitaminosis D sun exposure vitamin D inadequacy INTRODUCTION Vitamin D plays an important role in optimizing health and prevent- during the winter season and to identify groups with increased risk ing disease [1]. Emerging evidence suggests that hypovitaminosis D of vitamin D deficiency (VDD). Particular attention was paid to the is widespread worldwide, affecting different age groups and demo- role of sun exposure in the development of vitamin D status. graphics [2-4]. Due to its key role in the musculoskeletal system, immune function and inflammatory response, vitamin D levels may MATERIALS AND METHODS directly affect an athlete’s overall health and athletic ability [5-9]. Study design and participants. This cross-sectional study included During recent years, some studies have examined vitamin D status 150 athletes, 57 females and 93 males aged 15 to 26 years. Athletes in athletes. The available data show that vitamin D inadequacy were enrolled from the Elite Sport Centres of Kairouan (latitude, ranges from 16% to 100%, varying according to latitude, season, 33.2° N) and Tunis (latitude, 36.5° N) (Tunisia) from January to gender, type of sport and socio-cultural and ethnic factors [10-16]. February 2012. All participants were identified as being non-smokers Vitamin D is mainly produced endogenously following incidental skin and free from illness or current injury. Athletes who admitted having exposure to ultraviolet B irradiation with little derived from dietary taken vitamin D supplements, fish oils or multivitamins during the sources [1,17]. In this regard, elite Tunisian athletes, who live in an past year were excluded. Athletes were divided into two groups ac- environment with a high potential for sun exposure and who benefit cording to the mode of training (indoors/outdoors) as a marker for sun from sustained nutritional support, are expected to achieve adequate exposure. Outdoor sports were athletics (n=83), while the indoor vitamin D status. However, this condition could be influenced by sports were judo (n=31), karate (n=21), boxing (n=6) and fencing factors such as season, duration/timing of exposure to sunlight, skin (n=9). Information on demographic characteristics, lifestyle factors, colour, amount/type of clothing, sun block usage, setting of training, athletic activity, dietary intake and supplements or medication use body composition, diet and supplement use. The present study aimed was collected. Athletes underwent a brief clinical examination includ- to examine vitamin D status among young elite Tunisian athletes ing blood pressure measure. Weight and height were measured with Biology of Sport, Vol. 32 No3, 2015 281 Sghaier-Ayadi A et al. athletes barefooted and lightly clothed, and body mass index (BMI) less than 10%. Following international guidelines [7,19] vitamin D was calculated. Biceps, triceps, sub-scapular and supra-iliac skin inadequacy, deficiency and severe deficiency were defined by plasma folds thickness were measured using skin fold callipers by experienced 25-OHD concentrations < 75, < 50 and < 25 nmol · l-1, respec- staff. Body density was calculated using the sum of the four skin tively. folds, and fat mass relative to total body weight was calculated using the Siri formula [18]. Athletes’ skin colour was classified by the study Statistical analysis staff as fair, brown or dark. Dietary intake data were collected by Statistical analysis of the data was conducted using SPSS software means of a nutritionist-administered three-day diet history method. (version 18.0; SPSS Inc., Chicago, IL, USA). The Gaussian distribu- Energy and nutrient intakes were calculated using a computer program tion of continuous variables was verified. Descriptive statistics were (Nutri Pro 7 software, CERDEN, Brussels, Belgium). performed and values are shown as mean (standard deviation) for Written informed consent was obtained from all the adult par- continuous variables and as percent for categorical variables. Com- ticipants and the parents of adolescent players after verbal and writ- parisons between groups were performed with Student’s t-test for ten explanation of the experimental design and potential risks of the independent samples for continuous variables, and χ² tests for cat- study. The study was conducted according to the Declaration of egorical (...truncated)