Body composition in children with juvenile idiopathic arthritis: effect of dietary intake of macronutrient: results from a cross sectional study

Introduction The aim of this study was to evaluate the relationship between macronutrient intake, body composition (lean body mass and fat mass) and bone mineral content in Moroccan children with juvenile idiopathic arthritis (JIA). Methods A cross-sectional study, conducted between May 2010 and June 2011, covering out patient with JIA. The characteristics of patients were collected. The nutritional status was assessed by a food questionnaire including data of food intake during 7 consecutive days using 24-hour dietary recall. Food intake was quantified using the software Bilnut (Bilnut version 2.01, 1991). Dietary intake of macronutrients was expressed as percentage contribution to total energy. Body composition was evaluated with DXA total-body measurements (bone mineral content BMC expressed in g, lean body mass LBM and fat mass FM expressed in kg). Results 33 patients were included. The mean age was 10.4 ± 4.3 years. The median disease duration was 2 (1-4.5) years. The median of LBM, FM and BMC were 19 kg (13.82-33.14), 5 kg (3.38-9.14) and 1044.90 g (630.40-1808.90) respectively. We found a positive correlation between LBM and dietary intake of carbohydrate (r= 0.4; p = 0.03). There were no significant association between LBM and intake of lipids, or protein. Moreover, no association was found between FM, BMC and intake of carbohydrates, lipids and proteins. Conclusion This study suggests that there is a positive correlation between carbohydrates intake and LBM; however, dietary intake does not influence FM and BMC. Prospective studies with larger numbers of patients appear to be needed to confirm our findings.


Introduction
In patients with juvenile idiopathic arthritis (JIA), growth impairment and altered body composition, including disturbed skeletal development, are well-known long-term complications [1].
Although, few studies have specifically addressed body composition in children with JIA.
Reduced bone mineral density (BMD) is also well recognized features [2]. Deficits of muscle mass have been described as a central factor in (secondary) bone loss [3]. The reasons for deficits in lean body mass are thought to be the disease activity itself, medication (corticosteroids), reduced physical activity, and malnutrition [4]. Apart from low BMD and lean mass, a higher fat mass was reported in children with rheumatic diseases [5].
Despite the considerable hereditary influence on body composition, the environmental factors, namely nutrition, play an important role as well [6]. Among the nutritional factors, macronutrients (proteins, carbohydrates and lipids), and their effects on bones receives most attention [7]. Inadequate dietary intake in childhood and adolescence might alter body composition with adverse implications later in life (obesity and osteoporosis). Therefore, understanding the effects of diet on body composition can guide the implementation of social policies and interventions that can help youths to develop healthy bodies.
In the literature, there was a very few studies assessing the relationship between dietary intake and body composition in children with JIA. In addition, there are no studies in a Moroccan population that evaluate the same subject. An abnormal body composition with low muscle mass and increased fat mass in children with JIA [4,5] prompted us to conduct this study which aims to evaluate the relationship between dietary intake of macronutrients , body composition (lean body mass and fat mass) and bone mineral content in Moroccan children with JIA.

Data collection
A cross sectional study of children with JIA was conducted between Assessment Questionnaire (CHAQ) [11]. Treatment with NSAIDs, steroids and disease modifying anti-rheumatic drugs (DMARDs) was determined.

Body composition
Body composition was evaluated with DXA total-body measurements (whole body bone mineral content BMC expressed in g, lean body mass LBM and fat mass FM expressed in kg) using the same DXA instrument (Lunar Prodigy; GE Lunar, Madison, WI). According to international consensus, DXA measurements without head were used. The instrument automatically alters scan depth depending on the thickness of the subject, as estimated from age, height, and weight. All scans were performed while the subjects were wearing light indoor clothing and no removable metal objects.
Medical history for bone fractures was negative in all patients. All subjects underwent plain Vertebral Fracture Assessment (VFA) to exclude unknown vertebral fractures [12].

Dietary evaluation
Nutrient intake was determined using the 24 hour diet recall during 7 consecutive days [13]. The food questionnaire identified all foods consumed during the day previous to the interview. Two

Results
Thirty three patients were included in this study. The mean age of our patients was 10.4±4.35. 54.5% of our patients were males. The median disease duration was equal to 2(1-4.5) years. Demographic and clinical characteristics of patients are shown in Table 1. The median of lean body mass (LBM), total body fat mass (FM) and bone mineral content (BMC) were 19 kg (13.82-33.14), 5 kg (3.38-9.14) and 1044.90 g (630.40-1808.90) respectively ( Table 1). Table 2. Mean values for diet composition indicated that carbohydrates provided 53% of energy, lipids provided 32.5%, and proteins provided 16.1%.

The dietary intake data are shown in
We found a positive correlation between LBM and carbohydrates intake (r= 0.4; p = 0.03). There were no significant association between LBM and intake of lipids or proteins. Also, no association was found between FM, BMC and dietary intake of carbohydrates, lipids and proteins ( Table 3).

Discussion
Our data show that there is a positive correlation between LBM and carbohydrates ingested (expressed as a proportion of energy intake) but not between LBM, lipids and proteins intake. In the study of Volek JS et al, they found that a carbohydrate-restricted diet resulted in a significant reduction in fat mass and increase in lean body mass, which may be partially mediated by the reduction in circulating insulin concentrations [15]. Chandler-Laney PC et al showed that maternal glucose concentration during pregnancy was positively associated with children´s lean mass and fat mass [16].
In the other study, Lean muscle mass was not associated with physical activity or dietary intakes [17].
Previous observational studies of dietary protein intake and body composition have shown mixed results. Protein intake was not associated with LM in cross-sectional studies [17,18]. In the Health ABC Study cohort, they found an association between protein intake and changes in LM over 3 years of follow-up [19]. However, few studies have examined the effect of protein intake on LBM in children.
The problem of overweight and obesity is a growing public health concern affecting numerous countries. The amount of fat ingested has been implicated as a causal or facilitating factor in the deposition of body fat. Thus, it is proposed that dietary fat can directly or indirectly manipulate human adipose tissue. There is suggestion in the literature that protein intake, not fat intake, may be associated with the development of adiposity in childhood [20].
It has been proposed that a high protein intake during early childhood stimulates insulin-like growth factor I production, thereby triggering precocious adipocyte multiplication [21]. In a prospective case-control study, they found that fat intake predicted gain in percentage of body fat in both adolescent girls with type 1 diabetes and healthy control girls [22]. In the other study, they did not find any association between dietary protein intake and percentage body fat [23]. Dietary carbohydrate expressed as a percentage of energy intake is often inversely related to body fat, including in childhood obesity [24]. In this study of children with JIA, there was no association between FM and intake of macronutrients.
Despite the methodological limitations of the present study; sample size, cross-sectional and non-controlled design, this study was the first Moroccan study that assesses the relationship between dietary Page number not for citation purposes 4 intake and body composition in children with JIA, but the causeeffect relationship remains to be determined.

Conclusion
This study suggests that there is a positive correlation between carbohydrates intake and LBM; however, dietary intake does not influence FM and BMC. Furthermore, Controlled feeding studies will be required to clarify possible roles of dietary intake in body composition of children with JIA.

Competing interests
The authors declare no competing interests.

Authors' contributions
SR, BA and NHH conceived the study and supervised its design, execution, and analysis and participated in the drafting and critical review of the manuscript. AH and SR did data management and statistical analyses. AB and KEK analyzed the food dietary. All authors participated in critical revision of the manuscript. AH wrote the paper with input from all investigators. All authors read and approved the final manuscript.    Results are presented in mean±SD; Differences were tested using t test