The Effect of Nutrition and Exercise on Bone Density in Boys with Autism Spectrum Disorder
Peak bone mass is an important determinant of future bone health. The childhood years are critical for development of bone mass, which depends upon many factors including genetics, nutrition, weight bearing activity, hormonal status, medication use and medical disease. Boys with autism spectrum disorder (ASD) have lower bone mineral density (BMD) than typically developing controls (TDC). Differences in nutrition and exercise may contribute to low BMD. Nutrition management of children with ASD is a challenge because children frequently have a restricted diet, either self-imposed and limited by taste or texture or imposed by parents to avoid potential allergens. Concurrent gastrointestinal diseases in children with ASD may affect absorption of nutrients. Children with ASD are also often less active physically and have a higher prevalence of hypotonia.
To examine macro- and micro-nutrient intake, serum levels of vitamin D and calcium, and self-reported physical activity in boys with ASD compared to TDC and the relationship of these variables with BMD.
Participants included 49 prepubertal and pubertal boys (25 ASD, 24 TDC), ages 8-17 years, recruited from a clinic population (ASD) or community advertisements (ASD and TDC) matched for age. In this cross-sectional study, we assessed BMD of the lumbar spine, femoral neck, total hip and whole body less head using dual energy X-ray absorptiometry, and three-day diet/supplement and physical activity records. Fasting levels of 25(OH) vitamin D and calcium were obtained.
ASD participants were approximately 9 months younger than TDC participants on average. Age adjusted BMI z-scores were similar. Body mass index and serum vitamin D and calcium levels were similar. BMD Z-scores were 0.7 to 1.2 standard deviations lower in ASD than TDC at all locations. Fewer boys with ASD were categorized as “very physically active” (27% vs. 79%, p<0.001). Boys with ASD consumed significantly less calcium, iron, phosphorous, selenium, vitamins A, riboflavin, niacin, B6, B12 and dietary folate equivalents, with deficiencies ranging from 19 to 35%. Boys with ASD consumed 16% fewer calories, 37% less animal protein, and 20% less fat than TDC, with a larger percentage of calories obtained from carbohydrates. Higher animal protein, calcium and phosphorus intake was associated positively with bone density measures in boys with ASD. Our data confirm reports of micronutrient inadequacies in the diets (food alone) of boys with ASD and that vitamin supplementation does not correct several of these inadequacies.
Boys with ASD were less active and had lower BMD Z-scores at the lumbar spine, femoral neck, total hip and whole body less head than TDC. Protein, calcium and phosphorus intake were lower in ASD than TDC and were associated positively with BMD. This suggests that encouraging diets higher in fortified dairy and animal protein as well as increased high-level exercise may improve bone health. It is important for practitioners to assess dietary intake of dairy and animal protein