When the boys were enrolled in the study, the researchers asked the boys' parents if the boys were taking over-the-counter or prescription medications, were taking any vitamin or mineral supplements, or were on a restricted diet.

During the study, researchers X-rayed the hands of 75 boys between the ages of 4 and 8 years old who had been diagnosed with autism or ASD. The researchers then measured the thickness of the bone located between the knuckle of the index finger and the wrist and compared its development to a standardized reference based on a group of boys without autism.


Dr. Hediger said that the research team measured cortical bone thickness. She added that this procedure was done as a substitute for a conventional bone scan, which measures bone density. Bone density is an indication of bones' mineral content. Less dense bones may indicate a risk of bone fracture.

The researchers used the measure of bone thickness because many of the boys were unable to remain still long enough for the conventional scan, which requires individuals to lie immobile for an extended period of time. To successfully complete the bone scan, many of the boys would have required sedation - a step the researchers were reluctant to take for an early study.

The hand X-ray, Dr. Hediger explained, offers an approximate indication of bone density. She added, however, that because the researchers were unable to use a conventional bone scan, the results of the current study should be confirmed by additional studies using conventional bone scans.

The investigators found that the bones of the boys with autism were growing longer but were not thickening at a normal rate. During normal bone development, material from inside the bone is transferred to the outside of the bone, increasing thickness, while at the same time, the bones are also growing longer.

At 5 or 6 years of age, the bones of the autistic boys were significantly thinner than the bones of boys without autism and the difference in bone thickness became even greater at ages 7 and 8.

The bone thinning was particularly notable because the boys with autism and ASD were heavier than average and would therefore be expected to have thicker bones.

The researchers do not know for certain why the boys had thinner than normal bones. A possible explanation is lack of calcium and vitamin D in their diets. Dr. Hediger explained that a deficiency of these important nutrients in the boys' diets could result from a variety of causes. Many children with autism, she said, have aversions to certain foods. Some will insist on eating the same foods nearly every day, to the exclusion of other foods. So while they may consume enough calories to meet their needs - or even more calories than they need - they may lack certain nutrients, like calcium and vitamin D.

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