Many people with autism are reported to suffer from nutritional problems. For example, some people with autism are reported to have abnormal levels of amino acids, vitamins and/or minerals. However there are also reports that people with autism have normal levels of these substances.
Some of the reported problems may be due to underlying factors, such as a damaged metabolism. Or they may be due to the lifestyles, diets and other interventions followed by some people with autism.
Some people believe that many of the other problems faced by people with autism (such as aggression, poor language skills etc) are actually caused by poor diet and nutrition.
However this view is not widely accepted by the scientific community.