I have talked and written about ‘social calories’ to describe the impact that social interaction has on me, usually in terms of trying to limit my intake of social calories. This would often mean a choice between one activity with lots of gentle socialising or another with shorter, intense interaction. Too many social calories make me (physically) sick if I don’t pace myself. In short, Daisy wrote of one social occasion, “a surfeit of ‘social calories’ – the effort of making social contact with so many unfamiliar people in such a short time, and eating unfamiliar food, made me feel sick.” The Enchanted Doors, “A Book to Read When You Have Asperger Syndrome”. You can watch a presentation with visuals — about 13 minutes in, I talk about social calories and social misunderstandings in The Spooky Powers of Normal People).
Summary: There has been insufficient research to suggest any diet specific to ASD, but plenty to know that everyone requires a balanced diet and sufficient exercise. Some off-the-shelf supplements may help. One excellent guide is the (unfortunately titled) book “Nutrition for Dummies” by Carol Ann Rinzler and you will find similar books at shelf-mark 613.2 in any local library.