Vitamin A is a fat-soluble vitamin. It is found in animal sources, such as eggs, meat, fish, milk, cheese.
Beta carotene, which the body converts into vitamin A, is found in vegetable sources such as carrots, squashes, and most dark green, leafy vegetables.
Some people believe that individuals with autism don't have enough vitamin A in their bodies, or that their bodies are poor at making use of the vitamin A available to them.
These people believe that these nutritional deficiencies may be the cause of some of the problems faced by people with autism - such as problems with vision, sensory perception, language processing and attention.
They also believe that some of these problems can be overcome by taking supplements of vitamin A - often alongside other vitamins and minerals.