Putting children with autism on special diets may not be such a good idea, researchers say.

Many families have turned to gluten-free, casein-free diets or added supplements to their children’s daily intake with an eye toward easing autism symptoms or to make up for picky eating habits common among those with the developmental disorder.

However, research published this month in the Journal of the Academy of Nutrition and Dietetics suggests that restricting certain types of foods or adding various nutritional supplements often leaves children without the proper balance of nutrients.

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For the study, caregivers of hundreds of kids with autism logged details for three days about food, drink and supplements consumed by the children, all of whom were on the autism spectrum and ranged in age from 2 to 11.

Overall, researchers found that kids with autism were consuming typical levels of micronutrients and they had deficiencies in vitamins D and E, calcium, potassium and choline similar to what’s seen in children generally.

Even among those with autism who were taking supplements, researchers found that calcium and vitamin D were still often lacking. At the same time, many of the kids taking supplements consumed levels of vitamin A, folic acid and zinc in excess of what’s considered safe.

Meanwhile, children on gluten-free, casein-free diets took in more magnesium and vitamin E and had more appropriate levels of vitamin D, the study found, but still took in too little calcium.

“In clinical practice, each patient needs to be individually assessed for potential nutritional deficiencies or excess,” said Patricia Stewart, an assistant professor of pediatrics at the University of Rochester Medical Center who led the study. “Few children with ASD need most of the micronutrients they are commonly given as multivitamins, which often leads to excess intake that may place children at risk for adverse effects. When supplements are used, careful attention should be given to adequacy of vitamin D and calcium intake.”