The results of a small clinical trial show that a chemical derived from broccoli sprouts may improve symptoms of autism like repetitive movements, irritability, hyperactivity, and communication problems.

Although one in 68 children in the United States has been diagnosed with autism spectrum disorder, no medications are currently available to cure this group of developmental disabilities. But the results of a recent small clinical trial, published in Proceedings of the National Academy of Sciences, suggest that a chemical derived from broccoli sprouts may reduce the behavioral symptoms of autism by targeting the root cause of the disorder.

“We believe this may be preliminary evidence for the first treatment for autism that improves symptoms by apparently correcting some of the underlying cellular problems,” said Dr. Paul Talalay, a professor of pharmacology and molecular sciences at the Johns Hopkins University School of Medicine, in a press release.

The compound, sulforaphane, is best known for claims that it may prevent certain cancers. But researchers have found that it also increases the activity of genes that help cells protect themselves from inflammation, oxidative stress, and radiation.

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Previous studies have also shown that sulforaphane can improve the body’s heat-shock response, a series of events that occurs in the body in response to heat or fever, which is what connects broccoli with autism.

According to the researchers, around half of parents of autistic children have reported that their child’s behavior improved during a fever, only to return to its previous state when the fever went away. A 2007 study in Pediatrics found similar results, but stronger fevers did not necessarily result in larger decreases in the autism symptoms.

To test whether sulforaphane could improve autism symptoms by mimicking what happens in the body during a fever, Talalay and his colleagues recruited 40 teenage boys and young men with moderate to severe autism. The researchers assigned them to one of two groups, with about half receiving a daily dose of sulforaphane — at a level high enough that it would be difficult to get by simply eating broccoli.

During the 18-week study, between 35 and 60 percent of those taking sulforaphane showed decreases in characteristic autism symptoms like repetitive movements, irritability, hyperactivity, and communication problems. The level of improvement depended on the assessment done by the parent or caregiver. Only about 20 percent of volunteers taking a placebo — an inactive compound — improved during the study.

When the young men were evaluated by trained clinicians, those who showed improvements in their verbal communication, social skills, and other behaviors were also taking sulforaphane. However, as the parents observed, not every person taking the compound improved.

Improvements in behavior occurred as early as four weeks after the patient started taking the compound, and increased over the course of the study. Compared to the rapid changes seen with a fever, sulforaphane appears to have a slower, more long-term effect on autism symptoms. Once people stopped taking the sulforaphane, their symptoms gradually returned to the level they were at the start of the study.

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Because sulforaphane is derived from broccoli, it can be classified as a food product, a nutritional supplement, or a drug, depending on how it is used. The researchers said that the compound is generally well tolerated, although those taking the compound gained more weight during the 18 weeks than those taking the placebo.

In addition, two of the subjects taking sulforaphane experienced seizures during the study, although they had a history of seizures before they started taking the compound. Larger clinical trials would be needed to determine whether sulforaphane can be used safely over long periods of time and whether there are other serious side effects.

More research is also needed to understand how many people with autism might benefit from sulforaphane. Autism is a complex disease, with many different genes involved, and symptoms range from minor to severe.

Although more work is needed, and the root cause of autism still remains elusive, this study targets the problem at the cellular level. As researchers better understand what makes autism tick, they can develop more effective treatments, either using sulforaphane or a drug that works in a similar way.

“We are far from being able to declare a victory over autism, but this gives us important insights into what might help,” said co-investigator Dr. Andrew Zimmerman, now a professor of pediatric neurology at the University of Massachusetts Memorial Medical Center.

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