New York: Researchers have found that diets similar to what people with diabetes follow to keep their blood sugar in check ameliorate signs of autism in mice.

Although preliminary and not yet tested in humans, the findings might offer clues to understanding one potential cause of autism.

Bread, cereal and other sugary processed foods cause rapid spikes and subsequent crashes in blood sugar. In contrast, diets made up of vegetables, fruits and whole grains are healthier, in part because they take longer to digest and keep us more even-keeled.

The research, published in the journal Molecular Psychiatry, showed that such low glycemic index diets reduced symptoms of the disorder in mice.

The number of people diagnosed with autism — a spectrum of disorders characterised by social avoidance, repetitive behaviours and difficulty communicating — has risen dramatically over the past two decades for reasons that are unclear.

“One thing that is driving a lot of general physiological changes in people is changes in the diet,” said the study’s corresponding author Pamela Maher, a senior staff scientist in the laboratory of professor David Schubert at the Salk Institute for Biological Studies in the US.

In the new study, the scientists used a mouse model of autism to ask whether lowering the level of a common by-product of sugar metabolism could alleviate symptoms of autism in the animals.

The scientists fed pregnant mice either the high or low glycemic index diet and kept their offspring on the same diet after birth and weaning, because their brains are still forming crucial connections.

The two groups of animals consumed the same number of calories and were identical in weight.

But mice that ate a high-glycemic index diet showed all of the expected behavioural symptoms of autism.

Their social interactions were impaired, they repeated actions that served no apparent purpose, and they groomed extensively.