TORONTO - Tina Szenasi's quest to cure her two autistic sons began with soy milk.

Ms. Szenasi switched to the milk substitute after reading testimonials from other parents who said their autistic children's symptoms had improved - even disappeared - when dairy and wheat were eliminated from their diet.

Her doctor dismissed it as farfetched. But the mother of three from Barrie, Ont., felt she had no choice but to try the gluten-free, casein-free (GFCF) diet for her boys, whose neurological disorder made them easily distressed and socially isolated. Introducing the diet "gave me a sense of hope," she says.

She quickly transformed her kitchen into a culinary laboratory. Her butterless cookies crumbled. Cakes made using rice flour were a disaster. Grocery bills topped $500 each week as she ordered gluten-free bread and potato-based milk substitutes that weren't available in her small city.

But her sons improved within weeks, she says. Now, Adam, 11, often hugs his parents and has fewer tantrums. Alex, an eight-year-old soccer and video-game enthusiast, behaves like most other kids. "He's almost fully recovered, I think because of the dietary intervention," Ms. Szenasi says.

More Canadian parents are adopting the controversial diet for their autistic children as support spreads through a fringe group of health professionals, commercial websites and chat forums. Supporters say gluten and casein are not well digested by autistic kids, who often exhibit digestive problems and food allergies.

The protein compounds, they say, wreak havoc with the children's neurological development. To eliminate those triggers, parents spend thousands of extra dollars on special foods, vitamins and enzyme supplements as well as laboratory testing in the United States.

But most mainstream scientists remain skeptical of the gut-brain connection in autism. They say there's no scientific proof that the diet works. Some doctors warn that parents' desperation, paired with the mystery surrounding autism's causes, makes the field ripe - as a top American pediatric gastrointestinal specialist put it - for "charlatanism."

"If there's nothing else that you think is going to help and you're desperate, you'll do anything," said Wendy Roberts, the head of the autism research unit at the Hospital for Sick Children in Toronto.

The GFCF diet eliminates two major food groups from an autistic child's diet: dairy products, which have casein, and grains such as wheat, barley and rye, which contain gluten. Children on the diet often eat a lot of meat and vegetables, plus wheat and dairy alternatives. Some families add vitamin and enzyme supplements.

Even supporters say it isn't clear how the diet works. One explanation involves the "leaky gut syndrome." Undigested bits of protein, according to this theory, are absorbed through the intestine into the body, affecting the brain and producing symptoms associated with autism.

To date, only one double-blind controlled clinical trial - the gold standard for health research - has tested the diet. Published in March, 2006, in the Journal of Autism and Developmental Disorders, the study found that the group of children on the diet saw no significant improvements compared with the control group. Researchers say more testing is needed because the study was based on a small sample.

"The information that's out there suggests that the diet probably does not have a substantial effect on children's behaviours," says Lonnie Zwaigenbaum, a University of Alberta associate professor and director of autism research at Edmonton's Glenrose Rehabilitation Hospital.

Yet almost every parent Dr. Zwaigenbaum sees has either tried the GFCF diet with their autistic child or heard of it, he says. Parents are leaping ahead before science has definitively proved whether such a treatment works, he says, because there are compelling anecdotal cases of improvement.

Autism's causes have long stumped experts. They know that genes play a major role - but increasingly, with diagnosis of the condition on the rise, researchers are looking to environmental triggers including prenatal hormones, toxins, food allergies and infections. As a result, treatments such as the GFCF diet, which focus on removing such triggers, are gaining ground.

"It's word of mouth," say Paul Cutler, a family doctor based in Niagara Falls, N.Y., who works one day a week in Burlington, Ont. "Thanks to the Internet, they're finding these alternatives."

About half of Dr. Cutler's 200 autistic patients are Canadian, and they travel to his offices from across Ontario and Quebec. He charges $150 for an initial assessment that includes a battery of tests - a cheap fee compared with other doctors, he says.

Dr. Cutler has been trained by a group called Defeat Autism Now! (DAN!), which holds annual conferences and instructional sessions for doctors from across North America. The group recommends biomedical treatments for autism that focus on intestinal problems, nutrition, detoxification and allergies. Twenty-six Canadian doctors are listed on the group's website as DAN! practitioners.

They include Wendy Edwards, a pediatrician in Chatham, Ont., who found the diet four years ago when her three-year-old son was diagnosed with autism. He improved so dramatically, she says, that the diet is now the first thing she recommends for autistic patients who travel to see her from across Ontario and even Manitoba. She also encourages other biomedical treatments, including supplements such as vitamin B6, magnesium and dimethylglycine, or DMG.

Some research suggests that up to 40 per cent of children with autism spectrum disorders could benefit from dietary changes, including the removal of gluten or casein, says Timothy Buie, a pediatric gastrointestinal specialist at Massachusetts General Hospital in Boston.

But Dr. Buie, who runs one of the largest practices for children with developmental disabilities in the United States, warns that parents may place so much hope in the diet that they falsely believe their child has improved. "The placebo response is gigantic," he says. "Parents can interpret a benefit because they want their kid to do better."

While parents travel to find doctors, they also ship urine and stool samples to U.S. labs to be analyzed for nutrient and vitamin deficiencies - tests that aren't widely available in Canada. One parent interviewed for this story said she paid up to $300 (U.S.) each for several lab tests.

Some in the industry may be peddling false hopes for big profit, critics warn. "People may choose to recommend things therapeutically that are in their financial interest," Dr. Buie says. "You walk out of a doctor's office and they give you a list of vitamins that they happen to be selling in their outside room."

Other doctors worry about the role of for-profit labs. "Many are not bona fide labs and they're making a fortune," says Dr. Roberts at Sick Kids in Toronto, who adds that parents have handed her results from U.S. labs that don't make any sense.

The Internet is where many parents go to share information, recipes and contacts. Brenda-Lee Olson from Terrace, B.C., moderates a popular online group called GFCFrecipes, whose membership has multiplied tenfold, to 3,400, in the past six years.

"It helps to know certain tricks," says Ms. Olson, who says many people don't believe her 17-year-old son is autistic, thanks to the diet. "The only way to get that information is from other parents."Ms. Szenasi says she'll keep her children on the diet despite the cost. She now keeps a folder stuffed with GFCF diet material at the health-food store where she works, so she can hand it out to other parents.

Shopping for answers

A week's worth of specialty foods for Tina Szenasi's family:

Dare fruit snacks $2.69

EnviroKidz rice bars $3.99

PC Organics potato chips $1.99

PC Organics bananas $1.67

PC Organics grapes $5.89

PC Organics carrots $2.99

Soy organic frozen dessert $6.99

So Nice cultured soy (5) $1.39 each

So Nice soy beverage $3.79

Hot Kid rice crisps (2) $2.49 each

PC Organics eggs $4.99

Tofutti soy-cheese slices $4.69

Piller's pepperoni sticks $6.99

PC natural peanut butter $3.69

EnviroKidz cereal $3.99

Nature's Path waffles $4.99

Glutino cookies $4.99

English Bay dairy-free drink $2.69

Rizopia rice pasta $2.49

PC Organics pasta sauce $3.99

PC beef burgers $7.99

Alexia organic fries $3.29

PC salad mix $4.99

Enjoy Life cookies $3.99

PC Organics popcorn $2.49

Quaker rice cakes $1.49

Organic strawberries $4.99

Organic blueberries $4.99

El Peto Italian bread $5.79

Ian's chicken cutlets $6.99

Total cost for week $132.43