When Roni Piterman started selling prepared meals last year, she hoped to build a business that would thrive on the appetites of clients who were too busy to cook.

But after being inundated with requests for sugar-free, gluten-free and allergy-sensitive meals, she realized there was money to be made catering to people with dietary restrictions and food allergies.

Even more important to her, Piterman quickly saw how many people - including her own son - she could help by opening a business for careful eaters.

Piterman learned that in addition to helping people avoid stomachaches and other allergic reactions, the right diet also seemed to help relieve symptoms in those diagnosed with autism, attention deficit hyperactivity disorder and a host of other conditions.

Although the medical community says there is no proof that certain diets can help those with autism and other diseases, Piterman and a number of her clients are convinced of dietary healing powers.

"Our original business was a make-and-take ...," said Piterman, who opened Your Dinner Secret in Woodland Hills with her sister, Ari Kosmal. "Then we found out about the gluten- and casein-free diet for families with autism. The surprise was how quickly it overtook our business."

As Piterman began researching food and its relationship to autism, ADHD and celiac disease - an abnormal response to gluten in wheat and other grains - she began to recognize some of her son's problems.

I was looking at it from a business standpoint, but it kept knocking on my mommy head and saying, `I should try this."'

Ethan, now 9, had been diagnosed with ADHD and was taking Ritalin. After studying casein - a protein found in milk - and its effect on some kids, Piterman decided to eliminate it and gluten from his diet. That process took two months, but the results were dramatic.

"When I removed casein from my son's diet, within three days, my parents walked into my house and he was watching the Cartoon Network. His grandpa said, `Hey Ethan, how you doing?' And he turned and said, `Hi Papa.' And we were just crying because it was the first time he ever did that."

Before the change in diet, there was no way to get Ethan's attention if he was hyperfocused on the TV. While acknowledging there's nothing harmful in removing gluten and casein from the diet, some doctors are far from convinced that it can improve conditions such as autism and ADHD, said Dr. David Heber, director of the UCLA Center for Human Nutrition.

"There are people who have genuine celiac disease and casein allergy. Both of those are real things that cause gastrointestinal problems," Heber said. "But when you start to connect it to ADHD and autism, you're on much shakier ground."

Still, he said that if people see results from a particular diet and it's healthy, they should continue it.

Plenty of other parents, like Piterman, say their kids have improved markedly after changing their diets.

"We see a much more expressive person," said Mary Spickler, who put her 6-year-old autistic son on a gluten-free, casein-free diet in September. "He is talking a lot more. The other day, I listened to him and his sister play International Space Station in his toy box for an hour. We never would have seen that a year ago."

Celebrity mom Jenny McCarthy boosted awareness of the diet-behavior connection with her 2007 book, "Louder Than Words," which chronicles her son's struggles with autism. McCarthy is the official spokeswoman for Talk About Curing Autism, a support group based in Newport Beach.

With all this attention on diet as a cure, the "free from" food business is booming. The market for gluten-free foods and beverages in the United States was about $700million in 2006, and it is projected to grow about 15percent to 25percent a year to $1.3billion in sales by 2010, according to Mintel, a consumer research group with a focus on the specialty-food industry.

Sales of gluten-free bread, cereal and pasta are driven largely by the increasing awareness of celiac disease, but the diet is quickly becoming associated with autism and ADHD in children. To appeal to worried parents, companies large and small are putting out gluten-free cookies, snacks and even gluten- and casein-free chicken nuggets.

Supermarkets are also picking up on the trend. In addition to Trader Joe's and Whole Foods, Gelson's is starting to stock more gluten-free foods, said Elaine Monarch, founder of Studio City-based Celiac Disease Foundation.

Piterman is quick to point out that the gluten-free, casein-free diet does not work for everyone. But most parents are willing to try something if they think it will help their child.

"It is no coincidence that the greatest numbers of new product introductions were in categories popular with kids, including bakery, dairy, desserts and ice cream, and snacks," the Mintel report said.

"It's important to me that he has food he enjoys," said Spickler, the Burbank mother. She said the family decided to go gluten- and casein-free as a team, so her son wouldn't feel left out, and for the most part it works. "My husband has the most difficult time. When he's at work, he'll go and have a big, fat pizza."

Spickler said she spends about $100 to $200 a month on gluten- and casein-free food from Your Dinner Secret, where a chicken cacciatore serving two goes for $20.75, and four hamburger buns cost $10.50. She buys about eight to 10 meals, plus daily bread, from the company, and the rest of the time she shops mostly Trader Joe's, which has some gluten-free items.

"I just had to move things around in our food budget," she said.

Another customer, Aimee Manis of Calabasas, said buying meals there actually saves her money.

"There's no way I could go to Whole Foods and buy the same quality of chicken for the same prices," said Manis, who buys gluten-free for herself because gluten makes her feel like she has the flu - her children don't have the allergy. She said it is possible to find all the ingredients to cook gluten-free at home, but Whole Foods is probably one of the only options, and it's expensive. She said nonallergenic take-out stores such as Your Dinner Secret are hard to find.

That explains the company's rapid growth. With 600 clients nationwide, Your Dinner Secret started making deliveries twice a month to a hyperbaric center in Irvine (hyperbaric oxygen therapy is one treatment for autism).

Your Dinner Secret has a gluten-free commercial kitchen at its Ventura Boulevard storefront. It also buys baked goods from a special bakery in Culver City.

To meet its demand in the East and Midwest, the company recently opened a distribution center in Missouri.

"It's become such a blessing," Piterman said. "It looked like a good opportunity and a wonderful way to help others. We wanted to give back to our communities."

barbara.correa@dailynews.com