"This is our medicine," said Bast, 52, founder and president of the National Foundation for Celiac Awareness, in Ambler. "This is how we stay healthy."
More people find it necessary, as the incidence of celiac keeps rising at a pace that is concerning and mysterious. One study showed men were 41/2 times more likely to have the disease today than a comparable group in the 1950s.
Some doctors think an explanation lies in the processed foods that make up so much of the American diet, or possibly in hybridization that changes the makeup of some wheats.
The only treatment is to stop eating gluten. Forever. That helped drive sales of gluten-free foods and drinks to $4.2 billion in 2012.
"It's here to stay," said Julia Stamberger, president of GoPicnic, a Chicago firm that signed a deal to put its packaged gluten-free meals in Regal theaters.
Some people think celiac disease is a trendy diagnosis, or an Oprah-ish prescription for healthy eating or weight loss. Actress Gwyneth Paltrow has gone gluten-free. So have tennis star Novak Djokovic and Saints quarterback Drew Brees.
"I have no idea what gluten is, either," a woman says to a man in a New Yorker cartoon, "but I'm avoiding it, just to be safe."
And many people switch simply because they think a gluten-free diet makes them feel better.
"This market is growing rapidly, in part because of self-diagnosis and a developing belief that many of our ailments are the result of diet," said Ronald P. Hill, a marketing professor at Villanova University.
But millions of others have a genuine intolerance of or allergy to wheat. Beyond that group is the estimated 1 percent of the population afflicted with celiac disease, an autoimmune disorder.
That's about three million people, roughly the population of Iowa. Most have not been diagnosed, suffering through chronic stomach distress that doctors can mistake for something else.
When people with celiac disease consume gluten, the main storage protein in wheat and similar grains, the body's antibody defenses attack the lining of the small intestine. That lining consists of hairlike projections called villi, which allow the body to absorb nutrients.
When villi are damaged or destroyed, the body can't take in nutrition. A person can become malnourished even while eating normally.
Even scarier, patients with unchecked celiac disease have an overall cancer risk almost twice that of the general population. The illness is linked to higher incidence of lymphoma and intestinal cancers, and to nervous-system disorders, rheumatoid arthritis, diabetes, and thyroid disease.
More people are being diagnosed because doctors know to look. But researchers say the disease also has become much more prevalent.
How do they know? The Air Force.
A few years ago at the Mayo Clinic, gastroenterologist Joseph Murray and colleagues learned of a collection of blood samples taken from 9,133 Air Force recruits between 1948 and 1954. They tested the blood for gluten antibodies, expecting to see the current 1 percent rate of disease. Instead, only 0.002 percent of the airmen tested positive. Further tests showed today's young men were 41/2 times more likely to have the illness.
"There's no doubt there's an increase in celiac disease," said Anthony DiMarino Jr., director of the Celiac Center at Jefferson University Hospitals. "It's real."
And troubling. These days, gluten is in practically everything, used as a filler in foods from ice cream to soup and even in medicines and vitamins, making it hard for the vigilant to fully exclude it from their diet.
Some people with celiac don't even try.
For one thing, gluten-free foods are expensive, generally more costly than their wheat-filled counterparts. They often don't taste as good, and can be hard to find. Some people who are asymptomatic simply decide that life is short, and go on eating as before.
The disease has long been misunderstood. Until 2004, the National Institutes of Health classified celiac as a rare, child illness. Today, its cause is unknown but its genetic connections are proved, its symptoms multiple and sometimes contradictory:
Stomach cramps. Fatigue. Depression. Migraines. People can suffer chronic diarrhea or constipation, weight loss or weight gain.
Diagnosis is generally a two-step process. First, a blood test to check for gluten antibodies. If that test is positive, it's followed by an upper endoscopy, in which a doctor inserts a scope down the patient's throat and removes several small patches of intestinal tissue for biopsy.
If the biopsy confirms celiac disease, there's one treatment: Stop eating gluten. Even small amounts can be hazardous.
Going gluten-free lets the intestine heal. Most important, doctors say, when celiac patients keep to a gluten-free diet, their risk of serious illness drops to normal.
Celiac groups tell businesses: An estimated three million people have the disease, and 18 million more have a sensitivity. That's 21 million customers.
"I hate to say it's a good time to have a disease, but things are blossoming," said Michael Savett, a Philadelphia lawyer who began writing the Gluten Free Philly blog after his 12-year-old son was diagnosed at age 3. This region has options at stores like Trader Joe's and Whole Foods, along with Taffets bakery in the Italian Market and Sweet Freedom bakery in Center City.
Drexel University began offering culinary students a course on gluten-free cooking, knowing future chefs will need to meet the needs of celiac-sufferers. In West Conshohocken, at the Hope Paige medical-identification company, "gluten-free" bracelets and necklaces have surged to become 10 percent of total sales.
"Twenty years ago, nobody had heard of it," said Bast, the Celiac Awareness president. Now, "every week I have somebody coming to me and saying they're starting a gluten-free food company or they're looking to carry gluten-free. . . . This is a community that's not going to go away."
Contact Jeff Gammage at 610-313-8205, firstname.lastname@example.org, or follow on Twitter @JeffGammage.