That was in the late 1950s, and once the then-28-year-old figured out why she had lost nearly 10 kilograms and felt sick to her stomach, she had few alternatives to eating wheat, which contains the problematic protein.

"I didn't bake anything, cookies, cakes, breads," the now-83-year-old recalls.

Today, gluten-free products are everywhere. And baking delicious cookies and cakes is not a problem - thanks in part to Sherratt's family business.

Her husband, Lowell, is the president of Honeyville Grain, which has corporate headquarters in Brigham City, Utah.

In addition to processing and selling loads of wheat flour, it also sells gluten-free flours including soy, rice, corn, potato and almond flour (also known as almond meal).

It's the almond flour that Honeyville is becoming known for in the gluten-free world. The company has been selling it for about seven years, but business started booming recently as the diet restriction moved beyond just those with celiac disease and less-extreme gluten sensitivities, to the mainstream.

Chris Ondatje, vice-president of Honeyville's e-commerce division, says almond flour is the company's number one online seller. It has sold about 181,500 kilograms of it in the past year, a 100 per cent increase on the previous year's sales.

"Sales growth remains hot," Ondatje wrote in an email.

"It's so sought after that we're constantly fighting to stay ahead of the demand curve."

Gluten-free food is an estimated $3.8 billion to $5.7 billion food industry, and projected to keep expanding, according to the market-research company Mintel. The growth is attributed to trendiness - a perception among shoppers that the will lose weight without gluten - and the improved taste of gluten-free products.

Almond flour, which is finely ground almonds, is healthier than the other wheat alternatives, says Diane Bell, owner of the Taylorsville, Utah, shop Against the Grain, which sells gluten-free baking mixes and baked goods.

"White-rice and brown-rice flour has one gram of fibre. Big whoopie," she says.

But one serving of almond flour has 6 grams of protein, compared with 3 grams in wheat flour. It also has fewer carbohydrates but more fibre and healthy unsaturated fats, which protect the heart.

Almonds are also cholesterol free and pack the antioxidant vitamin E.

"Everybody in the general population can benefit from it," Bell said of using gluten-free flours.

Almond flour is best suited to sweets - cookies, cakes, muffins and pancakes - says Lisa Barker, education and outreach coordinator at Honeyville.

Barker says it takes some experimentation and skill when using almond flour, unless the recipe is made for the nut.

But she says it's worth experimenting.

"This is an opportunity - just like a chef is looking for new products to play with." AAP