There is no doubt that food allergies are real, serious and dangerous. At the same time, there is a long history of paranoia about food that lies more in the mind than the stomach.
In a 1987 study that followed nearly 500 children from birth to age 3, 28% of parents and caregivers thought their babies had adverse food reactions, though only 8% ended up having confirmed allergies.
Not much has changed. Today, between one-quarter and one-third of people suspect an allergy in their children or themselves, even though rates are up to five times lower than that.
For some people, the problem is not an allergy but a more subtle sensitivity or intolerance. Lactose intolerance, for example, occurs when there's a shortage of the enzyme that breaks down milk proteins. About 50 million Americans have it, with symptoms after consuming milk products that include bloating, gas and diarrhea. The solution is simple: Avoid dairy, or supplement the diet with the enzyme lactase.
Gluten sensitivity, which is becoming more common -- in reality and also in people's perceptions -- is more complicated. It occurs when the body fights against gluten, a protein in wheat, barley and rye. At its worst, this sets off a cycle in which the body's immune system gets confused and attacks the small intestine. The result is celiac disease.
About one out of 133 people in the U.S. has celiac disease, though an estimated 90% of cases are currently undiagnosed. And rates are increasing. As many as 2.5% of the population will have celiac disease in a decade, predicts Daniel Leffler, a gastroenterologist at Harvard Medical School in Boston.
The good news is that celiac disease can be diagnosed with a blood test and intestinal biopsy. The bad news is that a large number of people don't have celiac disease and yet still feel lousy after eating gluten. Symptoms can be as vague as fatigue and stomach upset, possibly because gluten is a protein that is hard for everyone to digest. But there is no definitive intolerance test.
In that way, sensitivities to gluten resemble sensitivities to MSG, food dyes and nitrites. Some people insist they feel better without these chemicals in their diets. But scientists can't say for sure if they're right -- or whether what they're reporting is some kind of self-administered placebo effect. There are no data to help clear up the muddle.
"With most intolerances, there's nothing medically you can measure," Leffler says. "There's nothing you can see."
