Friday, June 7, 2013
Gluten-free diets: miracle or hype?
If you've ever made bread, you're intimately familiar with gluten. Gluten is the hunk of proteins that turns a ball of crumbling dough into an elastic, yummy ball of bread-to-be. The protein is found in wheat and related grains that are food staples in large parts of the world.
Gluten is rarely a health problem, but it does come locked into big, high-calorie servings of carbohydrates, pumping us full of unneeded calories and putting us at risk for obesity and diabetes.
For a small part of the population, gluten isn't just a part of the obesity epidemic. About 1 in 133 Americans develop an immune reaction to the protein leading to a condition called "celiac disease." Numbers are higher in Europeans and higher in people with typical symptoms and people who have family members with the disease. When gluten hits the gut in someone with celiac disease, it sets off an immune reaction which kills off the cells forming the inner lining of the small intestine.
Since many important nutrients are absorbed in the small intestine, patients can suffer problems related to malnutrition: osteoporosis, anemia, vitamin deficiencies. Abdominal pain and diarrhea are common but not universal, and some people suffer from significant weight loss.
The nice thing about celiac disease is that we understand very clearly how it works, and can eliminate its negative effects by avoiding foods with gluten. We can easily measure antibodies in the blood formed by people with celiac disease, and their intestine shows specific changes under the microscope.
A gluten-free diet can completely eliminate the symptoms of celiac disease. It has become easier and easier to find gluten-free foods as the public has become more aware of the disease. Some of that awareness has gone a bit overboard.
A quick Google search of the topic shows just how deep into the rabbit hole we can go with "gluten sensitivity." This poorly-defined syndrome is usually self-diagnosed by someone who feels unwell and then is better when following a "gluten-free" diet. People blame gluten for everything from child behavior and learning problems to chronic pain and fatigue.
As is often the case with vaguely-defined syndromes, many of the symptoms are vague and subjective, and few studies have confirmed that a disease even exists. The field is complicated by the fact that gluten-sensitivity diagnosis and treatment is often patient-driven. Doctors in the office are often confronted by the problem, and patients and doctors both are frustrated by the lack of knowledge.
But there is a lot we do know. People who feel they are gluten-sensitive but do not test positive for celiac disease do not have celiac disease. The usually don't have any pathology we can put a finger on, but this may be due to the lack of studies. People with celiac disease improve dramatically with proper diet, and sicken dramatically when they stray even a little bit. It is unclear what effect if any gluten-free or gluten-diminished diets might have on people with self-defined gluten sensitivity.
People with celiac disease usually have a certain type of cell surface receptor that helps set off the immune reaction. Is there another way that gluten may cause disease aside from the well-understood immune mechanisms of celiac disease? At this point, I haven't seen any convincing hypotheses.
Based on the available literature (and my clinical practice), I think that in a few years' time we will have found perhaps a small number of people who feel "better" on gluten free diets, either because of the decreased gluten or more likely because of avoidance of carbohydrates in general. The rest of the self-defined gluten-sensitive will find that there really is no dramatic change in their life that isn't due to chance alone or the natural course of other diseases, and the gluten-free craze will fade.
Peter A. Lipson, ACP Member, is a practicing internist and teaching physician in Southeast Michigan. After graduating from Rush Medical College in Chicago, he completed his internal medicine residency at Northwestern Memorial Hospital. This post first appeared at his blog at Forbes. His blog, which has been around in various forms since 2007, offers "musings on the intersection of science, medicine, and culture." His writing focuses on the difference between science-based medicine and "everything else," but also speaks to the day-to-day practice of medicine, fatherhood, and whatever else migrates from his head to his keyboard.
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