How a Gluten-Free Diet Can Be Harmful
Written by: Michael Greger M.D. FACLM  on February 23rd, 2016 

Gluten-Free Diets - Separating the Wheat from the Chat 

Until only a few years ago, almost the whole of the scientific world maintained that the wheat protein gluten would provoke negative effects only in people with rare conditions such as celiac disease or wheat allergies. But by the early part of 2013, it was largely becoming accepted that some non-celiac patients could suffer from gluten or wheat sensitivity. Indeed, a consensus panel of experts now officially recognizes three gluten-related conditions: wheat allergy, celiac disease, and gluten sensitivity.

What percentage of the population should avoid wheat? About 1 in 1,000 may have a wheat allergy, and nearly 1 in 100 may have celiac disease. Celiac disease appears to be on the rise, though there’s still less than about a 1 in 10,000 chance an American will be diagnosed with celiac in a given year. Our best estimate for wheat sensitivity is in the same general range as celiac, slightly higher than 1 percent. That’s still potentially millions of people who may have been suffering for years who could have been cured by simple dietary means, yet who were unrecognized and unaided by the medical profession.

Although gluten sensitivity continues to gain medical credibility, we still don’t know how it works. We don’t know how much gluten can be tolerated, if it’s reversible or not, or what the long-term complications might be of not sticking to a gluten-free diet. Considering the lack of knowledge, people with gluten sensitivity should consider reintroducing gluten back into their diet every year to see if it’s still causing problems.

The reason health professionals don’t want to see people on gluten-free diets unless absolutely necessary is that, for the 98 percent of people that don’t have gluten issues, whole grains—including the gluten grains wheat, barley and rye—are health promoting, linked to reduced risk of coronary heart disease, cancer, diabetes, obesity, and other chronic diseases.


Because some people have a peanut allergy doesn’t mean everyone should avoid peanuts. There is no evidence to suggest that following a gluten-free diet has any significant benefits in the general population. Indeed, there is some evidence to suggest that a gluten-free diet may adversely affect gut health in those without celiac disease, gluten sensitivity, or wheat allergy. A study out of Spain, highlighted in my video, Gluten-Free Diets: Separating the Wheat from the Chat, found that a month on a gluten-free diet may hurt our gut flora and immune function, potentially setting those on gluten-free diets up for an overgrowth of harmful bacteria in their intestines. Why? Because the very components wheat sensitive people have problems with, like FODMAP and fructans, may act as prebiotics and feed our good bacteria.

Gluten, itself, may also boost immune function. After less than a week on added gluten protein, subjects experienced significantly increased natural killer cell activity, which could be expected to improve our body’s ability to fight cancer and viral infections. Another study found that high gluten bread improved triglyceride levels better than regular gluten bread.

Ironically, one of the greatest threats gluten-free diets pose may be the gluten itself. Self-prescription of gluten withdrawal may undermine our ability to detect celiac disease, the much more serious form of gluten intolerance. The way we diagnose celiac is by looking for the inflammation caused by gluten in celiac sufferers, but if they haven’t been eating a lot of gluten, we might miss the disease. Hence, rather than being on a gluten-free diet, we want celiac suspects to be on a gluten-loaded diet. We’re talking 4-6 slices of gluten packed bread every day for at least a month so we can definitively diagnose the disease.

Why does it matter to get a formal diagnosis if you’re already on a gluten-free diet? Well, it’s a genetic disease, so you’ll know to test the family. But most importantly, many people on gluten-free diets are not actually on gluten-free diets. Even 20 parts per million can be toxic to someone with celiac. Many on “gluten-free diets” inadvertently eat gluten. Sometimes gluten-free products are contaminated; so, even foods labeled “gluten-free” may still not be safe for celiac sufferers.

As editorialized in The Lancet, the irony of many celiac patients not knowing their diagnosis, while millions of non-sufferers banish gluten from their lives, can be considered a public health farce.