Low gluten diet – evidence of link to type 2 diabetes

The low gluten diet craze has got to be one of the most frustrating fads that have hit the developed world in the last few decades. Without real evidence that gluten affects anyone but the tiny percentage with a genuine, diagnosed gluten sensitivity, pseudoscience supporters are pushing a low gluten diet to treat any number of issues.

The only benefit of the low gluten diet is that today a lot of products are labeled “gluten free.” Thus, the few individuals who have real gluten sensitivity have an easier time shopping for safe foods.

So a low gluten diet may have few benefits for the 99% or more of the population. But does it have risks? Well, a new study seems to indicate that it does, and we’ll let the feathery dinosaur have a go at it.

What is gluten?

Gluten is a protein found in wheat, along with similar proteins found in common grains such as barley and rye. Generally, we like gluten, because it gives elasticity to dough, allowing bread to have that chewy texture that is an important component of the pleasure of eating.

I’m certainly not a world-renowned chef, but I know gluten is important part of good food. It is critical in baking everything from bagels to cakes. Generally, kneading the dough forms long chain gluten protein molecules giving a chewier texture. Pastas, breads, and so many other foods are made through high gluten flour that is worked to create longer chain proteins from the gluten. I bet you didn’t know that good cooking requires more than a basic knowledge of chemistry.

Gluten can be removed from the milled flour (or it can be added back). Purified gluten, because of its texture, is actually used to create fake meat products, so beloved (or not) by vegans.

Real gluten sensitivity

Yes, there really are people who are sensitive to gluten. Celiac disease (also known as coeliac disease in British English) is an autoimmune disorder that afflicts the small intestine of certain  individuals who are genetically predisposed to gluten sensitivity. The disease afflicts between 1 in 1,750 and 1 in 105 people in the United States (or about 0.05 to 1%), a tiny number.

The disease is usually diagnosed during childhood, but it can show up at any age. It is not diagnosed by gastrointestinal issues alone – it requires a blood test and endoscopy with biopsy. Lacking this level of diagnosis, I am skeptical of anyone that claims that they are gluten sensitive. In fact, a proper diagnosis is necessary to rule out other, more serious diseases, that may appear to be celiac disease.

The disease usually presents, but not always, with chronic diarrhea, low pediatric weight gain, and fatigue in response to gluten. Individuals with celiac disease know that they have it because the symptoms are so disruptive. Furthermore, a low gluten diet wouldn’t work. Celiac disease is binomial – no gluten is good, any amount of gluten is horrible.

Although the disease is not completely understood, in an individual with celiac disease who is exposed to gluten, the immune system causes an inflammatory reaction of the lining the small intestine. This interferes with the absorption of nutrients. The only known effective treatment is a lifelong gluten-free diet. In addition, once gluten is removed from the diet, the damage from the inflammatory response is reversed

Celiac disease should not be confused with wheat allergy, which is also caused by a reaction to wheat proteins, generally not including gluten. There are over 20 different wheat proteins that have identified as causing wheat allergies, and gluten generally is not the cause of wheat allergy. Finally, wheat allergies are extremely rare, and the gluten form of wheat allergies is so rare that it would take a huge population to detect it. However, if you go to your local natural food store, you’d think that 75% of the population have either wheat allergies or celiac disease – it’s another silly food fad.

Low gluten diet and type 2 diabetes

Just for background, type 2 diabetes mellitus (or type 2 diabetes, T2DM) is a metabolic disorder that is characterized by high blood glucose with insulin resistance and relative insulin deficiency. In general, someone with T2DM produces low (or maybe even adequate) levels of insulin, but various cells and organs become resistant to insulin, so cells don’t remove or store blood glucose.

Although the cause of T2DM is not completely understood, it results from a complex interaction between diet, obesity, genetics, age and gender. Some of the causes of T2DM are under a person’s own control, like diet and obesity, but many of the factors aren’t.

Because they are often confused, it’s important to note that T2DM has a completely different cause and pathophysiology than type 1 diabetes mellitus (T1DM, and once called juvenile diabetes). Type 1 diabetes results from the inability of the beta cells of the pancreas to produce insulin, as a result of an autoimmune disease.

According to research presented to the spring 2017 American Heart Association meeting, lower consumption of gluten may be linked to a higher risk of type 2 diabetes.

In this long-term observational study, researchers found that most participants had gluten intake below 12 grams/day, and within this range, those who ate the most gluten had lower Type 2 diabetes risk during thirty years of follow-up. Study participants who ate less gluten also tended to eat less cereal fiber, a known protective factor for Type 2 diabetes development.

After further accounting for the potential effect of cereal fiber, individuals in the highest 20 percent of gluten consumption had a 13 percent lower risk of developing Type 2 diabetes in comparison to those with the lowest daily gluten consumption (approximately fewer than 4 grams).

The researchers estimated daily intake for nearly 200,000 participants in three different long-term health studies. The study included 4.24 million person-years of follow-up from 1984-1990 to 2010-2013, during which 15,947 cases of type 2 diabetes were diagnosed and confirmed.

Although this study seems, on the surface, impressive, there are several important issues to address:

  1. The results were presented at a meeting, and, as such, has not been peer reviewed, and a full paper is not available to read and critique. Generally, presentations at meetings are at the lower half of the hierarchy of scientific research. However, this is a large study of impressive quality, so we shouldn’t dismiss it like a “XYZ cures cancer” cell culture study presented at many meetings.
  2. This is an observational study where the study participants reported their gluten consumption in diaries. I’ve never been a fan of this type of study because it prone to error of memory.
  3. The study population included only nurses and other health care professionals. It’s a subsection of individuals that may be more careful with their health choices than the general public.
  4. The study lacks a control group that did not consume any gluten – this study was set up well before gluten became a food fad.

Obviously, the study’s limitations indicate that we might want to wait until follow-up studies confirm or refute this potential link. However, according to one of the researchers in this study, Geng Zong, PhD, from the Harvard University Department of Nutrition,

We wanted to determine if gluten consumption will affect health in people with no apparent medical reasons to avoid gluten. Gluten-free foods often have less dietary fiber and other micronutrients, making them less nutritious and they also tend to cost more. People without celiac disease may reconsider limiting their gluten intake for chronic disease prevention, especially for diabetes.

Low gluten diet, the summary

Food fads, especially ones based on no science or pseudoscience, can have long-term consequences for one’s health. I’ve been looking at all of these fads for years, and very few, if any, are supported by robust scientific evidence. I go with Michael Pollan’s summary of everything he learned about food and health, “eat food, not too much, mostly plants.” Yeah, Pollan’s views on food aren’t scientifically credible in some cases, but his point here was that we shouldn’t overthink nutrition – as long as you have a balanced diet, you will be fine.

Although I’m not fully convinced, this preliminary data is robust enough to consider the possibility of a link between a low gluten diet and type 2 diabetes mellitus. In addition, the researchers have provided plausible reasons why this may happen – gluten-free foods have less dietary fiber and other micronutrients that can contribute to the risk for type 2 diabetes.

For over 99% of the population who lack real, diagnosed gluten sensitivity, there is simply little to no value of a low gluten diet. And if there is a real risk of type 2 diabetes from this diet, with little to no benefit, it makes no sense. Don’t fall for this food fad that has no basis in science.

Citations

  • Di Sabatino A, Corazza GR. Coeliac disease. Lancet. 2009 Apr 25;373(9673):1480-93. doi: 10.1016/S0140-6736(09)60254-3. PubMed PMID: 19394538.

 

 

The Original Skeptical Raptor
Chief Executive Officer at SkepticalRaptor

Lifetime lover of science, especially biomedical research. Spent years in academics, business development, research, and traveling the world shilling for Big Pharma. I love sports, mostly college basketball and football, hockey, and baseball. I enjoy great food and intelligent conversation. And a delicious morning coffee!