Researchers warn that a gluten-free diet may lower the intake of whole grains that keep the heart healthy.
Celiac disease is an autoimmune disorder that affects more than 3 million people in the United States. Patients with celiac disease develop an intolerance to gluten, as the protein triggers intestinal inflammation.
However, there are also people who do not have celiac disease and avoid gluten all the same. For these individuals, gluten can still cause intestinal symptoms.
The biological basis for this non-celiac gluten sensitivity has not yet been identified, but an increasing number of medical professionals and laypersons are concerned that gluten has negative health effects, from increasing the risk of obesity to developing heart disease.
As a result, more and more people are adopting a gluten-free diet. In fact, since 2009, the number of people who do not have celiac disease but have gone gluten-free has tripled.
A new study, published in The BMJ, investigates the impact of long-term gluten intake in those without celiac disease.
As the authors explain, given that celiac disease has also been linked with a higher risk of coronary heart disease (CHD) - a risk that seems to be lowered by adopting a gluten-free diet - the new study set out to investigate whether or not the long-term consumption of gluten correlates with CHD.
CHD is a condition in which plaque builds up inside the heart's arteries, increasing a person's risk of a heart attack. It is estimated that every year, CHD is responsible for approximately 370,000 deaths in the U.S.
Gluten-free diet may deprive consumers of heart-healthy whole grains
For the new study, a team of researchers from universities across the U.S. accessed data on almost 65,000 women from the Nurses' Health Study and more than 45,300 men from the Health Professionals Follow-up Study.
They monitored the participants' gluten consumption over a 26-year period, from 1986 to 2010. At the beginning of the study, the participants did not have a history of CHD. They filled in a food frequency questionnaire in 1986 and continued to do so at 4-year intervals until 2010.
Researchers adjusted for various risk factors and found no significant association between long-term gluten consumption and an increased risk of CHD. In fact, after adjusting for refined grains and considering gluten as correlated with whole grain intake, the researchers found that an increased intake of gluten was associated with a reduced risk of CHD.
The authors point out that their study is purely observational and therefore cannot draw any conclusions as to cause and effect. However, they suggest that avoiding gluten may lead to a lower overall consumption of whole grains.
Because whole grains are thought to reduce cardiovascular risk, adhering to a gluten-free diet is not recommended for people who do not have celiac disease, the authors write.
The researchers also acknowledge some of the study's limitations. These include the fact that participants were not asked specifically whether they were trying to avoid gluten, or if they consumed gluten-free substitutes. The study also did not account for traces of gluten, and the participants' body mass index (BMI) was not examined in relation to gluten intake.
The authors conclude that:
"Long-term dietary intake of gluten was not associated with risk of coronary heart disease. However, the avoidance of gluten may result in reduced consumption of beneficial whole grains, which may affect cardiovascular risk. The promotion of gluten-free diets among people without celiac disease should not be encouraged."