A new study, published in The American Journal of Clinical Nutrition, has come to a conclusion that may frustrate many: your gluten-free diet (GFD) may not actually be gluten-free at all.

First spotted by the American Council on Science and Health, this meta-study, which looked at pre-existing clinical data sets, wanted to find out how much gluten is accidentally consumed while on a GFD. They did so indirectly, using measurements of indigestible gluten byproducts in stool and urine samples, as well as assessing changes to the intenstine.

The average inadvertent exposure to gluten by individuals with celiac disease on a GFD was estimated to be anywhere from 150 milligrams to 400 milligrams per day. If accurate, then it’s not clear where the extra gluten is coming from.

In any case, the team – led by celiac-focused biopharmaceutical company ImmunogenX – conclude that “many individuals following a GFD regularly consume sufficient gluten to trigger symptoms and perpetuate intestinal histologic damage.”

If you have celiac disease, this will clearly impact your life. For all others, here are some important caveats.

Celiac disease involves the inflammation of the small intestine upon eating gluten-based foods or drinks (beer, for example) – anything that contains wheat, barley and rye. This renders you unable to absorb nutrients, which leads to a range of symptoms, from uncomfortable digestive problems to fatigue, coordination problems, and even nerve damage.

Celiac disease is a diagnosable autoimmune condition, not an allergy or an intolerance to gluten, a dietary protein. Genetics and the environment play a part in its development and, as pointed out by the NHS, there is no cure. A gluten-free diet for life is necessary, which is why this latest revelation if corroborated with further research, is somewhat disconcerting.

Then there’s the issue of non-celiac gluten sensitivity (NCGS). Some people eating gluten foodstuffs can experience symptoms similar to celiac disease, but they vary wildly and there aren’t signs of intestinal damage. There are no associated antibodies indicating that this apparent sensitivity is an autoimmune condition.

In some cases, it could be a misinterpreted version of something else, like a wheat allergy. Coeliac UK notes that "gluten sensitive" people that go on gluten-free diets may feel better, but this may be a placebo effect.

The jury is out on whether NCGS is a bona fide condition or not, and it’s deeply unclear whether gluten is even causing its symptoms. It cannot currently be diagnosed. Their symptoms could also be due to something else in wheat – such as short-chain carbohydrates – but at this point, we simply can’t say for sure.

In sum, if you think you have NCGS or celiac disease, don't just assume you're right and suddenly take on a GFD. See a clinical practitioner first for advice.