If you have peripheral neuropathy, a form of nerve damage that affects your extremities, your doctor may test you for diabetes. It’s a common cause. But now research suggests something else to look for as well—celiac disease, the autoimmune disease marked by the body’s inability to digest gluten, the protein found in wheat, barley and rye.

If the new finding leads more doctors to test their neuropathy patients for celiac disease, that’s a good thing, since 80% of the 2.4 million Americans with celiac disease don’t even know they have the disease, according to population studies.

Here’s what you need to know about the neuropathy/celiac connection.

A NEW SYMPTOM OF CELIAC DISEASE EMERGES

Earlier studies had suggested a neuropathy/celiac link, but they were iffy. The new research makes the connection stronger. Swedish researchers identified 28,000 people who were diagnosed with celiac disease and compared them with 140,000 subjects who didn’t have celiac disease. At the beginning of the study, which lasted about 10 years, none of the subjects had been diagnosed with peripheral neuropathy.

Here’s what the researchers found…

• People with celiac disease were five times more likely to be diagnosed with peripheral neuropathy over the course of the study, compared to people without celiac. The percentages were small—less than a 1% chance of being diagnosed with neuropathy if you have celiac, but it translates into tens of thousands of Americans.

• In a separate analysis, the researchers followed people who were diagnosed with peripheral neuropathy over the course of the study but weren’t originally known to have celiac disease. It turns out that they were 80% more likely to end up being diagnosed with celiac than people who didn’t have neuropathy.

The new finding suggests that peripheral neuropathy may be an early warning signal for celiac disease. Researchers aren’t sure exactly how the two diseases are connected, but they note that celiac is an autoimmune disease, and many autoimmune diseases are linked to nerve damage. That damage may be related to the systemic inflammation that the autoimmune response evokes. (This study doesn’t say anything at all about nonceliac gluten sensitivity.)

The good news is that diagnosing and treating celiac disease may help forestall peripheral neuropathy. There is evidence that when people with celiac and peripheral neuropathy go on a gluten-free diet—the only effective treatment for celiac—the neuropathy may stop getting worse.

The bigger picture is that anything that helps diagnose people with celiac disease earlier is incredibly important. Undiagnosed, the disease can cause malnourishment, anemia, infertility, osteoporosis, heart problems and more. The earlier you get diagnosed and go on a gluten-free diet, which stops the disease from progressing, the less damage to your health.

WHAT YOU SHOULD DO NOW

The new finding means that anyone with either condition—or suspicious symptoms—should get tested…

• If you have peripheral neuropathy, ask your doctor to test you for celiac disease. That’s the recommendation of the authors of the study.

• If you suspect you have celiac disease—common symptoms include bloating and gastrointestinal distress after eating bread or pasta—don’t just stop eating foods containing gluten, because you can’t be properly diagnosed unless you have been eating gluten. Do go to your doctor for a proper diagnosis.

• A diagnosis requires a blood test, which if positive is confirmed by an endoscopic procedure in which a tiny sample of the lining of the small intestine is removed and studied. That’s how the people in the new Swedish study were diagnosed—and it’s the only way to really know.

• If you do have celiac disease, you’ll need to be on a completely gluten-free diet for life. Fortunately, that’s easier than ever, according to Bottom Line’s Guide to Going Gluten Free.