We all heard it growing up: Milk does a body good. But milk — along with beef products — may not be good for people living with the painful and sometimes disabling autoimmune condition, rheumatoid arthritis.

In a new study, researchers concluded that a strain of bacteria typically found in milk and beef may be linked to rheumatoid arthritis (RA).

While it’s been known that some patients’ RA symptoms may respond to adding or eliminating certain foods to their diet, this study is the first to specifically link bacteria found in beef and dairy to the ailment.

Researchers out of the University of Central Florida found that the bacteria strain mycobacterium avium subspecies paratuberculosis, also called MAP, can trigger RA in already susceptible individuals.

So while MAP may not necessarily cause RA in everyone, it can influence the development of the disease in people who are genetically predisposed to the condition.

This study piggybacks off previous research done by the same team of researchers that looked at the association of MAP and Crohn’s disease.

What the study revealed

The latest study was conducted by infectious disease specialist Saleh Naser and rheumatologist Shazia Bég. It was inspired by Naser’s previous study linking this bacteria and gastrointestinal diseases.

“Here you have two inflammatory diseases, one affects the intestine and the other affects the joints, and both share the same genetic defect and [are] treated with the same drugs,” Naser said in a press statement. “Do they have a common trigger? That was the question we raised and set out to investigate.”

So they set out to determine if MAP was that shared trigger.

Bég recruited 100 of her rheumatology patients for this study. These subjects gave clinical samples for scientific testing.

It was found that 78 percent of the patients with RA had a mutation in their PTPN2/22 gene — the same genetic mutation that’s found in people with Crohn’s.

In addition, 40 percent of that number also tested positive for the MAP found in beef and cow’s milk.

Because of this, the researchers believe that people born with this genetic mutation who also ingest MAP are prone to develop RA or Crohn’s.

Not all cattle are infected with MAP and other dairy products besides beef and milk weren’t looked at in the study.

“We don’t know the cause of rheumatoid arthritis, so we’re excited that we have found this association,” Bég said in a statement to the press about the study, which was published in the medical journal, Frontiers in Cellular and Infection Microbiology. “But there is still a long way to go. We need to find out why MAP is more predominant in these patients — whether it’s present because they have RA, or whether it caused RA in these patients. If we find that out, then we can target treatment toward the MAP bacteria.”

This isn't the first time that food and RA have been linked.

Another recent study showed that eating a bowl of muesli for breakfast each day could minimize your symptoms.

What people with RA think

People living with RA have mixed feelings about the MAP study’s findings, though.

Most admit that eliminating some animal products seems to help their RA symptoms, at least somewhat.

“I went vegan and gluten-free when first diagnosed with RA. It helped my pain and swelling a lot. Now, I occasionally eat meat, but veer toward chicken or fish over beef and pork. They make me flare more, so does dairy,” said Natalie Bills of Ontario, Canada.

“My rheumatologist had me give up red meat and dairy for three months when I was first diagnosed,” said Luanna Werner Baughman of Lakeland, Florida. “When I introduced them gradually, dairy did not affect me but red meat did. I try to eat it quarterly because I know the iron is good for me and I love steak.”

Some patients eschew processed dairy but make homemade yogurt. Dianna Henretty believes her homemade yogurt helps prevent the flu — and influenza exacerbates her RA symptoms.

Others avoid cow’s milk but not meat.

“I replaced regular milk with almond milk a couple months ago. My symptoms aren’t completely gone, but I do feel better and the one time I ‘cheated’ and drank a glass of cow’s milk, the next day I was horribly stiff,” said Beata Byrdack of Homer Glen, Illinois. “I do occasionally eat cheese but I have not noticed any worsened symptoms after, for some reason only milk. Overall I do try to keep away from dairy.”

But when it comes to diet, there may be a fine line between symptom management and deprivation.

After all, as Ashley Romero of Utah puts it, “Steaks make me happy… That’s good for RA, right? Being happy?”