While a healthy diet has a host of good-for-you benefits, nutrients alone are not likely to slow the progression of rheumatic and musculoskeletal diseases (RMDs) such as osteoarthritis and rheumatoid arthritis, finds a review of scientific research that was published in RMD Open in April 2022.
The researchers, who are affiliated with the University of Manchester in England, looked at 24 systematic reviews that were published between 2013 and 2018, as well as 150 additional original published studies. Their findings suggest that nutrients such as vitamin D, vitamin C, and omega-3 fatty acids — in food or taken as supplements — have a small but not clinically meaningful impact on RMD progression, and there are also not enough high-quality dietary studies in existence to support a positive effect.
“There are multiple potential reasons why dietary strategies have so far been found to be ineffective with RMDs,” says epidemiologist and corresponding study author Suzanne Verstappen, PhD, director of social responsibility for the School of Biological Sciences at the University of Manchester. “Perhaps some dietary strategies do have an effect on RMD outcomes, but these have yet to be tested in high-quality research — or dietary strategies may have subtle effects on RMD outcomes that may take a long time to develop and therefore are hard to pick up in clinical trials, which typically have relatively short follow-up durations.”
What the Researchers Found Regarding Diet and Disease Progression
In 2018, the European League Against Rheumatism convened an international task force to look at the potential impact of diet, exercise, weight, alcohol consumption, smoking habits, and paid work on disease progression — and to develop recommendations for clinicians and patients.
With regard to the dietary recommendations, the task force searched for previously published research on the impact of dietary components and supplements on pain, joint damage, and physical function for seven common RMDs: osteoarthritis, rheumatoid arthritis (RA), systemic lupus erythematosus, axial spondyloarthritis, psoriatic arthritis, systemic sclerosis, and gout. The majority of the studies they reviewed were about osteoarthritis and rheumatoid arthritis.
High-Quality, Published Studies Connecting Food and Systemic Disease Progression Don’t Exist
Their analysis showed that the success of dietary interventions for osteoarthritis was generally small and not clinically meaningful. The evidence for the effect of diet on rheumatoid arthritis was graded as poor or very poor, primarily because of the small number of studies and participants. There was moderate-quality evidence for the effectiveness of probiotics, vitamin D, and fish oil/omega-3s, but the impact was either negligible or too small to make much difference.
The evidence for the effect of diet on systemic lupus erythematosus was rated as moderate, but it showed no effect on outcomes. The evidence for all other studies on this condition was rated as poor or very poor, as it was for axial spondyloarthritis, systemic sclerosis, and gout.
Why the Research That Does Exist May Be Misleading
Dr. Verstappen says that while many studies have been published about the effect of diet on people who have osteoarthritis and rheumatoid arthritis, the findings have varied wildly, possibly due to publication bias or the influence of commercial sponsors.
But what does that mean?
“Publication bias refers to the fact that studies that show positive results (ie, that the dietary strategy works) are more likely to be published than studies with negative results,” says Verstappen. “If you only look at published literature — which is typically all that is possible — you will see all the positive trials (which are published), but won’t see all the negative trials (as some won’t get published), which will lead to a bias in the available data.”
It also says that some of the studies in the review were funded by the same company that manufactures the product being evaluated. “These conflicts of interest may be influencing the way the trial was conducted or reported, which could lead to a more positive interpretation of the final results, compared with a study done without these conflicts. However, this is impossible to prove.”
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What Can Help Stop Disease Progression?
So if a healthy diet isn’t likely to slow the progression of RMD, what else might help curtail the damage? Standard drug treatments like disease-modifying antirheumatic drugs (DMARDs) are still the gold standard. “Where available, DMARDs are certainly an effective method of limiting the progression of RMDs,” says Verstappen. “However, not all RMDs have effective disease-modifying treatments available, such as osteoarthritis.” Her team discovered that there are other lifestyle modifications that appear to be more effective than just ingesting certain nutrients, such as getting regular exercise, avoiding the overconsumption of alcohol, and maintaining a healthy weight.
Healthy Eating Still Matters for Good Health
While these findings suggest that diet may not make much of a difference in halting the progression of RMDs, it’s important to remember that paying attention to what you put in your mouth keeps you healthy in so many other ways. “Poor nutrition and diet are linked to a wide variety of negative health outcomes, independent of RMD progression, like cardiovascular disease and type 2 diabetes,” says Verstappen. “Therefore, it is important for everyone (including people with RMDs) to maintain a healthy, balanced diet.”
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