Written by Annie Lennon — Fact checked by Catherine Carver, MPH
Rheumatic and musculoskeletal diseases (RMD) are a range of conditions that affect peoples’ joints, cause pain, disability, and reduce health-related quality of life.
While some RMDs, such as rheumatoid arthritis, have effective pharmacological treatments to limit disease progression, for others, such as osteoarthritis, existing medications can only alleviate symptoms.
Knowing whether or not lifestyle factors, such as diet, could benefit RMD-related outcomes could help researchers and clinicians prevent or treat RMDs.
Recently, researchers at the European Alliance of Associations for Rheumatology (EULAR) conducted a review and meta-analysis of studies investigating the effects of diet on the progression of RMDs.
They found that no single dietary intervention has substantial benefits for people with RMDs, given current data.
“I doubt that there is no dietary effect, but trying to tease this out in terms of disease activity and/ or progression is too difficult to discern based on the available data, which is graded as ‘poor’ to ‘very poor’ in osteoarthritis and rheumatoid arthritis,” Dr. Vibeke Strand, adjunct clinical professor in the Division of Immunology and Rheumatology at Stanford University, who was not involved in the study, told Medical News Today.
The review appears in RMD Open.
RMDs and diet
For the study, the researchers analyzed 24 systematic reviews and 150 original articles exploring the link between dietary exposures and RMDs, namely:
- rheumatoid arthritis
- systemic lupus erythematosus
- axial spondyloarthritis
- psoriatic arthritis
- systemic sclerosis
Altogether, the studies investigated 83 dietary exposures, including:
- vitamin D
- vitamin B12
- fish oil or omega-3 fatty acids
- argan oil
- cherry juice
- green tea extract
- enriched milk powder.
The researchers noted that there were relatively few studies for most dietary exposures, and that evidence for any effects of these dietary factors was graded low or very low. Any results, therefore, have a moderate to high risk of bias.
Moreover, for many of the studies, such as that on chondroitin for osteoarthritis, or randomized controlled trials with larger sample sizes, such as the one on vitamin D for osteoarthritis, their effect sizes were small and not clinically meaningful.
The researchers added that studies often did not report on their randomization or allocation concealment processes, which may have inflated reported effect sizes. They also noted that there was limited reporting of adverse events.
When asked why these studies generally generated poor data, Dr. Strand said:
“The studies have generated poorly graded data in large part because we don’t have sensitive means to detect dietary effects — we don’t have any idea how long studies should be to tease such data out. Nor do we know how to ascertain these effects separately from lifestyle, physical activity, etc.”
Dr. Rik Lories, professor and head of the Department of Development and Regeneration at KU Leuven, Belgium, not involved in the study, told MNT that despite the poor data from the studies involved in the review, the review itself was well-performed.
“The absence of a strong effect from a specific intervention is not really surprising. Most studies performed are small in numbers and study very specific interventions. The diseases concerned also have high variability in clinical presentation, individual impact, and progression. This makes the field of non-pharmaceutical intervention trials particularly challenging,” he added.
The researchers who conducted the review concluded that no single dietary intervention studied to date has substantial benefits on outcomes for people with osteoarthritis or rheumatoid arthritis.
They noted, however, that due to few studies published for other RMDs, more research is needed to assess dietary impact. Current research nevertheless suggests that dietary interventions may not have much influence on health outcomes for these conditions either.
The researchers noted that further research on diet in RMDs should aim for higher methodological and reporting standards and should include long-term follow-ups.
They added that research into the additive or synergistic effect of multiple dietary components should be researched to reflect the complex and interrelated nature of people’s diets.
When asked what these results mean for the public, Dr. Lories said that an overall healthy diet and regular exercise remain important for people with RMDs due to their impact on weight and other comorbidities, such as cardiovascular disease.
“Limitations in mobility and joint function are essential parts of these diseases: Weight and physical form are important factors that can be controlled to support these functions,” he noted.
“For diseases where effective treatments are available now, such as rheumatoid arthritis or psoriatic arthritis, the evidence from this article suggests that there is no specific place for often expensive supplements and extra vitamins unless deficiencies are demonstrated,” he added.
He concluded that for conditions like osteoarthritis, for which there are medications to halt disease progression, findings from trials with modest evidence may be considered by physicians for patients on an individual basis.