About 30 years ago, early in his career as a rheumatologist, Dirkjan van Schaardenburg, PhD, says patients with osteoarthritis experienced terrible problems with inflammation. The landscape has improved to the point that “people can live with it now,” he says. But they still need help. For example, osteoarthritis affects 7% of the global population, according to the Global Burden of Disease Collaborative Network, with 2.2% of the global years of healthy life lost to disability.1 Prof. van Schaardenburg, a researcher and professor of rheumatology with Reade Center for Rheumatology and Rehabilitation and Amsterdam University Medical Center, The Netherlands, thinks a research-based initiative he is co-leading will help.
Plants for Health is being developed around recent studies examining how introducing a plant-based diet, combined with other interventions, affects patients with osteoarthritis (OA) and those at a high risk of developing rheumatoid arthritis (RA). His team has published papers describing these Plants for Joints studies, with results showing participants manifested improvements in stiffness, pain and improved physical function—while also losing weight.
Prof. van Schaardenburg and his co-authors are optimistic their findings portend a potential treatment breakthrough for patients with OA.
“If you take people who are not used to this kind of diet and you make such changes, it’s huge for them,” says Prof. van Schaardenburg. “We have shown … that if you change your diet, you can actually reduce inflammation in general, but also specifically the inflammation in joints will go down.” This makes disease control possible with less medication.
Prof. van Schaardenburg
Another very important aspect, he says, is that “people feel better, so their general well-being is increased. They have more energy. … So it’s easier to cope with the disease.”
Patients with OA have long taken medications, engaged in exercise therapy and received joint replacement surgery as treatments. But their overall options are limited and not always impactful in the long term. “There isn’t too much we can do for osteoarthritis,” says Amanda Sammut, MD, chief of rheumatology at NYC Health + Hospitals/Harlem and a professor at Columbia University, New York. “We really need better treatments and better ways to manage osteoarthritis because despite our efforts, a lot of patients still are suffering.”
The Plants for Joints project includes randomized controlled trials comparing participants with hip or knee metabolic syndrome-associated osteoarthritis (MSOA) and RA receiving the intervention against control groups, and a two-year extension study measuring adherence for all study participants.
The results of the MSOA trial, published last year in Osteoarthritis and Cartilage,2 show that the 32 patients receiving a 16-week intervention, including the outlined plant-based diet, physical activity and stress management plans in addition to regular care, manifested the following statistically significant changes (when compared with a 32-participant control group that did not receive this intervention):
- Mean improvements on the overarching Western Ontario and McMasters Universities Osteoarthritis Index (WOMAC) that was 11 points larger (11.7; 95% CI 6–16; P=0.0001), the WOMAC pain scale (1.89; 95% CI 0.77–3.01; P<0.01), WOMAC stiffness (1.3; 95% CI 0.75–1.85; P=0.0001), and WOMAC physical function (8.6; 95% CI 5.2–11.9; P<0.0001);
- Greater mean declines in weight, fat mass and waist circumference—5.3 kg, 3.9 kg and 6 cm, respectively; and
- Patient-Reported Outcomes Measurement Information System (PROMIS) measures of fatigue, pain interference, C-reactive protein, hemoglobin A1c, fasting glucose and low-density lipoproteins also improved.
Three participants in the intervention group decreased their pain medication use vs. none in the control group; five intervention group participants stopped using other drugs, vs. two in the control group.
“The ‘Plants for Joints’ lifestyle program reduced stiffness, relieved pain and improved physical function in people with hip or knee MSOA compared to usual care,” the researchers concluded.
“We hoped for these kinds of results,” Prof. van Schaardenburg says. “It turned out that this went very well.”
Dr. Sammut
This was the first study to test a plant-based diet combined with physical activity and stress management programs in MSOA patients, according to the researchers. “This study is important,” Dr. Sammut says, commenting specifically on the idea of discussing metabolic syndrome-associated osteoarthritis. “It’s wonderful that they’re talking about how osteoarthritis is not just one disease.” She was also pleased to see patients manifested improvements without having to take more medication.
Prof. van Schaardenburg’s team published the results of the other trial, in which 83 participants with rheumatoid arthritis were studied over 16 weeks, in Rheumatology last year.3 Applying the same intervention to a different patient population, the researchers found that the intervention group showed a mean 0.9-point greater improvement in the DAS28 scale measuring disease activity than the control group (95% CI 0.4–1.3; P<0.0001), and greater decreases in weight (3.9 kg), fat mass (2.8 kg), waist circumference (3 cm), HbA1c (1.3 mmol/mol) and low-density lipoprotein (0.32 mmol/l). Depression, fatigue and physical function scores did not significantly improve.
The DAS28 findings were especially important, Prof. van Schaardenburg says, adding, “It’s a real change.”
Based on this research, Prof. van Schaardenburg recommends rheumatologists counsel patients with OA about the value of a plant-based diet and show them where they can find more information about it. He also advises querying patients about their diets and stress levels, and encouraging them to shift toward a plant-based diet.
Rheumatologists see patients a few times annually, he notes, giving them more opportunities to sway their patients to change habits. When he advised his patients to try plant-based diets, they often returned to clinic and said, “I feel great.” (Note: Prof. van Schaardenburg retired from clinical practice last year.)
Limitations
The trial results did not surprise Dr. Sammut, she says, because researchers “put a lot of effort into the intervention group” without paying much attention to the control group. This strategy may have affected group differences in both trials, the authors acknowledged.
Dr. Sammut cautioned against drawing any broad conclusions or changing practice habits.
Despite promising results, both Dr. Sammut and Prof. van Schaardenburg noted this research has several other limitations. For one, the sample was not large. Dr. Sammut wondered if lifestyle factors in The Netherlands differ from those in the U.S., leading to lesser effects in the U.S. The U.S. culture, she says, discourages many patients from following a plant-based diet consistently. “I’m not sure [most people on their own] have the time to follow [a plant-based diet],” she says. Many of her patients do not follow the physical therapy regimen she recommends because they are too busy working.
What’s more, ACR guidelines do not include plant-based diets, Dr. Sammut notes. The guidelines do cite weight loss as a goal for OA, and many patients in the studies lost weight, she adds, noting, “The end result—losing weight—is the most important.” But she questions how much of that loss was due to diet vs. other factors. The MSOA trial “does not prove that a plant-based diet is something rheumatologists can recommend. We cannot conclude a plant-based diet is the reason for osteoarthritis patients manifesting improvements in this study,” she says.
The authors acknowledged that, noting that none of the individual impacts of the program’s lifestyle factors could be determined for either trial. “However,” they added in the MSOA paper, “chronic system inflammation is driven by multiple factors including diet, physical activity, and stress. This might explain a decrease in inflammation and an overall improvement of health that is not mediated by weight loss.”
The MSOA paper also may have been influenced by selection bias, “as only highly motivated individuals” who sought out the intervention were enrolled.
What’s Next
Prof. van Schaardenburg’s team is working on additional research to build on the trials. They expect to complete the two-year extension study this year and are launching a study examining why and how patients in the trials manifested better results than the control groups. The researchers are trying to see “how the changes in the food reflect changes happening in the gut with the bacteria residing there and how the interaction with the immune system is,” Prof. van Schaardenburg says. They are also planning for a phase 4 cohort study to test the original intervention in clinical practices.
The team shared results from the first year of the extension study at the European Congress of Rheumatology in June 2023. They found the 47 participants who completed the MSOA follow-up had a greater average change in total WOMAC score (–11.4 vs. –11.0) and weight (–5.3 vs. –3.7 kg) than those who did not finish, but showed less improvement in HbA1c (–2.1 vs. –2.9 mmol/mol). The total WOMAC score (–8.8) and individual WOMAC marks remained significantly improved compared with scores before participants started the program, except for stiffness. Weight stayed down as well. Of the 24 participants using pain medication at baseline, 11 decreased their dosages or stopped taking at least one drug.
Researchers also found the 65 participants who completed the rheumatoid arthritis follow-up showed a greater average decline in their total DAS28 score (0.9 vs. 0.05) than those who did not finish. They manifested a mean 1.01-point total DAS28 difference compared with baseline (95% CI 0.76–1.26; P<0.001), 45 patients showed better DAS28 scores with the same amount or less medication, and all facets of the DAS28 improved significantly. Of the 61 participants using anti-rheumatic medication at baseline, 27 decreased their dosages or stopped taking at least one medication. Weight did not show a significant difference.
“That’s great,” Dr. Sammut says of participants sustaining many of their positive results after the trial period. “We managed to maintain the results in the year after without them following the program anymore, so they had to do it on their own. They had some webinars and some newsletters to keep them on track. But they had to do it mostly by themselves, and then they did,” Prof. van Schaardenburg says.
Prof. van Schaardenburg says his team plans to publish a full extension study by the end of the year. He hopes patients show continued adherence and medication declines, which would provide momentum toward applying plant-based diets to rheumatology protocols. His team has established the Plants for Health program online, explaining their work and soliciting patients and health professionals.
Are advocates of such diets moving too fast? Plant-based diets are characterized by high levels of fiber and low levels of saturated fat, classifying them as low inflammatory, according to the researchers.
Plant-based diets have become more mainstream recently, but Dr. Sammut says this type of trend is not new. “Before this, we had [attention focused on] the Mediterranean diet,” she says.
Dr. Sammut would welcome verified programs suggesting combined lifestyle changes. But she believes the field needs to see much more evidence before she feels comfortable advising rheumatologists to regularly recommend plant-based diets. Rheumatologists are not nutritionists, she says, suggesting patients work with nutritionists too. In addition, she says, “I don’t think there’s one diet that works well for everyone.”
Dr. Sammut wants to catch patients with MSOA earlier, to educate them and help them make lifestyle changes before joint damage occurs. She also called for researchers to examine more comparison groups when studying plant-based diets, comparing specific diets against each other, with the diet being the only difference between groups.
Regardless of any new data that emerge from future studies, she says it will still be tough to get patients to follow the Plants for Health program consistently on their own: Nothing “would have me tell patients to eat foods they’re never going to eat,” she says, noting many of her patients simply cannot afford to consume this diet.
But Dr. Sammut credited Prof. van Schaardenburg and his team for their work. Osteoarthritis trials are difficult to conduct, she says. “Where we are right now is just not good enough, so I really applaud anyone who is studying osteoarthritis.”
Ryan Basen is a journalist, writer and editor in Washington, D.C.
References
- Osteoarthritis—Level 3 cause. Global Burden of Disease Collaborative Network. Institute for Health Metrics and Evaluation. 2019. https://www.healthdata.org/results/gbd_summaries/2019/osteoarthritis-level-3-cause.
- Walrabenstein W, Wagenaar CA, van de Put M, et al. A multidisciplinary lifestyle program for metabolic syndrome-associated osteoarthritis: The ‘Plants for Joints’ randomized controlled trial. Osteoarthr Cartil Open. 2023 Nov;31(11):1491–1500.
- Walrabenstein W, Wagenaar CA, van der Leeden M, et al. A multidisciplinary lifestyle program for rheumatoid arthritis: The ‘Plants for Joints’ randomized controlled trial. Rheumatology (Oxford). 2023 Aug 1; 62(8):2683–2691.
