Which diet should we recommend to patients with generalised inflammation, rheumatoid arthritis, ankylosing spondylitis, or psoriatic arthritis? Weight loss, omega-3 supplements, the Mediterranean diet? What about exclusion diets? Jérémie Sellam, MD, PhD, from Saint-Antoine Hospital in Paris, summarizes the key points of the first set of dietary recommendations of the French Society for Rheumatology.

The idea of coming up with dietary recommendations for patients with inflammatory rheumatic diseases came, quite simply, from our clinical practice. We see that when patients learn they have polyarthritis or spondylarthritis, they start to experiment with different diets. Many patients start exclusion diets and experiment in all sorts of ways with the food they eat. And although rheumatologists have been able to find some information here and there in the literature, they've been pretty much on their own when trying to come up with advice to give their patients. It was to address this issue that Daien and I set out to form a working group. Because when patients aren't able to get sound advice and authoritative guidance from their doctors, medical associations, or patient advocacy organizations, they often look for information online, and that information is not always reliable or validated.

This group was made up of rheumatologists, some who work at hospitals and others in private practice. Also involved were physician nutrition specialists and registered dieticians. Operating under the auspices of the French Society for Rheumatology, these multidisciplinary experts conducted out a systematic literature review for the purpose of establishing and drafting recommendations. The result was a declaration of eight general principles and nine recommendations.

General Principles 

The first of the general principles states that nutritional advice is not a substitute for the pharmacologic treatment of chronic inflammatory rheumatic diseases. As you know, whether it's methotrexate or biologics, pharmacologic treatments are essential for the proper management of chronic inflammatory rheumatic diseases. We know that these medications have an anti-inflammatory effect, reduce pain, and — particularly in the case of rheumatoid arthritis — have a structural effect. In other words, they prevent joint deterioration and destruction. There's currently no diet, and no dietary supplement, that has proven to be structurally effective. So, yes, dietary intervention might turn out to be promising for patients with chronic inflammatory rheumatic diseases, but pharmacologic treatment must still be part of the picture.

Another general principle emphasizes that dietary intervention is a way for patients to be actively involved in the overall care of their disease, beyond just taking their medication. We know that patients, when they suffer from chronic diseases, are looking for something more, beyond just taking medications. Encouraging them to take an interest in their diet, asking them about what they eat, giving them advice, and supporting their desire to become involved in this aspect of their treatment plan can give them a sense of empowerment.

Dietary interventions can have articular effects, and I'm going to speak about which interventions you can propose, but also which can be beneficial in terms of cardiovascular health and bone health. All of this is based on the literature. In these recommendations, we've taken into account not only laboratory experiments — where this or that diet is given to a mouse with arthritis — but also reviewed randomized controlled trials that compare an intervention group with a control group. This is the benchmark we used to determine whether or not a diet should be recommended.

The Recommendations

As for the recommendations themselves, we wanted to start off by emphasizing weight loss and what can be called weight-loss support. There's a link between obesity and the risk of developing rheumatoid arthritis, and also psoriatic arthropathy. And the more overweight a patient is, the more active their disease. In other words, patients with obesity are going to experience more pain, more instances of wakefulness, and more morning stiffness than their normal-weight peers. They're also going to show symptoms that suggest that disease activity is not controlled well.

Several randomized controlled studies have shown that weight loss will improve systemic joint symptoms. In one particular study, patients with psoriatic arthropathy were started on TNF inhibitor therapy and one group followed a prescribed diet and the other had no restrictions on eating. More patients in the diet group than in the no-diet group achieved minimal disease activity. Of course, in some cases — for example, patients with complicated morbid obesity — it might be necessary to have a discussion about bariatric surgery.

But practically speaking, how does one proceed? First of all, patients should be weighed at each visit and, if they're overweight or obese, the subject should be broached. But even after that conversation, the reality remains that it's not easy to lose weight. So in the recommendations, we focused on the fact that it shouldn't be left to the rheumatologist or treating physician alone to handle this challenging aspect of treatment. They should incorporate dietary and nutritional care by reaching out to a dietician or, in the case of complicated obesity — especially when the BMI is higher than 35 kg/m² — they can refer patients to a nutrition expert who can manage the patient's obesity, come up with a weight-loss plan, and handle any complications that might arise.

We don't speak about a low-calorie diet in the recommendations because a diet has a beginning and an end and, quite often, patients re-gain weight after stopping a diet. Instead, we speak about weight-loss support to point out that weight loss maintained through dietary changes brings about long-term control of disease activity.

In addition, we make two positive recommendations, which overlap, that can help patients control their disease: a Mediterranean diet and omega-3 supplements. One study showed that after participants with rheumatoid arthritis followed the Mediterranean diet for one year, those who also took omega-3 fish oil supplements were twice as likely to achieve remission (40% vs 20%). This explains the interest in having omega-3 as part of the diet. Other studies have shown a broad benefit of the Mediterranean diet.

We know this diet: fish, especially fatty fish; meat, but not every day, red and white meat; and fruits and vegetables. In addition, exercise and stay hydrated. All of this can help patients who want to use diet as a means to control their disease. And, as I said earlier, studies have shown that omega-3 supplements have beneficial effects. These are essential polyunsaturated fatty acids, which can help control the disease and joint symptoms. (We also suggest patients eat raw nuts, especially Brazil nuts, two a day,  and add fermented foods to their meals.)

Patients should be encouraged to eat unprocessed, natural foods.

We also provide some exclusionary recommendations. Not all studies are done well, but it's clear that there are no major benefits — in fact, no benefit at all — from vegan diets, gluten-free diets, or dairy-free diets. And with these diets, patients run the risk of developing deficiencies, so it's important that patients are aware of this. We also have to keep in mind that exclusion diets can increase social isolation. Patients need to take part in meals; such gatherings are times for sharing and having social interactions. And I would say that they must be told that there are no data in the literature in support of these diets. But if they ever insist on this kind of intervention, I think that it's better to advise them to do it under the supervision of a dietician and nutritionist, especially to prevent the development of deficiencies. We're talking about deficiencies in things like calcium, vitamin B₁₂, and selenium.


As you can see, we have positive recommendations when the patient wants to do something beyond pharmacologic treatment: the Mediterranean diet and omega-3 supplements. And we have negative recommendations, marked by a warning about the risk of developing deficiencies. But I think we all understand the importance of paying close attention to how our patients are experimenting with food. Their diets and eating habits can give us ideas for research and reviews that could allow us to deepen our understanding of the effect of diet on disease, because currently, the quality of the data on some of the diets and types of dietary interventions out there is rather tenuous.