In depth
Behcet's disease: common questions
The 2018 European recommendations say something rare about themselves, which is that they “attempt to highlight the shortcomings of the available clinical research”. That's an unusually frank thing for a guideline to say about its own evidence base. It sets the tone for everything on this page.
What the research found.
Patients with this diagnosis were asked which of the foods they ate set off their own symptoms. Walnuts were named by 35 percent of them, eggplant was named by 35 percent, and tomatoes were named by 13 percent. Those are reports of belief rather than anything anybody removed and then put back to check, which is a different kind of evidence.
Ersoy and colleagues, Mediterranean Journal of Nutrition and Metabolism, 2024
One study matched patients with this disease against a group of controls. The patients were more obese than the controls and they were a good deal less active. Their quality of life was lower on every subscale of the survey, and their depression scores were higher than the controls' scores.
Urhan and colleagues, Mediterranean Journal of Nutrition and Metabolism, 2022
One small study spanned the pandemic, measuring activity, pain, fatigue, depression, and sleep. Nothing changed much from before to during. Every P value came in above 0.05, and the study analyzed 16 people.
Baglan Yentur and colleagues, European Journal of Rheumatology, 2022
The 2018 EULAR recommendations cover managing Behcet's syndrome across six areas of the body. They say of themselves that they “attempt to highlight the shortcomings of the available clinical research”. That's an unusually frank thing for a guideline to say about its own evidence base, and it sets the tone.
Hatemi and colleagues, Annals of the Rheumatic Diseases, 2018
A guideline that says the research is thin
The 2018 European recommendations cover managing Behcet's syndrome, ranging over skin and mouth, joints, eyes, vessels, nerves, and the gut. They set out five guiding principles and add a new one on operating for vessel disease. Then the task force says something about its own work, which is that the recommendations “attempt to highlight the shortcomings of the available clinical research”.
That's an unusually frank thing for a guideline to say about itself, and it sets the tone for this whole page. A guideline admits its evidence is thin. So a page written for patients, built on that very research, has no business sounding surer than the guideline does.
What follows reports what the surveys found and says plainly what they can't settle. It also points at the one trial built to answer the central question, which hasn't reported. Those three things are the whole of the page.
The trial that would answer this
No trial of any diet in Behcet's syndrome has ever published a result anywhere in the literature, which is unusual even among rare diseases. Anything presented to you as a Behcet's diet isn't resting on a finished trial, because no finished trial exists for it to rest on. That's worth knowing before you weigh up any of it.
What that leaves behind it is the surveys, and a survey is a description of a group rather than an experiment on one. It can say what people with a disease eat, and it can compare their body composition with the body composition of people who don't have it. What it can't say is what changing any of it does.
That difference recurs through this page from beginning to end. Knowing something about a group of people is a different thing entirely from knowing what any one of them ought to do next. Most writing about diet in this disease slides straight over that.
What the surveys found
One study matched people with this disease against controls and found several things at once. The patients were more obese, they were less active, their quality of life was lower on every subscale, and their depression scores were higher. The controls ate more on average, and that held for energy, carbohydrate, fat, and fiber.
So patients reported eating less and weighed more, which usually points at two things. One of those is how much people move, and the activity finding in that study backs it up. The other is that people recall what they ate poorly.
A separate study measured body composition directly and found 47 percent of patients below the fiftieth percentile for mid-upper arm circumference. For triceps skinfold thickness it was 36 percent. For arm muscle circumference it was 14 percent, and for arm muscle area 27 percent. So this is a group where being undernourished and being obese both occur, which is no contradiction in a disease that makes eating hurt.
Trigger foods, and how to use them
That study also asked which foods patients thought set off their symptoms. Walnuts were named by 35 percent of them, eggplant was named by 35 percent, and tomatoes by 13 percent. Those three come up often enough in patient conversation to be worth writing down.
Look at what that finding is, though, because it's a survey of belief taken at one moment. No study removed those foods and watched, put them back blinded, or compared people who avoided them with people who didn't. So a food blamed by a third of patients might be causing symptoms in a third of patients, or it might be distinctive enough to get noticed.
The use of all that is as a starting point rather than a conclusion. If one of the three matches something you've noticed, drop it for a set period and then put it back. That tells you more about your own case than the survey does, and what it can't do is set a rule for everybody else.
Exercise, mood, and what is worth raising
There's very little exercise evidence here at all. One small study spanned the pandemic and found no real change in activity, pain, fatigue, depression, or sleep from before to during, with every P value above 0.05. It analyzed 16 people, which the record here calls severely underpowered, and the comparison study did find patients less active than controls.
Mood turns up in that comparison as well. Depression scores were higher and quality of life was lower on every subscale. That's a link found at one moment rather than proof of cause, and it's what anybody would expect in a relapsing disease with painful ulcers and threatened sight.
The most useful thing on this page isn't about food at all. Any new eye symptom in this disease needs urgent attention rather than a routine visit, because eye involvement threatens sight and it moves fast. Some other things belong in that group for reasons of their own.
New belly pain or blood in your stool, a new headache or new nerve symptoms, and swelling or pain in a leg all belong there. This disease affects vessels and organs well past the mouth. That's the part of this page worth remembering if you remember nothing else from it.
Common misconceptions.
Myth. There's a Behcet's diet with research behind it.
Reality. There isn't one, because no diet trial in this syndrome has ever reported a result. Everything held here in this area is a survey, and a survey describes what patients eat and how their bodies compare with other people's. It doesn't test what happens when they change anything, so a diet sold for Behcet's syndrome has no finished trial behind it.
Myth. Walnuts and tomatoes make the disease worse.
Reality. Those are the foods patients name most often, with walnuts at 35 percent, eggplant at 35 percent, and tomatoes at 13 percent. That's a survey of what people believe about their own symptoms, taken at one moment. So it's a fair place to begin your own test rather than a demonstration that dropping them changes anything.
Myth. Patients with this disease eat too much.
Reality. The comparison found the opposite of what most people assume. The controls ate more than the patients did, and that held for energy, for carbohydrate, for fat, and for fiber. Patients were more obese and less active all the same, and eating less while weighing more points at activity levels and at how badly people recall what they ate.
Myth. The guidelines will tell me what to do about lifestyle.
Reality. The 2018 European recommendations cover a great deal of ground. They cover skin and mouth, joints, eyes, vessels, nerves, and the gut, and they say of themselves that they “attempt to highlight the shortcomings of the available clinical research”. That's a treatment document in a disease where the research is thin, rather than a lifestyle guide.
Questions patients ask.
Is there a diet for Behcet's syndrome?
Not a tested one, because no diet trial in this syndrome has ever reported a result. What this site holds is surveys, which describe what patients eat and how their bodies compare with other people's. They don't say what happens when anybody changes anything, so nothing sold as a Behcet's diet has a finished trial behind it.
What about the foods people say set them off?
Those are written down and they're self-reports. In one study 35 percent named walnuts, another 35 percent named eggplant, and 13 percent named tomatoes. No study removed those foods and watched, and no study put them back blinded. If one of them matches what you've noticed, drop it for a set time and then put it back, which tells you more about your case than the survey does.
Should I follow a Mediterranean diet?
It has never been tested in this disease at all. One study measured how closely patients already ate that way, and the mean score came to 23.5, average in 60 percent of them and poor in 35 percent. That tells you where people are rather than what improving it would do. The general case for eating that way rests on heart evidence in other groups, and this disease does involve blood vessels. So that case is relevant without being about Behcet's.
Are mouth ulcers affecting my nutrition?
They can make eating hurt enough to change what you eat, and there's a measurement worth knowing about. In one study 47 percent of patients had a mid-upper arm circumference below the fiftieth percentile, and for triceps skinfold thickness it was 36 percent. Those measure body composition rather than diagnosing anything. They're still a reason to tell your team that eating has become hard.
Should I be exercising?
There's very little at all to go on here. One small study spanned the pandemic and found no real change in activity, pain, fatigue, depression, or sleep from before to during, with every P value above 0.05. It analyzed 16 people, which the record here calls severely underpowered. The comparison study did find patients less active than controls, which is a reason to pay attention rather than evidence about what to do.
Why is there so little research?
The syndrome is uncommon, how common it is varies hugely by region, and research money follows commoner diseases. The 2018 European recommendations say of themselves that they “attempt to highlight the shortcomings of the available clinical research”, which is unusually frank for a guideline. Diet and exercise sit well behind treatment in that queue.
Where does mood fit into this?
The comparison study found higher depression scores in patients than in matched controls, and quality of life was lower on every subscale too. That's a link found at one moment in time, and it is no proof that either one causes the other. It's also what you'd expect, because this disease relapses, brings painful ulcers, and threatens sight. So raise it at an appointment, because your mood is not something separate from the disease itself, and it is worth saying out loud.
What should I take to my next appointment?
Any new eye symptom needs urgent attention rather than a routine visit, because eye involvement in this disease threatens sight and it moves fast. Beyond that, several things belong on the list. New belly pain or blood in your stool, a new headache or new nerve symptoms, and swelling or pain in a leg. This disease affects vessels and organs well past the mouth.
References.
- Ersoy N; Bölek E; Farisoğullari B et al. A close look at the nutritional status and mediterranean diet adherence in patients with behcet’s syndrome. Mediterranean Journal of Nutrition and Metabolism. 2024;17:43-52. 10.3233/MNM-230053Prospective observational study
- Urhan M; Meseri R; Oksel F. Quality of life and diet: A paired match study on Behçet’s disease. Mediterranean Journal of Nutrition and Metabolism. 2022;15:381-391. 10.3233/MNM-211571Case-control study
- Hatemi G; Christensen R; Bang D et al. 2018 update of the EULAR recommendations for the management of Behçet's syndrome. Annals of the Rheumatic Diseases. 2018;77:808-818. 10.1136/annrheumdis-2018-213225International guideline
- Baglan Yentur S; Bilek F; Koca SS. Physical activity and psychosomatic status in patients with Behcet's disease during coronavirus disease pandemic. Eur J Rheumatol. 2022;9:144-147. 10.5152/eurjrheum.2021.20166Cross-sectional online questionnaire study with retrospective before/during comparison
This page gathers the published research on this subject into one place. The studies behind it were published between 1989 and 2026, and every figure links to the paper it came from. Those studies were peer reviewed. This summary of them was not. Dr. Sarah Luebker is reviewing these pages one at a time and has not reached this one yet, so it carries no medical review date and nothing here is her opinion or her advice to you. Each page gets updated as she reaches it. It is here in the meantime because the science is worth having in one organized place that is easy to find and easy to read. Talk to your own clinician before acting on any of it.