Diet for Psoriasis: Facts and Myths
Psoriasis can be a very frustrating skin disease. It's a chronic disease, and even the best therapies don't always clear the skin. It's no wonder, then, that so many patients with psoriasis turn to the Internet for ideas on alternative therapies or special diets.
What they find on the internet, though, can be very misleading.
I was working on a project with one of our Baylor medical students on quality of medical information. We started reviewing the top websites that came up on search engines when we searched for information on diet and psoriasis. I was very surprised, to say the least. While some of the websites had good, solid recommendations, others were focused on selling supplements, or focused on diets which weren't backed by much evidence. Some promoted certain foods or supplements without discussing the potential risks.
Medical information about the right diet for psoriasis patients can be misleading
This is one of the main reasons that I started to write about diet and dermatology. There are so many misconceptions in this area, and some websites publish misleading information. With any discussion of diet recommendations for particular health conditions, it's important to discuss the science and evidence behind those recommendations.
It's equally as important to discuss the limits of the recommendations (we still haven't found a diet that will cure psoriasis) as well as the limitations of the evidence. (That study of 30 patients can help guide us, but that's not definitive evidence, and their results may not apply to all psoriasis patients.) With that in mind, I've looked at many of the studies on diet and psoriasis. Here are my recommendations, based on the results of these studies.
1. The most important diet recommendation is to focus on eating foods that are whole or less processed. I recommend a diet based on whole and less processed foods. While this may sound very intimidating, I'm not talking about a raw food diet, or a purely organic diet, or even a vegetarian diet.
I'm talking about diets such as the Mediterranean diet or the DASH diet. There are several diets out there that are based on whole foods, and you can choose the one that works best with your lifestyle and your tastes. The Mediterranean diet and DASH diet are two great options. You don't have to invest any money in special cookbooks or supplements or food products, because there's lots of advice and recipes for these diets available for free on the internet. I've written about another dietary approach that's based on whole foods, the GLOW diet, which adds a few modifications to the DASH diet that are specific to skin health.
Why should patients with psoriasis follow a diet based on whole foods?
The main reason is to reduce the risk of heart disease and hypertension. This type of diet is also high in fiber, which has multiple health benefits. This pattern of eating also helps to reduce the risk of diabetes.
Why is this so important for patients with psoriasis? Multiple studies have shown that persons with psoriasis are at higher risk for high blood pressure, diabetes, and even heart disease. And one of the most important ways to reduce that risk is to eat healthy foods.
2. A combination of diet and exercise that leads to weight loss may help with psoriasis symptoms.
While there's no evidence that a particular diet will help improve the symptoms of psoriasis, several research studies have suggested that a diet and exercise program that leads to weight loss, in addition to psoriasis medications, may help with psoriasis symptoms. This hasn't been true in all research studies looking at diet and weight loss, so more research is needed to determine who might benefit, and how much weight loss would be required.
Importantly, this effect may be long-lasting. The results of one study were very promising, because it found that when weight loss resulted in an improvement of psoriasis, that benefit was seen even after a year later.
Losing weight is, of course, easier said than done, as we all know how challenging it is to achieve and sustain weight loss. It's important to realize, though, that even small amounts of weight loss may help with multiple health risks. If you are serious about weight loss, I highly recommend that you invest in an appointment with a nutritionist. Most will start by having you keep a food diary. Just that one step alone may highlight some easy steps to help you start the process of successful weight loss.
3. What about gluten-free diets?
When I was reviewing websites on diets for psoriasis, it seemed as though every other website was recommending that everybody should follow a gluten-free diet to help clear up psoriasis.
That's a very misleading statement. There have been reports of patients whose psoriasis improved after they went on a gluten-free diet. But this is more likely in patients with either celiac disease or antibodies to certain proteins, and even in those patients it may not always help.
Gluten-free diets are NOT recommended for all patients with psoriasis. They may be helpful, though, for some patients with certain antibodies found on blood testing.
In another study, 33 patients with psoriasis had elevated anti-gliadin antibodies (AGA). These antibodies are tested for by a blood test, and are considered a marker for gluten allergy or intolerance.
These patients were prescribed a gluten-free diet for 3 months. Their results were compared to a group of 6 psoriasis patients who did not have the AGA on testing. After the 3 months, 73% of the AGA-positive patients had improvements in their psoriasis, as compared to none of the AGA-negative psoriasis patients.
These are very promising results, but these patients don't tell the whole story. In another report, 3 patients with psoriasis who also had gluten antibodies were prescribed a gluten-free diet. After 6 months, they didn't note any further improvement in their psoriasis.
The truth is that some, but not all, patients with psoriasis may have celiac disease or antibodies that may indicate a gluten allergy or intolerance. While it may not work in all, it appears that some of these patients may benefit from trying a gluten-free diet.
How many patients with psoriasis have celiac disease? Not many.
If you look at the headlines, it can be very misleading. The headlines state that patients with psoriasis have a 2 or 3-fold risk of having celiac disease. BUT this is still a small number. Several studies have estimated that in the general population, 1 out of 1000 persons will have celiac disease. In patients with psoriasis, that number rises to 3 out of 1000. That's higher, but it's still a very small number.
What about gluten intolerance? There's still quite a bit of controversy on how to diagnose that, but some studies have looked at antibodies to a protein in gluten. These antibodies are called anti-gliadin antibodies (AGA). In one summary study that summarized the results of other studies, researchers estimated that 5% of the study subjects without psoriasis had AGA. In study subjects with psoriasis, that number rose to 14%.
That's a higher number, but it's not what I consider high. That's about 1 out of every 7 psoriasis patients. Those numbers aren't high enough to recommend a gluten-free diet to every single psoriasis patient.
That's because gluten-free diets definitely have their drawbacks. Whole wheat is a great source of fiber, antioxidants, and multiple nutrients, which means a gluten-free diet eliminates an entire category of healthful foods. Also, I have friends who've gained weight on a gluten-free diet, because instead of eating whole wheat bread they've switched to white rice. Or, because they can't eat some of the more commonly available foods, they've turned to gluten-free processed foods. And those processed foods, because they lack fiber and nutrients, and because sometimes they have added sugar and other additives, can contribute to weight gain.
When would I recommend a gluten-free diet (GFD)?
To start with, before I recommended a GFD, I would ask several questions. I'd start by asking about GI symptoms. Do you have any signs or symptoms of an allergy or intolerance to gluten? Specifically, do you have diarrhea, gas, or frequent bloating? Have you been diagnosed with any nutrient deficiencies? People with celiac disease have a problem absorbing certain nutrients. As one example, they're more likely to be diagnosed with iron deficiency anemia. If you have any of these symptoms, then I would recommend a blood test. This would test for certain antibodies, which may include antibodies to tissue transglutaminase, anti-endomysial antibodies, or anti-gliadin antibodies. If you test positive to one of these antibodies, you'll need to discuss the next steps with your physician. You may need further testing. But if you test positive for one of these antibodies, then I would recommend a trial of a gluten-free diet.
The bottom line: It all goes back to one of the core principles of medicine: everybody's different. That means it's important to discuss your symptoms and your medical history with your physician, and that's why lab tests may be needed in order to guide the best recommendations for your particular case.
Dr. Rajani Katta is the author of Glow: The Dermatologist's Guide to a Whole Foods Younger Skin Diet. To receive future updates on preventive dermatology and the role of diet, sign up here.