In most research that has studied a person’s diet and its impact on psoriasis, he explains, the sample sizes tend to be small, so the data is limited. Further, many people who participated in these studies continued to take their prescribed psoriasis medication in addition to changing their diet as part of the research. For these types of experiments, people are asked to make detailed logs of their behaviors, which may encourage them to take their medications as prescribed without skipping doses, Dr. Feldman says—and when it feels like a researcher is “watching” you via your logs, you may be more inclined to take your meds consistently. “So while it might look like the dietary intervention was beneficial, it may have been beneficial only in that it caused people to take their other medicines better,” Dr. Feldman says.
Unfortunately, because of the way many of these studies have been designed, it’s really hard to conclude which changes, including diet changes, are responsible for certain outcomes, like worsened or improved symptoms. That doesn’t mean it’s out of the question that certain diet changes can have a beneficial impact on psoriasis—it just means that more research that addresses these issues needs to be done so scientists have more solid data to work with.
With that said, it’s really unlikely that there will ever be one “psoriasis diet” to help each person with the condition. “You’re not going to cure psoriasis with diet—this is a chronic disease,” Dr. Feldman says. “But if you find that when you eat certain things they seem to exacerbate your psoriasis, avoiding those things makes entirely good sense.”
So far, there are two main diet approaches for people with psoriasis: additive diets and subtractive diets. With an additive diet, you’d focus on consuming more of a specific food or nutrient. With a subtractive diet, you’d slowly remove certain foods or nutrients.
This is tricky territory. Any time you make a diet change, especially if you have a chronic health condition, it’s best to talk to your doctor or a registered dietitian who is familiar with the disease, so they can guide you through the process and help you avoid risky side effects, like lower energy, unintended weight loss, or nutrient deficiencies.
Here’s a closer look at some popular diet changes people make when they have psoriasis—and what the science says about each one so far:
Psoriasis lesions are set off by inflammation in the body, so it makes sense to assume that “anti-inflammatory” foods could help tame that irregular immune response. Researchers believe that foods with certain nutrients may reduce oxidative stress in your body, a process that contributes to inflammation, but it’s an area of research that is still being explored. A typical list of “anti-inflammatory” foods is pretty expansive and diverse, including berries, green leafy vegetables, nuts, fatty fish, tomatoes, and so much more. The theory is that these foods may prevent inflammation from starting in the first place or reduce its impact.
For example, a fat called eicosapentaenoic acid (EPA) that is found in fatty fish like salmon is thought to help reduce the number of inflammatory chemicals in the body, according to Dermatology Online Journal1. However, in the case of psoriasis, researchers are still unsure if consuming EPA has much of an effect on a person’s symptoms. Many studies looking at EPA and psoriasis specifically involve using fish oil supplements instead of whole fatty fish, which may not offer the same theorized benefit. Dr. Feldman’s team found that fish oil studies have really conflicting results: Some people saw no improvement, some said their psoriasis got better, and others said their psoriasis actually got worse.