乌鸦传媒

Ketogenic diets have become an extremely popular way of achieving weight loss, but they may not be advisable for persons with psoriasis, Austrian researchers suggested.

Mouse studies indicated that different ketogenic diets affected skin inflammation differently, depending on the composition of the diet. Specifically, they found that ketogenic diets heavy in medium-chain triglycerides (MCTs), especially in combination with omega-3 fatty acids from fish oil and plant sources like nuts and seeds, exacerbated a murine model of psoriasis.

However, the researchers also found that ketogenic diets that were well balanced and limited to long-chain triglycerides (LCTs) such as olive oil, soybean oil, fish, nuts, avocado, and meats, did not exacerbate skin inflammation.

Writing in the, Felix Locker, PhD, of Paracelsus Medical University in Salzburg, Austria, and colleagues noted some evidence that ketogenic diets (usually consisting of 75%-80% kcal from fat, 5%-10% from carbohydrates, and 15%-25% from protein) have anti-inflammatory properties. In addition, because of the anti-inflammatory and anti-angiogenic effects, there has been interest in the use of omega-3 fatty acids in dietary interventions in inflammatory skin diseases, the team added.

Locker and co-authors noted that ketogenic diets differ in composition from classic high-fat diets, and that no previous studies have evaluated the effect of these diets on psoriasis. The team therefore wanted to evaluate the impact of ketogenic diets alone or supplemented with omega-3 fatty acids on imiquimod (IMQ)-induced psoriasiform inflammation in mice.

These mice exhibited increased erythema at 4 days when fed with an LCT/MCT diet, compared with mice on a standard diet. In addition, the LCT/ MCT group showed a trend toward increased cumulative disease severity (based on a 12-point scale) compared with the standard diet group (8.2 ± 1.1 vs 6.2 ± 0.7), which was significant in comparison with the LCT group (8.2 ± 1.1 vs 5.9 ± 1.7) after 4 days of IMQ treatment.

The team also found that LCT/MCT with omega-3 supplementation induced skin inflammation, even in Vaseline-treated mice, which was reflected by significant increases in erythema, scaling, and thickening, as well as the cumulative disease severity scores, compared with mice on a standard diet at day 4.

Locker and colleagues also observed that LCT/MCT + omega-3 skin "showed neutrophil-derived myeloperoxidase levels that were significantly higher than standard diet + omega-3 skin upon psoriasis induction and Vaseline treatment."

"Accordingly, we detected a significantly higher number of [the rat monoclonal neutrophil antibody] NIMP-R14+ neutrophils in LCT/MCT +[ omega-3] skin compared to [standard diet + omega-3] skin," the researchers reported.

The study's co-lead investigator, Roland Lang, PhD, also of Paracelsus Medical University, said in a news release, "Ketogenic diets supplemented with MCTs not only induce the expression of pro-inflammatory cytokines, but also lead to an accumulation of neutrophils in the skin resulting in a worse clinical appearance of the skin of the mice. Neutrophils are of particular interest since they are known to express a receptor for MCTs, and therefore a ketogenic diet containing MCTs may have an impact on other neutrophil-mediated diseases not limited to the skin."

Asked for his perspective, Bruce Brod, MD, of the University of Pennsylvania Perelman School of Medicine in Philadelphia, who was not involved with the research, said the study "raises some good and important points," but that there are many factors that influence psoriasis, and a lot more work needs to be done to determine how translatable the findings are to humans -- "for example, is this translatable to all patients with psoriasis, or just patients with certain subsets of psoriasis?"

"There are multiple factors that can influence psoriasis," Brod continued. "One is body mass index. Infections can play a role, medications can play a role, as can things like stress and alcohol. So [a ketogenic diet] might be another factor that plays a role in psoriasis in certain subsets of patients. But at this point in time it is probably too early to have this study influence our clinical practice."

"I think when we're counseling our patients on dietary recommendations that those recommendations need to be made very carefully within the clinical context of that patient, and that patient's specific medical condition," he said.

Comment