Diet and Dermatology: Google Search Results for Acne, Psoriasis, and Eczema

Researching medical information currently is the third most common use of the Internet in the United States,¹ with the majority of adults using the Web as their first source for health information before seeing a physician.² When assessing health-related information online, resources can be grouped into 4 categories: (1) those attributed to self-proclaimed experts, (2) promotional, (3) social media, and (4) educational.³ Access to such a wide range of sources may give readers the opportunity to share personal anecdotes and opinions, thereby serving as a forum for information that essentially cannot be validated. Although such websites may include useful information and cite current literature, in other instances health-related information may be misleading or fabricated.³

In a study evaluating 291 skin conditions and related Google trends, acne, psoriasis, and eczema were among the most burdensome diseases, with acne yielding the highest number of search results.⁴ Results of the study indicated a positive correlation between disease burden and online search interest.⁴ The impact of these online searches and the validity of Google search results are topics worth considering, as more dermatology patients are relying on holistic and nonpharmaceutical approaches to treatment and disease management.⁵ The purpose of this study was to evaluate content on diet and dermatology available on the Internet for acne, psoriasis, and eczema.

Methods

Google searches were performed in December 2017 using the terms diet and acne, diet and psoriasis, and diet and eczema. The first 10 results for each respective search were reviewed for recommendations about which foods to incorporate in the diet and which to avoid. They also were classified according to the following 4 website categories: (1) those attributed to self-proclaimed experts, (2) promotional, (3) social media, and (4) educational. The recommendations gathered from the 30 websites were then compared to the current literature assessing the impact of diet on these respective conditions by conducting PubMed searches of articles indexed for MEDLINE using the same terms.

Results

The results of this study are outlined in the eTable.

Acne
Our Google search using the term diet and acne produced 17,500,000 results. Of the first 10 search results, 40% (4/10) were websites attributed to self-proclaimed experts, 40% (4/10) were educational resources, and 20% (2/10) were promotional websites. Most of the websites advised acne patients to avoid high glycemic index foods (90% [9/10]) and dairy products (90% [9/10]). When discussing which foods to include in the diet, 70% (7/10) of websites recommended that patients incorporate omega-3 fatty acids and antioxidants in the diet.

Research has shown that a low glycemic index diet can lead to a decrease in patients’ acne lesion counts in some instances.^6,7 In a case-controlled study of 2258 patients on a popular weight loss diet that emphasized low glycemic index foods, 87% of participants reported a reduction in acne and 91% reported a decrease in their dosage or number of acne medications.⁷ Still, the exact correlation between acne development and consumption of glycemic index foods has not been confirmed. However, high glycemic index diets have been linked to hyperinsulinemia, indicating that insulin levels may play a role in acne formation.⁸ The majority of other currently available studies evaluated the potential link between dairy consumption and acne. A retrospective analysis of 47,355 women spanning 12 weeks showed a positive link between increased dairy consumption, specifically skim milk, and acne formation. Despite the positive trend, limitations such as recall bias made it difficult to draw a conclusion based on these findings.⁹ However, results of a longitudinal questionnaire-based population study evaluating the impact of dairy consumption on acne in 2489 adolescent patients confirmed a positive correlation.¹⁰ Studies conducted in 2009 and 2011 concluded that milk consumption results in elevated insulinlike growth factor 1 levels, which were linked to comedogenesis.^8,11

Currently, there are well-described mechanisms to explain the association of dairy consumption and glycemic index with acne. Confirming a correlation between acne development and dairy consumption suggests that a dairy-free diet may benefit acne patients.⁵ Other trials indicate that low glycemic index diets are beneficial in treating acne.^6,7 Therefore, some of the recommendations made in our search results may be of merit; however, there is minimal evidence proving the benefits of the other dietary recommendations made in the websites we evaluated.

Psoriasis
Our Google search using the term diet and psoriasis yielded a total of 9,420,000 results. Of the first 10 search results, 40% (4/10) were websites attributed to self-proclaimed experts, 30% (3/10) were promotional, and 30% (3/10) were educational. Seventy percent (7/10) of websites recommended avoiding alcohol and 60% (6/10) recommended avoiding gluten, with others discouraging consumption of red meat. Most of the websites encouraged patients to consume omega-3 fatty acids and antioxidants, while a few also recommended vitamins A, D, and E, as well as evening primrose oil supplements.

Although current research indicates a positive correlation between excessive alcohol use and psoriasis severity, it is still unclear whether alcohol consumption can be directly linked to the disease.^12-14 Likewise, despite belief that increased oxidative stress likely contributes to inflammation in psoriasis, there is little evidence linking antioxidants to improvement in psoriasis symptoms.¹² However, the current literature is inconsistent regarding the effects of fish oil supplementation on psoriasis.¹² In a randomized double-blind study of 145 patients, there was no significant difference in psoriasis area and severity index scores between a control group and a treatment group receiving fish oil supplementation.¹⁵ In another RCT of 45 participants, those given daily very long-chain omega-3 fatty acid supplements saw no difference in psoriasis symptoms.¹⁵ Despite debate, literature assessing the impact of gluten-free diets has described improvement in psoriasis lesions in patients with celiac-specific antibodies.¹⁶ Although some observational studies described vitamin D supplementation to be beneficial in the treatment of psoriatic lesions, a more recent RCT found no significant difference between control and treatment groups.^17-19

Studies also have revealed that certain eating patterns, such as those associated with the Mediterranean diet that is rich in fruits, vegetables, whole grains, and omega-3 fatty acids may be linked to improved endothelial function scores and reduced C-reactive protein and IL-18levels.^20,21 In a double-blind RCT of 75 patients with plaque psoriasis, mean (SD) psoriasis area and severity index scores decreased by 11.2 (9.8) in a group treated with omega-3 fatty acids compared to 7.5 (8.8) with omega-6 fatty acids (P=.048).²²

Although excessive alcohol use may be linked to psoriasis, there is no conclusive evidence indicating causation, thereby discrediting online claims.^12-14 Research has revealed that gluten-free diets in psoriasis patients with celiac disease may improve psoriasis treatment¹⁶; however, sufficient evidence is lacking for diets low in gluten and high in polyunsaturated fatty acids or antioxidant supplementation. Of the dietary supplements recommended in the search results we reviewed, fish oil appears to be the most promising, but no recommendations can be made based on the current research.

Eczema
Our Google search using the term diet and eczema yielded 1,160,000 results, with 50% (5/10) of websites attributed to self-proclaimed experts, 30% (3/10) to educational websites, and 20% (2/10) to promotional sites. Of the first 10 results, 80% (8/10) recommended that patients with eczema avoid milk/dairy and 50% (5/10) advised to avoid soy and wheat/gluten. Other websites indicated to avoid eggs, nuts, and artificial sweeteners. Patients were encouraged to incorporate omega-3 fatty acids in their diets, and a few sites recommended bananas, coconut oil, olive oil, and various teas.

In a review of 11 studies with a total of 596 participants, supplementation with vitamins D and E, fish oil, olive oil, and linoleic acid was evaluated for the treatment of eczema.²³ Although results indicated modest improvement of eczema severity with supplementation of fish oil, evidence favoring this treatment is limited and unconvincing. Furthermore, some evidence indicates that elimination diets are only appropriate for patients with food allergies.²⁴ In a study evaluating an egg-free and dairy-free diet for eczema patients, only participants with positive egg-specific serum IgE levels saw improvement in disease severity.²³ Even though IgE-mediated food allergies have been reported in 40% of children with moderate eczema, the contribution of these allergies to eczema is questionable.²⁵

There is little evidence in the literature to indicate a definitive correlation between the foods mentioned in the search results we evaluated and the development of eczema; however, for patients with food allergies and eczema, elimination diets may decrease disease severity.^25,26 There is insufficient evidence to suggest a benefit from evening primrose oil or fish oil supplementation, thereby debunking claims found online.