Diet for Acne Patients - Is it Beneficial? Yes

Speaker- Dr. Rieke Driessen (Radbound University medical center Nijmegen, The Netherlands)

Acne vulgaris had been recognized as one of the most common diagnoses in dermatology for centuries, dating back to ancient Greek times. A 1925 article by a dermatologist from Stanford University Medical School discussed the treatment of juvenile acne vulgaris. At that time, treatment methods differed significantly from contemporary practices, involving alkaline dressings, heavy metal peelings, and even x-ray exposure. The emphasis was on management of acne with focus on correcting any underlying constitutional disturbances, such as habitual constipation, dyspepsia, and improper diet. He specifically recommended reducing sugars and starchy foods due to their impact on sebaceous secretion, pointing out on a dietary concern.

In 1969, the first studies examining the relationship between diet and acne emerged, one study concluded that chocolate had no effect on acne severity, based on a small crossover design involving 65 participants who were given chocolate and placebo bars. However, the study had significant shortcomings, including its brief duration of only four weeks, which may have been insufficient to detect meaningful differences. More than half of the participants were young adult male prisoners, raising ethical concerns about the study's design. There was no stratification among subjects, and while the authors claimed the study was blinded due to the similar taste of the bars, a detailed description of the statistical methods used was absent, with reported differences deemed significant without clear justification. Furthermore, the study was funded by the Chocolate Manufacturers Association of the United States of America (USA), objectifying its validity.

A few decades later, a general practitioner conducted significant fieldwork on the island of Kitava, located in eastern Papua New Guinea. Kitava was known for its non-westernized population, who lived simple lives and followed a basic diet. This diet resembled a paleolithic diet, consisting of tubers, fruit, fish, and coconut. They performed general health examinations on 1,200 subjects and found remarkable health outcomes, reporting no cases of obesity, hypertension, or cardiovascular disease. Notably, there was not a single case of acne among the inhabitants of this non-westernized society.

A systematic review published in the Blue Journal in 2022 addressed the role of diet in acne. The authors reviewed over 400 citations but ultimately included only 34 studies in their analysis. Most of these were observational studies, with only a few interventional studies available. The majority of observational studies found a positive association between acne and diets with a high glycemic index or low overall dietary quality, as well as with dairy consumption. Similar findings were reported in the limited number of interventional studies, where three out of four indicated a positive association with high glycemic index or glycemic load products. The review noted a distinction between glycemic index and glycemic load; glycemic index measures the relative rise in blood glucose levels two hours after consuming a food, while glycemic load accounts for the glycemic index multiplied by the carbohydrate content of a serving, reflecting the actual amount of food consumed. No interventional studies specifically focused on dairy were identified.

In 2007, a study comparing the effects of a low glycemic load (LGL) diet to a control group was conducted. After 12 weeks, the study found a significant decrease in both total lesion count and inflammatory lesion count in the LGL group compared to the control group. However, there was also a notable reduction in weight among participants in the LGL group, which could have acted as a confounding factor in the study. 

In 2012, another similar study demonstrated significant results. After 10 weeks, a marked reduction in acne severity in the LGL diet group compared to the control group was seen. The effects were most pronounced for inflammatory lesions, while the reduction in non-inflammatory lesions was slightly smaller.

A meta-analysis published in Clinical Nutrition in 2019 examined the association between dairy consumption and acne. The analysis included a forest plot that illustrated a significant relationship between total milk intake and acne. The findings indicated an overall odds ratio of 1.48, suggesting a notable association between milk consumption and the prevalence of acne. 

One relevant study was the Nurses’ Health Study, which asked nurses about their high school diets and conducted a retrospective evaluation of over 40,000 questionnaires. The study found a positive association between acne and the intake of both total and skim milk. Notably, skim milk was linked to a higher risk of inducing acne, as its fats are replaced by whey proteins. These whey proteins are well known in clinical practice to be associated with severe acne in young people who consume protein shakes containing them. Thus, whey proteins were identified as a contributing factor to acne development.

Acne vulgaris was characterized as a metabolic syndrome of the pilosebaceous follicle, similar to conditions like obesity and diabetes. This syndrome was mediated by mammalian target of rapamycin complex 1 (mTORC1), a protein kinase that regulates cell growth, proliferation, and survival. Additionally, insulin-like growth factor 1 (IGF-1) played a central role, as it is a growth factor that promotes childhood growth and has anabolic effects. The Western diet and puberty influenced the activation of IGF-1, which indirectly activated mTORC1 through various pathways. This process ultimately led to hyperseborrhea or dysseborrhea, resulting in inflammation and comedogenesis.

Laurent's syndrome provided intriguing insights, as individuals with this condition were found to be deficient in IGF-1. While one would expect these patients to have short stature, they also exhibited a notable absence of acne. This observation supported the conclusion that IGF-1 plays a central role in the pathogenesis of acne.

In conclusion, acne was identified as a typical disease of Western civilization, linked to dietary products with high glycemic loads and dairy, both of which may increase inflammation. A central role was attributed to IGF-1 and mTORC1 in its pathogenesis. Consequently, a diet beneficial for acne patients was recommended, emphasizing a low intake of fast carbohydrates, minimal dairy—particularly avoiding protein shakes—and a rich fibre content. This approach aligned with the principles of what is considered healthy eating.

Diet for Acne Patients. Is it Beneficial? No

Speaker-Jerry Tan, (Windsor, Ontario, Canada)

The proposition addressed was whether diet is beneficial for acne patients. In this context, "diet" did not refer to a specific supplement or dietary changes in response to ongoing treatments like oral isotretinoin. Instead, it specifically referred to a prescribed nutritional plan tailored to a particular condition, in this case, acne. The question of benefit was raised: was the diet intended to improve overall health or to target acne specifically. The argument was approached from multiple perspectives. 

Mechanistically, the well-established pathways of acne, including the roles of insulin-like growth factor 1 (IGF-1) and insulin, indicated that diet could play a significant role. It raised the question of how food could not be relevant in managing acne. Secondly, evidence from the study, including several meta-analyses, was considered, although the findings required scrutiny. Finally, dietary recommendations were acknowledged to impact the entire family, as adherence to such regimens could involve financial burdens. For families with children or adolescents, this could lead to the ethical issue of "diet shaming," particularly when financial limitations prevent adherence. It highlighted the need for a critical evaluation of the subject. 

The pathogenesis of acne has evolved significantly, transitioning from a simpler model with four primary pillars to a more complex version resembling a Swiss watch with numerous interconnected components. Hormonal effects have been identified as key triggers, particularly their influence on the pilosebaceous unit. Among these triggers, high glycemic foods and dairy products have been shown to stimulate IGF-1 and insulin, activating Forkhead Box O1 (FOXO1) and Mechanistic Target of Rapamycin (mTOR) pathways. 

Despite this understanding, questions remain regarding the direct impact of diet on acne outcomes. One randomized controlled trial (RCT) demonstrated that a low glycemic index low glycemic load diet could reduce insulin-like growth factor 1 levels. However, the study did not examine the effects on acne itself. While the trial was well-designed, biochemically measured, and highly controlled, the absence of acne outcomes left a gap in the study. Conducted in 2018, the study raised expectations for clinical outcomes, but these findings have yet to materialize. It highlights a significant gap in the literature, raising questions about the link between diet and acne management. In developing acne treatment guidelines, a panel addressed specific questions about the effectiveness and safety of dietary interventions. These included the impact of low glycemic index diets, low dairy consumption, and reduced whey intake. In clinical practice, for instance, some practitioners have adopted slogans like "If you have acne, no whey," underscoring the potential importance of avoiding whey protein. Additional dietary factors such as omega-3 and chocolate consumption were also considered in these guidelines, reflecting the evolving understanding of diet's role in acne pathogenesis. 

The evidence summary for the low glycemic index diet revealed mixed results. The low glycemic index concept, originally developed in Toronto by endocrinologists aiming to manage diabetes, has been applied to acne treatment. Despite the diet's Canadian origins, the RCT results showed varying levels of evidence. Studies were categorized by quality: orange for low-quality evidence, green for medium-quality evidence, and none reached the level of high-quality evidence. The overall outcome was generally positive, with one exception. The negative result came from a study where both groups also used benzoyl peroxide, raising questions about whether the topical treatment could counteract the effects of the low glycemic index diet. 

The challenges of conducting diet-related clinical trials were highlighted, particularly the difficulty in blinding patients. Participants often improve their skincare routines if they believe they are receiving an interventional diet, a phenomenon known as the Hawthorne effect. It introduces bias, making it nearly impossible to ensure that the outcomes are solely due to the diet. Additionally, benzoyl peroxide’s ability to negate the impact of the low glycemic diet adds another layer of complexity to interpreting these findings. 

When considering the practical application of this diet in clinical settings, key questions remain unanswered, including the appropriate dosage for a low glycemic index diet and the length of time patients should follow it. The uncertainty limits the ability to provide clear recommendations. Shifting the focus to dairy consumption, meta-analyses of 14 studies indicated that milk, yogurt, and cheese were associated with increased odds of developing acne. However, these studies relied on retrospective recall, subject to significant biases. Patients often struggle to accurately recall their dairy intake over time, making it difficult to draw definitive conclusions. Large observational studies like the Nurses' Health Study and the ABOMO study highlighted potential links between diet and acne but underscored the need for further, more rigorous study. 

The issue of whey protein in acne was examined in a six-month, double-blind, randomized study focusing on male acne. The results showed a non-inferior difference, meaning that whey protein did not significantly impact acne outcomes compared to other factors. Despite this, whey protein continues to be a topic of interest because certain individuals experience more acne when consuming whey protein, and when they stop, their acne improves. These cases represent what are known as "N of 1" studies, where individual responses may differ, even if larger population studies show no significant effect. This highlights the distinction between population-based studies and individual variations, or "outliers. In light of these findings, the most recent acne guidelines, published earlier this year, concluded that there is insufficient evidence to link whey protein to acne. For those who prefer to act on emerging trends, the low glycemic index diet might seem like a good preventive measure despite the lack of solid evidence. However, the "wave" of conclusive study has not yet arrived for those waiting for strong evidence before making recommendations. Economically, low glycemic index diets are more expensive than high glycemic index diets. High glycemic foods are calorie-dense and typically produced by large corporations, such as fast food chains, which makes them more affordable. Studies from countries worldwide—including France, the UK, Australia, and the US—demonstrate that low energy-density diets (often associated with low glycemic index foods) result in higher costs. On average, recommending a low glycemic index diet increases food costs by 20%, with the impact being even more significant for low-income patients. For these individuals, the required increase in their food budget could be as high as 30 to 40%, presenting a substantial financial challenge. 

A significant portion of patients in many countries live at or just above poverty levels. Data from Eurostat shows that about 20% of people in the EU, whether in households with or without children, live in poverty or near-poverty conditions. This trend is also consistent in Canada and the US, meaning many patients in our practices face financial constraints. Advising them to spend more money on dietary changes for their acne, such as following a low glycemic index diet, can be problematic. Patients often seek advice on the latest study; for some, adopting a low glycemic index diet might seem appealing. However, this advice must be given thoughtfully, considering that not all patients are financially equipped to follow such recommendations. The approach to treating acne should be nuanced, recognizing that diet is only one aspect of acne’s multifactorial etiology, and the link between IGF-1 and acne remains hypothetical. The study, such as the two-week study on low glycemic diets, has not conclusively shown clinical outcomes. The ambiguity in the evidence, highlighted by the American Academy of Dermatology’s statement on insufficient evidence, raises the question of how to recommend such a diet. Should it be a general suggestion for all patients or tailored to individual circumstances? A simple recommendation to "follow a low glycemic index diet" lacks clear guidelines on duration and cost. Advising patients to follow this diet for at least three months without strong proof can be challenging, particularly given the financial burdens many face. The rising cost of living, inflation, and global recession exacerbate these challenges. Finally, recommending dietary changes can carry ethical considerations. There is a risk of further burdening patients with limited means or inadvertently shaming them for not following recommendations. Thus, while dietary modifications may be beneficial for some, they must be approached with caution and consideration for the individual patient’s financial and social situation.

33, European Academy of Dermatology and Venereology Congress, 25-28 September 2024, Amsterdam