Acne (acne vulgaris) is a skin condition characterized by the excessive production of sebum by sebaceous glands, inflammation and hyperproliferation of a bacterium present in our skin (Propionibacterium acnes)(1). The resulted skin lesions are called comedones which are related to the pilosebaceous unit. This unit includes a hair follicle and a sebaceous gland, mostly found on the face and upper parts of the body. A comedo occurs when the opening of the hair follicle is clogged by an excess of keratin, a protein present in the outer layer of skin, combined with sebum produced by sebaceous glands.
It is one of the most common dermatological conditions, especially among adolescents. This could be explained by the fact that androgens, hormones present in both sexes which increase during puberty, appear to have a stimulating effect on the sebaceous glands, thus leading to mild/severe acne during this period(1).
Further investigation is required to confirm the dietary influence on acne, although many studies give evidence supporting the association between food and acne development or aggravation. The attention is given mostly to high-glycaemic diet and milk, but also to chocolate, vitamins…
First, some studies suggest that acne may develop in populations that changed dietary habits from rural or traditional areas to the Western nutritional style. Areas not affected by the Western diet are observed to have less frequent incidence of acne(1).
Glycaemic index (GI) is a ranking system for food containing carbohydrates according to how they increase glucose (sugar) in blood levels(2). Commonly, the Western diet is rich in carbohydrates with a high GI, which means a fast release of glucose in blood, leading to elevated insulin levels, the hormone that promotes its absorption. Hyperinsulinemia results in a cascade of reactions that stimulate the androgens’ secretion and consequently the sebum secretion(1).
Trying to replace high GI foods (e.g. white sugar, white bread and rice) with medium to low GI foods (e.g. beans, fruit and vegetables) could help the blemish-prone skin. High fibre foods may also help to regulate insulin and keep the hormones balanced, while vitamin A and E (antioxidants) have been recommended as factors that reduce the formation of comedones(3).
Milk has also been addressed by many studies. It derives from cows and exposes us to the effect of hormones produced to stimulate the growth, also elevating insulin levels. The milk hormones are androgen precursors which can be transformed into androgens, the acnegenic factor described before. Observational studies suggest that it imparts a higher risk of acne; however, randomized controlled trials are necessary before milk restriction diet can be made(4).
Consumption of chocolate is a controversial topic because some studies on the effect of chocolate are inaccurate due to additional ingredients in it, such as milk or sugar(5), which have the evidenced impact discussed before. Dark chocolate contains less milk and more antioxidants than milk chocolate, leading much smaller comedogenic effects, but there is still no clear answer(6).
Nevertheless, a randomized cross-over study assessed the development of new acne lesions following ingestion of chocolate versus a nonchocolate candy, both with similar glycaemic load. The participants were 54 college students, randomly assigned to receive a milk chocolate bar or jellybeans (control group). A statistically significant increase in acne lesions was found in the chocolate consumption group, compared with the jellybean consumption group(7). Furthermore, Netea et al demonstrated chocolate has an active role in overinflammation, which is an important contributor to acne pathogenesis(8).
In summary, taking together evidences, an association between diet and acne is suggested. Diet is not demonstrated to be the cause of acne, but there’s evidence that it influences this condition to some degree. However, there are gaps in the literature and limitations in research, a situation which should challenge dermatologists to design a quality research in order to develop dietary interventions for acne treatment.
So, do we need to worry every time we eat a chocolate candy or a huge pasta dish? Not necessarily. Despite decades of research, there is still little proof, and the effects depend also on the individual. What can we do to diminish the apparition of new acne lesions? The best solution is to follow a diet rich in antioxidants, fresh fruits and vegetables, fish and seafood, with low-fat meat and low glycaemic load.
References
1. Wyrzykowska, N., Wyrzykowski, M., Zaba, R. W., Silny, W. & Grzymisławski, M. Diet and acne vulgaris. Prz. Gastroenterol. 2013, 8, 93–97.
2. https://www.health.harvard.edu/diseases-and-conditions/glycemic-index-and-glycemic-load-for-100-foods (accessed on November 11th, 2019)
3. https://int.eucerin.com/acne/article-overview/acne-and-nutrition-420 (accessed on November 11th, 2019)
4. Bronsnick, T., Murzaku, E. C. & Rao, B. K. Diet in dermatology: Part I. Atopic dermatitis, acne, and nonmelanoma skin cancer. J. Am. Acad. Dermatol. 2014, 71, 1039.e1-1039.e12.
5. https://www.healthline.com/health/does-chocolate-cause-acne#2 (accessed on November 5th, 2019)
6. Kucharska, A., Szmurło, A. & Sinska, B. Significance of diet in treated and untreated acne vulgaris. Postep. Dermatologii i Alergol. 2016, 33, 81–86.
7. Delost, G. R., Delost, M. E. & Lloyd, J. The impact of chocolate consumption on acne vulgaris in college students: A randomized crossover study. J. Am. Acad. Dermatol. 2016, 75, 220–222.
8. Netea, S. A. et al. Chocolate consumption modulates cytokine production in healthy individuals. Cytokine 2013, 62, 40–43.