Acne is a common skin condition characterised by formation of comedones, pustules and papules in the sebaceous glands of the face, neck, back and chest.  Although the condition is most common in adolescence, acne can occur at any age.
Acne is almost universal in adolescence in Australia and New Zealand, with an estimated 93% of young people experiencing the condition.  In adulthood, 64% of 20-29 year olds and 43% of 30–39 year olds will experience acne.
Acne has a significant impact on self-esteem; irrespective of severity, acne is associated with an increased risk of anxiety and depression and negatively affects quality of life.
Older research showed a Western diet high in fat, highly refined carbohydrates and dairy contributed to the development and exacerbation of acne. [1,4] Diets with a high glycemic index, have been associated with the development of acne.[5,6]
More recent research shows that acne patients have significant differences in the composition of the gut microbiome, with underrepresentation of major genera such as Bifidobacteria, Butyricicoccus, Coprobacillus, Lactobacillus, Allobaculum. A Western style diet, low in plant-based foods, high in fat and low in dietary fibre is likely to exacerbate an imbalanced microbiome. Studies of traditional populations which show acne is largely non-existent, support this observation.
In addition, dairy has been widely studied for its link with acne. A large systematic review and meta-analysis including 78,529 subjects showed the odds ratio for development of acne was 1.25 for subjects who included any dairy. 9] Yoghurt, cheese, low fat milk and full fat milk were all associated with an increased risk of acne, and the risk increased with increased dairy consumption.
The nutrition prescription
Following a whole food plant-based diet will help reduce acne via several mechanisms:
- A whole food plant-based diet has a naturally low glycaemic index and improves insulin sensitivity.
- Reducing dairy intake will reduce Insulin-like Growth Factor-1 (IGF-1) and therefore decrease sebum production.
- Polyphenols, found in high quantities in fruits and vegetables, have anti-inflammatory and anti-bacterial properties, and reduces the inflammation associated with acne.
- A whole food plant-based diet induces beneficial and anti-inflammatory changes in the gut microbiome, which reduces systemic inflammation and contribute to an improvement in acne.[11,12]
Ensuring a wide variety of plant foods are consumed each day including whole grains, fruits, vegetables, legumes will ensure that nutrient requirements are met and the overall dietary pattern has a low glycaemic index. Low fat intake in particular (especially saturated fat) appears to be important for those suffering acne and an abundance of fruits and vegetables provides fibre, antioxidants and polyphenols, all of which may help to improve the inflammatory response seen in acne.
Medical supervision of diet change is essential
Shifting to a low fat plant-based diet can lead to rapid reductions in medication needs. Patients with any existing conditions or disease history are advised to consult with a plant-supportive, qualified healthcare professional such as a GP or dietitian before undertaking diet change.
Video overview from NutritionFacts.org
Bifidobacterium and Lactobacillus have been shown to suppress cytokine function via generation of regulatory dendritic cells.  Butyricicoccus, produces butyrate, which, along with providing an energy source to the colonic epithelium, has antiinflammatory and protective effects on the mucosal barrier of the colon. 
It is postulated that the increased risk of acne with dairy consumption is linked to the insulinotropic effect of amino acids contained within milk, which has the downstream effect of increasing IGF-1 synthesis,  known to increase follicular keratinisation and follicular epithelial growth. 
Kucharska A, Szmurło A, Sińska B. Significance of diet in treated and untreated acne vulgaris. Adv Dermatol Allergol Dermatol Alergol. 2016;33(2):81-86. doi.org/10.5114/ada.2016.59146
Brown H, Tapley A, van Driel ML, et al. Acne in primary care: A cross-sectional analysis. Aust J Gen Pract. 2019;48(11):781-788. https://doi.org/10.31128/AJGP-02-19-4864
Yazici K, Baz K, Yazici AE, et al. Disease-specific quality of life is associated with anxiety and depression in patients with acne. J Eur Acad Dermatol Venereol. 2004;18(4):435-439. https://doi.org/10.1111/j.1468-3083.2004.00946.x
Melnik B. Dietary intervention in acne: Attenuation of increased mTORC1 signaling promoted by Western diet. Dermatoendocrinol. 2012;4(1):20-32. https://doi.org/10.4161/derm.19828
Pappas A. The relationship of diet and acne. Dermatoendocrinol. 2009;1(5):262-267. Accessed May 10, 2021. ncbi.nlm.nih.gov/pmc/articles/PMC2836431/
Burris J, Shikany JM, Rietkerk W, Woolf K. A Low Glycemic Index and Glycemic Load Diet Decreases Insulin-like Growth Factor-1 among Adults with Moderate and Severe Acne: A Short-Duration, 2-Week Randomized Controlled Trial. J Acad Nutr Diet. 2018;118(10):1874-1885. doi.org/10.1016/j.jand.2018.02.009
Yan H-M, Zhao H-J, Guo D-Y, Zhu P-Q, Zhang C-L, Jiang W. Gut microbiota alterations in moderate to severe acne vulgaris patients. J Dermatol. 2018;45(10):1166-1171. https://doi.org/10.1111/1346-8138.14586
Cordain L, Lindeberg S, Hurtado M, Hill K, Eaton SB, Brand-Miller J. Acne Vulgaris: A Disease of Western Civilization. Arch Dermatol. 2002;138(12). doi.org/10.1001/archderm.138.12.1584
Juhl CR, Bergholdt HKM, Miller IM, Jemec GBE, Kanters JK, Ellervik C. Dairy Intake and Acne Vulgaris: A Systematic Review and Meta-Analysis of 78,529 Children, Adolescents, and Young Adults. Nutrients. 2018;10(8):1049. doi.org/10.3390/nu10081049
Kahleova H, Tura A, Hill M, Holubkov R, Barnard ND. A Plant-Based Dietary Intervention Improves Beta-Cell Function and Insulin Resistance in Overweight Adults: A 16-Week Randomized Clinical Trial. Nutrients. 2018;10(2):189. doi.org/10.3390/nu10020189
Clark AK, Haas KN, Sivamani RK. Edible Plants and Their Influence on the Gut Microbiome and Acne. Int J Mol Sci. 2017;18(5):1070. doi.org/10.3390/ijms18051070
Polkowska-Pruszyńska B, Gerkowicz A, Krasowska D. The gut microbiome alterations in allergic and inflammatory skin diseases – an update. J Eur Acad Dermatol Venereol JEADV. 2020;34(3):455-464. doi.org/10.1111/jdv.15951
Melnik BC. Linking diet to acne metabolomics, inflammation, and comedogenesis: an update. Clin Cosmet Investig Dermatol. 2015;8:371-388. doi.org/10.2147/CCID.S69135
Kwon H-K, Lee C-G, So J-S, et al. Generation of regulatory dendritic cells and CD4+Foxp3+ T cells by probiotics administration suppresses immune disorders. Proc Natl Acad Sci. 2010;107(5):2159-2164. doi.org/10.1073/pnas.0904055107
Rich-Edwards JW, Ganmaa D, Pollak MN, et al. Milk consumption and the prepubertal somatotropic axis. Nutr J. 2007;6:28. doi.org/10.1186/1475-2891-6-28
Tasli L, Turgut S, Kacar N, et al. Insulin-like growth factor-I gene polymorphism in acne vulgaris. J Eur Acad Dermatol Venereol JEADV. 2013;27(2):254-257. doi.org/10.1111/j.1468-3083.2011.04299.x