European Journal of Nutrition & Food Safety

Background: Acne vulgaris, a skin condition prevalent among teenagers and young adults, can be physically and psychologically detrimental to the sufferer’s quality of life [1]. A common perception is that diet can cause or worsen acne symptoms [2]. In recent years there has been an emergence of studies looking at links between diet and acne symptoms, the primary focus of which has been dairy products and glycaemic load. Despite this, there are currently no dietary guidelines or recommendations surrounding treatment for acne. The aim of this study was to review the available evidence from both observational studies and controlled trials to determine the effect of dairy products and glycaemic load on acne vulgaris. It is the first systematic-type review since 2005 to consider the influence of dairy foods and glycaemic load on acne and/ or the quality of the studies in this area.
Methods: Search terms “Acne AND (Carbohydrat* or sugar or glycemic or glycaemic or Glucose or dairy or milk or lactose or diet*) were entered into seven databases, including Medline and Science Direct. Abstracts of papers published between January 2005 and January 2013 were screened for suitability by two researchers. Comprehensive inclusion and exclusion criteria, robust quality assessment criteria and associated quality ratings (2= all or most criteria, 1= some criteria, 0=no criteria met) were applied (Centre for Reviews and Dissemination 2009). 
Results: 10 studies among adolescents and young adults, scoring 2 or 1 in the quality assessment, were identified and included in the review. Six studies, including two prospective cohort studies, three case controls and one cross sectional study examined dairy products and acne. Of these five found statistically significant independent positive associations i.e. increased consumption of dairy products was associated with greater risk of acne. Overall, the effect sizes for these associations (prevalence ratios and odds ratios), where stated were modest ranging from 1.17-1.78 (p<0.05), but particularly evident for skimmed milk. Three studies reported the association between glycaemic load and prevalence of acne. Two case control studies showed significantly higher dietary glycaemic load among acne cases compared to controls (p<0.05). One prospective cohort study showed no significant association between glycaemic load and development of acne. Treatment of acne vulgaris with low glycaemic load diets was explored in three controlled trials. Two showed improvement in acne symptoms with a low glycaemic load diet over periods of 10 and 12 weeks, respectively. The third trial reported improvements in acne associated with both low and high glycaemic load diets but with no baseline dietary data with which to assess change in the glycaemic load of diets since the start of the intervention, was methodologically flawed. 
Discussion: Our review supports previous findings that a diet lowers in both dairy products and glycaemic load may help prevent or improve acne. The studies included in the review had a number of strengths with large sample sizes and validated measurement tools, but also methodological weaknesses in some studies, such as poor assessment of diet or acne, and unknown causal direction of associations in the cross-sectional study. High-quality randomised-controlled trials of the effect of both dairy foods and glycaemic load on acne vulgaris are required to make the evidence base more robust before dietary recommendations can be proposed.
Conclusion: The message that a healthy, balanced diet, lower in glycaemic load may prevent or improve acne vulgaris in adolescents and young adults could help to improve the diets of teenagers. When considering restriction of dairy foods, however, calcium intake needs to be closely monitored and advice regarding this in relation to treatment of acne vulgaris should only be given by qualified practitioners.