Many causative dietary factors have been studied for their role in acne. These include glycemic index, dairy consumption, high and low carbohydrate diets, gluten free diets, high protein diets, candida elimination diets, probiotics, multivitamins, chocolate and more. Currently, the greatest body of evidence in the study of acne and diet exists for the role of low glycemic index diets.
Glycemic index (GI) is a scale that measures the rise in blood sugar as triggered by any particularly carbohydrate as found in various foods and drinks. Researchers have further refined the glycemic index as the glycemic load (GL), which takes into account the changes in blood sugar with a typical serving of a given food. A food that raises blood sugar quickly is a high glycemic index food. A food that raises blood sugar slowly is a low glycemic index food. Low GI foods include green vegetables, fruits, raw carrots, beans, lentils, and bran cereals. Medium GI foods include corn, bananas, raisins, oatmeal, and multigrain bread. High GI foods include rice, white bread, and potatoes.
With respect to acne, and particularly hormonal acne, there are many studies that have established a connection between glycemic index and severity of acne. High GI/GL diets lead to elevated levels of insulin, which is secreted by the body in response to sugar in the blood. This release of insulin also leads to increased levels of insulin like growth factor (IGF-1). These molecules have been shown to increase oil production and increase shedding of skin cells, which leads to plugging of the oil glands. They also increase the production of acne-causing hormones and their receptors, leading to increased hormonal activation of acne. In clinical studies, it has been shown that patients on a low GI/GL diet have lower levels of acne causing hormones, lower levels of oil production, and less clinically apparent acne. Further studies have shown that many patients on low GI/GL diets are able to reduce their usage of oral and topical acne medications as well. Specific diets such as the south beach diet and Mediterranean diet, both of which utilize low GI/GL principles, have also been examined and patients on these diets have had reduced acne.
Milk consumption has also been linked to acne pathogenesis. Similar to carbohydrates in other foods, carbohydrates in milk elevate insulin and IGF-1, which increases acne formation through increased oil production, inflammation of the follicle and increased acne hormones. Additionally, milk contains bovine IGF-1, which is identical to human IGF-1 and acts in a similar fashion. Milk also contains several hormonal triggers of acne as well. Clinical studies have supported this connection, with two large studies showing that all types of milk cause acne, and one study showing that only skim milk causes acne. Importantly, whey protein in milk and in supplements have recently been shown to contribute to acne as well.
Lastly, there have also been small studies that suggest a role for certain vitamin and supplements in the treatment of acne. In one small study, intake of omega 3 fatty acids resulted in acne improvement. In another study, the use of probiotics along with routine antibiotic treatment for acne resulted in lower acne lesion counts. Zinc, vitamin A, and vitamin D have also been studied, but the role of these vitamins in acne remains unclear. Nicotinamide, a derivative of vitamin B3, has also been used as a supplement to improve acne, and there are several studies that support its use, though the studies are small and mainly observational. There is an FDA approved combination of nicotinamide that contains folic acid, zinc, and copper and is purported to improve acne. However, caution must be taken with these supplements, as there have also been side effects reported with high dose supplementation.
At this time, the role of diet and acne continues to be elucidated, with increasing interest in specific dietary changes that can be made to reduce acne and the need for topical and oral medications. Further research remains to be done on specific subsets of acne, such as hormonal acne in adult women, and the role of diet on the microbiome and acne is an active area of study. The greatest body of evidence exists for low glycemic index/glycemic load diets and some evidence exists for low dairy diets. Both interventions can be considered as an integral part of an approach to acne treatment. While dietary changes may not treat all types of acne or may not be sufficient to treat moderate to severe acne, further research is likely to reveal causative factors that can be implemented for integrative long term acne management. An experienced dermatologist can assess the severity of acne and tailor an approach that combines oral and topical therapies along with diet and lifestyle management.