July 27, 2007 — A low-glycemic-load diet reduced acne lesions in male patients aged 15 to 25 years, according to the results of a randomized controlled trial study published in the July issue of the American Journal of Clinical Nutrition.

"Although the pathogenesis of acne is currently unknown, recent epidemiologic studies of non-Westernized populations suggest that dietary factors, including the glycemic load, may be involved," write Robyn N. Smith, MD, from RMIT University in Melbourne, Australia, and colleagues. "Recently, there has been a reappraisal of the diet and acne connection because of a greater understanding of how diet may affect endocrine factors involved in acne.... Hyperinsulinemia has been implicated in acne pathophysiology because of its association with increased androgen bioavailability and free concentrations of insulin-like growth factor I (IGF-I)."

In this 12-week, parallel design, investigator-blinded study, 43 male acne patients aged 15 to 25 years were randomized to receive a low-glycemic-load diet (25% energy from protein and 45% from low-glycemic-index carbohydrates) or a control diet rich in carbohydrate-dense foods without consideration of the glycemic index. Outcome measures included monthly dermatologic evaluation of acne lesion counts and severity. Using the homeostasis model assessment, insulin sensitivity was determined at baseline and at 12 weeks.

Mean reduction in total acne lesion counts at 12 weeks was -23.5 ± 177; 3.9 in the low-glycemic-load group and -12.0 ± 177; 3.5 in the control group ( P = .03). Compared with the control diet, the low-glycemic-load diet was also associated with a greater decrease in weight (-2.9 ± 0.8 vs +0.5 ± 0.3 kg; P < .001) and body mass index (-0.92 ± 0.25 vs +0.01 ± 0.11 kg/m ²; P < .001) and a greater improvement in insulin sensitivity (-0.22 ± 0.12 vs +0.47 ± 0.31; P = .026).

Study limitations include the possibility that topical application of a mild skin cleanser may have contributed to acne improvement; inability to rule out the effect of other dietary factors, such as zinc and vitamin A intake, on acne improvement; and reliance on self reporting of dietary intakes.

"The improvement in acne and insulin sensitivity after a low-glycemic-load diet suggests that nutrition-related lifestyle factors may play a role in the pathogenesis of acne," the authors write. "However, further studies are needed to isolate the independent effects of weight loss and dietary intervention and to further elucidate the underlying pathophysiologic mechanisms."

Meat and Livestock Australia supported this study.

Am J Clin Nutr. 2007;86:107-115.

Clinical Context

Study Highlights

• In this randomized trial, 43 male patients with mild-to-moderate acne aged 15 to 25 years were recruited for a 12-week, parallel design, dietary intervention to either low-glycemic-load or the control group.
• The experimental treatment was a low-glycemic-load diet composed of 25% energy from protein and 45% energy from low-glycemic-index carbohydrates.
• In contrast, the control group received carbohydrate-dense foods without reference to the glycemic index.
• A washout period of 6 months was required for subjects who had previously taken oral retinoids or 2 months for subjects who had taken oral antibiotics or topical antibacterial or retinoid agents.
• Topical therapy, in the form of a noncomedogenic cleanser, was standardized for both groups.
• Acne lesion counts and severity were assessed during monthly visits, and insulin sensitivity (using the homeostasis model assessment) was measured at baseline and at 12 weeks.
• Results demonstrated that at 12 weeks, mean total lesion counts had decreased more (P = .03) in the low-glycemic-load group (-23.5 ± 3.9) than in the control group (-12.0 ± 3.5).
• Inflammatory lesion counts fell by 17.0 (45%) in the low-glycemic-load group and by 7.4 (23%) in the control group (P = .02).
• The experimental diet also resulted in a greater reduction in weight (-2.9 ± 0.8 vs 0.5 ± 0.3 kg; P < .001) and body mass index (-0.92 ± 0.25 vs 0.01 ± 0.11 kg/m²; P = .001) and a greater improvement in insulin sensitivity (-0.22 ± 0.12 vs 0.47 ± 0.31; P = .026) than did the control diet.
• Limitations of the study include a possible direct effect from the skin cleanser used by all of the participants; other dietary factors (eg, zinc and vitamin A intake) may have confounded the relation between diet and acne improvement; and self-reporting of dietary intakes may lead to measurement error.

Pearls for Practice

• In Western populations, acne is most prevalent in adolescents; however, individuals older than 25 years and men and women of middle age are still affected.
• After 12 weeks, the low-glycemic-load diet was demonstrated to significantly reduce acne lesion counts and improve insulin sensitivity when compared with a high-glycemic-load diet.

CME Test