Glycemic Control Improves Acne

Acne (a.k.a. pimples, spots, or zits) has been the scourge of adolescence since time immemorial, affecting as many as 85% of teenagers at one time or another. As far back as ancient Egypt, history records several pharaohs who were afflicted with acne. The word itself derives from the ancient Greek word for “point” or “peak” — apparently a corruption of the word “acme.” Treatments for acne have ranged from the ancient Roman solution of hot, sulfurous baths to laxatives for “chastity pimples,” to the more recent introduction of antibiotics and other drugs, such as tretinoin (Retin A®) and isotretinoin (Accutane®), and laser and blue/red light therapy. Unfortunately, these drugs carry high risks of birth defects, depression, and psychosis. However, the ultimate tragedy for many teenagers and young adults is that they may carry the scars of acne inflammation and festering for the rest of their lives.

While diet has long been implicated in the etiology — and consequently in the treatment — of acne, there has been no consensus on the nature or even the reality on its precise role. At one time or other, foods high in sugar or grease, foods such as milk, nuts, chocolate, seafood, French fries, and potato chips, among others have been implicated as causes, not to mention hygiene, bacteria, and sex, especially the solitary variety. To some extent these are all true (well, maybe not the sex), but the data have been sparse and often conflicting.

Why Is the Glycemic Control So Important?

New evidence from Australian researchers shows for the first time that a key dietary factor related to acne is glycemic control, ie, selecting the carbohydrates we eat based on their glycemic index (GI). GI is a ranking system based on carbohydrates’ effect on blood glucose levels and consequently, on blood insulin levels. A low-GI characterizes carbohydrates that break down slowly during digestion, so that glucose enters the blood stream slowly and gradually. These foods include complex carbs, such as lentils, fruit, vegetables (but not root vegetables, eg, potatoes, beets), oats, buckwheat, whole barley, bran, and others.

High-GI carbs (simple carbohydrates), such as sugar (sucrose), sodas and other drinks sweetened with high fructose corn syrup or other caloric sweeteners, corn products, white potatoes, white rice, foods made with processed white flour, and sweetened “junk foods” of all kinds — break down rapidly, causing a rush of glucose into the blood stream.

The lower, slower glycemic response of low-GI foods triggers a smaller insulin demand, better long-term blood glucose control, and a reduction in blood lipids (eg, cholesterol, triglycerides). By contrast, high-GI foods trigger large, long-lasting insulin “spikes,” which can lead to insulin resistance (decreased insulin sensitivity), type 2 diabetes, and cardiovascular disease. Thus, the GI index provides a direct measure of the body’s insulin response to a given food.

Researchers have known about the importance of GI for years, but there has been little consensus on their value. However, just last month, a major meta-analysis published by the Cochrane Library, the “gold standard” of such studies, found that low-GI diets are substantially better than high-GI diets.1 Diets with an overall low-GI (low glycemic load, or low GL) were found to reduce body weight and body mass index (BMI). In addition, low-GI diets lowered total cholesterol and LDL cholesterol, important independent risk factors for cardiovascular disease.

Other very recent research has also shown a link between dietary glycemic index and age-related macular degeneration, a major cause of blindness in the elderly.2

This new Australian study — the first ever randomized, controlled study of its kind — confirms that a diet comprised largely of low-GL foods not only significantly reduces body weight and BMI, while improving insulin sensitivity — but it also significantly reduces the occurrence of acne lesions.(3

The Australian researchers recruited 43 males, aged 15 to 25 years, with mild-to-moderate acne. The men were assigned to either a low-GL diet (25% energy from protein, 45% from low-GI carbs, and 30% from fats) or to a “normal” high-GL diet. The study lasted 12 weeks.

As shown in Figure 1, inflammatory acne lesions decreased in both treatment groups, but at 12 weeks, the decrease in the low-GL diet group was significantly greater than that in the high-GL diet control group. The mean number of inflammatory lesions fell by 17.0 (45%) in the low-GL group vs. just 7.4 (23%) in the high-GL group.

In addition, the men in the low-GL diet group lost significantly more weight than those in the control group (-2.9 kg vs. +0.5 kg, respectively) and BMI ( 0.92 kg/m2 vs. +0.01 kg/m2, respectively). Insulin resistance in the low-GL diet group also declined significantly compared to control by one measure (HOMA-IR) but just missed significance according to another measure (OGIS).

How Does High Glycemic Load Cause Acne?

Research indicates that high-glycemic load diets probably increase the risk of acne outbreaks by increasing insulin demand and other factors associated with insulin resistance, including hyperphagia (overeating), elevated nonesterified fatty acid levels, and obesity. As insulin resistance rises, the body’s cells demand more insulin, which the pancreas supplies (if it can). The resulting hyperinsulinemia (high insulin levels in the blood) in turn increases the production of androgens (testosterone and DHEAS) and decreases a polypeptide protein hormone similar in molecular structure to insulin for insulin growth factor-1 (IGF-1). IGF-1 plays an important role in childhood growth and continues to have anabolic (tissue building) effects in adults.

The sum total of these events may influence one or more of the major underlying causes of acne: 1) increased proliferation of basal keratinocytes within the pilosebaceous ducts surrounding hair follicles; 2) abnormal desquamation of follicular corneocytes; 3) androgen-mediated increases in sebum production; and 4) colonization and inflammation of the comedo (the acne lesion, consisting of a plug of keratin and sebum within the dilated orifice of a hair follicle) by the bacteria Propionibacterium acnes.

Although the Australian researchers could not entirely eliminate the possibility that weight loss due to the low-GL diet might have contributed to the decline in acne lesions, the direct relationship between hyperinsulinemia and acne is supported by other studies. Even though further research is needed to clarify this ambiguity, it seems very likely that food’s glycemic index will turn out to be a major factor in the etiology and treatment of this age-old curse of teens and young adults. The importance of low-GI diets and the glycemic control that it engenders now appears to be a cardinal health value for people of all ages.

Why Acne?

The most common form of acne is known as acne vulgaris, which translates as common acne, although those with a serious case might have a different idea about that designation. Acne is defined as an inflammatory disease of the skin that results from changes in the pilosebaceous units (skin structures consisting of a hair follicle and its associated sebaceous gland).

Acne occurs when otherwise normal hair follicles become blocked. Hyperkeratinization and the consequent formation of a plug of keratin and sebum is the earliest change. Increased androgen production at puberty contributes to the enlargement of sebaceous glands and to an increase in sebum production, which promotes the overgrowth of P. acnes, which leads to the characteristic inflammation of acne lesions. The presence of large amounts of androgen accounts for the prevalence of acne during the teenage years; the role of bacteria explains why antibiotics can sometimes be helpful in treating acne. The tragedy is that many individuals wear the scars of acne lesions for the rest of their lives. This new research suggests that a simple alteration in diet may help avoid that tragedy.


  1. Thomas DE, Elliott EJ, Baur L. Low glycaemic index or low glycaemic load diets for overweight and obesity. Cochrane Database of Systematic Reviews 2007, Issue 3. Art. No. CD005105.
  2. Chiu CJ, Milton RC, Gensler G, Taylor A. Association between dietary glycemic index and age-related macular degeneration in nondiabetic participants in the Age-Related Eye Disease Study. Am J Clin Nutr. 2007;86:180-188.
  3. Smith RN, Mann NJ, Braue A, Makelainen H, Varigos GA. A low-glycemic-load diet improves symptoms in acne vulgaris patients: a randomized controlled trial. Am J Clin Nutr. 2007;86:107-115.

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