February 2019 Issue
The Diet-Acne Connection
By Densie Webb, PhD, RD
Vol. 21, No. 2, P. 38
An Overview of the Latest Research and Tips for Counseling Patients
Acne is a scourge for as many as 50 million Americans, including 90% of adolescents and young adults.1 While it's often viewed as a minor ailment of adolescence, it can have serious psychosocial effects during a critical period of development. But acne isn't limited to teenagers; some middle-aged adults are forced to deal with breakouts right along with developing wrinkles.
Countless creams, face washes, pills, supplements, and prescription medications are designed to both prevent breakouts and deal with them once they occur. Their efficacy varies greatly, depending on the treatment or combination of treatments and the severity of the acne.
Cost can be a major factor in choosing a treatment; the price of brand-name acne medications increased 195% between 2009 and 2015.2 Accutane, with an 80% success rate, is the most effective treatment for acne. However, even with the generic alternatives to Accutane that recently became available, it can be quite expensive over the typical four- or five-month course of treatment. With regular visits to the doctor and regular blood tests, which are required because of Accutane's possible side effects, the price can reach several thousands of dollars, depending on a patient's insurance coverage.
However, recent research suggests that a diet-acne connection, which has been both revered and relegated to myth over the years, may be a possible cause and a potent acne treatment. In fact, studies suggest that simple dietary changes may help reduce the frequency and severity of acne breakouts.
But it may not be the changes you think.
Today's Dietitian attended a session on diet and acne at the Food & Nutrition Conference & Expo™ in October 2018, presented by Jennifer Burris, PhD, RD, CNSC, CSSD, CDE, CSG, from California State University, Los Angeles. She has studied the subject extensively and has published several papers on the topic. Much of this article is based on that presentation.
What Causes Acne?
Acne is the result of several factors—excess sebum (oil) production from the sebaceous glands, follicular occlusion (plugged hair follicles) caused by overproduction of follicular cells, and hormonal fluctuations. All together, they create the perfect environment for the growth of Propionibacterium acnes bacteria. Overgrowth of the bacteria triggers an immune response resulting in inflammation, which, if left unchecked, eventually can cause scarring.
Androgen hormones and insulinlike growth factor-1 (IGF-1) influence sebum production, contributing to the development of acne. In addition, insulin, endogenous proteins, and inflammatory mediators produced by the body also may play roles. Diet influences these factors, providing the link between diet and acne. But heredity has been shown to be the major risk factor for developing acne.3
The Dietary Link
In the late 19th and early 20th centuries, dermatology textbooks often recommended dietary changes as part of standard treatment for acne. Studies had suggested that chocolate, dairy, sugar, fat, and sodium were possible contributors to inflammation and breakouts. The belief in a diet-acne connection was later discounted as a result of studies in the late 1960s and early 1970s and, after that, dietary changes were seldom recommended as a part of medical therapy for acne.4 However, another reversal of opinion has taken place, based on studies showing that diet influences the endocrine and immune responses in such a way that can affect the development of acne.
Today, the following four diet-acne hypotheses are either being researched or discussed:
• dietary glycemic index/glycemic load (GI/GL);
• dairy and/or milk;
• omega-3 fatty acids; and
Of the four diet-acne hypotheses studied, the GI/GL theory has the most research behind it; much of it is quite recent, though it's mostly observational rather than clinical. GI ranks the potential of carbohydrate-containing foods to raise blood glucose and insulin concentrations. GL takes portion size and type of carbohydrate into consideration. Foods with a high GI are rapidly digested and absorbed, resulting in hyperglycemia and reactive hyperinsulinemia.4 Foods with a low GI elicit a more gradual response.
In her presentation, Burris suggested that diet-induced hyperinsulinemia and increased IGF-1 concentrations may aggravate acne. "Hyperinsulinemia and IGF-1 are viewed as the pivotal drivers in the diet-acne hypothesis," she said.
Observational research backs up the hypothesis. A cross-sectional study of 64 adults with no, moderate, or severe acne were instructed to fill out a five-day food record. Blood was drawn to measure factors associated with acne, including glucose, insulin, and IGF-1.
While participants with moderate or severe acne consumed more total carbohydrate and had greater insulin and IGF-1 and greater insulin resistance, there was no significant difference in acne between the groups, despite the fact that 61% of participants self-reported that their diet influenced acne breakouts.5
A 2007 study, which compared the effects of a low-GL diet with a high-GL diet on acne in males aged 15 to 25, found that those on the low-GL diet lost weight and experienced reduced free androgen, increased insulinlike growth factor binding protein (which would result in reduced levels of IGF-1), and an improvement in insulin sensitivity compared with those on the high-GL diet.6 However, the authors pointed out that after adjusting for BMI, the association between a low-GL diet, insulin resistance, and acne lesions was no longer significant. This suggests that a reduction in hyperinsulinemia, whether by weight loss or diet, may reduce factors associated with the development of acne. It doesn't mean that weight loss, per se, can reduce acne.
In a more recent randomized controlled trial of 66 adults with moderate to severe acne, a two-week low-GI and low-GL diet significantly reduced IGF-1 concentration, an established factor in the development of acne. Researchers provided participants with diet counseling and some low-GI staple foods. Burris and coauthors suggested that diet might affect acne by influencing some endocrine pathways.7
A recent pilot study found that women who had mild to moderate acne and were given supplements of 100 mg fructooligosaccharides and 500 mg galactooligosaccharides per day experienced positive effects on glycemic levels, possibly as a result of changes in the microbiome.8 In theory, based on previous findings, improvements in glycemic control may translate to improvements in acne. The researchers pointed out that the study was uncontrolled and small, and that further research is needed.
However, not all studies have found a low-GL diet to be beneficial. A recent study compared the efficacy of a low-GL diet plus a topical benzoyl peroxide gel (a commonly prescribed topical preparation for acne) with the topical gel alone and found no significant improvement in the group following the low-GL diet while using the gel.9
The role of milk in acne development is controversial. However, according to Burris, the number of studies investigating the relationship between milk and acne has substantially increased, but most have been observational rather than clinical.
A retrospective study by Harvard researchers asked 47,355 women to recall their high-school diets and whether they had physician-diagnosed acne. Women who reported consuming at least two glasses of nonfat milk per day during their teenage years had a 44% increased risk of acne as an adolescent. A smaller increased risk also was reported for total milk intake.10
A second study by the same research group, this time a prospective study, evaluated dietary intakes of 6,094 girls aged 9 to 15 using food frequency questionnaires, and found that consuming two or more servings of milk per day (total, whole milk, low-fat milk, and skim milk) was associated with acne.11
A third study from the research group evaluated the association between milk consumption and acne among 4,273 boys aged 9 to 15. A positive association was found between consuming at least two cups of skim milk per day and acne.1
In all three studies, the researchers suggested that milk contains hormonal constituents or factors that can influence endogenous hormones and, in turn, can affect the development or aggravation of acne. However, the studies were all based on self-reported dietary intake and self-reported acne. The retrospective study required that adults recall dietary habits from decades earlier, and the validity of this study in particular has been called into doubt.
Three meta-analyses published in 2018 further examined the relationship between dairy and/or milk and acne. One analysis of 13 studies found that study participants who consumed milk had a 16% increased risk of acne compared with those who didn't drink milk.12 Moderate to severe acne was associated with milk consumption, while no significant association was found between mild acne and milk consumption. As in earlier studies, a stronger association was found among participants who drank skim milk compared with low-fat or full-fat milk. According to Burris, it's unknown why the association between milk and acne appears to be stronger for nonfat compared with full-fat milk. But results have been inconsistent, with some showing total milk intake is associated with acne.
Another meta-analysis of 14 studies that included children, adolescents, and adults ranging in age from 7 to 30 found a 41% increased risk of acne with consumption of one glass of milk (any kind) per day.13 In this study, yogurt and cheese also were associated with increased risk. The researchers said that due to the lack of consistency across the studies included in the meta-analysis, the findings should be interpreted with caution.
In another meta-analysis of observational studies, researchers found no association between yogurt and cheese consumption and acne, but total milk, whole milk, low-fat milk, and skim milk consumption was positively associated with acne.14
While these observational studies suggest that dairy and/or milk consumption may initiate or aggravate acne, there are no randomized controlled trials to verify the link.
Omega-3 Fatty Acids
"Limited research has examined the relationship between omega-3 fatty acid supplements or fish and acne, and there have been conflicting results, with some research indicating a protective effect and others showing no association," Burris said.15-18 Assessing the findings has been especially difficult; the studies haven't reported the type of fish consumed. Some of the dietary questionnaires weren't validated, and the length of the studies and supplement doses varied.
While this is probably the most often-cited diet-acne link, the evidence for any association is weak. The studies behind the origin of this claim date back to the 1960s and '70s. However, according to Burris, the studies were poorly designed, controlled, and analyzed, and no recent studies have been conducted.
In evaluating the evidence, some research suggests a diet-acne link, but most studies have been observational and have relied on self-reported dietary intake and acne occurrence. The dietary links that appear to offer the most promise are GI/GL diets and milk/dairy intake, but all of these studies have limitations and caveats. While experts agree that the findings for diet and acne are far from conclusive, opinions differ on how to apply the findings.
"It may be a bit premature to counsel patients on lowering dietary GI/GL as a means of influencing acne development/severity, but the results of the most recent study suggest that this is certainly a promising area of research," says James M. Shikany, DrPH, PA-C, a professor of medicine in the division of preventive medicine at the University of Alabama at Birmingham. Nevertheless, Burris sounded slightly more positive when she suggested that dietary counseling may be appropriate for some patients with acne.
When counseling clients and patients with acne, dietitians shouldn't ignore that a low-GI/GL diet can provide a long list of other proven health benefits, such as weight loss, improved insulin resistance, and lower lipid levels. Research does suggest that diet may offer an alternative approach to preventing and treating acne for some people, but it's also important to remember that heredity is always going to be the strongest risk factor for this irksome skin condition.
— Densie Webb, PhD, RD, is a freelance writer, editor, and industry consultant based in Austin, Texas.
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