We use these opportunities as chances to educate patients about “acne myths,”including the acne-food correlation. In the not-so-distant past, when discussing acne and dietary intake, we would tend to deny any specific connections between food and acne. But as we’ve read more on the subject, we’ve begun to question the validity of our own advice because we have reviewed the growing body of literature that argues in favor of a link between certain foods and acne.
An Issue of Importance “Again”Over the past several years, associations between particular food groups, specifically dairy products and acne, have again come under scrutiny. We say “again,” because despite the seemingly recent interest in a causal link between food and acne, this question is not a new one.
In fact, the first study linking acne with diet dates back to the mid-1960s, when Dr. Jerome Fisher, a dermatologist in private practice in Pasadena, CA, collected dietary histories on more than 1,000 of his acne patients. He compared the results of his dietary histories with those of more than 5,000 teenagers in New York City. Analysis of this data showed a 50% to 300% increase in milk consumption in acne patients in Pasadena over their non-acne suffering counterparts in New York. Further, limiting dairy intake in the Pasadena group led to amelioration of their acne.1
These data were never published but have resurfaced over the years. Most recently, we have seen consistent outcomes in the work of clinicians who have made similar observations of their acne patients and have found that their patients’ skin improved after they eliminated dairy products from their diets.
Examining the Theories
Several hypotheses have been offered to explain the connection between milk and acne.
The Nurses Health Study II (NHS II), an ongoing cohort study designed to assess the relationship between lifestyle factors and occurrence of diseases in women, bolsters the milk-acne theory by confirming an association between dairy consumption and acne.
In a retrospective analysis of data from the NHS II, Adebamowo, et al assessed the relationship between various foods and acne. More than 47,000 women, aged 25 to 42, responded to a questionnaire regarding their high school diet and presence of “physician-diagnosed severe teenage acne.”
The investigators found a positive association between acne and total milk (whole milk, powdered milk, lowfat milk and skim/non-fat milk) and skim milk consumption. Other dairy products found to be associated with acne included instant breakfast drinks, sherbet, cream cheese and cottage cheese. Interestingly, sweets, pizza and French fries, did not show a positive association with acne.2
Critics question the validity of this study for several reasons. First, the questionnaire relies on recollections of respondents’ high school eating habits, some 10 or more years later. Second, critics challenge the identification of acne sufferers based on patient recall, as well as the arguably ambiguous characterization of “physician-diagnosed severe teenage acne.” Finally, some find fault with the study for not controlling for potential confounding variables, like heredity, nationality and socioeconomic status.3
The Hormone Theory
Some physicians believe that the pathogenesis of acne, as related to cow’s milk, rests on the hormones present in dairy products. Support for this theory comes from studies of hormone content in milk from pregnant cows, which provide 75% to 90% of the U.S. supply.2 This milk contains increased levels of progesterone and other hormones.
Moreover, research has shown that the enzymes necessary to convert these hormones to dihydrotestosterone (DHT), the androgenic hormone thought to play a key role in acne pathogenesis, are present in sebaceous glands. Taken together, these observations indicate a potential connection between bovine hormones present in milk and the development of acne.4
Insulin-Like Growth Factor and Iodine TheoriesWhile some dismiss the milk-acne correlation entirely, others agree that although dairy may be the link, the hormones in milk are not the sole contributing factor. Researchers have delineated additional elements in milk and dairy products that may play a role in acne pathogenesis, including growth hormones, specifically insulin-like growth factor-1 (IGF-1) and iodine.
Multiple population studies of non-westernized civilizations, including the Kitavan, Ache, Okinawans prior to World War II, Inuits leading a traditional lifestyle, rural Brazilians, Bantu in South Africa, and Peruvian Indians, explain the possible IGF-1-acne connection.
These studies have demonstrated that the prevalence of acne is lower (and almost nonexistent) among rural, non-westernized people compared with fully modernized Western societies. Environmental factors may be at the root of these astonishing differences in acne prevalence. The processed, hyperinsulinemic foods typical of the Western diet, along with the high dairy intake, stimulate production of endogenous IGF-1. High IGF-1 increases levels of comedogenic androgens and promotes growth of all tissues, including the follicle. It is hypothesized that follicular stimulation by IGF-1 may lead to acne by increasing hyperkeratinization and epidermal hyperplasia. Moreover, some patients with adult acne have high serum IGF-1 levels in addition to elevated androgen levels.4,5
In addition to IGF-1, iodine in milk has been proposed as another potential factor in acne pathogenesis. Because iodine is known to exacerbate acne, some believe the high iodine content in milk to be the culprit comedogenic factor.
The iodine in milk is a result of iodine-fortified feed given to cows to prevent infection and iodine-based solutions used to sanitize cows’ udders and milking equipment. Milk intake, and subsequently high iodine intake, may worsen acne in those who are predisposed to the condition of acne.6
An Association Only Between Dairy Products and Acne
Despite the growing body of literature emphasizing the relationship between acne and dairy consumption, it must be noted that, although the evidence may seem solid, these studies show only an association between the two. There are no controlled trials demonstrating a causal link between milk and acne, which makes patient counseling somewhat difficult.7
For those patients and practitioners wishing to learn more about the putative milk-acne connection, there are several Web sites devoted to this topic. These Web sites explain the hypothesized associations and potential pathophysiology underlying the dairy-acne association. Many also contain dietary guidelines, which may be followed by acne sufferers wishing to implement a dairy-free lifestyle. Additionally, there are several diet books on the market that recommend a dairy-free diet as part of an anti-acne regimen.8
Although we have no experience with these diets in the management of acne, they may be appropriate for a certain subset of highly motivated acne patients who wish to pursue alternative treatment modalities and who are able to adhere to the sometimes-stringent requirements.
Which Patients Would Benefit Most from Avoiding Dairy Products?The patients most likely to benefit from such diets, in our estimation, are those suffering from polycystic ovary syndrome, the metabolic syndrome or other states of hormonal imbalance that may contribute to their acne. In these patients, trial of a dairy-free diet may provide a potential adjunctive treatment, although we would caution against using diet as monotherapy, given the number of excellent medical treatments available on the market today. Also, calcium must be supplemented if dairy is eliminated.
The issue of diet and acne no longer seems as clear-cut as we were first taught. While it is evident that more work needs to be done on this topic, it is difficult to ignore the evidence laying claim to milk’s potential role in acne.
In counseling our patients, we have recently begun to move away from denying any food-acne linkage. Instead, we suggest they come to their own conclusions on this topic, based on their personal experience, and advise avoidance of whatever specific trigger foods a particular patient may have found to induce his or her acne flares. Finally, we should always caution against any extreme diets or dietary practices.