Is acne related to our diet?
One of the most frequently asked questions by acne patients has to do with the dietary restrictions they should follow. Some patients claim that by avoiding specific foods such as pizza, chocolate, french fries and fats in general, they noticed an improvement in their clinical picture, while others applying the same restrictions to their diet saw no difference at all. Therefore finally acne and diet are related or is this a myth?
Recently when we discussed acne and diet we denied any correlation. But as we learned more about the subject we began to question this theory. In fact the first study linking acne to diet dates back to the mid 1960's. Dr Jerome Fisher collected the dietary history of a sample of 1000 acne patients and compared it to a sample of 5000 teenage New Yorkers who did not have acne. The results showed that acne patients had an increased consumption of milk. Following the reduction in dairy intake, their acne improved. This evidence was never published, but surfaced in recent years.
1. Nurse Health Study II
The Nurse Health Study II (NHS II) is conducting a study to assess the relationship between lifestyle and the occurrence of acne in women. This study reinforces the theory of the association between the consumption of dairy products and acne.
These researchers demonstrated a positive correlation between acne and milk (whole milk, powdered milk, low-fat milk, skim milk), as well as milk derivatives such as cream cheese, cottage cheese. Interestingly, sweets, pizza or French fries have no association with acne.
Critics of this particular study have many reasons to question it. First, the questionnaire is based on answers given by the respondents about the eating habits they had at school, that is, more than 10 years ago. Second, critics of the study question the recall of acne sufferers, as well as the ambiguous designation of "medically diagnosed severe adolescent acne." Finally, some find fault with the study that it doesn't account for potential factors linked to acne such as heredity, ethnicity, and socioeconomic factors.
2. The hormonal theory
Some argue that the pathogenesis of acne in relation to cow's milk is based on the hormones that dairy products carry. This hypothesis is based on studies conducted on the hormone-containing milk of pregnant cows, which constitutes 75-90% of the milk supplied in the United States.
This milk contains increased levels of progesterone and other hormones. In addition, research has shown that the enzymes necessary to convert these hormones into 2-hydrotestosterone, the androgenic hormone, are thought to play a key role in the pathogenesis of acne, as they are located in the sebaceous glands. The above observations show the possible connection of the hormones present in cow's milk with the development of acne.
3. Insulin-dependent growth factor and iodine
While some have completely dismissed the acne and milk association, others agree that while dairy products may be the link, milk hormones are not the only factor contributing to the development of acne. Researchers have delineated additional evidence that milk and milk products may play a role in the pathogenesis of acne, particularly growth hormones such as insulin-dependent growth factor I (IGF-1) and iodine.
Multiple epidemiological studies in non-Western populations, rural Brazil, the Bantu in South Africa, the Indians of Peru, can explain the possible relationship between the hormone IGF-1 and acne. These studies argue that the prevalence of acne is lower (almost non-existent) among rural, non-Westernized societies than in Western societies. Environmental factors may be at the root of this surprising difference in acne prevalence. Processed, hyperinsulinemic foods, typical of the Western diet, combined with a high intake of dairy products, stimulate the production of endogenous IGF-1. High levels of IGF-1 increase androgen hormone levels and promote the growth of all tissues, including the ovary. It is hypothesized that follicular stimulation by IGF-1 hormone may lead to acne by increasing hyperkeratinization and epidermal hyperplasia.
Additionally, some adult acne patients have high levels of IGF-1 combined with elevated androgen levels. In addition to IGF-1, iodine in milk has been suggested as another possible factor in the pathogenesis of acne. Because iodine is known to worsen acne, milk's high iodine content is blamed for acne blackheads. The presence of iodine in milk is a result of iodine-enriched feed given to cattle to prevent infections. Thus, milk intake, and consequent high iodine intake, may worsen acne in predisposed individuals.
Despite the growing body of literature emphasizing the relationship between acne and dairy consumption, it should be noted that although the evidence seems strong, studies only demonstrate a link between the two. There are no peer-reviewed studies proving a causal link between milk and acne. Thus, counseling the patient on the subject becomes particularly difficult.