Why does acne run in the family?A 2013 study puts the cost of acne treatment in the US alone at over $3 billion /year.[ref] About 80-95% of teens deal with acne, and over 40% of adults in their 20s are still struggling with it.[ref] Moderate to severe acne affects 20% of teens. Researchers estimate that acne is about 80% heritable, so there is a strong genetic link to the susceptibility to acne.[ref] There is no single gene that causes acne. Rather, there are multiple genetic variants (small changes in a gene) that increase the risk of acne -- when combined with the right environmental factors. There have been quite a few studies digging into the genetic variants that may increase the susceptibility to acne. These genetic studies tell us a lot about the root causes of acne, and they also point towards several solutions. The genetics research (details in the genetics section below) shows that there are four genetic factors that can be involved:
- inflammatory genes
- dairy (lactose) genetic variants
- hair follicle growth genes
- vitamin A conversion
What are the causes of acne?There are four factors that you need for acne:
- bacteria, specifically Propionibacterium acnes (P. acnes),
- plugged pore, known as "infundibular hyperkeratinization of the pilosebaceous unit"
- excess sebum, an oily/waxy substance produced by sebaceous glands
Can diet affect acne?I've always 'known' teens get acne due to their poor diet, but it turns out, the diet may not be as big a factor as I thought. (A lot of things that I've always 'known' turn out not to be backed by a lot of science!) The studies on dietary factors causing acne are not all that convincing when it comes to solid results. Many studies are inconclusive or contradictory.[ref] Here are a couple of dietary links with acne that seem to be backed by several studies: According to a meta-analysis, dairy intake increases the risk of acne by about 25-40%, depending on the frequency of dairy consumption.[ref] So why would dairy matter? One theory is it upregulates mTOR and IGF-1 due to its amino acid composition.[ref] But... not all studies on dairy and acne agree. This may be due to population differences and whether as adolescents/adults they are likely to still produce lactase (the enzyme that breaks down lactose in milk). A Danish study (with 93% of participants producing lactase as adults) found dairy consumption decreased acne only in people who still produced lactase.[ref] In general, people of Asian descent are much less likely to produce lactase as an adult. So the meta-analysis results on dairy may be more accurate in populations that tend to not produce lactase. The majority (over 90% usually) of people of Northern European heritage still produce lactase. Other population groups vary between those two extremes.
Related article: Lactose Intolerance Genes
Does sugar make acne worse?Everyone knows that sugar is the devil... Instead of being able to directly point a finger at sugar, it seems insulin resistance may be a problem with acne. In a study comparing teens with acne and without, their fasting blood glucose levels were actually very similar. Interestingly, though, insulin levels were higher in the group of teens with acne compared to those without.[ref] Thus a diet with a high glycemic load (whether sugar or other highly processed foods) may play a role in acne. An individual's response to sugar and starch may be important -- e.g. two people can eat the same diet and have a different glycemic response. Not getting enough vitamin A in your diet could also increase the risk of acne. A new study shows that vitamin A is important in the skin's defense against pathogens, such as P. acnes.[ref] Vitamin A derivatives, known as retinols, are often used topically for acne.[ref]
Related Article: BCO1 Gene: Converting Beta-Carotene to Vitamin A
Is acne caused by inflammation?A recent study used biopsies of acne skin to see which genes were upregulated, or turned on, more than normal. Most of the upregulated genes were in the inflammatory pathways.[ref]
The genetics of acne risk:
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