Prevalence of acne vulgaris has increased in parallel to the industrialization of the food system and with greater availability of processed foods, in particular dairy. Multiple meta-analyses have shown the statistical significance of the association between dairy consumption and acne.7,10 This link has also been found in an analysis of Nurses Health Study II data,8 a Norwegian study of almost 4000 teenagers,9 and even a case controlled study of almost 600 subjects.11 These are only a few of many studies investigating and supporting the correlation between dairy and acne. Considering this, I am proposing a theory to why this may be.
INSULIN LIKE GROWTH FACTOR (IGF-1)
While a good chunk of the research into the association between acne and dairy has focused on the glycemic index or insulinogenic properties of dairy, I believe it is actually the hormone, Insulin Like Growth Factor 1 (IGF-1) which is the major trigger. IGF-1 is found in dairy and helps a calf to develop and grow. IGF-1 is also a naturally occurring human growth hormone, and there are only minimal differences between it and bovine IGF-1. Bovine IGF-1 has been shown to have similar potency and receptor binding capability as human IGF-1.17 A healthy person should have a certain amount of IGF-1 if in homeostasis. Levels peak during puberty and decline with age.2This peak and decline parallels acne prevalence.
Lynn DD et al. 2016 Figure 3B
IGF-1 INDUCED SEBUM UPREGULATION
There is evidence that that excess sebum production is often one of the prime offenders when it comes to acne.5 IGF-1 levels have been positively correlated with acne vulgaris, especially in women6. An in vitro experiment by Kim H et al 2017, showed IGF-1 increasing sebaceous cell production of sebum.1Considering this, exogenous IGF-1could be having an in vivo effect on sebaceous glands, causing them to overproduce sebum and trigger acne.
IGF -1 BIOAVAILABILITY?
To add substance to this theory we do need evidence that ingested IGF-1is actually bioavailable. There isn’t any research out there that I could find that looks at this in humans but there are at least a few indications that it does get absorbed intestinally, albeit a small amount in pigs. Colostrum (IGF-1) fed to neonatal pigs increased circulating IGF-1 and tissue protein synthesis.15 Building on those results, Sharon et al. directly measured the absorption of IGF-1using radio assay and found that about 3-5% was absorbed into the plasma. While small, and only researched in neonatal pigs, the large quantities found in dairy milk and differences in adult human physiology may make this small percentage a significant modulator of skinhomeostasis. Until adult human studies look at IGF-1 bioavailability and absorption, there is little reason to doubt the potential of exogenous IGF-1 making its way into circulation. Lastly, the common treatment of dairy cattle with recombinant bovine growth hormone has been shown to significantly increase the levels of IGF-1 in the milk produced from those cows.12,13
Lynn DD et al. 2016 Figure 1B
MORE CONCENTRATED IN WHEY VS CASEIN PROTEIN
Over-consumption of dairy products in developed countries2, where it is abundant and cheap, is likely the main driving force of the acne epidemic, however it may depend on the type of dairy. Since IGF-1 is water soluble, it may be found in higher concentrations in whey compared to casein protein. The majority of the IGF-1 hormone could be solubilized in the liquid whey component of milk and is likely being separated out when making cheese etc. Many processed foods have “whey” as an added ingredient. Read the label of your favorite cheesy puff, Dorito, or Velveta and you’ll likely see it listed. Not to mention one study correlating whey protein with acne.18 More research still needs to be done but overall this is likely why some dairy products have acne potentiating effects while others do not. There is also data showing that fermentation has IGF-1 degrading potential. Also, pasteurization does not seem to degrade IGF-1 in dairy.14
Image of Curds Separated from Whey
Considering this, for those prone to acne, choosing dairy options that likely have less IGF-1 due to their lower whey protein levels may be wise. Examples of low whey dairy includes: cheeses, Greek yogurt, and butter. Aside from this choosing low whey dairy, avoiding processed food ingredients like whey, dry milk, and condensed milk may be the easiest steps to lower IGF-1 ingestion.
CONCLUSION
There are also some other genetic and/or other environmental factors that can influence an individual’s susceptibility to acne, so it’s not all dairy’s fault, but the majority may still be. For example, dietary deficiencies of certain vitamins4 and essential omega-3 fatty acids have a negative effect.3 There is also the factor of skim vs full fat dairy. Retinol (Vitamin A) is used in many topical skintreatments. Dairy fat naturally contains vitamin A, and removing the fat also removes the vitamin A. This could explain why some studies looking at the associations between full fat dairy and acne aren’t as conclusive as those using skim dairy. For now, I’m leaning towards IGF-1being the main driver of skindysbiosis, acne, and inflammation.
