If the main thrust of the question is indeed expressed in the title and tags of the question:
Q “There is a very strong correlation between consuming dairy products — such as milk — and acne, skin breakouts and aging.”
Then the jury on that really isn't finished deciding:
Is acne related to the ingestion of dairy products? It is not a new idea. It goes back to the early days of the last century and beyond. The counter-claim, that there is no relationship between diet and acne, has reached mythic proportions. It has never been substantiated, but it is repeated as gospel in all major dermatology textbooks. Epstein, commenting on contributions on the subject by Waisman, Bickers, and Rosenberg, trod the middle road. Inexplicably asserting that "Controlled studies indicate that foods have no effect on acne," he nonetheless allowed, "the patient should receive any assistance that dietary control may impart." In a review of 274 clinical trials of acne, the massive 2001 Evidence Report on the Management of Acne found one solitary paper that mentioned diet, but no trial reported specifically on patients’ diets.
Dairy products have been implicated as a possible factor in the etiology of prostate cancer in several large epidemiological studies, but not in all. The possible influences of dairy hormone in breast cancer are likewise unclear and in need of further definition.
The next few years will be fascinating for those of us interested in hormones and "the blight of youth." One wonders what the impact will be upon our patients, our practices, and the industries that make milk, hormones, and acne products. Time alone will tell.
F. William Danby: "Acne and milk, the diet myth, and beyond", J AM ACAD DERMATOL FEBRUARY 2005
While it seems very much up for debate to either substantiate whether indeed industrialised milk production schemes result in increased hormone presence in milk sold, whether there is a difference between production methods and 'ingredients' in milk sold, whether this is then true for all dairy products.
Case in point: water soluble pharmacologically active compounds will be greatly reduced in butter and ghee, molecules found in whey greatly reduced in most cheeses, and anything greatly processed is another game entirely. If yeasts, worms, insects bacteria ferment the milk-product, how much of the hormones is reduced by those organisms? –– or amplified?
Milk as is not the main product consumed by most people and all dairy products are clearly not the same. Kefir is different from cheese, fresh or aged, with bacteria or fungi, from whey, from butter, from ghee, from protein-isolate and so on. Given the different profiles for all those products they either have to have something in common across the board or they have to be analysed separately.
It is of course quite interesting to look for evidence that shows how much different modern milk and milk products are compared to just a few decades ago. Be it in nutritional or now even pharmacological profiles.
But to start a comparison with dairy, hypothesising about hormones, then linking that all up to skin disorders seems very premature and theoretical. At least if there are not clear epidemiological indicators of indeed a possible link.
Which suspects would there be to observe in the proposed link between acne and skin?
Only the most prominent are:
Prolactin, Somatostatin, Gonadotropin-releasing hormone, Luteinizing hormone, Thyroid-stimulating hormone, Thyreotropin-releasing hormone, Epidermal growth factor, Insulin-like growth factor 1, Insulin-like growth factor 2, Insulin, Vitamin D, Transferrin, Lactoferrin, Prostaglandins
Now which of these are contained in fresh milk under which circumstances and therefore concentrations in the first place? How much of this is linked to milking pregnant cows?
Acne and milk
Milk and other dairy products contain more than 60 molecules including prolactin, somatostatin, gonadotropin-releasing hormone, luteinizing hormone, thyroid-stimulating and thyreotropin-releasing hormones, insulin, epidermal growth factor, nerve growth factor, IGF-1 and 2, transforming growth factors, vitamin D, transferrin, lactoferrin and prostaglandins (Koldovsky, 1995). This makes it difficult to distinguish which of these factors could have an acneigenic effect, especially when this fact is combined with the broad range of dairy products (Table 25.2, Figure 25.4).
The most important factor of the ones mentioned above is the insulin-like growth factor. The IGFs are proteins with high sequence similarity to insulin. IGFs are part of a complex system that cells use to communicate with their physiologic environment. Cow milk contains IGF-1 and -2, even after pasteurization and homogenization, and bovine and human IGF-1 share exactly the same amino acid sequence (Melnik and Schmitz, 2009). High milk consumption increases IGF-1 levels 10%-20% in adults and 20%-30% in children (Hoppe et al., 2004 a, b) and milk and dairy products raise IGF-1 levels more than dietary proteins such as meat (Hoppe et al., 2005).
Milk also contains carbohydrates, including lactose, and therefore its consumption produces a glycemic response and an insulinemic response. The insulinemic response to ingested milk is actually three to six times what would be predicted from the carbohydrate load in the milk serving (Ostman et al., 2001). This happens for skimmed and full-fat milk, but not for cheese (Holt et al., 1997; Hoyt et al., 2005). The reasons are not yet understood, but they may relate to the insulinotropic effects of some of the other multiple hormones that are present in milk (Koldovsky, 1995).
A glass of milk added to a low glycemic index meal can boost the insulin response up to 300% of the level produced by a high glycemic index meal and cow milk-formula does this even better than human breast milk (Liljeberg and Bjorck, 2001; Lucas et al., 1980). Different studies suggest that insulin rises in response to the whey component (20% of milk protein), whereas casein is responsible for the IGF-1 increase (Hoppe et al., 2006). Because whey and casein are both involved in stimulating androgen production, there is little point in further differentiating them in dietary restriction, since both should be avoided.
If the result of the above is indeed true: "whey and casein should both be avoided" then this is still incomplete as to whether it is for example whey-protein itself (essentialist reading) or what's commonly in there (varying by methods of production) as well and surely not encompassing 'all dairy', as butter for example is largely free of both.
Then it remains a stretch to conclude that "stimulating androgen production" is just "all bad/causes acne" on the one side and on the other side there are other types of causes that are "stimulating androgen production": hyperinsulinemia for example, which can also activate or upregulate IGF receptors.
It is simply too simplistic to reduce the focus to just one or a few pathways and "reason the rest" from there.
But take note that this is not the sole point of that article. The very next item was about 'glycemic index'. To give more context:
- Androgen excess, peroxisome proliferator-activated receptors and inflammation are the main pathogenetic mechanisms of acne.
- Nutrition seems to play an important role in skin biology and pathology, affecting the onset and clinical manifestation of several dermatologic disorders, including acne.
- The typical Western diet consists of numerous dairy sources and foods with high glycemic indices.
- A study performed by Adebamowo et al. (2005) demonstrated the association between dairy products and acne.
- A study provided by Smith et al. (2007) showed the link between high glycemic load intake of carbohydrates and acne.
- High glycemic carbohydrates and milk appear to raise serum insulin levels, free IGF-1 and insulin resistance, thus contributing to the pathogenesis of acne.
- IGF-1 seems to be the most important acneigenic factor contained in diet.
- At the genomic level, the effects of insulin and IGF-1 are mediated by the nuclear concentration of the transcription factor FoxO1.
- At the promoter level, SREBP-1c expression is suppressed by nuclear FoxO1, which is an important co-repressor of the retinoid X receptor and liver X receptor.
- Dermatologists should be able to include dietary restriction in acne therapy management.
- Skin reflects individual age, health and beauty.
- Nutritional customs affect several skin diseases including psoriasis, atopic dermatitis and acne.
- Epidemiological studies with milk and dairy products support the association of milk consumption with acne
onset and clinical course.
- High glycemic load diets are also considered to be involved in acne pathogenesis because of the consequent
hyperglycemia and hyperinsulinemia.
- Dermatologists should include restrictive dietary management in acne therapy in their daily clinical practice.
A.I. Liakou, C.I. Liakou and C.C. Zouboulis: "Acne and nutrition", Victor R. Preedy (Ed): "Handbook of diet, nutrition and the skin", Wageningen Academic Publishers, Wageningen, 2012.
Note especially that 'dairy' is not unique in containing these molecules, concentrationand consumption patterns have to be observed as well. Dosis facit venenum. But even if the same molecules are measured, the effect may not be same after all, as the milk vs meat example aboive illustrates. And how much of those are even present in milk 'now' compared to 'earlier times' is partly dependent on the alleged production methods of "pregnant cows". How much has that changed? We can hardly know.
One of the more prominent papers investigating a possible link comes sponsored from a food-giant:
Bodo C. Melnik: "Evidence for Acne-Promoting Effects of Milk and Other Insulinotropic Dairy Products", Clemens RA, Hernell O, Michaelsen KF (eds): Milk and Milk Products in Human Nutrition. Nestlé Nutr Inst Workshop Ser Pediatr Program, vol 67, pp 131–145, Nestec Ltd., Vevey/S. Karger AG, Basel, © 2011.
And that is quite a problem. The dairy side sponsoring research to show how "good it is for you", and from animal-rights over vegan to frankenfood-companies financing the other side of ideology. All sides looking for evidence that they were right, from the start. This is more like gnosis that science and it is extremely difficult to weed out all the chaff thrown in to the pool of knowledge.
A meta-analysis can help inform the debate about the epidemiological evidence on dairy intake and development of acne. A systematic literature search of PubMed from inception to 11 December 2017 was performed to estimate the association of dairy intake and acne in children, adolescents, and young adults in observational studies. We estimated the pooled random effects odds ratio (OR) (95% CI), heterogeneity (I2-statistics, Q-statistics), and publication bias. We included 14 studies (n = 78,529; 23,046 acne-cases/55,483 controls) aged 7–30 years. ORs for acne were 1.25 (95% CI: 1.15–1.36; p = 6.13 × 10−8) for any dairy, 1.22 (1.08–1.38; p = 1.62 × 10−3) for full-fat dairy, 1.28 (1.13–1.44; p = 8.23 × 10−5) for any milk, 1.22 (1.06–1.41; p = 6.66 × 10−3) for whole milk, 1.32 (1.16–1.52; p = 4.33 × 10−5) for low-fat/skim milk, 1.22 (1.00–1.50; p = 5.21 × 10−2) for cheese, and 1.36 (1.05–1.77; p = 2.21 × 10−2) for yogurt compared to no intake. ORs per frequency of any milk intake were 1.24 (0.95–1.62) by 2–6 glasses per week, 1.41 (1.05–1.90) by 1 glass per day, and 1.43 (1.09–1.88) by ≥2 glasses per day compared to intake less than weekly. Adjusted results were attenuated and compared unadjusted. There was publication bias (p = 4.71 × 10−3), and heterogeneity in the meta-analyses were explained by dairy and study characteristics. In conclusion, any dairy, such as milk, yogurt, and cheese, was associated with an increased OR for acne in individuals aged 7–30 years.
However, results should be interpreted with caution due to heterogeneity and bias across studies.
Christian R. Juhl et al: "Dairy Intake and Acne Vulgaris: A Systematic Review and Meta-Analysis of 78,529 Children, Adolescents, and Young Adults", Nutrients 2018, 10(8), 1049, DOI
So it remains currently at this:
Dairy and Acne
There's no definite link between dairy and acne, but there are theories about it.