SovereignDove
Jedi
I was reading this this morning, and found it interesting(as I have had acne most of my life, and did eat a large amount of cheese, still in the process of phasing it out of my diet) in reference to the Paleo diet. I recieved an automatic mailing email from a Paleo website(the paleodiet.com), which contained a link to this paper. The figures/flow charts did not copy over.
Looks like another downside to the consumption of dairy. Any thoughts on this?
This is the link: http://dl.dropboxusercontent.com/u/24415266/Diet-and-Acne-New-Findings.pdf
or: http://thepaleodiet.com/emails/free-download-6-file/
Looks like another downside to the consumption of dairy. Any thoughts on this?
This is the link: http://dl.dropboxusercontent.com/u/24415266/Diet-and-Acne-New-Findings.pdf
or: http://thepaleodiet.com/emails/free-download-6-file/
Diet and Acne: New Findings
By
Loren Cordain, Ph.D.
Following our 2002 publication in The Archives of Dermatology1 demonstrating
that acne was not present in two non-westernized populations, there has been renewed
interest in the role that diet may play in the pathogenesis of this disease. In the past two
years, three studies now support the link between diet and acne2-5. Although these
reports will need to be followed up by more extensive experiments, they are important for
two reasons: 1) they represent the only well controlled, modern studies of diet and acne
that have been published in more than 35 years6, and 2) they are contrary to the long held
belief that acne is not caused by diet7-9.
Diet and Acne: The Most Recent Data
In addition to our ecologic study demonstrating the absence of acne in the Kitavan
islanders of Papua New Guinea and the Ache hunter gatherers of Paraguay 1, two recent
observational epidemiological studies also support the notion that diet is linked to acne 2,
3. In a retrospective cohort of 47, 355 women, after accounting for age, age at menarche,
body mass index, and energy intake, Adebamowo and colleagues found a positive
association between acne incidence and total and skim milk intakes 2. In a prospective
cohort of 6,094 girls, aged 9-15 years studied from 1996 to 1999 milk drinking of all
kinds (total, whole, low fat and skim) was positively associated with acne 3. These two
observational experiments are important in that they are the first evidence in westernized
populations to show that diet (and milk in particular) is associated with acne. In order to
establish causality, future randomized controlled trials, in which milk is either added to or
excluded from the diet and acne symptoms assessed, will be needed to confirm these
preliminary epidemiological observations.
Mann and colleagues recently completed a more powerful randomized controlled
trial evaluating the effect of a low glycemic load, high protein diet upon acne symptoms
in 43 male acne patients aged 18. 3 + 0.4 years 4, 5. Subjects were randomly assigned to
either an experimental group with a diet consisting of 25% energy from protein and 45%
energy from low glycemic index carbohydrates or to a control group consuming their
usual diet. Following the 12 week dietary intervention, total and inflammatory lesion
counts decreased significantly in the treatment group compared to the control group 4.
The hormonal profile of the treatment group improved concomitantly with the reductions
in acne lesion counts as measured by significant declines in dehydroepiandrosterone
sulfate and the free androgen index 5. Milk and dairy products were a component of the
treatment diet in this study, hence it is unclear if further improvement in lesion counts
would have occurred had these foods been excluded.
Diet and Acne: Underlying Physiological Mechanisms
Acne results from the interplay of six proximate factors: 1) increased proliferation
of basal keratinocytes within the pilosebaceous duct, 2) delayed keratinocyte apoptosis,
3) incomplete separation of ductal corneocytes from one another during desquamation via
impairment of desmosomal disintegration and subsequent obstruction of the
pilosebaceous duct 4) androgen mediated increases in sebum production, 5) colonization
of the comedone by Propionibacterium acnes, and 6) inflammation both within and
adjacent to the comedone 10-14. Despite the wholesale dismissal of diet as a potential
environmental factor underlying the development of acne7-9, a large body of evidence
now exists which demonstrates how certain foods and food substances may adversely
influence hormones and cytokines that influence five (1-4, 6) of the six previously listed
proximate causes of acne 1, 6, 15.
The Dietary Glycemic Index
The glycemic index, originally developed in 1981, is a relative comparison of the
blood glucose raising potential of various foods or combination of foods based upon
equal amounts of carbohydrate in the food 16. In 1997, the concept of glycemic load
(glycemic index x the carbohydrate content per serving size) was introduced to assess
blood glucose raising potential of a food based upon both the quality and quantity of
dietary carbohydrate 17. Refined grain and sugar products nearly always maintain much
higher glycemic loads than unprocessed fruits and vegetables. From an endocrine
perspective, the importance of the glycemic index and load is that they are closely related
to the insulin response 19. An exception to this general rule is dairy products, which
exhibit low glycemic indices and loads, but paradoxically elicit high insulin responses
similar to white bread 20. Highly glycemic and insulinemic foods are ubiquitous elements
in western diets and comprise 47.7 % of the per capita energy intake in the U.S. 21.
Figure 1 shows how high glycemic and insulinemic foods including dairy products set off
a hormonal cascade that may ultimately result in acne.
Figure 1. Hormonal changes elicited by high glycemic load diets which promote acne.
Adapted from 6.
Dairy Products and Acne: New Findings
In addition to having a potent insulin response, similar to eating a slice of white
bread 20, a recent dietary intervention showed that a high milk diet for only seven days
caused insulin resistance in a group of 24 eight year old boys 22. Insulin resistance in
turn may promote acne via the hormonal cascade depicted in Figure 1.
Milk is essentially filtered blood and as such contains the full complement of
hormones which are also present in blood 23. Traditional theory held that consumption
of cow milk would not result in the transfer of cow hormones into human circulation for a
number of reasons. First, in industrialized countries, milk is usually consumed many
hours or days after it is initially procured. Many hormones such as the insulin
secretagogues (GIP, GLP-1) have very short half lives (< 10 min) 24 and simply would
not be present in commercial milk. Secondly, the heat of pasteurization (149 ° F for 30
min) may degrade or inactivate thermally labile hormones. Further, the acidity of the
stomach and peptidase enzymes in the small intestine would also make it difficult for any
peptide hormones in cow’s milk to reach the intestines intact with full biological activity.
Finally, the most daunting task of all would be for intact peptide hormones to cross the
gut barrier which normally prevents intact proteins and large peptides from entering the
epithelial cells lining the gut.
The Epidermal Growth Factor Receptor
Only 12 short years have elapsed since the discovery that humans bear a
hormonal receptor in their gastrointestinal tract called the epidermal growth factor
receptor. This trans-membrane, hormonal receptor is very unusual in that it is expressed
luminally – meaning that it faces the gut contents rather than the bloodstream 25, 26. The
location of the EGF receptor puzzled scientists for years – why was it expressed
luminally and what was its function 27? Since, hormones always arrive at tissues from the
circulation, why should the EGF receptor face the gut contents, which in effect are
outside the body?
It turns out that the primary function of the luminally facing EGF receptor is to
stimulate healing and maintain the integrity of the cells lining the gastrointestinal tract 26,
28. In humans, the primary source of the hormone (EGF) which binds to the EGF
receptor in the gut comes from saliva 29. Hence by swallowing saliva, the residual EGF
contained in saliva helps to maintain the integrity and promote healing of the epithelial
cells lining the gut.
The EGF receptor is a promiscuous receptor in that it doesn’t just bind a single
hormone (EGF), but rather binds a large family of hormones including betacellulin
(BTC) 30. Cow’s milk contains no EGF, but does contain high concentrations of BTC,
amounting to 1,930 ng/liter 31, 32. Additionally, BTC is quite stable and survives the
pasteurization process and is even found in high concentrations in cheese 32. Further, a
low ph, such as may be found in the gut, does not impair or prevent BTC from binding its
receptor 33. Finally, bovine milk contains peptidase inhibitors which prevent human gut
enzymes from degrading EGF receptor ligands 34. In summary BTC maintains all the
physical characteristics needed to arrive in the gut intact and with full biological activity.
But more importantly, it can breech the gut barrier and enter circulation by the
transcellular EGF-R route as depicted in Figure 2.
Figure 2. Route by which bovine BTC reaches systemic circulation in humans.
Once within circulation BTC then has the capacity to bind EGF receptors bound
in all epithelial cells, including keratinocytes. BTC can bind the specific receptors
depicted in Figure 3 30.
Figure 3. The four families of the epidermal growth factor receptor (ErbB1, ErbB2,
ErbB3 and ErbB4). Each of the four receptors combines to form a pair with a different
receptor (a heterodimer) or itself (a homodimer). The 10 hormones which can bind the
various receptors are depicted in boxes above the receptors. Their binding specificities
are indicated by the arrows 30.
BTC from ingested bovine milk may contribute to the pathogenesis of acne by its
ability to increase keratinocyte cell proliferation and to decrease keratinocyte apoptosis
35. Further, BTC up-regulates its own receptor 30, thereby causing additional signaling
through the EGF receptor pathway. In support of the notion that increased flux through
the EGF receptor pathway by exogenous BTC from milk may promote acne is the
observation that EGF receptor blocking pharmaceuticals cause non-comedonal acne in
most patients who are administered these drugs 36, 37.
Future studies will be able to clarify these issues, and the myth that “diet and acne
are unrelated” will one day be relegated to the bin of false medical dogma.
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