Milk consumption and acne in teenaged boys

1. Milk consumption and acne in teenaged boys Adebamowo C. et al Harvard school of public health, Boston, MA Jaad May 2008 787-793

2. Introduction • Acne vulgaris is a common, chronic and self-limiting skin disease, that causes physical and psychologic morbidity in up to 90% of adolescents and young adults. • In Western countries, it affects all ages, but peaks in prevalence at 16 to 18 years when 75-98% of this age group is affected. • Even though more common in girls overall and below the age of 12, after 15, it becomes more common in boys.

3. -Pathophysiology: -androgen-stimulated hyperkeratinization and obstruction of the pilosebaceous follicles secondary to failure of normal desquamation of the follicular epithelium. -androgen-stimulated sebum production -subsequent colonization of the follicles by Propionibacterium Acnes and Malassezia. • -variably inflammation

4. -Previous studies show an association between dietary intake of milk and prevalence of teenaged acne. -favoured by a Western diet -the majority of 1925 patients in a study presented acne flares concomittant to the intake of milk -In a restrospective study of US female nurses with severe acne, a positive association was made with the intake of skimmed milk... -...the authors also found a positive association between milk consumption(NOS) and acne in US girls aged 9-15.

5. -such a finding wasn't done in boys (probably because of the androgen factor) -therefore a prospective study of US boys to evaluate occurence of acne associated with dietary intake.

6. Methods • -Study population -out of the GUTS (Growing up today study) cohort of 9039 girls and 7843 boys -semiquantitative FFQs and calculation of nutrient intake -participants (399, 305 agreed to participate) asked how frequently they used a typical portion size of specified foods on average during the past year. -dairy group: total milk, chocolate milk, instant breakfast drink, ice cream, yogurt, cottage cheese, cream cheese, cheese, milkshake, butter -also asked what type of milk drinked: -whole milk -2% milk -1% milk -skim non fat milk -soy milk -unknown or doesn’t drink milk -other foods: French fries, pizza, chocolate candy -nutrient intakes computed by multiplying the frequency of consumption by the nutrient value (USDA)

7. -assessment of non dietary factors: Age, Tanner stage, weight, height -Identification of acne cases -subjects asked “compared to other people of your age, how would you describe your acne?”: -I almost never have any pimples -I sometimes get a few pimples -I usually have a few pimples -I sometimes get a lot of pimples -I usually get a lot of pimples

8. -Statistical Analysis -To assess the potential for selection bias, boys with acne who responded to those who didn’t with Wilicoxon rank sum test. -for subject response: “sometimes a few was excluded”, the other responses were kept and 2780 boys were left for analysis. -Because the exact onset of acne wasn’t known and in order to simulate a prospective study: the diet habits in 1996, 1997-1998, 1996-1998 were compared with history of acne in 1999. Analysis was also done for diet and patients younger than 11 in 1996, an age of low acne prevalence. ……………………..

9. Results -Table 1: Boys who did not respond to the 1999 questionnaire that was used to define acne were slightly older than those who did, otherwise there was no notable difference between the two groups. -Most of the boys (45%) drank whole or 2% milk, 23% drank low-fat milk, 29% drank skim milk, 0,4% drank soy milk, 3% didn’t drink milk. -79% reported sometimes few or more pimples, 44% reported usually a few or more pimples.

10. -Table 2: Comment table: -The addition of BMI or Tanner stage to the stratified models did not appreciably alter the prevalence ratios. -Intakes of calcium, total Vit D or Vit D from foods, total fat, vit A (total and from food) were not associated with acne. There was a weak positive association with intakes of vitsmin D from supplements. -There was no associations between acne and intakes of other dairy foods, chocolate cany, French Fries or Pizza.

11. -sensitivity analysis: the authors tested the robustness of the anlaysis by including “ sometimes a few” as cases of acne (previously omitted) and secondly by including them among the non-cases: same results. Reverse causation was tested by studying the group under 11, and the results correlated negatively.

12. Discussion -In this study, the most consistent factors associated with prevalence of acne were age, Tanner stage, height, and intake of skim milk. -No association was found with total fat, dairy fat, total vitamin A, and vitamin A from foods. There was though a weak positive association with vitamin D supplements (increases kertinocyte differention and decreases proliferation and favors wax ester accumulation and decreases triglycerides).

13. -Milk may favour comedones because it contains androgens, precursors such as 5-alpha reduced steroids (DHEA)…Many of these bioactive molecules survive processing and for example in the case of cheese, more precursors are synthesized as the result of fermentation. Other milk proteins such as lactalbumin alpha also have androgenetic effects in animals (willingness to engage in physical activity, mass gain, less percentage of body mass…).

14. -These findings contrast with the previous findings in girls which could be explained by the earlier peak of IGF in girls at 15 (end of the growth spurt) whereas it is at 18 in boys which would be consistent with a more “mature” endogeneous hormonal system.

15. Milk may also influence comedogenicity through the IGF-1 pathway, which inceases levels of circulating androgens. The association with high plasma androgen levels and high IGF-1 correlated the most in skimmed milk. IGF-1 would increase as the result of a hyperinsulinaemic response to the ingestion of milk. Also IGF-1 in the milk (bovine same structure as human) could be ingested in the gut after being protected from digestion by a linkage to a binding protein. Therefore a decreases insulinaemic state would favour less comedogenicity.

16. Limitations -only boys who responded to the questionnaire were studied: selction bias? -self reporting by the subjects with no validation. -use of steroids not recorded -no body location specified (non facial acne is only in 5% of cases) -The Mantel-Haenszel estimation of PR: this method intrinsically controls for the main effects and higher order interactions of all confounders, whether significant or not, may lead to loss of statistical power

17. Conclusion -Skim Milk is implicated in the prevalence of acne in adolescent boys: -maybe due to an increase in androgen levels -maybe IGF mediated stimulus -maybe because of DHEA precursors in the milk -also an implication for prostate cancer, these relationships should be evaluated further