Dietary Implications for the Development of Acne: A Shifting Paradigm
A
report by Loren Cordain, Ph.D., Professor, Department of Health and Exercise Science, Colorado State University
Following our 2002 publication in The Archives of
Dermatology 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 acne. Although these reports will need to be followed-up by
more extensive experiments, they are important for two
reasons: they represent the only well controlled, modern
studies of diet and acne that have been published in
more than 35 years; and they are contrary to the to the longheld
belief that acne is not caused by diet.
Establishing Cause and Effect Between
Diet and Disease
One of the challenges faced by nutritional scientists,
when they ultimately make recommendations regarding
what we should and should not eat, is to establish cause
and effect between a dietary element and the subsequent
development or prevention of disease. Figure 1
demonstrates the four primary procedures by which
causality is established between diet and disease.
No single procedure alone can establish cause and
effect, nor can any single study prove causality.
Observational epidemiological studies can only show
relationships among variables and cannot provide
decisive evidence by themselves either for or against
specific hypotheses. In order to establish cause and
effect between diet and disease, it takes more than just
observational epidemiological evidence. There must
also be biological plausibility in which evidence
gathered from tissue, animal and short-term human
metabolic studies support causality. When observational
epidemiological evidence is augmented by
biological plausibility studies and confirmed by
randomized controlled trials, the case for causality
becomes ever-more convincing.
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,two recent observational epidemiological studies also
support the notion that diet is linked to acne. In a
retrospective cohort of 47 and 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 (prevalence ratio = 1.22; p=0.002) and skim
(prevalence ratio = 1.44; p=0.003) milk intakes. In a
prospective cohort of 6,094 girls, aged nine to 15 years
studied from 1996 to 1999, milk drinking of all kinds
(total, whole, low-fat, and skim) was positively
associated with acne.3 After accounting for age at
baseline, height and energy intake, the prevalence
ratios and p-values were as follows: total milk (1.20;<0.001), whole milk (1.19; <0.001), low-fat milk
(1.17; <0.002) and skim milk (1.19; <0.001). 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 (p<0.05) in the treatment
group compared with the control group. 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.
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.
Dietary Implications for the Development of Acne, Part 2 is HERE.