The relationship between acne and diet remains
as unclear today as it was 50 years ago. Back then, acne was
reputed to be caused by hamburgers, malt sodas, and other foods
popular to teenagers. Today, around one in every three teenagers,
medical students, doctors, and nurses still believe in a link
between acne and diet.
Interest regarding this “link” has been overwhelming
due to rising concerns for health and nutrition, but much of
what experts know are still largely based on pseudo-scientific
hearsay and myths. Actual studies about the link between acne
and diet have been hampered by commercial issues, and irrefutable
evidence based on good-quality research is still elusive.
At this point, a consensus of popular opinions on the topic
is the most reliable source of information regarding the link
between acne and diet. While this may be questionable, it is
important to note that most medical treatments initially stem
from people’s perceptions.
Acne and diet link
The link between acne and diet may have grown from the comparison
of western societies with non-western ones. Acne was found in
lower incidences in the non-western societies, but was also
found to increase that when these societies migrated to a western
lifestyle. For instance, the Inuit Indians of Canada had practically
no knowledge of acne prior to their adoption of a western lifestyle.
When they did, the acne incidence levels soon paralleled those
seen in Western Caucasian societies. Similar observations were
also noted in other populations undergoing the same migration.
Hyperinsulinemia effect on acne
Chronic hyperinsulinemia (high insulin resistance) may be a
key link between acne and diet. It is believed that hyperinsulinemia
causes acne by stimulating androgen production and affecting
the sebaceous glands and follicular keratinization. It is caused
by diets that are high in fat and carbohydrates, which is common
in western societies.
SHBG (sex hormone binding globulins) acts against testosterone,
binding to free molecules of testosterone and rendering them
inactive. More SHBG reduces testosterone, and consequently reduces
androgen hormone activity. Testosterone may maintain insulin
levels and promote insulin resistance at different levels.
Studies in women with polycystic ovarian syndrome have shown
that hyperinsulinemia increases androgen production and decreases
SHBG production in the liver. This results in unusually high
insulin resistance levels and may prove to be a cause of acne.
Dietary influence on sebum composition and secretion rate
Another possible link between acne and diet was shown in sebum
studies on animals and humans. Animals produced more sebum while
subsisting on a high-fat or carbohydrate diet, and humans showed
changes in sebum composition and a 40% reduction in sebum secretion
after subjected to total and prolonged calorie deprivation.
Pappas et al also disproved the once-popular opinion that sebaceous
glands produced sebum on their own and did not derive any of
its components from the bloodstream. They convincingly showed
that the sebaceous glands in fact draw fatty acids from the
bloodstream and use it to produce sebum. While this and other
discoveries suggest that dietary fat and carbohydrate may have
affect sebum production, it still fails to prove the link between
acne and diet.
Several studies have been made in an attempt to prove the relationships
between acne and diet, but so far many of these have failed
to produce any links. 2,720 soldiers were studied for any link
between acne and obesity, and while a link was found in older
subjects, adolescents showed no such relation. 16 acne sufferers
showed no difference in sugar consumption with those without
acne in another study.
Monozygotic and dizygotic twins were also subjects of a large
and important study that found no significant differences in
weight, height, birth weight, BMI (body mass index), and reproductive
factors between acne and non-acne affected twins.
Chocolate - a cause?
A 1969 study on the supposed worsening effects of chocolate
on acne suggested relation. Negligible differences in the moderate
acne of 65 volunteers were found, even when one part of the
group ate a daily candy bar containing ten times the normal
amount of chocolate and the other part eating a similar bar
with no chocolate.
However, critics have found several serious flaws in the study’s
methodology, the most important of which involved the quality
of acne lesions. The study only measured the number of lesions
(both comedones and pustular flares) combined, but the conversions
of comedones to pustular flares were not taken into account.
This was a vital hole in the study, as patients with food-related
acne complain of pustular flares more imperatively than comedones.
Larger, better-designed studies have not been conducted since.
Is there a link between acne and diet? The jury’s still
out on this one.