Acne, Milk And The Iodine Link
“Dermatologists seem to agree that something in milk and dairy products may be linked to teen-age acne.
But is it hormones and “bioactive molecules,” as a study in the Journal of the American Academy of Dermatology suggested, or is there something else? ”
[Read on]
July 1st, 2007 at 1:44 pm
It is time for you to report on my reply to Dr. Arbesman’s iodine concept.
Go to the JAAD January 2007
Acne and iodine: Reply
To the Editor: Dr Arbesman’s letter1 is a welcome
addition to the debate linking milk and acne. It raises
3 questions: whether levels of iodine in milk are too
high and therefore contribute to acne; what is the
source of the iodine; whether there is a valid link
between iodine and acne vulgaris per se.
The Food and Drug Administration’s Pennington2
states: ‘‘The iodine content of milk available to the
US public appears to be relatively stable with an
overall mean of [23 6 9 g/100 g]. One cup of milk
provides, on average, 56 g of iodine, approximately
37% of the adult Recommended Dietary
Allowance for this nutrient. This concentration of
iodine in milk does not pose a public health threat
with regard to this element.’’ Although isolated
instances of high iodine content in farm milk may
occur, the pooling of commercial milk makes this a
highly unlikely occurrence in the marketplace. As a
useful point of reference, the iodine level in human
breast milk is quite comparable to that in dairy end
products.3
Iodine is an essential dietary ingredient for human
and animal health. The literature supports the conclusion
that iodine deficiency remains a greater
health risk than overdosage. Iodine deficiency is still
a problem in many parts of the world, including
developed countries such as Germany4,5 and the
Netherlands.6 Measured urinary iodine concentrations
have also dropped more than 50% in the United
States between 1971-1974 and 1988-1994.7 Safe upper
levels of iodine intake have been set at 1000 to
2000 g/d. Upper limits of milk iodine levels have
been set at 500 g/L. An extensive array of studies
from numerous countries indicates that this value
is not exceeded in fluid milk at the milk plant level
(oral and written communication, T. Hemling,
National Mastitis Council, January 24, 2006).
Feed additives have the biggest potential impact
on milk iodine levels, and use levels have been
regulated in many countries. Postmilking teat dipping
can contribute to milk iodine levels up to a level
of 100-130 g/L. Proper udder cleaning or wiping
before milking has been shown to minimize the
potential iodine contribution from postmilking teat
dipping. Predipping with wiping before milking
does not increase milk iodine levels more than
about 35 g/L, even for a 1% iodine teat dip.
Continued education on proper use of iodine
premilking and postmilking teat dip as well as iodine
feed additives should help to minimize the risk of
elevated milk iodine levels. New developments in
the dairy industry such as robotic milking, with automated
teat dip application, or the use of iodine barrier
dips may warrant further study ( personal communication,
T.Hemling, National Mastitis Council, January
24, 2006). In the meantime, the present approach is
to maintain a balance of iodine exposure and iodine
feed additives, which yields a dairy milk iodine level
comparable to that in human mothers’ milk.
Whether iodine in any concentration causes true
acne is debatable. Kelp is recognized as causing an
acneiform eruption8where the iodide source is indeed
high, and there is little doubt that a papular and papulopustular
acneiform eruption can be triggered by
halides, but the hallmark of acne, the comedo, is
not part of the initial lesion in this picture. Comedones
may appear as secondary lesions.9 The development
of an inflammatory lesion is fully consistent
with iodide’s ability to enhance the inflammatory
reaction.10
Although excess milk intake could lead to excess
intake of iodide, if one wished to consume sufficient
milk to approximate the 750 mg daily therapeutic
dose of potassium iodide provided as therapy to a
patient with erythema nodosum,11 that would require
daily ingestion of 1140 L of milk containing
500 g iodide per liter. A study by the Food and
Drug Administration in 1990 concluded that some
individuals can tolerate very high levels of iodine with
no apparent side effects and that iodine intakes less
than or equal to 1.0 mg/d are probably safe for the
majority of the population, but may cause adverse
effects in some individuals.12 The definitive work
needed to answer the question would be a blinded
trial of a very high iodide diet in a teenaged or
young twenties population. I suspect it would be
a significant challenge to obtain ethics approval, let
alone volunteers, for such a study.
To summarize, there is no evidence to support
iodides as a cause of comedonal acne.
J AM ACAD DERMATOL
JANUARY 2007
July 31st, 2007 at 9:37 pm
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