Equine Veterinary Science,
Reprinted with permission
MSM-A DIETARY DERIVATIVE OF DMSO
There is a dearth of scientific literature regarding
feed additives and supplements for the horse. One reason
is that little work has been done in this area. But, perhaps,
a more important reason is that most studies in this area
are done by commercial feed companies that wish to guard
I believe that when exciting information about new
equine feed supplements surfaces, everyone in the horse
industry would like to know about it. Therefore, I pass
the following information along that was sent to me from
Dr. John Metcalf.
John is an equine practitioner in Auburn Washington.
He has pioneered the use of dimethylsulfoxide (DMSO) in
horses. Some 20 years ago he was asked by Dr. S.W. Jacob
to try this promising drug on horses. Dr. Jacob had been
involved in research with the drug in humans. Since then,
John has used it on a variety of cases. He has given it
IV and tried various concentrations topically.
Now John has another interesting story about a substance
chemically similar to DMSO. He was asked to try this substance
much in the manner he first tried DMSO years ago. His
communique to me is printed below. WEJ
John Metcalf, DVM
MSM, a new dietary supplement, is a metabolic end
product of Dimethyl sulfoxide, DMSO, available in liquid
and gelled forms, is a standard therapeutic modality in
equine medicine today. While the therapeutic value is
generally well accepted in our profession, its use has
side effects to the patient and veterinarian, which include
skin irritation and dryness, itching, together with the
maltaste and offensive breath imparted with skin contact.
This communication introduces veterinary medicine to
a new, basic development stemming directly from ongoing
DMSO research. Evaluation is yet in the early stage, but
findings to date suggest that the stable metabolite of
DMSO negates the nuisance type side effects, while providing
interesting health normalizing actions in man, the horse,
and the dog.
Let me preface this preliminary report by admitting that
my conclusions of the case histories which follow are
subjective observations, not following a carefully controlled
double--blind protocol. Fortunately, this stable metabolite
of DMSO presents those physical and chemical properties
required to conduct valid controlled studies, and these
will follow. I have, however, been in practice for 30
years, so my experience serves, in a real sense, as the
The reason for authoring this preliminary report is that
I am genuinely excited about the potential of this new
substance, and hopeful of stimulating other veterinarians
to evaluate and possibly confirm my initial findings with
controlled evaluations. I use the term "substance" with
special purpose since the subject of this paper better
qualifies as a dietary supplement rather than as a drug.
I was in practice in Portland, Oregon when the medical
benefits of DMSO were discovered some twenty years ago
by Robert Herschler and Stanley Jacob of the University
of Oregon Medical School. They, at that time, were somewhat
apprehensive about the effects of the medication on some
medical problems shared by man and horses. I was pleased
to be invited into the study evaluating the effects with
my equine practice.
Today I have little reluctance using DMSO with nearly
any condition presented in animals since DMSO demonstrates
a remarkable margin of safety and is free of serious side
effects. One major problem with DMSO, however, is the
imparted odor and other nuisance-type side effects which
essentially blocks all manner of doubleblind type contorolled
studies. The team at the Oregon Medical School has spent
a great deal of time developing DMSO formulae with minimal
nuisance-type side effects.
During this research towards a side effect free DMSO,
Herschler and Jacob developed the dietary supplement,
which is the stable, odorless DMSO metabolite. The substance
is methyl sulfonylmethane, conveniently abbreviated as
MSM. Do not confuse MSM with the new feed additive DMG
(dimethylglycine). While MSM, recognized as a normal dietary
factor of vertebrates, should be considered in the dietary
factor category, it possesses certain bio-medical properties
similar to DMSO together with additional biological activity
not possessed by DMSO. It is most interesting that MSM
has no exceptional activity, in vivo, where biological
normalcy is presented. The original paper on the subject
referenced MSM as factor N, implying the property of returning
the abnormal health state to normal.
Chemically, MSM is DMSO with one added, stabilizing atom
of oxygen onto the sulfur, i.e. CH3SO2CH3.
Being ubiquitous to the diet of all vertebrates, MSM (and
precursors) derive from vegetables, fruit, fish and meat.
Any processing of a foodstuff, even the drying of alfalfa,
may drive off a portion of the fugitive MSM. Physically,
MSM is an odorless, white crystalline, water soluble molecule.
Interestingly, one of the richest sources of MSM in the
diet of mammals is milk. The first paper by the developers
of this supplement1 describes a number of health
normalizing activities attributed to increased MSM in
My evaluation of MSM began during May of 1983. The intent
of the developers in supplying the first MSM to me was
to determine any possible effects with the unhealthy horse.
At that time it had been studied rather extensively in
man. I elected to evaluate the supplied crystalline MSM
on myself. Much to my surprise, I found that my allergy
problem was helped and that I had freer breathing. I had
been through allergy testing some months before and was
found to have a severe allergic reaction to just about
everything having to do with the horse, including the
horse itself. Since my practice is limited to horses,
this allergy was a significant problem. After starting
to add MSM to my diet, I felt better than I had in years.
Not convinced that my improvement was attributable to
MSM, I withdrew added MSM, and returned to the earlier
antihistamine therapy. My condition deteriorated. I again
began to add 2 grams of MSM to my daily diet as a split
dose and rapidly improved.
Because of this personal experience, and being an equine
practitioner, the possible merit of MSM with the bleeding
race horse came to mind. It seems logical that any agent
that will improve pulmonary function stands a good chance
of helping the bleeder. Beyond the pulmonary effect of
MSM, it is also a mild diuretic. Presently very little
of my practice is race track related, therefore no extensive
testing of MSM with bleeders is underway. There are limited
studies in progress, and hopefully results will justify
a further report on MSM in equine practice.
My evaluation of MSM with the horse was not a straight
line venture. After noting desirable benefits personally,
I next decided to try it with my own eleven year old black
lab. She has severe arthritis, particularly involving
the hips and has been maintained on 400 mg of phenylbutazone
per day. Her condition has been so severe, she frequently
required help gaining her feet. We started adding a heaping
teaspoon (6-7 grams) of MSM to her food B.I.D.; stopping
the phenybutazone. For about a month, there seemed to
be no benefit. Then she gradually improved, and now gains
her feet regularly without help.
Even though my practice is limited to horses, the horse
owners frequently ask questions about their dog problems.
For this reason, four additional dogs with similar histories
to mine have been given the same measure of MSM simply
added to the food. There is a general consensus that MSM
has turned back the clock on all five - to their soundness
state of roughly three to four years ago.
Beyond the general improvement in the active state of
these five dogs, it has been noted that with MSM added
to their diet the hair coat improves in appearance and
the toe nails seem to grow faster. Personally, my own
fingernails require clipping about twice as often since
increasing my intake of MSM beyond that normal to my diet.
Following this personal observation, it came to mind
that MSM might be of benefit in the horse with the poor
growing, flinty foot. An evaluation of the idea is underway,
and it looks favorable, but it is too soon to report conclusively.
One additional observation made by a dog owner is interesting.
His old female would consistently leave brown, killed
grass spots wherever she urinated on the lawn. Since MSM
was added to her diet there is no grass browning following
urination. A study is underway to determine physical (such
as pH) as well as chemical changes attributable to MSM.
Two world class human distance runners ingesting up to
4 grams per day of MSM in divided portions contend that
MSM reduces the time required for recovery from a maximum
competitive performance effort.2 Recovery time
to normalcy is about 25 percent of their pre-MSM experience.
One must wonder what applications MSM might have for the
The MSM supplied to me thus far is received in purified
crystalline form. Before use, I have the individual charged
with administration dissolve the crystals in a small amount
of hot water. MSM is readily soluble in warm water. It
is then poured over the feed. No horse, nor dog for that
matter, has demonstrated any reluctance in feeding.
The supplier of MSM advises they are formulating a high
energy MSM content supplement which will make MSM even
easier to use.
The first horse studied was one of my own in hunter training.
The four-year-old horse had been unsuccessful in race
training, having a history of chronic muscle soreness.
Before MSM was added to his feed he was reluctant to do
his job - ears back with frequent tail action. This horse,
and all other adults studied thus far receive 12-15 grams
twice daily in their feed. With this horse it took about
a week to see a significant change. He is now a different
animal, appearing to enjoy his job.
The second trial was with a yearling filly that moved
like a wobbler or herpes victim. This filly was to be
examined shortly for a select thoroughbred yearling sale.
The owner was unwilling to allow the work-up required
to determine a specific diagnosis. With the hope that
it was herpes involvement, MSM was given at a level of
6-8 grams BID. The filly went through inspection and was
passed by a tough inspector. The rational for trying MSM
with this case stems from success using intravenous DMSO
with a few herpes incoordinate individuals. Systemic DMSO
not excreted by the renal pathway is enzymatically converted
to methyl sulfonylmethane or MSM. It is doubtful whether
one could successfully treat the wobbler problem with
Another condition responding exceptionally well to the
MSM supplement approach is epiphysitis. I have treated
seven individuals with confirmed diagnosis, and each has
improved much faster than with conventional therapy. With
these young horses, the supplement addition in each case
was 6-8 grams added twice daily in the feed.
Calcium/ phosphorous balance is critical in the horse,
where these elements comprise roughly 70 percent of the
mineral content of the body. Neither calcium nor phosphorous
deficiency is desirable. Deficiency can cause a stimulation
of excessive secretion of parathyroid hormome resulting
in a dietary deficiency condition termed nutritional secondary
hyperparathyroidism. Calcium denied for bone development
results in an enlargement of structurally defective fibrous
tissue. The condition results in a stress inflammation
termed epiphysitis. That MSM corrects this condition suggests
the supplement moderates basic mineral balance.
The most dramatic epiphysitis case was a filly, again
being prepared for the select sale. When first seen she
appeared extremely sore - with marked reaction on palpation,
and was reluctant to come out of the stall. The farm manager
facitiously said, "no hurry on this one Doc, she doesn't
get inspected for a week." Her total intake of MSM during
this week was roughly 100 grams. She was inspected after
a weeks treatment and passed.
Two other conditions responding to a dietary increase
of MSM are acute laminitis and early navicular disease.
As one example, my daughter's hunter pony had to be scratched
from her last two classes (while on phenybutazone) in
her last show because of a navicular problem. The horse,
on 12 grams of MSM B.I.D. for one month showed sound in
8 classes over fences and 7 flat classes over a four day
period. She now appears totally sound, and will be followed
to determine whether the effect is lasting.
To date, MSM has been provided to about 100 horses presenting
a variety of disorders. Many are still being followed.
Only a select few cases are described here to illustrate
the range of problems seemingly responsive to MSM.
A filly foal was seen with marked pleuritis, demon-strating
no active infection but extremely noisy lungs. MSM was
added to the feed at 12-14 grams/ day as a split feed
addition over five days. No medication was used in conjunction
with the MSM. The fibrous pleurisy cleared and her lungs
were sound-free after the fifth day.
A yearling filly had an on-going problem with a history
of frequent recurrent digestive tract disturbances beginning
when she was a suckling. She seemed to respond to treatment
with cimetidine, aloe-vera, and coating agents. With treatment
termination, she demonstrated varying degrees of discomfort
within a short time. MSM has been supplemented in her
diet at 12-14 grams/day as a split addition for approximately
ninety days and is problem free. A second example in this
general category of disorder is of a suckling with signs
of acute gastritis responding well to cimetidine. Symptoms,
however, returned when treatment was discontinued for
10 days. The foal has been given a combination of MSM
and aloe-vera over a ten day period and appears to be
again in good health.
I trust that my peers recognize and understand my purpose
in providing this preliminary report on a new mode and
method for the treatment of disorders seen in veterinary
practice. I sincerely hope the reader also appreciates
the potential value of MSM in maintaining an animal in
good health, probably at a lower supplement levels than
were used in this study.
1. Jacob, S.W. & Herschler.
R.J. (1983) Dimethyl Sulfoxide after Twenty Years,
XIII-XVII. Annals of the N.Y. Acad. Sciences. Vol.
411, Biological Actions and Medical Applications of
Dimethyl Sulfoxide. J.C. de la Torre Ed.
2: Jacob, S.W. (Personal communication).