The Critical Need for
Dietary Research into the
Cause and Progression of
Multiple Sclerosis
by Ashton F. Embry
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Preface
This essay was submitted in January, 2000 to the Institute of
Medicine (IOM) Committee on Multiple Sclerosis: Current Status and
Strategies for the Future which was commissioned by the National
Multiple Sclerosis Society (NMSS). The purpose of the essay was to
convince the Committee to include a recommendation for research into the
likely role that diet plays in MS onset and progression.
Introduction
I am pleased that the IOM committee is taking such a wide-ranging
look at the current status of research into MS and strategies for future
research efforts. I would note the committee has an impressive line-up
of experts although I think that the committee would have been enhanced
by at least one member from outside the medical field (eg an expert on
chaos theory). Also there is no one from the client side of the fence,
the inclusion of which might have also provided some unique
perspectives. I suppose the committee can consider this input as being
both from a scientist completely outside of medicine and also from a
client.
I have
been a geological research scientist for over thirty years (click here
for details) and have worked mainly on large, multi-factoral problems
such as the origin of the Arctic Ocean and the occurrence and causes of
global base level changes. In 1995 my oldest child was diagnosed with MS
and I have spent a great deal of time since then reading the extensive
MS literature with the goal of identifying plausible causal factors of
MS. In geology we accept the fact we can never know anything with
absolute certainty and we concentrate on the simplest solution(s) which
fit all available data. I have applied this same strategy to the
epidemiological and pathogenesis database for MS. I would note that I
have nothing to gain and all to lose from subjectively favouring one
causal factor over another.
MS Cause
I would hope that the committee would unanimously agree that both
genetic and environmental factors play significant roles in MS. My main
interest is in the identification of the environmental factors and I
believe this is a very important area for future research. Given the
current data base for MS, I have concluded that the simplest (best)
explanation for MS is that CNS autoaggressive T cells are activated in
the periphery by foreign antigens and that these effector cells then
cross the BBB and precipitate an autoimmune attack against one or more
autoantigens associated with myelin. I note that this is not the only
plausible cause for MS, just the one that best fits the data.
Furthermore it is the one which is seemingly favoured by most
researchers at this time.
This
leaves important questions of what are the sources of the foreign
antigens, how do they activate the autoaggressive T cells, and when does
this happen. Again the simplest answers to these questions, given all
the constraints of the data, are 1) sources of foreign antigens are both
infectious agents and food, 2) activation of both naïve and memory Th
cells is mainly by cross reactions induced by molecular mimicry between
foreign and self antigens, and 3) such activation happens throughout the
course of the disease in a chaotic fashion. I stress that all of these
answers are not proven or either widely accepted, they just seem to me
to be the best ones if all the data are honoured. I expect most members
of the IOM committee would agree somewhat with this analysis with the
notable exception of my inclusion of food being a source of foreign
antigens which can result in the activation of CNS autoaggressive T
cells. The main reason for this submission to the IOM committee is to
expand on this concept and to argue for the need for research which
determines whether or not food-derived antigens play a substantial role
in MS onset and progression.
Food-derived Antigens
As stated earlier, I think most of the IOM committee, and indeed
most MS researchers, would agree that foreign antigens play a major role
in MS. So the question at hand is whether or not it is plausible that
food-derived antigens are part of the foreign antigen load which drives
MS. My arguments for why food antigens quite possibly play a role in MS
are below. Once one accepts that it is plausible (ie there is a
reasonable chance) that food antigens contribute to MS progression, then
there can be no doubt that research is necessary to decide the issue
beyond a reasonable doubt. Furthermore, given the lack of industrial
incentives for doing such research (no significant financial reward),
only charitable and governmental organizations like NMSS and NIH can
provide the necessary promotion and funding for such research.
Clearly,
if it is found that food antigens do indeed play a role in MS onset and
progression, then that will revolutionize MS research and treatment. How
many other proposed research topics have that potential! So what is the
circumstantial evidence that indicates that food antigens may be a
significant factor in MS?
First of
all, from a big picture view, it is reasonable to expect that food
antigens may play a role in a disease like MS which can be lumped with a
large number of chronic diseases in which both genetic and environmental
factors play major roles. Eaton and Konner (1985) published a very
important paper in NEJM which introduced the concept of Paleolithic
nutrition. Simply stated, it argues that foods introduced into the human
diet by the agricultural revolution (~6000-8000 years ago for northern
Europeans) can potentially cause biochemical failures which lead to
chronic illnesses in genetically susceptible people because humans have
not had time to genetically adapt to such foods. Thus in a given
population there will be a given percentage of people who are
genetically incompatible with one or more of the newly introduced foods.
These "new" foods include dairy products, grains, legumes and yeast as
well as large increases in the consumption of sugar, salt and saturated
fat. The pre-agricultural diet (Paleolithic diet) consisted of lean wild
meat (low fat, low % of saturates), fruits and vegetables. There can be
no doubt that the newly introduced foods have contribute substantially
to other genetic-environmental (chronic) diseases such as heart disease,
hypertension, stroke, type 2 diabetes and various forms of cancer. The
question is do these new foods also contribute to autoimmune diseases
including MS. The evidence which indicates that these foods do indeed
play a role in autoimmune disease include:
- The
geographic variations in the prevalence of autoimmune diseases tend to
match variations in food supply with higher prevalence occurring in
areas where the new foods dominate the diets (temperate climates). For
example it was shown that the correlation between milk consumption and
MS prevalence was .84 (Malosse et al, 1992). Even more impressive was
the almost one for one correlation between type 1 diabetes prevalence
and consumption of a specific type of beta casein (.98!) (Elliott et
al, 1999).
- Animal
experiments show that foods such as milk, wheat and soy can
precipitate IDDM and RA in mice, rats and rabbits (Coombs and Oldham,
1981; Elliott et al,1984; Welsh et al, 1985; Scott, 1996). Little has
been done in this regard for MS although I was recently in contact
with Dr John Elliott of the University of Alberta who told me that his
recent experimental work has demonstrated that NOD mice fed an
elemental diet were resistant to MOG-induced EAE but lost that
resistance when milk protein was added to the diet (J Elliott, pers.
comm., 1999).
- People
with autoimmune diseases have T-cells and antibodies which cross react
with both self proteins and food proteins (Martin et al, 1991; Perez-Maceda
et al, 1991; Cheung et al, 1994; Ostenstad et al, 1995 ).
-
Molecular studies of proteins from wheat, milk, yeast and legumes show
that they can have very similar molecular structures as self proteins
and that peptides derived from food proteins activate autoreactive
T-cells derived from people with autoimmune disease ( Singh et al,
1989; Ostenstad et al, 1995; Cavello et al, 1996; Honeyman et al,
1998).
-
Clinical trials with people with RA and Crohn’s disease, both
organ-specific, cell-mediated autoimmune diseases with numerous
immunological similarities to MS, show that avoidance of proteins from
wheat, dairy and legumes results in major symptom improvement (Panush
et al, 1986; Darlington and Ramsey, 1992; Riordan et al,1993; Haugen
et al, 1994; Beattie and Walker-Smith, 1994; Husby et al, 1995;
Kavanaghi et al, 1995; Fukuda et al, 1995; Zoli et al, 1997).
- Gluten
proteins from a variety of grains are the primary cause of two
autoimmune diseases, celiac disease and dermatitis herpetiformis
(Marsh, 1992; Bodvarsson et al, 1993). Also of note is that persons
with celiac disease are much more susceptible to other autoimmune
diseases including RA, IDDM, autoimmune thyroid disease, Addison’s
disease and alopecia areata ( Lepore et al, 1996; Kaukinen et al,
1999).
To me,
when all this epidemiological, experimental, clinical and theoretical
evidence is considered as a whole, it is very reasonable to postulate
that food proteins, especially those recently introduced into the human
diet, may well play a role in a variety of autoimmune diseases including
MS.
Infectious Agent-Diet Model for MS
Given this, it is still necessary to provide a theoretically
plausible pathogenesis for MS which involves food proteins and there
should be no major contradictions with the available epidemiological
data base. Below is a simple hypothesis for MS pathogenesis, which for
the most part follows the one currently favoured by most researchers.
Essentially the addition of food proteins is nothing more than a small,
but potentially critical, modification of this widely accepted model.
The
"infectious agent-diet model" for MS cause is as follows:
-
Infection with one or more childhood illnesses (e.g.
Epstein-Barr,HHV-6) results in an autoimmune reaction against tissue
in the CNS by molecular mimicry (Wucherpfennig and Strominger, 1995).
Such autoimmune reactions are suppressed before any demyelination
occurs. However memory cells against the infectious agent are produced
and such memory cells can be seen as an autoimmune time bomb because
they are also potentially autoaggressive and are much more easily
activated than naïve cells (Lovett-Racke et al, 1998).
- With
time, intestinal permeability increases due to various factors
including food allergies, alcohol consumption, candida overgrowth and
non-steroidal anti-inflammatory drugs (Doe et al, 1979). The
consumption of gluten and legumes also increases intestinal
permeability through the action of lectins (glycoproteins) (Freed,
1991, 1999).
- With
increased intestinal permeability, intact food proteins begin to
escape the gut as do gut bacteria products (Walker and Isselbacher,
1974; Gardner, 1988).These antigens are likely presented mainly by B
cells (non-professional APC) and precipitate an autoimmune response by
molecular mimicry of the childhood infectious agents and/or self
antigens in the CNS. Cordain (1999) has discussed such three way
mimicry in celiac disease and the results of both Singh et al, (1989)
and Ostenstad et al (1995) indicate that three way mimicry between
antigens derived from self, food and infectious agents is a plausible
mechanism for the development of autoimmune disease. Such
cross-reactions result in the activation of the autoaggressive memory
cells which do not require co-stimulation. These initial, rather
limited reactions are most commonly successfully suppressed by a
reasonably well functioning immune system before any clinically
detectable damage is done.
- The
chronic activation of the autoaggressive memory cells by food and
bacteria mimics which are escaping through the intestine wall on a
near daily basis (MS never sleeps!), combined with major reactivation
events precipitated by rare infections, finally results in a failure
of the suppressor side and a major autoimmune attack occurs. This is
eventually suppressed, and depending on the strength of the immune
system and its ability to suppress subsequent autoimmune reactions,
the individual experiences a benign course, a relapsing-remitting
course (younger, healthier immune system) or a progressive course
(older, degraded immune system).
The only
difference between this model and the currently favoured model of
infectious agent-driven MS is the addition of food antigens which
potentially cause small, autoimmune reactions on an almost daily basis.
Thus we may have two different modes of autoimmune reactions occurring
in MS, one small and frequent (food-driven) and one large and rare
(infectious agent-driven). Many geological processes (e.g. erosion) have
a similar duality in terms of magnitude and frequency and many debates
have been held on the relative importance of each type of action. Is the
landscape mainly shaped by almost imperceptible, day to day erosion or
by the powerful 1000 year storm? It is now agreed that both processes
play important roles in landscape evolution. Of course for MS it is
important at this time to establish if the high frequency, low magnitude
process of food-driven autoimmunity even exists and, if it does, whether
or not it is of any significance.
I would
further suggest that the addition of such food-driven reactions to the
model improves its compatibility with the epidemiology of MS. One of the
nagging problems with the infectious agent-driven model has been the
fact that the geographic prevalence differences for MS are not matched
by differences in the prevalence of the various infectious agents
postulated to play a role in MS. The major differences in MS prevalence
in Australia (McLeod et al, 1994) are certainly not matched by notable
differences in infection types, rates or timing. Also it has been
documented that MS is more prevalent in inland farming communities than
coastal fishing communities when genetics and latitude are held constant
and these significant differences are especially difficult to
rationalize with the infection-driven model. For example MS prevalence
in the outports of Newfoundland is 25/100000 (Pryse-Phillips, 1986)
whereas in the farming communities of Alberta it exceeds 200/100000 (Svenson
et al, 1994). With genetics and latitude being essentially the same for
these two areas of Canada, such a near ten fold difference cannot be
easily explained by the infectious hypothesis. However, with the
addition of the food antigen factor, which would take into account the
dominance of high fat meats, dairy and grains in the Albertans’ diet in
contrast to the dominance of fish and vegetables of the Newfoundlanders’
diet, this major difference in prevalence becomes much better
understood. This difference between farming and fishing communities has
also been documented in Norway (Swank et al, 1952) and in the islands
north of the Scotland (Shetlands vs Faroes) (Fog, 1966) and again the
food antigen factor helps to explain such differences.
Required Research
Given that dietary research is required for MS, the next question is
what type of research would effectively answer the question of whether
or not dietary proteins play an important role in MS. To me I think the
best approach would be one or more clinical trials with the subjects
using a Paleolithic diet as the therapy. Such a diet emphasizes lean
meats, fruits and vegetables and excludes dairy products, grains, yeast
and legumes. Other features include a more balanced ratio of fat types,
a reduction in salt and sugar intake and no alcohol. The main variable
to be measured would be lesion load as determined by serial MRI scans
over a one to two year time period. I leave the details of such a trial
to those who are experienced in such matters but to me such clinical
trials, if properly designed and run, would decide the issue to most
people’s satisfaction.
I hope
that the IOM Committee finds my reasoning compelling enough to recommend
research into food antigens and MS. This would constitute extraordinary
research (in the sense of Kuhn, 1970) which has been exceedingly rare in
the MS research agenda for the past decade (oral tolerance research
being a notable exception) (Weiner et al, 1994). There is no doubt we
need the normal, inductive science which has completely dominated MS
research for decades. However, most breakthroughs in science have not
come linearly from such plateau science although such science is
absolutely necessary for novel concepts to be conceived in the first
place. The suggested dietary research is clearly not safe, predicable
research which commonly has little or no impact (most MS research papers
are rarely if ever cited). It is risky research which can potentially
yield major returns for a relatively small investment.
Conclusions
In summary, I believe there are substantial data and theoretical
considerations which make the concept that food proteins play a role in
MS progression a very plausible hypothesis. As such, I think such a
hypothesis should be tested as quickly and thoroughly as possible with
clinical trials being the best research method. The MS research
community rarely is presented with a plausible, testable hypothesis for
MS progression and it behooves the community and the main funding
agencies to act expediently in testing it. Of course those with MS, most
of whom are consuming the potentially problematic food proteins every
day, would be most interested to know beyond a reasonable doubt if their
current dairy and grain-dominated diets affect the progression of their
MS or not. Right now no responsible researcher, including all those on
the IOM committee, can guarantee persons with MS that food proteins from
such foods as dairy and grains will not affect the progression of their
MS. In this atmosphere of uncertainty some persons with MS have even
opted for diet revision over use of one of the recommended drugs to try
to slow MS progression. I am sure most of the IOM Committee members
would not support such an action but until reliable information on diet
and MS is available it is impossible to say with confidence if such a
choice will be detrimental or not.
Above all
else, I think it is imperative that sufficient research be done as soon
as possible so that MS researchers and clinicians can provide persons
with MS with a definitive statement on the role of dietary proteins in
MS. Statements such as "we do not know" and "there is no definite proof
that food proteins are involved in MS" (an ambiguous way of saying we do
not know) are not adequate and are potentially harmful. I hope the IOM
Committee will recommend that sufficient research be done to finally
settle this important question which continues to plague many persons
with MS and which could open up entirely new fields of research and
therapy for MS.
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