Hygiene Hypothesis 2012

[Carl Custer]

FYI:
A Darwinian View of the Hygiene or “Old Friends” Hypothesis
Micrbe Magazine-ASM Apr
When urban living reduced contacts of humans with microbes and worms,
it increased our risk for chronic inflammatory disorders
Graham A. W. Rook
Summary
● Microorganisms and macroorganisms such as helminths from mud,
animals, and feces play a critical role in driving immunoregulation.
● The term "old friends" is broader than "hygiene" to describe this
hypothesis, and it implicates exposures to microbes and other
organisms during critical phases of human development.
● Diseases and conditions of the modern era, including multiple
sclerosis, type 1 diabetes, and allergies, involve disrupted
immunoregulatory circuits, likely reflecting reduced exposures to "old
friend" organisms with which humans coevolved.
● Several clinical trials are testing these concepts, determining
whether renewed exposures to "old friend" organisms can help to combat
these modern-era diseases.

The notion that urban life is associated with increases in chronic
inflammatory disorders traces back to the 19th century, when
physicians in Europe noticed that allergies were rare among farmers.
In sharp contrast, hay fever was regarded as the hallmark of
prosperous, educated city sophisticates.

Several rigorous epidemiologic studies of more recent vintage lend
support to the idea that growing up in a farming environment protects
children against developing hay fever or other allergies. Further, in
1989 epidemiologist David Strachan of St. George's University in
London, United Kingdom, observed allergies as being less common in
children with older siblings, especially boys, suggesting to him that
microbial encounters might protect against allergic disorders.

Strachan's and other studies led to the view that microorganisms and
macro-organisms from mud, animals, and feces with which mammals
coevolved play a critical role in immunoregulation and in inhibiting
inappropriate immune responses to self, gut contents, and allergens.
In describing this phenomenon, I prefer the term "old friends" to the
more common "hygiene" hypothesis. The former term is broader, and
implicates the effects of prenatal, neonatal, and adult exposures to
such organisms as well as the crucial effects of microorganisms found
in the gut, skin, lung, and the oral and nasal passages of the host.
This area of clinical research is set to become a major branch of
Darwinian medicine, with the potential for yielding new strategies for
preventing and treating a widening variety of diseases.

Several Types of Disease Are Associated with Urban Living
, , ,
Much More at:
<http://www.microbemagazine.org/index.php/04-2012-home/4700-a-darwinian-view-of-the-hygiene-or-old-friends-hypothesis>

[Aqu...@aol.com]

Carl,

 

I am not sure that immunity can be simplified as only an acquired response to favorable external stimulus. Confounding the issue is the effect of external immunosuppressive agents. How do we differentiate between external agents that allegedly boost the immune system versus those that suppress it? What about lifestyle considerations, etc.?

 

 If city dwellers have immune issues that country dwellers do not, wouldn't you want to tally all factors that favorably and unfavorably affect the immune system? Wouldn't you have to assign weighted factors to each in order to assess the composite picture?

 

If we only acquire immunity through exposure to stressors, how do we explain survivors of new pandemics?

 

Alan Ismond, P.Eng.
Aqua-Terra Consultants

 

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[Carl Custer]

I don't think the article attempted to simplify. There are certainly
exceptions. The environment is not homogeneous nor are humans.
Did you read the rest of the article including diet?

On Sat, Apr 14, 2012 at 2:40 PM, <Aqu...@aol.com> wrote:
> Carl,
>
> I am not sure that immunity can be simplified as only an acquired response
> to favorable external stimulus. Confounding the issue is the effect of
> external immunosuppressive agents. How do we differentiate between external
> agents that allegedly boost the immune system versus those that suppress it?
> What about lifestyle considerations, etc.?
>
>  If city dwellers have immune issues that country dwellers do not, wouldn't
> you want to tally all factors that favorably and unfavorably affect the
> immune system? Wouldn't you have to assign weighted factors to each in order
> to assess the composite picture?
>
> If we only acquire immunity through exposure to stressors, how do we explain
> survivors of new pandemics?
>
> Alan Ismond, P.Eng.
> Aqua-Terra Consultants

[Robert A LaBudde]

Although there are certain areas where the Hygiene Hypothesis is
attractive, e.g., eating fermented foods, there are others where the
proponents greatly overstate the evidence.

1. The article Carl quoted made one claim based on evidence: People
on farms have lower incidence of 'hay fever' than city people.
Obviously this is an observational conclusion subject to many
alternative conclusions other than 'exposure renders immunity'. One
is that people with hay fever wouldn't tend to continue to live where
allergens abound. Another is that there are different sources of
allergens in the country and in cities. Others relate to lifestyle
differences, etc. Why leap to the HH conclusion?

2. Some diseases are less dangerous when encountered young. This
includes polio, where paralysis incidence depends upon age. However,
most of the diseases we worry about today are much more deadly one
encountered young. This is a much more common event.

3. The inverse of the HH is just as likely to be true: Exposure to an
allergen or agent will trigger, not immunity, but severe autoimmune
response. This is common in severe infections. It's a big reason why
you don't want a Salmonella or Campylobacter episode. The HH assumes
the immune system is always benevolent. It's not.

4. I have searched, and not found significant credible evidence that
Helminth parasite infection has beneficial effects, as per the HH,
despite constant claims of this. Otherwise such treatments would be
ethical in the USA. Instead, ongoing studies of HH here use only
non-pathological parasites that clear within a couple of weeks.

5. I have an open mind about the HH, but at the moment it appears to
be mostly unsupported conjecture, somewhat like claims about
nutriceuticals for treating disease.

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================================================================
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Least Cost Formulations, Ltd. URL: http://lcfltd.com/
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Virginia Beach, VA 23464-3239 Fax: 757-467-2947

"Vere scire est per causas scire"
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[Luca Bucchini]

The Hygiene Hypothesis may be partially or totally true, or eventually disproved. It is an interesting scientific hypothesis, partially backed by data.

As a food safety professional, I am concerned with some of the proposed implications. On one hand, if proved, the HH could lead to disease reduction, more health, thanks to further technological progress. If HH is true, I can't see why we should not revisit the way homes or offices are cleaned. Are there better ways? Should we replace the cleaning agents? On another level, should food for infants be enriched with some beneficial bacteria or antigens on top of vitamins and minerals? Should we spray the bacteria in their rooms? Should we remove some chemicals from their environment? Should we find better technologies to transform foods, while ensuring safety? Potentially, all great stuff.

It's also clear to me that, whatever is recommended for allergy prevention, children need exposure to nature. Ensuring that the exposure is safe is sometimes a challenge (see petting zoos).

What troubles me is the equating of the HH to good ol' days mythology, when people drank raw milk, and some died without too much fuss because of pathogens in it; or Londoners drank pure untreated well water, used simple traditional sanitation, and we had the occasional, deadly cholera outbreak; or Germans ate that wonderful botulin toxin laden ham. And so on.

I believe that this last implication does not follow logically from the HH. It's either based on unacceptable ethical standards (i.e., some raw milk deaths are ok as long as we can eat "traditionally") or on suppression of evidence (i.e., foodborne disease is an invention of food industry). That's where I think there's not been enough clarity.

Luca

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