The story begins in 18th century with the famous
treatise by Russian physiologist Ilia Metchnikov "The
Prolongation of Life," later translated into English
(New York, SP Putmans sons, 1908.)
Metchnikov speculated that Bulgarian centenarians
achieved their longevity in part due to the
consumption of large quantities of fermented milk
containing different cultures of lactobacilli, then
known to the lay public as "Bulgarian staff" and after
Metchnikov's treatise known as probiotics.
Described as single or mixed cultures of live microbes
that beneficially affect our health by improving the
properties of the friendly bacteria residing in our
intestinal tract, probiotics
should --
- contain live micro-organisms, freeze-dried or in a
fresh or fermented product (though even heat-killed
forms can be effective in some cases);
- be effective when applied in food, pill, capsule
form, as an aerosol, or locally; and
- improve the health and well being
Bacteria and yeasts have been used for years: in
sourdough breads, wines and fermented dairy products.
Now regarded as beneficial to our health, probiotics
are quickly gaining interest as functional foods. Some
of the research-supported supplement manufacturers'
claims include:
- improving intestinal health
- enhancing the immune system
- enhancing the bioavailability of nutrients
- reducing lactose intolerance
- decreasing the allergy reaction
- reducing risk of certain cancers
- controlling bacteria-related ulcers
- reducing serum cholesterol
- antagonising microbial contamination of food
- reducing tooth decay
The mechanisms of the health-promoting effects of
probiotics are still mostly unknown. Researchers think
that they may involve --
- normalizing gut pH;
- antagonizing pathogenic microbes through production
of anti-microbial and antibacterial chemicals;
- competing with pathogenic microbes for available
nutrient
- stimulating immune cells, e.g., the lactobacillus
casei strain "shirota;" and
- producing the ferment lactase to digest lactose.
A newly identified probiotic, bifidobacterium lactis
(HN019), was proved to protect against salmonellas.
According to New Zealand's Milk and Health Research
Center: "[D]ietary supplementation with HN019 provides
a unique opportunity for developing immune-enhancing
probiotic dairy food products with proven health
benefits."
What's Available Over the Counter?
Thus far, studies have shown low viability of
probiotics in market preparations. It is generally
agreed that a probiotic must be capable of colonizing
the intestinal tract to influence human health; this
requirement disqualifies many of the species currently
used in fermented dairy products.
Many -- but not all.
In the Netherlands, the anti-pathogenic effects of
commercial fermented dairy products were clearly
demonstrated. The products included buttermilk and
three types of yogurt. The natural raw buttermilk
successfully fought both yeasts and bacteria, but this
was not observed with pasteurized buttermilk products.
Lactobacillus GG, a variant of lactobacillus casei
mentioned above, has been studied extensively in
adults and children. When consumed as a dairy product,
it multiplies in the intestinal tract and from
colonies. It was shown that this probiotic
successfully fights many forms of diarrhea, bacterial,
virus and antibiotics-caused.
Sources
J Am Diet Assoc 2001;101(2):229-38
Curr Opin Pediatr 2000;12(5):477-81
Microbiol Immunol 2000;44(4):213-22
J Dairy Sci 2000;83(4):894-907 and 641-7
Eur J Clin Nutr 2000;54(3):263-7
Immunol Cell Biol 2000;78(1):80-8
