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Probiotics

by Mona Rosene, MS, RD

Definition

Over 400 different species of live microorganisms, known as probiotics, inhabit the human gastrointestinal tract[1]. Our unique defense system depends primarily on our ability to secrete plasma cells and the gut happens to be a major contributor to this system, supplying 70% to 90% of the immune cells.[2] There are about 10 billion immune-producing cells per meter of human small bowel! These live microorganisms have been known to have a health benefit on man or animal when ingested.

Background

Many probiotic strains have been used for centuries to manufacture cultured dairy products; therefore they have obtained GRAS status (Generally Recognized as Safe).[3] According to a recent FAO/WHO report,[1] probiotics used in foods must be able to survive gastric juices and exposure to bile. In addition, they must be able to propagate and colonize the GI tract, as well as be safe, effective, and maintain their potency for the duration of the shelf-life. Milk and milk products have been used to transport probiotics because the milk protein provides protection to the bacteria as it passes through the stomach and the lactose can be utilized as an energy source for the organism.[4]

Interest in researching the possible benefits of probiotics has increased rapidly over the past decade. This research has significantly improved our understanding and ability to characterize specific probiotic organisms and attempts to verify their assigned health benefits.[5] The natural products industry has taken full advantage of this surge in research and US sales of probiotic supplements were estimated at $764 million in 2005 and are expected to increase at an average annual growth rate (AAGR) of 7.1% to $1.1 billion by 2010. Food products dominate the market and sales were estimated at $498 million in 2005 and will rise at an AAGR of 7% to $700 million by 2010. Yogurt, kefir, and cultured drinks are representing the major categories of the food applications.[6] Have consumers spent their money wisely, that’s the million dollar question, or in this case, the $700 million question.

Immune Function

Our immune system may experience deficiencies as a consequence of old age, stress, infectious illness, and malnutrition. Dietary intervention is an attractive way of enhancing and optimizing physiological functions including the immune system. Fermented foods are among the dietary interventions which have been demonstrated to improve certain key immune responses that are important in maintaining health.[7]

The ability of a dietary supplement to optimize immune function is especially important for those who may have an underdeveloped immune system, such as infants, or a poorly functioning immune system typically seen in the elderly or immunocompromised population. There is has been research in this area that suggests dietary supplements are beneficial for this population.[8] [9] [10] The question is will dietary supplements such as probiotics, be beneficial to a healthy population? Sheih et al[11] asked that same question. In their study they supplemented two groups with 1 billion CFU/g L. rhamnosus HN001, which was consumed in reconstituted low fat milk or lactose free milk. They found significant increases in phagocytic activity and Natural Killer (NK) cell killing activity. Increased phagocytic activity is thought to be important in anti-microbial defense mechanisms, while NK cell killing is important for control of viral-infected cells. Another study conducted by Takeda[12] NK cell activity of healthy, middle aged and elderly subjects with low levels of NK-cell activity after consuming fermented milk containing 40 billion live L. casei strain Shirota daily for three weeks. Results for the middle aged subjects indicated a significant increase in NK-cell activity after the start of the fermented drink. And it remained elevated for the next 3 weeks. In the elderly group, NK-cell activity was not influenced by intake of L. casei Shirota, however it inhibited the decrease of NK-cell activity in this population. This study concluded that consuming fermented milk that contains L. casei shirota can augment NK-cell activity, which results in the maintenance of a healthy life and prevention of disease.

Urogenital Health

Vaginal infections may be caused by oral and vaginal sex, however many cases of urinary tract infections (UTI) and vaginitis arise from ascension of the person’s own microorganisms. These microflora originate in the gut and ascend via the rectum. Lactobacilli normally reside in the vaginal canal, however their concentration may become low due to this abnormal bacteria moving into the vaginal canal, which results in an environment prime for pathogenic yeast or bacteria.[13] Studies have shown that daily oral intake of L. rhamnosus GR-1 and L. fermentum RC-14 can modify the vaginal flora. One placebo controlled trial tested daily supplementation with these strains for 60 days. The results indicated the restoration of microflora from asymptomatic bacterial vaginosis to a normal lactobacilli colonized microflora in the treatment group compared to placebo group (37% vs. 13%.) In addition, there was significantly less yeast in the vagina during daily doses of these two probiotic strains for 60 days.[14]

A study on the prevention of UTI’s used a once-weekly vaginal suppository that contained 1 billion L. rhamnosus GR-1 and L. fermentum B-54 for one year and compared the results to the previous year. Twenty-five women participated and reported a significant decrease in UTI’s while using probiotics from the previous year, an average of 6 episodes were reported in the previous year and 1.6 episodes were reported during supplementation – a 30% reduction with no side effects.[15] This is comparable with the results obtained through the use of antibiotics, however many subject experience uncomfortable side effects with antibiotics.[16]

The following strains of probiotics are easily attainable in the US and have some positive research behind them: [13]

Lactose Intolerance

There is some evidence to suggest improved lactose digestion with the use of Lactobacillus bulgaricus and Streptococcus thermophilus[17] for reasons such as: the active enzyme b-galactosidase in bacteria-containing fermented and non-fermented milk products is able to survive the gastric acidity and is released into the small intestine and supports lactose digestion. Second, if gastric emptying and intestinal transit time are slowed (caused by a greater viscosity and lower pH) the residual action of b-galactosidase is prolonged in the small intestine and the osmotic load of lactose is decreased. Lastly, symptoms may be alleviated due to acute and chronic ingestion of lactose and bacteria in fermented milk products that may affect pH, microflora, lactose fermentation, and other variables in the intestine, as well as the sensitivity of the subject to GI disorders. The following strains are effective at improving lactose digestion compared with milk; however they are less effective than yogurt or unfermented S. thermophilus or L. bulgaricus milk.

Keep in mind that probiotic bacteria may alleviate clinical symptoms of lactose intolerance or malabsorption for other reasons such as colonic flora or colonic pH.[17]

Conclusion

The addition of fermented milk products, in the form of yogurt, kefir, and cultured drinks is one simple step Americans can take to improve health. For specific health problems, the first step is to obtain an accurate diagnosis from your physician or healthcare practitioner and then decide which form of treatment is best for the diagnosis. There is quite a bit of research supporting the use of probiotics for health, however in some cases more studies need to be conducted. According to the research cited above, probiotics may have a positive affect on our health. Since receiving GRAS status, it may be beneficial to incorporate them into your daily regime. Probiotics are not the magic bullet we all search for, however increasing evidence suggests the use of proven probiotic strains and manipulation of the host’s intestinal microflora may be valuable options to help restore health.

References

  1. ^ a b ftp://ftp.fao.org/es/esn/food/probio_report_en.pdf Joint FAO/WHO report on Health and Nutritional Properties of Probiotics in Food including Powder Milk with Live Lactic Acid Bacteria 2001
  2. ^ Brandtzaeg P, Halstensen T S, Kett K, Krajci P, Kvale D, Rognum TO, Scott H, Sollid LM. Immunobiology and Immunopathology of Human Gut Mucosa: Humoral Immunity and Intraepithelial Lymphocytes. Gastroenterology 1989;97:1582-84.
  3. ^ ftp://ftp.fao.org/es/esn/food/gilli.pdf Gilliland SE. Technological & Commercial Applications of Lactic Acid Bacteria; Health & Nutritional Benefits in Dairy Products. Animal Science Dept.; Oklahoma St. University
  4. ^ Charteris et al. Antibiotic susceptibility of potentially probiotic Lactobacillus species. J Food Prot. 1998 Dec;61(12):1636-43
  5. ^ Senok AC, Ismaeel AY, Botta GA. Probiotics: facts and myths. Clin Microbiol Infect 2005;11:958-966.
  6. ^ http://www.the-infoshop.com/study/bc31434-probiotics.html Probiotics: Ingredients, Supplements, Foods 2005.
  7. ^ de Simone C, Rosati E, Moretti S. Probiotics and stimulation of the immune response. Eur J Clin Nutr 1991; 45(Suppl):32-34.
  8. ^ Gill HS, Darragh AJ, Cross ML. Optimizing immunity and gut function in the elderly. J Nutr Health Aging 2001;5(2):80-91.
  9. ^ Chandra RK. Effect of vitamin and trace-element supplementation on immune responses infection in elderly subjects. Lancet 1992;340:1124-27.
  10. ^ Chandra RK. Graying of the immune system: can nutrient supplements improve immunity in the elderly? JAMA 1997;277:1398-99.
  11. ^ Sheih YH, Chiang BL, Wang LH, Liao CK, Gill HS. Systemic immunity-enhanced effects in healthy subjects following a dietary consumption of the lactic acid bacteria Lactobacillus rhamnosus HN001. J Am Coll Nutr 2001;20(2):149-56.
  12. ^ Takeda K, Okumura K. Effects of a Fermented Milk Drink Containing Lactobacillus casei Strain Shirota on the Human NK-Cell Activity. J Nutr 2007; 137: 791S–793S.
  13. ^ a b Reid G, Burton J, Devillard E. The rationale for probiotics in female urogenital healthcare. Medscape Gen Med 2004;6(1).
  14. ^ Reid G, Charbonneau D, Erb J, Kochanowski B, Beuerman D, Poehner R, Bruce AW. Oral us of lactobacillus rhamnosus GR-1 and L. fermentum RC-14 significantly alters vaginal flora: randomized, placebo-controlled trial in 64 healthy women. FEMS Immunol Med Microbiol 2003 Mar20;35(2):131-4.
  15. ^ Reid G, Bruce AW, Taylor M. Instillation of Lactobacillus and stimulation of indigenous organisms to prevent recurrence of urinary tract infections. Microecol. Ther 1995;23:32–45.
  16. ^ Brumfitt, W., and J. M. Hamilton-Miller. Efficacy and safety profile of long-term nitrofurantoin in urinary infections: 18 years experience. J. Antimicrob. Chemother 1998; 42:363–371
  17. ^ a b de Vrese M, Stegelmann A, Richter B, Fenselau S, Laue C, Schrezenmeir J. Probiotics--compensation for lactase insufficiency. AJCN 2001; Feb;73(2 Suppl):421S-429S.

Mona R. Rosene, MS, RD, works as a Nutrition Research Scientist for WhiteWave Foods Company. In addition, she provides individual or group nutrition counseling and is available for nutrition presentations.

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