The Health Effects of Lactobacillus acidophilus Oliver Wyckoff , Beloit College

1. The Health Effects of Lactobacillus acidophilus Oliver Wyckoff , Beloit College ABSTRACT Lactobacillus acidophilus is a species of bacteria commonly found in the human body. My hypothesis is that L. acidophilus is beneficial to humans immunologically, may help to lower cholesterol, and reduce the risk for cancer. This poster provides peer reviewed journal articles with studies validating the health effects of L. acidophilus, including: the immunological benefits, effects on carcinogenesis, and cholesterol. L. acidophilus has many health benefits and should be integrated into a balanced, healthy diet. Based on peer-reviewed studies, a daily dosage of 109 colony forming units, or approximately 1 cup of yogurt, is most beneficial. DISCUSION The research regarding L. acidophilus is confronted by two major challenges: the presence of multiple strains of L. acidophilus and the difference between in vitro and in vivo studies. There are many different strains of L. acidophilus and each strain can produce different results. Some studies have used strains found in other mammals, and others have used separate strains found in humans (13). This could be a factor in the conflicting results found between studies. The other major challenge regarding research are studies that test L. acidophilus in vitro versus those that test the bacteria in vivo. Because L. acidophilus is part of a dynamic digestive tract with hundreds of other microorganisms, and because there are many different interactions going on in the human body, in vivo studies are greatly preferred. However, many researchers have used in vitro studies to support grand hypotheses without in vivo experiments. In vitro studies should be viewed with a more critical eye because they cannot replicate the complexity of the human body. METHOD The author reviewed relevant peer-reviewed journal articles and peer-reviewed websites to gather information related to L. acidophilus. INTRODUCTION Lactobacillus acidophilus is one of the most important probiotic species. L. acidophilus is a symbiotic lactic acid producing bacterium found in the mouth, gastrointestinal tract, and vagina. L. acidophilus, along with other probiotic microorganisms, enters the human body through the consumption of foods containing high concentrations of the organism (1). L. acidophilus is commonly found in yogurt and other fermented dairy products. L. acidophilus naturally produces several compounds that are beneficial to the human body, including: vitamin K, the enzyme lactase, and the antibiotics acidolin, acidolphilin, lactocidin, and bacteriocin (2). L. acidophilus has been shown to aid in the synthesis of B-vitamins during the production of dairy products. Shahani et al found that L. acidophilus increased the concentrations of niacin, pantothenic acid, pyridoxine, biotin, and folic acid in diary products when they are fermented. Many different doses of L. acidophilus have been used in clinical studies, but a daily dose of 109 colony forming units has been found to be the most beneficial (1). Translated into yogurt, the suggested daily dosage varies greatly because different brands have varied concentrations, and concentrations can also vary between containers. However, one serving of approximately one cup of live-culture yogurt per day should provide an adequate amount of live L. acidophilus cells. Figure 1. Probiotics and Colon Cancer (11) Figure 2. Human Colonic Microflora (13) RESULTS L. acidophilus has been shown to be beneficial immunologically, especially with diarrhea and intestinal disorders. In a study of Bolivian children, Grandy et al (3) found that L. acidophilus combined with other probiotics and a rehydration solution decreased the duration of diarrhea. Several other studies have found that L. acidophilus can both prevent and treat diarrhea. In a meta-analysis McFarland (4) found that probiotics, particularly a mix of L. acidophilus, Saccharomyces boulardii, and Bifidobacterium bifidum, significantly prevented traveler’s diarrhea. In a Korean Study of irritable bowel syndrome (5), Hong et al found that L. acidophilus reduced pain and discomfort in patients with irritable bowel syndrome and could be considered “safe and effective” in patients who excrete normal or loose stools. L. acidophilus has also been shown to have a significant effect on necrotising enterocolitis, the rapid tissue death of portions of the bowels, in infants. Guthmann et al (6) found that L. acidophilus, especially when used with Bifidusbacterium spp., was a safe and beneficial treatment for necrotising enterocolitis. Out of 1,117 infants randomly selected to receive probiotics, none experienced unwanted side effects. L. acidophilus has been shown to have many general immune enhancing functions, including increasing the normal immune system response towards bacteria in the gastrointestinal tract and upper-respiratory tract, a higher white blood cell count, and increased vaccine response. Paturi et al found that L. acidophilus enhanced specific gut and immune responses in mice; particularly L. acidophilus increased the number of IgA producing cells, and enhanced the secretion of anti-inflammatory and pro-inflammatory cytokine. In a similar study (7), researchers found that L. acidophilus triggered the expression of viral defense genes. L. acidophilus was also found to double the number of white blood cells with phagocytic activity after three weeks of consumption. Glück and Gebbers (8) found that the consumption of L. acidophilus, through a probiotic drink, reduced potentiallypathogenic bacteria in the upper respiratory tract by 19 percent, significant to the 99th percentile. In a separate study, Link-Amster et al (7) found the consumption of L. acidophilus mixed with B. bifidum after vaccination increased total IgA antibodies by 60% over the control. L. acidophilus has been studied to determine if it fights and prevents cancer. Early studies by Bailey and Shahani (1) found that milk fermented with L. acidophilus reduced tumors in mice by 16-41%. However, further studies that have tried to elaborate on these properties have had only moderate success. Yazdi et al (9) found that L. acidophilus decreased the tumor growth rate in mice through the production of immunomodulatory cytokine IL-12. Urbanska et al (10) found that the daily consumption of microencapsulated L. acidophilus by mice resulted in significant suppression of colon tumor incidence, tumor multiplicity, and reduced tumor size as well as the stabilization of animal body weight and a decrease of bile acids. In reviewing the relevant literature, Wollowski et al (11) found that L. acidophilus fights colon cancer by binding mutagens, decreasing the excretion of mutagens, stimulating the immune system, manipulating enzymes, and decreasing the DNA damage in colon cells. The effect of L. acidophilus on serum cholesterol is mixed with studies showing a reduction from 0 – 20 percent (1). L. acidophilus has been shown to reduce cholesterol in vitro, but studies that have tried to replicate these results in vivo have not been able to produce consistent results. A recent double-blind,placebo-controlled, cross-over study, however, has shown promising results. Anderson and Gilliland in the Journal of American College of Nutrition found that L. acidophilus reduced the level of serum cholesterol concentration in subjects (12). The combined analysis of two treatment studies showed that the bacteria reduced serum cholesterol by 2.9%. The researchers concluded that, since a 1% reduction in serum cholesterol is associated with approx. a 2 – 3% reduction in the risk for coronary heart disease, the regular consumption of L. acidophilus could reduce the risk of coronary heart disease by 6 to 10% (12). • REFERENCES • Shahani, Khem, and Amadu Ayebo. "Role of Dietary Lactobacilli in Gastrointestinal Microecology." The American Journal of Clinical Nutrition, 1980. • Clinic, Mayo. Lactobacillus acidophilus. June 1, 2010. http://www.mayoclinic.com/health/lactobacillus/NS_patient-acidophilus (accessed September 24, 2010). • McFarland, L. (2005). Meta-analysis of probiotics for the prevention of traveler's diarrhea. Seattle: Department of Health Services Research and Development. • Grandy, G., Medina, M., Soria, R., Teran, C., & Araya, M. (2010). Probiotics in the treatment of acute rotavirus diarrhoea. A randomized, double-blind, controlled trial using two different probiotic preparations in Bolivian children. BMC Infectious Diseases . • Hong KS, K. H. (2009). Effect of probiotics on symptoms in korean adults with irritable bowel syndrome. Gut and liver , 101-107. • Guthmann, F., Kluthe, C., & Bührer, C. (2010). Probiotics for prevention of necrotising enterocolitis: an updated meta-analysis. Klinische Pädiatrie , 284-290. • de Roos, Nicole M, and Martijn B Katan. "Effects of probiotic bacteria on diarrhea, lipid metabolism, and." American Clinical Journal of Nutrition, 2000. • Glück, Ulrich, and Jan-Olaf Gebbers. "Ingested probiotics reduce nasal colonization with pathogenic bacteria (Staphylococcus aureus, Streptococcus pneumoniae, and ß-hemolytic streptococci)." Travel Medicine and Infectious Disease., 2007. • Yazdi, MH, et al. "Oral administration of Lactobacillus acidophilus induces IL-12 production in spleen cell culture of BALB/c mice bearing transplanted breast tumour." British Journal of Nutrition, 2010. • Urbanska, AM, J Bhathena, C Martoni, and S Prakash. "Estimation of the potential antitumor activity of microencapsulated Lactobacillus acidophilus yogurt formulation in the attenuation of tumorigenesis in Apc(Min/+) mice." Digestive Disease and Sciences, 2008. • Wollowski, Ingrid, Gerhard Rechkemmer, and Beatrice L. Pool-Zobel. "Protective role of probiotics and prebiotics in colon cancer." American Journal of Clinical Nutrition , 2001. • Anderson, J. W., & Gilliland, S. E. (1999). Effect of Fermented Milk (Yogurt) Containing Lactobacillus Acidophilus L1 on Serum Cholesterol in Hypercholesterolemic Humans . Journal of American College of Nutrition , 43-50. • Rastall, R.A. "Bacteria in the Gut: Friends and Foes and How to Alter the Balance." The Journal of Nutrition, 2004.