Helicobacter pylori
Helicobacter pylori is the bacteria that causes most stomach ulcers, stomach inflammation (chronic gastritis) and gastric cancer. Catechins of green tea have been found to inhibit the growth of several microorganisms so a study published in 2003 tested the effectiveness of catechins on H. pylori.1
There were 56 strains of H. pylori tested for catechin susceptibility, 19 of the strains were resistant to the antibiotics metronidazole (MTZ) and/or clarithromycin (CLR). Additive effects of epigallocatechin gallate (EGCG) and the antibiotics were observed, meaning that the combination treatment showed more antimicrobial activity that either treatment alone. The only catechins in green tea that showed anti- H. pylori effects were EGCG and epicatechin gallate (ECG). The sensitivity to the two gallates was observed in the antibiotic-resistant strains as well as the non-resistant strains.
As H. pylori strains continue to develop resistance to antibiotics, scientists are searching for other methods of controlling the bacteria. A study published in 2008 used an experimental treatment of green tea catechins and sialic acid on human stomach cells in the laboratory and on a murine model.2
In the human stomach cells, the catechins and sialic acid treatment resulted in an additive effect for inhibiting H. pylori growth. In the murine model, the anti- H. pylori treatment combination was 100% effective against H. pylori infection. When the treatment combination was applied after infection by H. pylori the result in the murine model was suppression of 60% of the H. pylori infections. Next treatment effects must be tested in human subjects.
Candida albicans
Candida albicans is the most prevalent fungal pathogen infecting humans.3 Candida species are an ordinary resident in mucous membranes (mouth, gastrointestinal tract and vagina). The microflora composition in the membranes can become altered or the immune system can become compromised, leading to an unchecked growth of the Candida species and resulting in disease or infections.
Treatment usually involves the use of antifungals in the azole family but they do not reliably control fungal infections because they are not toxic in nature. They inhibit enzymes that have a role in producing cholesterol but are not potent enough to prevent recurrence of infections, and sometimes they confer no anti-microbial activity at all.
EGCG has been found to inhibit folate activity.3,4 The potential of EGCG to alter Candida albicans metabolic pathways was the focus of a study by Navarro-Martinez and colleagues.5 Their results showed that EGCG is effective at arresting folate metabolism in Candida albicans. An additive effect on growth and survival inhibition of Candida albicans was observed when EGCG was administered along with topical azole antifungals.
Salmonella spp.
Researchers in Japan, noting the antimicrobial properties of green tea catechins, conducted a study to test their effectiveness on Salmonella-tainted grains.6 It is possible for foodstuffs to come into contact with animals or soil and become infected with Salmonella bacteria. The bacteria do not grow in grains because they do not have adequate moisture content. In this case they form spores, in which they stay dormant until conditions are favorable for their growth.
This study tested the adequacy of catechins to inhibit Salmonella growth in grain flakes and flours. Grain flakes were dipped in solutions of varying concentrations of catechins and were inoculated with Salmonella enteritidis and Salmonella aureus. The catechins adhered to the flakes. After conducting various tests to ensure desired conditions were met, milk was added to the grain flakes and Salmonella populations were counted. Upon statistical analysis of the population counts, they were able to suggest that catechins might be effective as a food additive to prevent microbial activity.
1A combination effect of epigallocatechin gallate, a major compound of green tea catechins, with antibiotics on Helicobacter pylori growth in vitro. Yanagawa Y, Yamamoto Y, Hara Y, Shimamura T. Curr Microbiol. 2003 Sep;47(3):244-9.
2Effective prevention and treatment of Helicobacter pylori infection using a combination of catechins and sialic acid in AGS cells and BALB/c mice. Yang JC, Shun CT, Chien CT, Wang TH. J Nutr. 2008. 138(11):2084-90.
3Influence of green and black tea on folic acid pharmacokinetics in healthy volunteers: potential risk of diminished folic acid bioavailability. Alemdaroglu, NC; Dietz, U; Wolffram, S; Spahn-Langguth, H and Langguth, P. Biopharm Drug Dispos. 2008. 29(6):335-48.
4Effects of folate cycle disruption by the green tea polyphenol epigallocatechin-3-gallate. Navarro-Perán, E; Cabezas-Herrera, J; Campo, LS and Rodríguez-López, JN. Int J Biochem Cell Biol. 2007. 39(12):2215-25.
5Tea polyphenol epigallocatechin-3-gallate inhibits ergosterol synthesis by disturbing folic acid metabolism in Candida albicans. Navarro-Martínez MD, García-Cánovas F, Rodríguez-López JN. J Antimicrob Chemother. 2006. 57(6):1083-92. Epub 2006 Apr 3.
6Survival of foodborne pathogens in grain products and the effect of catechins. Ui, J; Kondo, K; Sawada, T and Hara-Kudo, Y. Shokuhin Eiseigaku Zasshi. 2009. 50(3):126-30.
