Clyde, I'm curious about stevia. I've read pro and con reports about its safety. Is there any hard safety data? Any long-term studies? My understanding is that it has been used in Japan for the past couple of decades. Ray Kurzweil is enthusiastic about it, and cites two papers in support of its safety in his book "Fantastic Voyage". I have not read either paper, and given that I'm not a biochemist or nutritionist, I'd probably need expert help to evaluate these papers anyway. Also, neither of these is a long-term study. Have there been any? Curious to read your thoughts. Thanks, Ray
1. Koyama E, Kitazawa K, Ohori Y, Izawa O, Kakegawa K, Fujino A, Ui M. "In vitro metabolism of the glycosidic sweeteners, stevia mixture and enzymatically modified stevia in human intestinal microflora." Food Chem Toxicol. 2003 Mar;41(3):359-74. [abstract at: http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=12504168&dopt]
ANSWER: The above study merely shows that stevia is not broken down enzymatically any differently by digestive microflora in the human digestive tract than it is in rats. I really appreciate your sending this to me, because it is the first study I have ever seen where human feces are used as one of the 'reactants.' In the methods section of this paper it is stated that: "Degradation was examined by incubating stevia mixture, enzymatically modified stevia, stevioside, rebaudioside A, alpha-monoglucosylstevioside, alpha-monoglucosylrebaudioside A and the aglycone, steviol with pooled human faecal homogenates (obtained from five healthy volunteers) for 0, 8 and 24 h under anaerobic conditions." READ 'We mixed stevia with crap and put it in a tupperware so air could not get to it to simulate the human bowel since there is no oxygen there either." A good laugh. Lets see what the other paper has to offer!
2. M. Matsui, K. Matsui, Y. Kawasaki, Y. Oda, T. Noguchi, Y. Kitagawa, M. Sawada1, M. Hayashi, T. Nohmi, K. Yoshihira, M. Ishidate, Jr and T. Sofuni "Evaluation of the genotoxicity of stevioside and steviol using six in vitro and one in vivo mutagenicity assays" Mutagenesis vol. 11 no. 6 pp. 573-579, 1996 [online at http://mutage.oxfordjournals.org/cgi/content/abstract/11/6/573]
ANSWER: This particular paper just shows that steviol, a metabolic by-product of stevia, is mutagenic. This was shown over ten years earlier in a paper published in the Proceeding of the National Academy of Sciences [Pezzuto JM et al., PNAS 82 (1985) 2478]. The important question is whether or not the human metabolic processes generate steviol. To answer this question, we go to paper #1 (where stevia mixtures are combined with feces in a sealed container). This paper states: "Stevia mixture, stevioside and rebaudioside A appeared to be hydrolyzed to steviol by human intestinal microflora: this observation is consistent with previous rat metabolism studies. Similarly, enzymatically modified stevia appeared to be metabolized via stevia components and, finally, to steviol. This study suggests that there are apparently no species differences in intestinal metabolism of stevia mixture between rats and humans." I don't know about you, but to me THIS SOUNDS HORRIBLE. Steviol is formed in the intestine, and the other papers quoted above show that steviol is a mutagen. Lets keep our eyes and ears open on this one, and in the meanwhile keep stevia intake in moderation, just like with everything else. You are correct that long-term studies have not been conducted, and just because stevia has been in use for a long time in Japan and elsewhere does not mean that in larger amounts it does not cause problems.