X-Message-Number: 20446 From: "michaelprice" <> References: <> Subject: warning: accelerated aging by nicotinamide Date: Fri, 15 Nov 2002 11:17:51 -0000 The study abstract Doug cites is misleading, taken in isolation. A little knowledge is dangerous thing.... Nicotinic acid versus nicotinamide (both forms of vitamin B3) is discussed in http://www.longevity-report.com/lr91.htm "Vitamin B3 (niacin) is a precursor to the coenzymes NAD and NAD-phosphate (NADP). Although not strictly a vitamin - our bodies can produce NAD/NADP from dietary tryptophan - it functions like one since this production is not very efficient. Dietary consumption of niacin elevates NAD tissue concentration, in animals and humans[27d, 27e], which up-regulates the activity of PARP, increasing the DNA repair efficiency and reducing the induced[27c, 27f] cancer rate and lowering over-all long-term human mortality[27g]. High PARP activity is associated with longevity in humans[126d]. Similar cancer prevention, and possibly longevity, is expected in humans, who are typically more NAD deficient than many animals[27d]." "Vitamin B3 (as nicotinamide) may be toxic in the range 3-6gm/d[85]. Niacin, as nicotinic acid, is generally considered less toxic[40], but, still, in some individuals large doses of niacin have caused abnormal liver behaviour. Also niacin can cause an uncomfortable, although, as far as we know, harmless and temporary skin flushing. Taken as inositol hexanicotinate, which is generally regarded as non-toxic, unlike some other slow-release formulations[73], removes this problem." See http://www.longevity-report.com/lr91.htm for the references and context. The study Doug cited was also discussed on sci.life-extension a few months back. Locate with google using the string: "PMID: 12297502" or use the URL: http://groups.google.com/groups?hl=en&lr=&ie=UTF-8&safe=off&threadm=xBco9.11 972%24975.639501%40newsfep2-win.server.ntli.net&rnum=1&prev=/groups%3Fq%3D12 297502%26hl%3Den%26lr%3D%26ie%3DUTF-8%26safe%3Doff%26selm%3DxBco9.11972%2524 975.639501%2540newsfep2-win.server.ntli.net%26rnum%3D1 Here was my summary: ------------------ My thanks to Lou Pagnucco for bring this study to oiur collective attention. Having digested the full text version (free on PubMed) I recommend it to everybody. It provides a lot of useful background on the relationship between Sir2, SIRT1/2, NPT1, p53, NAD+, nicotinic acid, nicotinamide and the importance of distingishing between the last 3, which hitherto I had been lax about. (Niacin is loose term which can mean any of the forms of vitamin B3.) High level summary: nicotinic acid good, nicotinamide/niacinamide bad (maybe!) One major qualifer is the validity of extrapolating 'aging' in yeast to multicellular organisms. It seems that Sir2 extends replicative lifespan in yeast by both decreasing the formation of ERCs (extrachromosomal rDNA circles) and inhibiting apoptosis (cell death). The ERCs are of doubtful relevance to multicellular eukaryotes such as us who also require apoptosis for tumour suppression; however mutant Sir2+ nematodes live longer, so perhaps Sir2 is is relevant to multicellular lifespans. Also of note is that *nicotinamide* has extended fruit-fly lifespans. --------------------- Cheers, Michael C Price Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=20446