1. Animal studies of TS (tobacco smoke) exposure and lung cancer. Yes, until recently they did not find much conclusive evidence. But now we have animal models where TS clearly causes lung cancer (the lifespan of TS models due to other diseases is discussed in the next post.) Should we take some average value of all animals models and then conclude that for humans smoking cannot be cannot cause lung cancer? Obviously not, we do not do this for other characteristics like intelligence or amount of body hair. Smoking as shown can clearly cause lung cancer certain species/models and humans happens to be another.
2. Animal studies of TS and lifespan. Yes, there is the hamster study showing lifespan increase from TS (tobacco smoke. Was in hamsters prone to amyloidosis which is a rare cause of death in humans, even if we count Alzheimers as due to amyloidosis (which is not proven). TS is also well known for capacity to reduce weight. The hamsters, as well as the animals in several other TS animal studies, showed a large weight reduction. CR, which TS thus may cause, is the factor with best evidence for lifespan extension. So the CR effect may offset the harmful effect of the smoke itself in these animal studies. Also, there are studies where TS causes a lifespan reduction. May be criticized for not representing the human situation but neither does amyloidosis prone hamsters on CR. More generally, the value of animal studies is very limited since humans are not short-lived animals with different metabolism and diseases.
3. TS causes an upregulation of certain defence systems such as antioxidants and detoxication. That is what you expect from toxic substances. Upregulation cannot compensate for a heavy toxic insults. If you want to do upregulate with a mild toxic insult , then there are safer methods such as moderate exercise and ALA.
4. Nicotine may have certain beneficial effects when given alone like modulation of the immune system which may be beneficial under certain conditions. It not evidence for what TS with its enourmous amount of substances will do. The effect may well be the opposite due to the effects of other substances. If you want nicotine, despite it being extremely addicting, then it is better to only take nicotine. The same applies to other possible good substances in TS.
5. Certain nations like Japan and Spain have a long average life expectancy despite high prevalence of smoking. These nations do a lot of other healthy things. In particular good average diets. Smoking is important but not the only factor determining life expectancy.
6. Jeanne Calment, the person with longest confirmed lifespan, smoked. She was an exception. Very long-lived people in general do not smoke and those who do are sicker.
7. There may be some confounding factors missed by epidemiologists in the thousands of studies showing harmful effect of TS. Of course theoretically possible, just very, very unlikely. Epidemiologists have certainly not ignored obvious ones like smoking being more prevalent among those with lower SES in every study. If ignoring evidence for not being 100% certain, then there is no evidence for any prescription drugs either, also placebo-controlled, randomized studies rely on probability, there is always an a very small chance that the result showing an effect is a false positive due chance or a confounding factor missed even by controlled experiments.
8. TS may protect against certain diseases like Parkinson or Alzheimer among those with Apo E4. A double standard, epidemiologic evidence is only accepted when the result happens to favor TS. Does not change the situation for most diseases and the overall morbidity/mortality.
Edited by Blue, 01 March 2010 - 02:32 PM.