420
Founder
Although marijuana and tobacco smoke are packed with cancer-causing chemicals, other qualities seem to keep it from promoting lung cancer, an American report says.
The difference rests in the often opposing actions of the nicotine in tobacco and the active ingredient, THC, in marijuana, said Robert Melamede, of the University of Colorado, who reviewed the scientific evidence supporting this contention in a recent issue of the Harm Reduction Journal.
Whereas nicotine has several effects that promote lung and other types of cancer, THC acts to counter the cancer-causing chemicals in marijuana smoke - it "turns down the carcinogenic potential", Dr Melamede said.
Laboratory research indicates that nicotine activates a body enzyme that converts certain chemicals in tobacco and marijuana smoke into cancer-promoting form. In contrast, studies in mice suggest that THC blocks this enzyme activity.
Another key difference, he said, is in the immune-system effects of tobacco and marijuana. Smoke sends irritants into the respiratory system that trigger an immune-regulated inflammatory response, which involves the generation of potentially cell-damaging substances called free radicals. These are thought to contribute to several diseases, including cancer.
But cannabinoids - both those found in marijuana and the versions found naturally in the body - have been shown to reduce this inflammatory response, Dr Melamede said.
Another difference between tobacco and marijuana smoking involves cells that line the respiratory tract.
While these cells have receptors that act as docks for nicotine, similar receptors for THC and other cannabinoids have not been found.
Dr Melamede said nicotine appears to keep these cells from committing "suicide" when they are genetically damaged, by smoking, for instance. When such cells do not kill themselves off, they can become tumours. THC, however, does not appear to act this way in the respiratory tract.
All of this backs studies that have failed to link marijuana smoking with a higher risk of lung cancer, although there is evidence that pot users have more problems such as chronic cough, and frequent respiratory infections, he said.
If marijuana does not promote lung cancer, that could be a factor in the debate over the medical use of marijuana. Dr Melamede believes "marijuana has loads of medicinal value", from conditions such as multiple sclerosis, to chronic arthritis pain, to nausea caused by cancer treatment.
Source: Sydney Morning Herald (Australia)
Copyright: 2005 The Sydney Morning Herald
Contact: letters@smh.com.au
Website: Australian Breaking News Headlines & World News Online | SMH.com.au
The difference rests in the often opposing actions of the nicotine in tobacco and the active ingredient, THC, in marijuana, said Robert Melamede, of the University of Colorado, who reviewed the scientific evidence supporting this contention in a recent issue of the Harm Reduction Journal.
Whereas nicotine has several effects that promote lung and other types of cancer, THC acts to counter the cancer-causing chemicals in marijuana smoke - it "turns down the carcinogenic potential", Dr Melamede said.
Laboratory research indicates that nicotine activates a body enzyme that converts certain chemicals in tobacco and marijuana smoke into cancer-promoting form. In contrast, studies in mice suggest that THC blocks this enzyme activity.
Another key difference, he said, is in the immune-system effects of tobacco and marijuana. Smoke sends irritants into the respiratory system that trigger an immune-regulated inflammatory response, which involves the generation of potentially cell-damaging substances called free radicals. These are thought to contribute to several diseases, including cancer.
But cannabinoids - both those found in marijuana and the versions found naturally in the body - have been shown to reduce this inflammatory response, Dr Melamede said.
Another difference between tobacco and marijuana smoking involves cells that line the respiratory tract.
While these cells have receptors that act as docks for nicotine, similar receptors for THC and other cannabinoids have not been found.
Dr Melamede said nicotine appears to keep these cells from committing "suicide" when they are genetically damaged, by smoking, for instance. When such cells do not kill themselves off, they can become tumours. THC, however, does not appear to act this way in the respiratory tract.
All of this backs studies that have failed to link marijuana smoking with a higher risk of lung cancer, although there is evidence that pot users have more problems such as chronic cough, and frequent respiratory infections, he said.
If marijuana does not promote lung cancer, that could be a factor in the debate over the medical use of marijuana. Dr Melamede believes "marijuana has loads of medicinal value", from conditions such as multiple sclerosis, to chronic arthritis pain, to nausea caused by cancer treatment.
Source: Sydney Morning Herald (Australia)
Copyright: 2005 The Sydney Morning Herald
Contact: letters@smh.com.au
Website: Australian Breaking News Headlines & World News Online | SMH.com.au
