Q: In your articles about marijuana, I hoped you would explain the difference between smoking it and ingesting it as hemp oil or cannabis oil. I understand the difference is crucial, and I would like to read your comments on this. Thank you! – J.Y., Vaasa, Finland
Dr. Micozzi: I am glad to hear from my good readers in Finland (Suomi). I fondly recall doing research with my Finnish colleagues, led by Ole Heinonen, on nutrition and health during the late 1980s. Finland was far ahead of the U.S. on its understanding of good nutritional policy including, as I recall, banning iron supplementation in foods and encouraging selenium supplementation.
A major difference between ingesting cannabis (marijuana) versus smoking it is that smoking exposes lung tissues to dangerous combustion products emitted by burning plant leaves. Many experts are concerned that smoking marijuana carries many times the risk of lung cancer and other lung diseases compared to smoking tobacco. Here in the U.S., we have to witness the sad spectacle of many clueless politically correct politicians and political activists who are vehemently “anti-tobacco” campaigning to make it legal to smoke all the marijuana one might want.
The real science shows that there is a threshold below which smoking tobacco does not significantly raise the risk of diseases in most people. Although the U.S. government will never tell us this, according to research, that threshold appears to be less than 10 cigarettes per day. I do not advocate smoking either tobacco or marijuana, but I am an advocate for sharing the real science.
But, unlike with tobacco, we don’t have enough scientific evidence about smoking marijuana because scientists have been unable to conduct research on an illegal product. Therefore, I think it’s best to play it safe and avoid smoking marijuana altogether. And, from the tragic effects I have observed it to have on the mental abilities, habits and manners of habitual users, I would never want to go anywhere near it.
What about ingesting the oil from marijuana plants? Well, what little science there is has typically focused on the effects on the brain once cannabis is absorbed into the bloodstream (which occurs either through the lungs from smoking or through the gastrointestinal tract from ingestion). A study published last year reported that MRI scans of young recreational marijuana users showed brain abnormalities—and those abnormalities increased as marijuana usage went up.
Of course, further research needs to be conducted. But while awaiting the scientific studies from universities in states where marijuana is now legal for medicinal or recreational use, I would conservatively estimate that the effects on the brain would be about the same whether marijuana was ingested or smoked. Namely, not so good.
 “Cannabis Use Is Quantitatively Associated with Nucleus Accumbens and Amygdala Abnormalities in Young Adult Recreational Users.” Journal of Neuroscience, 16 April 2014, 34(16): 5529-5538.