Regular stoners may have a higher risk of developing heart disease or having a heart attack, according to a new study in the journal Cell. The researchers found that smoking a joint triggers a rapid increase in pro-inflammatory compounds that can harm blood vessels – but a molecule from soy may help to alleviate this damage.
Despite the growing interest in medical cannabis, the drug’s effects on cardiovascular health are largely unknown. To shed light on the matter, the study authors looked at the medical records of 157,331 people in the UK, including 34,878 who admitted to using cannabis.
Of these, 11,914 claimed to ingest the drug more than once a month. Overall, these monthly users were 16 percent more likely to have had a heart attack and were also more susceptible to premature heart attacks before the age of 50.
Digging a little deeper, the researchers then analyzed blood samples from 18 people immediately after smoking a joint, finding that pro-inflammatory cytokines increased within 90 minutes. These compounds are heavily implicated in atherosclerosis, the thickening of blood vessel walls due to the accumulation of fatty plaques.
After applying THC – the psychoactive ingredient in cannabis – to isolated human endothelial cells, the authors found that the compound also suppressed antioxidant genes, thus contributing further to inflammation within the lining of blood vessels.
Commenting on these findings, study author Mark Chandy explained that “as more states legalize marijuana use, I expect we will begin to see a rise in heart attacks and strokes in the coming years,” adding that “THC exposure initiates a damaging molecular cascade in the blood vessels.”
The researchers found that the negative effects of THC on blood vessels are mediated via the cannabinoid 1 (CB1) receptor. Researchers have attempted to counteract the activity of THC using CB1 antagonists, which block the receptor, although most of these compounds are unsuitable for use due to their psychiatric side effects.
However, using machine-learning techniques to screen a large database of CB1 antagonists, a compound called genistein was identified as a potential solution to the cardiovascular issues generated by THC. Found in soybeans, genistein has a very limited ability to penetrate the brain, which means it shouldn’t produce any of the harmful side effects associated with other CB1 blockers.
To investigate the compound’s efficacy, the team fed a high-fat diet to mice that had been bred to have high cholesterol. Adding a standard dose of THC to the rodents’ diets caused them to develop larger plaques within their blood vessels, yet treatment with genistein prevented this increase in plaque size.
“We didn't see any blocking of the normal painkilling or sedating effects of THC in the mice that contribute to marijuana's potentially useful medicinal properties,” said Chandy. “So genistein is potentially a safer drug than previous CB1 antagonists. It is already used as a nutritional supplement, and 99% of it stays outside the brain, so it shouldn't cause these particular adverse side effects.”
While the use of THC and genistein has yet to be trialed on human subjects, the researchers suggest that this combination may enable medical cannabis users to continue to enjoy the drug’s beneficial effects without increasing their susceptibility to heart disease.