But puffing pot probably won't help. The findings, reported in the journal Nature, "should not be taken to mean that smoking marijuana is beneficial for the heart," says Michael Roth, MD, a professor of medicine at UCLA medical school.
It takes a very specific amount of THC -- marijuana's key chemical -- to help the arteries. That dose is too low to produce mood-altering effects in the brain, according to the new study.
Smoking Pot: Bad for the Heart?
"These effects lower the exercise threshold for chest pain [angina], and are an independent risk factor for heart attack and stroke," he writes. Inhaling marijuana smoke can also impair oxygen delivery via the blood, says Roth.
The best way to take advantage of THC's artery-protecting effects may be by developing new prescription drugs "rather than using marijuana or oral THC as medicines," he writes.
Testing THC on Mice
The new study was conducted on mice, not people. First, mice went on an 11-week fatty diet designed to clog their arteries. For the last six weeks of the diet, some mice also got an orally administered low dose of THC along with the high-fat food.
Afterward, the mice who had received THC had fewer signs of atherosclerosis. None of those mice died during treatment or showed unhealthy behavior, says the study.
The results may be due to THC's anti-inflammatory properties, write the researchers, who included François Mach, MD, of the cardiology division at University Hospital in Geneva, Switzerland. Inflammation has been shown to be associated with the development of atherosclerosis.
Tracing THC's Effects
The researchers took a closer look at THC. They knew the chemical has two receptors, called CB1 (mainly found in the brain) and CB2 (mostly found outside the brain).
When they used another drug to block CB2 receptors in the mice, THC couldn't protect the animals' arteries. As for the CB1 receptors, the THC dose used in the study was too low to affect them, so no "high" was created.
The study and editorial appear in Nature's April 7 edition.