Below is an approximation of this video’s audio content. To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video.
Hibiscus tea, also known as roselle or Jamaica, is enjoyed around the world hot or cold for its bright red color and tart cranberry-like flavor. It’s the “zing” in Red Zinger tea. I talk about its benefits in the chapter on high blood pressure in How Not to Die––working as well as some leading antihypertensive medications in head-to-head tests, or even beating the drugs out.
Within three hours of drinking hibiscus tea, changes in hundreds of metabolites can be detected in the human bloodstream with “creative” names like hibiscic acid, or hibiscin, or hibiscitrin. Alterations in human gene expression at the three-hour mark after drinking it suggest a downregulation of cholesterol synthesis and an improvement in metabolism. But randomized controlled trials failed to consistently find cholesterol-lowering benefits. An interesting side-effect popped up, though: weight loss.
In Mexico, hibiscus tea has been traditionally used for the treatment of obesity, sparking lots of research interest. Computer modeling studies have suggested that certain hibiscus compounds might bind to the fat-digesting enzyme lipase like a lock-and-key. Test tube studies screening a variety of medicinal plants did indeed find hibiscus inhibited lipase more than most of the others, and hibiscus has been found to reduce body fat in hamsters, mice, and rats, increasing fecal fat excretion. But it wasn’t tested in people, until this study published in 2014.
The title gives the findings away. Spoiler alert: Hibiscus can inhibit obesity and fat accumulation—in humans—and improve fatty liver. To create a randomized double-blind trial, instead of trying to create some artificially colored and flavored placebo tea, they dried the hibiscus tea into a powder and put it into capsules. After 12 weeks, there was a greater reduction in waistlines and percent body fat in the hibiscus group, compared to those who got placebo capsules. But the dose they ended up using was the equivalent of about nine cups of hibiscus tea a day. I recommend people stick to no more than a quart a day on a regular basis, due to the high manganese content. Manganese is an essential trace mineral, but nine cups a day might result in be too much of a good thing.
Finally, in 2018, this study was published using a reasonable dose—the equivalent of about a single 12-ounce glass of hibiscus tea a day. The complicating factor is that they also added lemon verbena to the mix. That’s another herbal tea, better known for improving recovery after intense bouts of strength training, but there were some promising in vitro data on effects of lemon verbena on fat cells in a petri dish. So, they tried a combination. It comes out to be about a cup and a half of hibiscus tea and a quarter cup of lemon verbena tea, once a day, for two months.
Both the tea and placebo groups were fed diets containing the same amount of calories, yet those randomized to the tea group lost significantly more weight—five pounds compared to three pounds. That’s only an extra pound or two a month, but an extra pound a month eating the same number of calories. That’s the advantage of fat-blocking interventions that actually cause you to lose more calories, beyond just reducing hunger, and making you feel fuller longer in hopes that you’ll eat fewer calories in the first place.
Why not just pop pills instead of brewing tea? There are all sorts of herbal extract supplements on the market, but that presumes we know enough to extract out the right active ingredients. For example, it does not appear to be the red anthocyanin pigments in hibiscus, since white varieties seem to have similar effects. When the various compounds in hibiscus tea are isolated out and tested in various combinations, synergistic effects are found, meaning the whole may be greater than the sum of its parts. As with any sour food or beverage, though (like after eating citrus) it’s important to wash the natural acids off your teeth by rinsing your mouth out with water to protect your tooth enamel. You also want to wait at least an hour before brushing, so as not to erode your enamel when it’s in a softened state.
Please consider volunteering to help out on the site.