How Much Licorice Is Safe?

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Eating licorice or drinking licorice tea can cause the loss of body fat by blocking the effects of a stress hormone, but at what cost?

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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.

The three ways to alleviate the fattening effects of stress are #1: treat the cause by alleviating the stress. If that’s not possible, you can, #2, modify your diet to lower the production of the adrenal stress hormone cortisol, as I described in my video on the effect of animal protein on adrenal function. And if all else fails, you can #3, try to block the effects of cortisol on our fat cells.

If you drip cortisone onto fat samples taken deep inside people undergoing abdominal surgery, you can accelerate the formation and growth of new fat cells. But you can disrupt this process, though, with a compound that blocks the enzyme that activates cortisol in body fat. The compound is called glycyrrhetinic acid, which is what our gut bacteria make and ferry into our bloodstream when we eat glycyrrhizin. Any guess as to where in our diet glycyrrhizin is found? I’ll give you a hint: it derives from the Greek words glykos, meaning sweet, and rhiza, meaning root. We may be able to block some of the effects of cortisol in our body fat when we eat licorice.

What works to slim fat cells in a petri dish, or mice in a lab, may not work in a person, but the licorice compound appears to work even when just applied to the skin. Researchers in Italy tried rubbing the licorice compound on women’s thighs to see if it would help with cellulite. After a month of application, the thickness of the superficial fat layer on their thighs (as measured by ultrasound) was significantly reduced. The reason we know it wasn’t just due to massaging it in is because there was no change on the control thigh, or among the women who rubbed on placebos. The difference was only a few millimeters, but the researchers suggested it could be a “gentler alternative to cosmetic surgery.”

What about eating licorice or drinking licorice tea? Dozens of trials have been published on the effects of various licorice preparations on weight loss, and overall, there’s just a small effect—about a pound of extra weight loss over a month or two, compared to placebo. One reason it may not be higher is that licorice causes you to lose body fat but retain water. Check this out. After two months on licorice, no change in overall weight, but the women dropped their percentage fat mass by nearly 3 percent; at the same time, though, increasing their water retention by about the same amount. Then, when they stopped the licorice, they lost the water but gained back the fat. Licorice can cause you to burn so much fat, the surface of your abdomen heats up a degree (in Fahrenheit) within an hour of consumption. But it has the opposite effect on cortisol in your kidneys, which, it turns out, is actually a problem.

In body fat, licorice blocks an enzyme that activates cortisol. But in our kidneys, licorice blocks a different enzyme that deactivates cortisol, causing your kidneys to hold on to extra water and sodium, and to lose potassium. If you lose too much potassium, it can cause weakness and abnormal heart rhythms, which is why the FDA sent out a consumer advisory warning: “If you’re 40 or older, eating 2 ounces of black licorice a day for at least two weeks could land you in the hospital with an irregular heart rhythm …. No matter what your age, don’t eat large amounts of black licorice at one time. If you have been eating a lot of black licorice and have an irregular heart rhythm or muscle weakness, stop eating it immediately and contact your healthcare provider.” Just because licorice is one of the oldest and most popular herbal medicines in the world doesn’t mean it’s safe to eat in large amounts.

The retention of fluid and sodium can lead to blood pressure elevation eating less than two ounces of licorice a day. The regular consumption of just a few ounces a day can land you in the hospital in a coma with a blood pressure of 200/140. As many as 3 percent of hospitalizations due to high blood pressure are caused by licorice. Those with hypertension should probably avoid licorice completely, as should pregnant women, as licorice use during pregnancy is associated with preterm delivery and infant cognitive dysfunction. 

For nonpregnant individuals with normal blood pressure, what would be a safe dose? The problem is that glycyrrhizin levels vary in different licorice products, and some people are more sensitive than others. Now, a lot of licorice sold in the U.S. doesn’t even have any true licorice, and is instead artificially flavored or cut with anise oil. So ironically, it’s the black licorice you might find at a natural food store that may pose the greatest concern! Including a broad safety factor, the European Scientific Committee on Food suggests regular consumption of no more than six grams of genuine licorice candy a day. A Hershey-funded study found that “hard-coated licorice candies” have 0.06 mg/g. Presuming that’s referring to Good & Plenty, the limit would be about a box a day.

Licorice tea allows you to access the herb without all the crap in candy, but a study of 33 brands found such varying levels of glycyrrhizin that the safe daily dose ranges from just a tenth of a cup up to 20 cups a day. A life-threatening arrhythmia reported in a case entitled “Dying for a cup of tea” was in a woman who was drinking 15 bags a day. Based on the average level, a half a cup of licorice tea should be safe for most people, though it’s not clear that would be enough to have a fat-reducing effect, which is why licorice never made it into my book How Not to Diet.

Finally, cortisol isn’t the only steroid hormone licorice can muck with. It also interferes with the production of testosterone. Feed men the equivalent of about 50 boxes of Good & Plenty, 9 oz of black licorice, or just a tablespoon of licorice root powder every day, and they experience a 44 percent drop in testosterone levels within four days, though blood levels bounced back within four days of stopping. The researchers suggest men with high blood pressure or decreased libido should be questioned about their licorice habits.

Please consider volunteering to help out on the site.

Motion graphics by Avo Media

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.

The three ways to alleviate the fattening effects of stress are #1: treat the cause by alleviating the stress. If that’s not possible, you can, #2, modify your diet to lower the production of the adrenal stress hormone cortisol, as I described in my video on the effect of animal protein on adrenal function. And if all else fails, you can #3, try to block the effects of cortisol on our fat cells.

If you drip cortisone onto fat samples taken deep inside people undergoing abdominal surgery, you can accelerate the formation and growth of new fat cells. But you can disrupt this process, though, with a compound that blocks the enzyme that activates cortisol in body fat. The compound is called glycyrrhetinic acid, which is what our gut bacteria make and ferry into our bloodstream when we eat glycyrrhizin. Any guess as to where in our diet glycyrrhizin is found? I’ll give you a hint: it derives from the Greek words glykos, meaning sweet, and rhiza, meaning root. We may be able to block some of the effects of cortisol in our body fat when we eat licorice.

What works to slim fat cells in a petri dish, or mice in a lab, may not work in a person, but the licorice compound appears to work even when just applied to the skin. Researchers in Italy tried rubbing the licorice compound on women’s thighs to see if it would help with cellulite. After a month of application, the thickness of the superficial fat layer on their thighs (as measured by ultrasound) was significantly reduced. The reason we know it wasn’t just due to massaging it in is because there was no change on the control thigh, or among the women who rubbed on placebos. The difference was only a few millimeters, but the researchers suggested it could be a “gentler alternative to cosmetic surgery.”

What about eating licorice or drinking licorice tea? Dozens of trials have been published on the effects of various licorice preparations on weight loss, and overall, there’s just a small effect—about a pound of extra weight loss over a month or two, compared to placebo. One reason it may not be higher is that licorice causes you to lose body fat but retain water. Check this out. After two months on licorice, no change in overall weight, but the women dropped their percentage fat mass by nearly 3 percent; at the same time, though, increasing their water retention by about the same amount. Then, when they stopped the licorice, they lost the water but gained back the fat. Licorice can cause you to burn so much fat, the surface of your abdomen heats up a degree (in Fahrenheit) within an hour of consumption. But it has the opposite effect on cortisol in your kidneys, which, it turns out, is actually a problem.

In body fat, licorice blocks an enzyme that activates cortisol. But in our kidneys, licorice blocks a different enzyme that deactivates cortisol, causing your kidneys to hold on to extra water and sodium, and to lose potassium. If you lose too much potassium, it can cause weakness and abnormal heart rhythms, which is why the FDA sent out a consumer advisory warning: “If you’re 40 or older, eating 2 ounces of black licorice a day for at least two weeks could land you in the hospital with an irregular heart rhythm …. No matter what your age, don’t eat large amounts of black licorice at one time. If you have been eating a lot of black licorice and have an irregular heart rhythm or muscle weakness, stop eating it immediately and contact your healthcare provider.” Just because licorice is one of the oldest and most popular herbal medicines in the world doesn’t mean it’s safe to eat in large amounts.

The retention of fluid and sodium can lead to blood pressure elevation eating less than two ounces of licorice a day. The regular consumption of just a few ounces a day can land you in the hospital in a coma with a blood pressure of 200/140. As many as 3 percent of hospitalizations due to high blood pressure are caused by licorice. Those with hypertension should probably avoid licorice completely, as should pregnant women, as licorice use during pregnancy is associated with preterm delivery and infant cognitive dysfunction. 

For nonpregnant individuals with normal blood pressure, what would be a safe dose? The problem is that glycyrrhizin levels vary in different licorice products, and some people are more sensitive than others. Now, a lot of licorice sold in the U.S. doesn’t even have any true licorice, and is instead artificially flavored or cut with anise oil. So ironically, it’s the black licorice you might find at a natural food store that may pose the greatest concern! Including a broad safety factor, the European Scientific Committee on Food suggests regular consumption of no more than six grams of genuine licorice candy a day. A Hershey-funded study found that “hard-coated licorice candies” have 0.06 mg/g. Presuming that’s referring to Good & Plenty, the limit would be about a box a day.

Licorice tea allows you to access the herb without all the crap in candy, but a study of 33 brands found such varying levels of glycyrrhizin that the safe daily dose ranges from just a tenth of a cup up to 20 cups a day. A life-threatening arrhythmia reported in a case entitled “Dying for a cup of tea” was in a woman who was drinking 15 bags a day. Based on the average level, a half a cup of licorice tea should be safe for most people, though it’s not clear that would be enough to have a fat-reducing effect, which is why licorice never made it into my book How Not to Diet.

Finally, cortisol isn’t the only steroid hormone licorice can muck with. It also interferes with the production of testosterone. Feed men the equivalent of about 50 boxes of Good & Plenty, 9 oz of black licorice, or just a tablespoon of licorice root powder every day, and they experience a 44 percent drop in testosterone levels within four days, though blood levels bounced back within four days of stopping. The researchers suggest men with high blood pressure or decreased libido should be questioned about their licorice habits.

Please consider volunteering to help out on the site.

Motion graphics by Avo Media

Doctor's Note

I’m so glad I was finally able to publish this. It was removed from How Not to Diet due to space considerations, but I always found this topic so fascinating.

The video I mentioned about animal protein and adrenal function is The Effect of Animal Protein on Stress Hormones, Testosterone, and Pregnancy.

For less risky ways to accelerate weight loss, check out How Not to Diet from your local public library or, for a taste, see the book trailer or my Evidence-Based Weight Loss presentation.

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