My doctor tells me that licorice can make my high blood pressure worse. Is that really true? How does that work?
Licorice lover in L.A.
It might. The mechanism is complicated, but I think it's a fun one! (OK, I perversely enjoy complicated mechanisms.) And you can certainly understand it if you want to hang on and read below. For even greater detail, with published references, read my licorice chapter from Herbs Demystified.
The occasional licorice induced hypertensive crisis does occur, typically with already hypertensive folks sitting around eating gobs of licorice every day for weeks at a time having to be admitted to the emergency room. This sort of crisis isn't all that common, however.
That's because you have to consume a lot of licorice, and it has to be REAL licorice. Most of the licorice sold in the US has had its active, blood pressure-raising ingredient removed. If you look at a product label for US licorice, you will often see the term "de-glycerrhizinized licorice". This sort of licorice won't raise your blood pressure.
In fact, a lot of US "licorice" candy has no licorice in it at all, and is flavored with similar tasting anise! (Anise, and fennel, for that matter, do not have this active ingredient, although they all taste similar.)
Europeans have always preferred real licorice. I can find it in some European import stores in my neighborhood, and it is some pretty strong stuff! (For an added hypertensive kick, the imported, Scandinavian type of licorice has a ton of salt added to it! It's an acquired taste.)
Also, the demand for real licorice in the US is rising, and you can now find in health food stores marketed as "real" licorice candy. Certainly a lot of "herbal" teas which are not labeled "licorice" still use licorice as a sweetening ingredient. You would have no idea licorice is in it unless you looked at the list of ingredients.
I mention this since one case study involved a man who drank a several cups of a tea containing licorice every day for years before he went to the emergency room.
The active ingredient in licorice root is a steroid-like, sweet tasting molecule called glycerrhizin. (Yes, it looks like Welsh to me, too.)
Glycerrhizin overdose mimics a syndrome called "Apparent Mineralocorticoid Excess". This can result in a trip to the emergency room where a patient presents with a crisis resembling an excess of the hormone aldosterone. Aldosterone causes you to retain sodium and pee out potassium, and it raises your blood pressure.
Scientists used to think that licorice simply mimicked aldosterone, especially since it LOOKS like the steroid hormone aldosterone. That's a very reasonable conclusion, but it's wrong!
The mechanism is a bit complicated, but basically glycerrhizin turns off a class of enzymes called "short chain dehydrogenase reductases", or SDRs.
Interestingly, one effect of turning off these enzymes in you gut is that the gut makes more mucous and less acid (the SDRs would otherwise disable prostaglandins that do this trick) so it does seem likely that real licorice can help soothe an inflamed gut.
On the other hand, the glycerrhizin turns off the SDR enzyme that ordinarily keep cortisol from acting on the kidney. Since cortisol acts just like aldosterone, binding to aldosterone receptors on the kidney, and cortisol levels are a lot higher than aldosterone, normally, this causes the kidney to "think" that aldosterone is sky high. Cortisol in the guise of aldosterone causes potassium loss, sodium retention, and consequent water retention with hypertension.
From what I can tell of all the case studies I've read of licorice eaters going to the emergency room, it takes a LOT of licorice to do this trick. So the occasional moderate snack of real licorice probably isn't going to hurt.
So, if you do have high blood pressure, perhaps you should have de-glycerrhizinized licorice, rather than real licorice, or keep your consumption of real licorice down to reasonable levels.
I hope that helps!