On Chinese Mandarin...it’s pu, silly.

Stuffed pu. Photo by createdrinkwrite.com

Oh, how tempting it is, looking at all the new citrus-stuffed puerh out there to buy, especially over the winter when local fresh veggies and fruits are difficult to find in my part of the world. Even worse are those massively plump grapefruits sitting in stores, reminding me of childhood boxes received from Texas and Florida where my father’s friends wintered and thought to send us the best of local citrus. I’m a huge lover of grapefruits, and haven’t had any now in more than two years.

No, you won’t be seeing any reviews of mandarin-stuffed puerh on my blog because alas I cannot have any. You’ll have to look elsewhere for lucky bloggers able to indulge at will. I’ve mentioned before that I cannot have this type of puerh, and since several people have asked for a specific explanation, I can clarify the medication interaction issue behind many citrus types which may hopefully inform others in the same non-citrus boat that I am.

I think most people are familiar with grapefruit juice as a caution for many medications. The issue that is very difficult to sort out when assessing other types of citrus is twofold: 1) the taxonomy of citrus fruit is not entirely clear, and 2) the specific piece of fruit staring you in the face may not be terribly clear either. Let’s start with taxonomy.

While citrus fruit in general is one of the oldest foods that humankind consumed, citrus has evolved, morphed, grafted and traveled its way all over the world, changing as it goes. The entire taxonomy of citrus and hybrids is a complicated business, and while a whole branch of taxonomy is dedicated to it. Complicated means something like this:

wut? (deviant art)

Even a scholar who has the potential to sort out this mess won’t have enough funds to do wide studies to work out every single type of fruit available. And, if you live in California or Arizona or some other southern state, you might have citrus in your own backyard that grew there well before you moved in.

Several fruits are on a parallel with each other. Oranges, lemons, grapefruits and pomelos appear to go back to original strains somewhere long in time in southeast Asia. Mandarin oranges are parallel to pomelo strains. Original mandarins are actually green skinned and not the orange skinned ones you find in the stores nowadays to eat around the holiday season. The Xinhua Mandarin grown in Yunnan may well have a number of varietals, but its ancestral relative is likely the pomelo or some grapefruit/pomelo hybrid.

I dunno what all these are, but Ruby takes my love to town. (www.cell.com)

These fruits contain what are called furanocoumarines, which are the culprits in citrus causing problems with drug interactions. “Furanocoumarin” sounds a lot like the blood thinner “coumadin,” and for a reason! Now, fruits vary a whole lot in the amount of furanocoumarin. Some fruits have a concentrated amount in the juice, some may have concentrations in the white pulp. One grapefruit or pomelo may vary a great deal from another grapefruit or pomelo. See the possibilities for a high degree of variability, and why it isn’t remotely possible to test every single piece of fruit?

Calcium channel blocker medications rely on the same enzymes for absorption and elimination that furanocoumarins love to bind with. Specifically, the enzyme known as CYP3A4 and located in the intestinal tract is responsible for slowly digesting and eliminating a calcium channel blocker medication. As with most medications, only a small amount of medicine in a pill you swallow actually gets absorbed and used by your body. Most of the medicine is removed and excreted, usually via urine at some point. Hence why we have issues with our water supplies, people are peeing out medications constantly and we have no idea how many of them are in tap water these days. But as for medication efficacy, pills are designed with elimination in mind, a dosage is based on how much your body will actually “get” once the absorption and elimination process is complete. Pill dosages rely on knowledge of how the body will get rid of most of the medicine and keep only the amount your body weight requires for the desired effect.

Unfortunately, our citrus fruits come along and interfere with this process by binding to the enzymes needed to process and eliminate most of the medicine. For example, I take Nifedipine, a calcium channel blocker designed to lower my blood pressure. I take a 24 hour extended release form of the pill. It goes into my intestine, then hangs on to the side of the intestine and sits there while the enzymes slowly work on the pill. Some of the medicine gets absorbed into my blood stream via the intestinal wall, this is the medicine I actually want to get. The rest of the pill gets worked on by the enzyme CYP3A4 and excreted. Let’s see a Pac Man version of what happens with my Nifedipine pill when I eat a citrus fruit containing furanocoumarin.

My gut on overstuffed Pu. The blue dots are CYP3A4 enzymes

In this cartoon, you can see that the citrus is binding up all the enzymes, leaving none for my nfd Nifedipine pill. That forces it to dissolve in the tract, going nowhere except into my blood stream since it is stuck in its pill state. This means that too much medicine hangs on in my body, and I can get a lethal dose of the medicine as a result. My blood pressure can fall so low as to be fatal. Even worse, this effect lasts for days. Up to five days later, because the citrus removed so much of the enzyme that my body will need nearly a week to make more. Now if I put yet another pill tomorrow into this situation, I can expect never to leave my bed again. You can see from the Pac Man who is going to win and it isn't my pill. 

But you might be thinking, what effect can a small piece of dried pomelo or mandarin possibly have? A small piece broken into a tea cup or a bit of juice in the tea surely cannot have that much of an effect. As a matter of fact, it can. First off, I don’t know how much furanocoumarin is in a particular piece of fruit. American doctors are working with information gained from readily available citrus to American consumers, such as Florida plantation citrus, or maybe Texas citrus. But this information relies on the product manufacturer to be honest. In general, orange juice might be okay, but how do I know that the maker didn’t sneak in some cheap grapefruit juice or pomelo as filler instead of 100% sweet and juicy navel oranges? I don’t know that.

If you live in the UK, your doctor may well tell you to avoid citrus altogether if you are taking a calcium channel blocker. And if you think “well this won’t be me,” think again. If you have African Caribbean descent, calcium channel blockers are an even more effective heart and blood pressure group of medications for you than for someone else, and a doctor will consider these first when you show up with your BP on the high side. 

I would love to ditch this Nifedipine and have a huge glass of grapefruit juice right now. In fact, I won’t allow any in the house because I can’t keep away from it. My mouth waters thinking about it. Even more difficult for me are the tempting photos of stuffed puerh teas. I have that little voice inside me saying “just a teensy, weensy little bit.” I rarely ignore that little voice. I even tried to rationalize saving money for tea by taking Nifedipine only once a week and drinking grapefruit juice on the other days. Nifedipine ain’t cheap. In fact it costs more than the damned stuffed puerhs.

I can imagine what my doctor might say, though, when she hears the idea of a Nifedipine/citrus cocktail and I know where that conversation will go, out the door along with my ass. As it is, she doesn’t know how much tea I drink. She knows the reading on the blood pressure monitor when I go into her office, and I know that look of satisfaction on her face when she determines she knows her medicine well. And she’s been a missionary doctor in Africa and takes no crap from this old nun, which is why I keep her. And why I take my pill as prescribed and avoid any funny business. This is the point when guessing on that citrus puerh is just not worth it for me.

So, you all enjoy your overstuffed puerh! 

I’ll be over here. By myself. Taking my pill.