Greetings Ninjas in Training!
We all get those people, don’t we?
“You need citric acid for the citric acid cycle, you should be devoid of energy, and dead!”
“You can’t react to citric acid, you have citric acid in your body! Why aren’t you dead?!”
Well my ninjas, now you can smack down these fools with your nunchucks of science.
You might notice that I have this information here on the site. Good job! Please pretend that you didn’t notice, and that this post is filled with entirely new, riveting content. Thanks to the awesome Shidoshi John for pointing me towards some actual numbers on how much citric acid is in your body, and where, because this gives us more fun things to learn. (And while learning is fun, being right is even MORE fun, so prepare yourselves for the hypothetical smackdown of the century!)
“But it’s part of the Citric Acid Cycle! You’ll die without it!”
This argument is incorrect. Take a look at the schematic below: the white part is outside the cell, the tan part is inside the cell, and the purple part is the mitochondrion — where the Citric Acid Cycle occurs.
If you look at what’s going into the cell, you’ll see not citric acid, but glucose! Glucose (sugar) is the one thing our cells need from an external source (food) in order to make energy; the citrate in the Citric Acid Cycle is made from this glucose in the mitochondria. Even someone on a 100% citric acid-free diet can make energy, because dietary citric acid is not used as part of Citric Acid Cycle.
“But there’s Citric Acid in your body! Even if you don’t need to eat it, it’s still there in the Citric Acid Cycle. You can’t be allergic to yourself, you’ll die!”
Wrong again, masked stranger. Take a look again at the schematic: the Citric Acid Cycle occurs inside the mitochondria, which is inside the cell. Reactions to foods and chemicals take place in extracellular spaces; the reaction mediators are outside our cells and never “see” the citrate that is formed in our mitochondria, therefore they cannot react to it. Location, location, location!
“But there’s NO WAY there is absolutely zero citric acid in your body. WHY AREN’T YOU DEAD?!!”
Well, okay… despite your inexplicably vehement desire to see me dead, I will give you credit for that one. There is, in fact, citric acid in everyone’s blood and urine, not to mention saliva, sweat, tears, and yes- even breast milk and semen. My immune system can “see” all of that inside my body (uhm… well, most of it), so why am I not dead? The first — and most obvious — reason is that I’m a ninja. However, there’s a more boring reason, which has to do with things like severity and tolerance; I shall explain it using two more pedestrian immune conditions: peanut allergies and lupus.
Well, sometimes it is lupus. To grossly oversimplify, when someone has systemic lupus erythematosus, their immune system forms antibodies against the person’s own tissues (e.g. heart, lung, and kidney), so the immune system attacks the body. If severe enough it can be fatal, but 80-90% of patients with lupus will survive as long as a healthy person. Lupus is a type III hypersensitivity and, along with hundreds of other autoimmune conditions, exists for the sole purpose of proving my point: depending on the severity of the attack, one can survive one’s own immune system attacking things native to their bodies.
In addition to people’s remarkable ability to survive declaring war on themselves, people’s immune systems also have different thresholds at which these wars–and wars on foreign offenders–begin. For example, both my brother and my college roommate have the classic type 1 hypersensitivity known as peanut allergies. My brother is able to eat peanut butter toast, as long as he only has it once a week on a full stomach. If he goes beyond his tolerance and has it a couple of days in a row, he will begin to suffer unpleasant GI symptoms. My roommate’s tolerance is much lower: when we went on an adventure to see RENT in California, we had to book on a peanut-free airline, lest being trapped thousands of feet in the air with peanut dust lead her to take the show’s “live each moment as your last” theme a bit too literally.
People who react to citric acid also have different tolerance levels. One food pretty much guaranteed to make a ninja flee the scene is lemons, which contain anywhere from 40,000-80,000ppm (parts per million) citric acid. Some ninjas can eat blackberries (4,000ppm), some can only tolerate as high as pears (2,000ppm), and a few can’t even consume peas (200ppm). Compare that to the 15ppm in blood, 4-25ppm in saliva, or 1-2ppm in sweat, and we’re talking orders of magnitude of difference: even those who react to the un-citrusy-est of vegetables are safe from the tears they’ll cry when they must choose between life and that blackberry pie they’re craving.
But what about things like urine (100-700ppm), breast milk (500-1250ppm) and semen (2000-4000ppm)? It is here that we return to one of our earlier arguments: location, location, location! Not all areas of our bodies are equally responsive to evil things, thanks to differences in their reaction mediator inhabitants. As long as low-tolerance ninjas don’t put these things (this is life-or-death ninja science here, no laughing!) in their mouths or other sensitive areas, they’re probably going to stay not dead. It’s worth mentioning that most ninjas with extremely low tolerance were born with a much higher, or even normal tolerance, and they were inducted to ninjahood later in life thanks to medications or illness. However, some babies do react to breast milk for any number of reasons; perhaps infant ninjahood is one of those reasons. Also worth mentioning: there are people who have allergic-like conditions involving the bladder, and semen allergy is an actual thing that has been medically documented in women. These ninjas can get by thanks to their reaction severity, as we discussed earlier.
In sum: if there exists a human whose tolerance for citric acid is lower than the small amount circulating in the responsive areas of their body, and who has life-threateningly violent reactions to citric acid, that person is probably not alive, and probably not me. (I say probably because, although it is unlikely I can type from the beyond, you never know. I am a ninja, after all.)
TTFN, my ninjalings. Until we meet again, when life gives you lemons, RUN!
The Lemon Ninja