Monday, November 26, 2007

It's Only Natural

Well, after a week of cushy home living where the staples of my diet included artisan asiago cheese bread and home-cooked garlic mashed potatoes, it's back to the college student life where breakfast, when consumed, consists of sausage biscuits and a can of coffee-flavored energy drink. For the intrigued, Java Monster is pretty tasty, about on par with the Starbucks canned iced coffee but in larger cans for the same price.

Which brings me to the point of today's entry. My hasty student "breakfast" sounds terribly unhealthy. A cured frozen meat product loaded with salt and preservatives served on--gasp--a croissant roll made with bleached flour? A beverage loaded with glucose, sucrose, and even a touch of sucralose--a compound that contains chlorine, for crying out loud? Surely I could've done better, perhaps a low-glycemic index organic whole-grain bagel with just a touch of ultra lite-omega-3-heavy spread and a glass of fortified organic soy milk?

I dunno. The latter breakfast sounds pretty terrible to me from a "food enjoyment" perspective, and I'm not sure whether it'd be any "better" for me in the long run. Maybe not everyone agrees on the taste issue. And that's where I'm headed with this; the whole issue is one of personal preference.

I was having a conversation with an acquaintence at a social gathering about a week ago; she mentioned that she'd been having some "girly problems" because our table consisted of myself and three other women. I don't think she expected me to take interest in this sort of thing, but apparently she'd just switched oral contraceptive regimens lately and she'd had a terrible reaction to the new one, namely a generalized skin rash. Her husband had been surgically sterilized some time ago; her reason for taking OCs was to control other problems, namely what sounded to me like polycystic ovarian syndrome. She was very concerned that taking "artificial" hormones was going to increase her risk of dying of cancer, but she admitted that she didn't know much about the subject and that no one had gone to any length to explain it to her. I forwarded her a couple articles, including one from the Guardian about how OCs decrease long-term cancer risk in women.

When she brought up how she wished she didn't have to take "artificial" hormones, I asked her what "natural" hormones were. "I'm not entirely sure," she replied, "I guess the ones in my own body." What she really seemed to mean was that she didn't want to take extra hormones, because she didn't realize that ethinyl estradiol differs from estradiol, the most common and potent "natural estrogen," by only one chemical group, the triple bonded carbons at the 17th position (in the upper right on the image). Estrogen isn't a single compound; it's a group of compounds with similar actions on the body.

It seemed logical to my acquaintence that her body could tell the difference between the estrogen that it made and estrogens that she introduced. "I can tell the difference between real sugar and Sweet-n-Low," she said. One is natural insofar as it is made by plants (sucrose) and the other is made in a lab.

And I'm sure she's right. She can tell which one she thinks tastes better. But to decide what foods are healthiest based on personal preferences regarding taste is an example of the "ick reaction" fallacy, the idea that something must be bad just because of gut reactions. If that were true, and gut reactions to foods based on taste were an indicator of nutritional quality, we'd all eat nothing but cake and ice cream. I recall not liking beets as a child. I still don't like beets; the very idea of eating beets is almost gag-worthy. Beets must be terrible for me! The true believers in natural foodstuffs are going to stand up and tell me something about how I've been brainwashed against healthy food and that the food industry is putting mind control chemicals in my orange juice or something. Moving right along.

Human beings have a wide variety of sensory data that they can use to evaluate their environments. We use vision, smell, and taste to determine what is and isn't objectionable to introduce into our bodies. All of this information is an aggregate of signals from numerous electrochemical receptors, filtered through our brains and interpreted based on existing information, and is remarkably imperfect. Antifreeze is sweet and delicious but highly toxic to the kidneys. Your feelings about a particular food or substance are not necessarily predictive regarding how good (or bad) it is for you.

Here's the clincher. Your individual cells have no eyes, ears, or taste buds. How do they interpret environmental information? It's time for a review of biology.

Every cell in the human body has a number of surface receptors, protein structures stuck in the cell's membrane. These surface receptors are the eyes and ears of the cell; when appropriate substances float by in the fluid environment of the body, a chemical reaction occurs between the substance and the cell receptor. The cell interprets the binding of a substance to its receptor as a message, much the way sticking your car's key in the ignition and turning it is a signal to your car to start the engine. And these receptors are fairly specific, too. Much like you can't use the keys to your 88' Oldsmobile to start the BMW your neighbor carelessly parked in front of your house, cell receptors won't bind compounds totally at random. They have to be properly shaped, in a chemical sense--they have to fit.

Suppose you own that BMW and you put the keys on a really tacky keychain. Will the key still start the car? Of course, you're thinking, the keychain isn't part of the mechanical workings of the ignition. It's totally superfluous. Your car has no idea that you have such bad taste, and it operates just fine even though there's a pink plastic Elvis hanging on the side of your steering column.

And so it is with cell receptors. All cell receptors care about is whether or not the key fits properly, which means that the only thing important for cellular response is the chemical structure of a compound, not whether it was synthesized by a plant or a chemist. Your cell's "senses" are totally reliant on the ability of a compound to form chemical bonds with the cell's receptors. There is simply no way for them to tell the difference in origin between two compounds as long as their chemical structures are totally identical. "Natural" vitamin E is no different from vitamin E made in a lab as long as they're both alpha-tocopherol.

If you've been paying attention, I did note earlier that estradiol and ethinyl estradiol are not chemically identical. They have slightly different structures. How do you reconcile this issue? If they're not exactly the same, how can I tell my friend that they are?

The tacky pink Elvis is part of the structure of my hypothetical keychain, but the car only cares about the key. Pharmaceutical chemists can modify compounds to alter other properties of a drug while retaining the important shapes--the key--that are required to activate cell receptors. Estradiol will have almost no effect if you swallow it in tablet form, because the liver will rapidly break it down into inactive compounds, and the liver is the first stop for any orally ingested drug product. But by modifying estradiol into ethinylestradiol (EE), the compound will survive the trip from the stomach and intestines to the bloodstream and be able to have the same effect that estradiol made in the sex organs would have.

I came up with three different car analogies regarding the liver's rapid metabolism of estradiol, but I'll spare you my prose. And in case you're curious, it is possible to take estradiol orally and have it be effective, but the dose must be considerably larger. Your typical oral contraceptive has 0.035 to 0.05 milligrams of EE, whereas oral estradiol used for the treatment of menopausal symptoms is dosed at 0.5 to 2 mg. These doses aren't necessarily equivalent in terms of their effect, but the point is that EE is a lot more convenient for oral administration in women who are taking low doses of estrogens to prevent pregnancy.

The whole natural versus artificial dichotomy is a ruse; it's a marketing ploy, when we're talking about interactions at the molecular level. You might be able to taste the difference between organic food and non-organic food ("inorganic food" would be something else entirely), but that's only because your higher brain is able to interpret the hundreds of chemical signals recieved by your taste buds and shuttled into the central nervous system. Your opinions about subjective information like taste are colored by expectations, prior experiences, and other emotional data that individual human cells lack. Drug-cell interactions consist of comparatively fewer elements without any cognitive components, only a set of cell receptors that can or cannot be activated by a substance floating around in the bloodstream. Those chemicals are a bunch of keys, floating idly through the body without intention or purpose; all that matters is their coincidental ability to fit into a cell's preset locks.

1 comment:

Caveat said...

Very interesting.

I'm no egghead but I've said for years that almost everything is made of chemicals - it's just a matter of getting the right combination. Or key, in this case.

I doubt, by the way, that most people can honestly tell the difference between 'organically grown' buzzlewubs and those made in the lab...

Cool blog!