We had to file papers yesterday, and things have been horrible around here. It's been one of those weeks law students always hear about but never really believe; one of those weeks where you bill 80, 90, 100 hours -- more hours than you even realized a week could contain. My caffeine aversion has taxed me lately, and I've been compelled to self-medicate with drinkable stimulants from time to time. My firm cafeteria has a soda fountain that dispenses Coca-Cola brand drinks, but the vending machines on each floor are Pepsi turf. The cafeteria is closed for a majority of the 24-hour day, and even when open it's just too far from my desk, so I've been relying on Diet Pepsi to give me a jolt.

This is surely the most vile of all the major cola products on the market today. Coke is better than Pepsi -- if you can't admit this you probably aren't a real American. And regular cola is better than diet cola -- if you can't admit this you're probably not the kind of person who would read a blog like mine. So in the game-theoretic matrix of colas, Diet Pepsi is clearly the worst of all possible outcomes.

What is it about diet soda that makes it so horrible? Three simple syllables:

AS-PAR-TAME

Have you ever finished a diet soda, and swallowed a few minutes later? You probably noticed an aftertaste, something between the bitterness of overcooked asparagus and the funk of new-car vinyl. That's how you know you've introduced something into your body that by rights does not belong there. That something is aspartame: a chemical designed to trick your tastebuds into sensing sweetness even in the absence of sugar. It feels like sugar at first, but the flavor is hollow, and rotten inside.

Aspartame was approved as a food additive in the early eighties, right around the time that the popular artificial sweetners cyclamate and saccharin fell into disrepute as potential carcinogens. Turns out that saccharin probably only causes cancer in lab rats, and then only if you gorge them on the stuff, but it has never recovered in the market. Today you'll likely only find it in Sweet-N-Low packets -- when was the last time you saw a can of Tab?

Conspiracy theorists believe that the bureaucratic process that introduced aspartame to America reflect the chemical's sinister side. They have built websites with such colorful names as "aspartamekills.com" and "The Aspartame Toxicity Info Center", claiming that aspartame causes brain tumors, MS-like symptoms, headaches, memory loss, and other neurological harm. It's pointed out that Donald Rumsfeld (yes, that Donald Rumsfeld) was brought in as CEO of G.D. Searle, aspartame's inventor and original manufacturer, in the late seventies after a decade of failed efforts to win FDA approval (which had incidentally led to a federal inquiry into whether G.D. Searle had falsified research submitted to the FDA). A few years later, Reagan is sworn in, Rumsfeld sits on the committee that picks his new FDA director, and presto! Nutrasweet! A full -- if biased -- timeline of the history of aspartame can be found here.

Distrust of aspartame runs broad and deep. If you do a Google search on it, you'll find half a dozen sites declaiming it before you find a single positive statement. You know something's up when the industry has a public information campaign to argue that its product is not dangerous -- you'll notice that the Google results on aspartame include a paid advertisement linking to an aspartame apologia.

When metabolized, aspartame breaks down into, among other things, formaldehyde -- a compound commonly used in embalming that has devastating neurotoxic effects -- and methanol -- the kind of alcohol that in large doses will blind and kill you. The body is famously inefficient at eliminating and excreting methanol, and at least one published study in rats has documented that aspartame consumption can produce formaldehyde in the body that then binds to tissues.

Aspartame also contains phenylalanine, an essential amino acid (i.e., an amino acid that is needed by the body but that the body cannot produce on its own). The warnings you see on aspartame-enhanced products regarding phenylalanine are really only for the benefit of those unlucky individuals who suffer from a relatively rare disorder called phenylketonuria, which prevents them from properly metabolizing phenylalanine, sometimes leading to neurological damage.

Of course, the amounts of aspartame you actually consume in a diet soda are vanishingly small (although over time it can build up with regular consumption). Nevertheless, in light of the roaring debate over whether it is, well, poisonous, I'm finding it harder and harder to justify allowing aspartame into my body. The fact that it tastes god-awful sure doesn't help. Frankly, if I need the caffeine that bad, I think the extra 200 calories of a non-diet soda will be the least of my worries.