Soda

There's been lots of chatter about Pepsi lately, so I thought I'd run with the theme. I don't have much to add to the media commentary - I'm just sad to see some of my favorite bloggers leave this space - but I've got plenty to say about soft drinks. And little of it will please Pepsi.

The first thing is that a soda tax is a great idea. Here's a compelling chart from a recent report published by US Department of Agriculutre's Economic Research Service (via Yglesias):

Some of these calories, of course, will be shifted to other categories of food - we'll drink less Pepsi, but we'll consume more Doritos. Nevertheless, there's compelling evidence that such "sin" taxes are actually quite effective. Just look at cigarettes: If you want to decrease the numbers of smokers, raising the price of cigarettes is the only proven solution. In fact, a 10 percent increase in the price of cigarettes causes a 4 percent reduction in demand. Teenagers are especially sensitive to these price changes: a 10 percent increase in price causes a 12 percent drop in teenage smoking. (The only bad news is that raising the price of cigarettes tends to increase the demand for marijuana. Apparently, the two products are in competition.) And let's not forget that nicotine is an extremely addictive substance. So I think there's good reason to think that a 10 percent hike in the price of sodas might be even more effective than a cigarette tax.

And while we're on the subject of Pepsi, it's also worth noting that diet sodas don't work. Consider this recent paper in Behavioral Neuroscience, which found that rats fed artificial sweeteners gained more weight than rats fed actual sugar. Here's the abstract:

Animals may use sweet taste to predict the caloric contents of food. Eating sweet noncaloric substances may degrade this predictive relationship, leading to positive energy balance through increased food intake and/or diminished energy expenditure. Adult male Sprague-Dawley rats were given differential experience with a sweet taste that either predicted increased caloric content (glucose) or did not predict increased calories (saccharin). We found that reducing the correlation between sweet taste and the caloric content of foods using artificial sweeteners in rats resulted in increased caloric intake, increased body weight, and increased adiposity, as well as diminished caloric compensation and blunted thermic responses to sweet-tasting diets. These results suggest that consumption of products containing artificial sweeteners may lead to increased body weight and obesity by interfering with fundamental homeostatic, physiological processes.

The scientists argue that fake sugar is dangerous because it subverts a crucial homeostatic mechanism, as the the brain uses the sweetness of a food to keep track of its intake. More sugar implies more calories; the tongue is a natural energy detector. The problem with diet sodas is that they make this system unreliable, so that the presence of of intense sweetness no longer means anything. (And it's not just rodents: a similar effect has been observed in humans.) The hypothalamus gets confused. The end result is that we lose touch with the energetic needs of our body. Instead of eating to sate a hunger, we just eat. And eat.

This is the curse of soda: it's so bad for us that even diet sodas make us fat.