This is your brain on sugar — and sugar substitutes

There’s no question that artificial sweeteners have fewer calories than sugar, but does using a sugar substitute lower the total number of calories we consume? Research indicates we might actually eat more.

Currently there are five sugar substitutes approved for use in the U.S. They compete with each other not only to provide a sense of sweetness, but to do so without leaving a detectable or unpleasant aftertaste.

Saccharin (SweetN’ Low) has always been known for its bitter or metallic aftertaste. Food processors try to minimize this by combining it with other sweeteners.

Acesulfame potassium or acesulfame K (Sunett) also has a bitter aftertaste at high concentrations.

Aspartame (NutraSweet, Equal) tastes odd to some people. It’s said to have a “watery” aftertaste.

Neotame is chemically similar to aspartame and reportedly does not leave an aftertaste, perhaps because it takes much less of it to create a sense of sweetness. Aspartame is 180 times sweeter than sugar. Neotame is 8,000 to 13,000 times sweeter.

Image source: Feingold Association

And then there’s sucralose (Splenda, SucraPlus). Sucralose is made from sugar. In a process called chlorination, three of the hydroxyl groups (OH) in the sugar molecule (sucrose) are replaced with chlorine (Cl) atoms. Sucralose is 600 times as sweet as sugar, twice as sweet as saccharin, and 3.3 times as sweet as aspartame. This means, of course, that you need less of it to get the same amount of sweetness. As far as I know, it has no aftertaste.

By itself, sucralose has no calories. The nutritional information on a packet of Splenda says that one gram has zero calories. That’s not quite true. The FDA allows manufacturers to list zero calories if there are fewer than five. Splenda needs to be “bulked up” with dextrose and maltodextrin, which adds 3.75 calories per gram.

Splenda used to advertise with the tagline “Made from sugar, so it tastes like sugar.” Technically this is true. They were sued, however, by the manufacturer of Equal, who argued that the statement was misleading. The case was settled out of court, but when Equal took up the same battle in France, Splenda lost. The Sugar Association complained to the FTC that “Splenda is not a natural product. It is not cultivated or grown and it does not occur in nature.” In advertising, Splenda now says it “starts with sugar, tastes like sugar, but is not sugar.”

Fat rats

When rats are fed artificially sweetened yogurt in addition to their regular food, they eat more and gain weight. The experimenters who conducted this study believe that artificial sweeteners may undermine the brain’s ability to keep track of calories. The result: The rats don’t know when to stop eating.

What about real people? In a study at UC San Diego, 12 women sipped water sweetened either with Splenda or real sugar. In terms of taste, the women couldn’t tell the difference. But their brains, monitored by functional MRIs while they were sipping, showed a significant difference. For one thing, sugar activates pleasure-related regions of the brain much more extensively than does Splenda.

But something else showed up. Splenda was more effective in connecting the different taste areas of the brain. It takes an expert on the brain to interpret what this might mean. According to the lead researcher in this experiment, Frank Guida: “Our hypothesis is that Splenda has less of a feedback mechanism to stop the craving, to get satisfied.” Splenda activates our reward system, but can’t satisfy it.

Or, put another way:

If you eat a pound of chocolate, you’re done with it. At least for most people, your brain says, ‘That’s enough.’ This is hypothetical and needs to be tested, but maybe the sucralose sets the sweet taste response in motion but it might not turn the brain response off.

It appears that sugar – the real thing — may satisfy our desire for the sweet taste in a way that artificial sweeteners simply cannot. Just goes to show what we should have suspected all along: You can’t fool Mother Nature.

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