How Artificial Sweeteners Work - a look at saccharin, aspartame, sucralose, sugar alcohols and stevia

Marshall Brain

At many restaurants you find that container on the table - it holds little packets of sugar along with little packets of artificial sweeteners. And anyone who is on a diet is familiar with artificial sweeteners - they are a big part of the dieting scene because they make low-calorie soft drinks and desserts possible.

Even though they are ubiquitous, artificial sweeteners are also a little mysterious. What is happening when you eat or drink an artificial sweetener? The appropriate starting point is sugar, also known a sucrose. This is the real sweetener against which all artificial sweeteners get measured. What is sugar and what makes it "sweet"?

Sucrose is officially known as a disaccharide, meaning that it has two saccharides. One of the saccharides is a glucose molecule ad the other is a fructose molecule. When sucrose hits your tongue, it triggers the sweetness sensors in your taste buds and sends a "sweet" message to your brain. Any molecule that shares the same characteristics that trigger the taste buds will cause the same "sweet" message to go to your brain. So an artificial sweetener is simply any molecule other than sucrose that happens to trigger the taste buds in way similar to sucrose. In most cases, when scientists are looking for artificial sweeteners, they want the substitute molecule to have less calories than sucrose, or to have some other difference that makes it better than sucrose in some way. For example, an artificial sweetener might cause fewer cavities than sucrose, or might work better for diabetics than sucrose.

The granddaddy of all artificial sweeteners is saccharin, which has been around for more than a century. Compared to sucrose, saccharin is hundreds of times sweeter when it hits the human tongue. The only problem with saccharin is the aftertaste that this same molecule triggers elsewhere on the tongue. Where sucrose only seems to interact with sweet-sensing taste buds, saccharine also interacts with taste buds that send bitter signals to the brain. Saccharin's advantage is that it has zero calories - perfect for dieters - and saccharin does not really enter the bloodstream, so for diabetics it is a win as well. People either live with the aftertaste, or food scientists blend saccharin with other artificial sweeteners in the hope of masking the aftertaste.

The most popular artificial sweetener is aspartame, sold under the brand names like Nutrasweet and Equal. Aspartame burst onto the scene around 1974 when the Food and Drug administration approved it in the United States. Aspartame quickly started to replace saccharine because it does not have that bitter aftertaste. The only real problem with aspartame, from a taste standpoint, is that it keeps triggering the taste buds for too long. As with saccharine, blending aspartame with other artificial sweeteners can help address its taste problem.

If you are a manufacturer, aspartame has two problems. First, it does not like heat. So you won't see aspartame used in baked products like cookies or cakes. Aspartame also degrades with time and loses its sweetness. So a can of soda that contains aspartame can lose its sweetness over time. You may recall that sodas started getting expiration dates after aspartame came out. This is one reason why.

If you look up Aspartame on the Internet, you will find quite a bit of material claiming that it is poisonous. This video is typical of the genre:

Sucralose, sold under the brand name Splenda, is the next most popular artificial sweetener. To make sucralose, a manufacturer starts with sucrose and chemically changes it by adding chlorine atoms. Of the artificial sweeteners, it is the sweetest - about twice as sweet as saccharin, which is already hundreds of times sweeter than sucrose. Combine that with the fact that the body does not digest most of the sucralose you ingest and it is a zero-calorie sweetener. Sucralose lacks the bitter aftertaste of saccharin and the stability problems of aspartame, so it is likely to overtake aspartame as the most popular artificial sweetener in the near future. It was approved by the FDA in 1998, which is why it feels much newer than saccharin and aspartame.

This video makes the interesting claim that a packet of Splenda actually contains calories because of the bulking agents used:

Is this true? According to Splenda.com it is true: "Like other no-calorie sweeteners on the market, SPLENDA® No Calorie Sweetener Packets and SPLENDA® No Calorie Sweetener Granulated products contain small amounts of carbohydrate (less than 1 gram per serving) to provide volume and texture. These common food ingredients are dextrose (packets) and maltodextrin (packets and granulated). These ingredients provide so few calories per serving that all SPLENDA® No Calorie Sweetener Products meet the Food and Drug Administration's criteria for no-calorie foods (<5 calories/serving)"." Per gram, therefore, these Splenda products actually contain as many calories as normal sugar.

Because of the chlorine in sucralose, it has attracted some of the same kind of negative press that aspartame has:

Then there are sugar alcohols (Xylitol may be one sugar alcohol that you have heard of). Sugar alcohols do have calories (2.5 calories per gram vs. 4 calories per gram for sugar), but not as many as sucrose. One big advantage is the fact that they won't cause cavities and are safer for diabetics. One caution is that, for many people, Xylitol acts like a laxative when consumed in larger quantities.

And finally Stevia, derived from plant fibers, which has been gaining momentum since its FDA approval in 2008. It is about as sweet as saccharine without the bitter aftertaste, and has zero calories.

Two introductions to Stevia:

What this means is that the little restaurant container on the table is getting more and more complex. It once contained only sugar and saccharine. Now it may contain three or four different artificial options. Pick the one that tastes best to you.