How Artificial Sweeteners Work

Sweetness doesn't just come from sugar -- there are hundreds of organic, synthetic, and inorganic compounds that taste sweet. Many plants contain sugar derivatives known as glycosides. Stevia, for example, is a plant high in glycosides that has been used for centuries to sweeten foods and drinks.

The degree of sweetness we taste depends on how well the receptors in our tongue interact with the molecules. The stronger the interaction, the sweeter we perceive the taste. (Check out this animation to learn more about how taste buds work.)

Taste scientists at a company called Senomyx have identified the taste bud receptor that is responsible for finding what we consider "sweet." Sugar and artificial sweeteners bind to this receptor, creating the sweet sensation that we get when we eat them. The receptors are found on the surfaces of cells all over the tongue and inside the mouth. They send messages to the brain to tell it that we're eating something sweet.

Artificial sweeteners are compounds that have been found to elicit the same (or a similar) "sweet" flavor we get from sugars. Some are low-calorie because they so much sweeter than sugar that only a tiny amount is needed. Others are low-calorie (or no calorie) because our bodies can't metabolize them. They simply pass through our digestive system without being absorbed.

Next, we'll learn about the history and use of artificial sweeteners.

Saccharin, the first artificial sweetener, was discovered in 1879 by a scientist who failed to wash his hands before dinner and noticed that his fingers tasted sweet. Other artificial sweeteners have also been discovered simply because scientists licked their fingers while testing a new drug or smoked a cigarette that was placed near a sweet-tasting compound. Poor personal hygiene has been the dieting industry's windfall.

These laboratory discoveries underscore the fact that these sweeteners are artificial, regardless of how they're advertised. Splenda^®, the newest sweetener, has been sued by the sugar industry for trying to make people think it is more natural than it really is. In a study by the Center for Science in the Public Interest (CSPI), 57 percent of people thought Splenda was a natural product, not an artificial sweetener [ref].

Why are there so many different artificial sweeteners? The answer is that there is no one sweetener that can be used in every product that calls for sweetness. Sucralose (Splenda), for example, is used in baked goods because it can withstand heat. Aspartame is found in "light" and sugar-free dairy products like yogurt. Sugar alcohols like xylitol and sorbitol are routinely used in sugar-free ice cream. The tricky part about sugar alcohols is that while they don't affect blood sugar or promote tooth decay, they have almost as many calories as sugar.

In addition to "light" and "sugar-free" food products, you can find artificial sweeteners in liquid and chewable medications (particularly children's medications), throat lozenges, cough drops, chewable vitamins, toothpaste, mouthwash, and anything else that could benefit from a little sweetness but shouldn't use sugar. Some products that could use sugar use artificial sweeteners simply because they're less expensive. A recent report from the Food Commission (UK) found that some orange sodas that were not marketed as "diet" were using blends of artificial sweeteners. Aspartame costs only two cents per liter of beverage, compared with six cents per liter for sugar.

If you don't want to ingest artificial sweeteners, you'll have to check ingredient labels and make sure you know the "real" names as opposed to the product names.

Next, we'll look at some of the controversy surrounding artificial sweeteners.

Fear of artificial sweeteners rose shortly after the first sweeteners were introduced in the food market. When public health trends, such as an increase in certain types of cancer, show up, scientists look to newly-introduced substances. Saccharin and cyclamate have been around the longest, and both were eventually linked to cancer in laboratory mice and rats. Studies associating saccharin with bladder cancer may have spurred the long-term perception that all artificial sweeteners could cause cancer. The press is often blamed for reporting on possible carcinogenic effects without having the scientific evidence to back it up.

In addition to cancer, thousands of Web sites and forums have information on other dangers and side effects associated with aspartame, sucralose, and other artificial sweeteners. Multiple sclerosis, Alzheimer's disease, brain tumors, nervous disorders and other health problems have been blamed on them. Aspartame is getting most of the criticism, but sucralose is also under scrutiny.

The FDA stands behind the products that it has approved. A question and answer page on the FDA Web site includes the following:

Medical groups such as the American Heart Association and the American Diabetes Association also approve of the use of artificial sweeteners by diabetics and for weight control.

If diet soft drinks and sugar-free foods are readily available, why are so many people still overweight? A recent study by researchers at Purdue University found that drinking diet soft drinks might actually be part of the problem. Professors in the Department of Psychological Sciences found that artificial sweeteners may interfere with the body's natural ability to "count" calories. Our bodies' ability to match how many calories we need with how many calories we take in is partially based on how sweet a food is. The sweeter and denser it is, the higher it is in calories. Our bodies use this as a gauge to tell us when to stop eating.

Artificial sweeteners, however, throw a wrench into this process. By eating and drinking foods and beverages that use artificial sweeteners (and therefore have lower calories), we may be retraining our bodies to no longer associate sweetness with higher calories. That means that when we eat or drink foods sweetened with real sugar, our bodies miscalculate the true calories associated with that food. As a result, we consume more calories.

In the Purdue study, rats that had been given both artificially-sweetened liquids and sugar-sweetened liquids for 10 days proceeded to eat more of a sugar-sweetened (high-calorie) chocolate snack than rats that had been given only the sugar-sweetened liquids for 10 days. The rats that experienced the inconsistent relationship between sweet taste and calories had lost some of their ability to compensate for the calories in the food [ref].

The National Soft Drink Association argued that the study was flawed and that many other studies showed that the use of low-calorie sweeteners does promote weight loss.

In the next section, we'll discuss how artificial sweeteners make it in the food chain.

The Delaney Clause in the Food Additives Amendment of 1958 states that no food additive can be considered safe if it is found to induce cancer when ingested by humans or animals. This is tested by feeding large dosages of the additive (in this case artificial sweeteners) to small numbers of rats and mice.

Large dosages are used to compensate for the fact that a relatively small number of animals are used -- perhaps a few hundred. The large dosages also compensate for the possibility that rodents may be less sensitive to the chemical than people might be. Although it may seem that only a large dose of any chemical can cause cancer, small doses can too -- just less often.

Companies that want to market a new sweetener (or any food additive) must petition the FDA for approval, unless the new sweetener is made up of components generally recognized as safe (GRAS). The FDA usually requires strong evidence, including animal studies, to show that the sweetener will not cause harmful effects if humans consume unexpected quantities of it. Companies may also submit studies of the additive's affect on humans.

When deciding whether an additive should be approved, the FDA considers its composition and properties. For instance, does the sweetener break down into harmful by-products? What is the amount likely to be consumed, and what are the probable long-term effects? Because they can't determine absolute safety, the FDA has to decide if the sweetener is safe based on the best scientific knowledge available.

If a sweetener is approved, the FDA determines the types of foods in which it can be used, the maximum amounts to be used, and how it should be identified on food labels. It is then said to be GRAS. They FDA continually monitors consumption as well as any new research on the sweetener's safety to assure that its use continues to be within safe limits.

The Adverse Reaction Monitoring System (ARMS) serves as an ongoing safety check for all food additives. The system monitors and investigates all complaints that are believed to be related to specific food additives. If reported adverse reactions represent a real public health hazard, the FDA will take action.

Next, we'll take an in-depth look at some artificial sweeteners, starting with saccharin.

Basics

Saccharin (the Latin word for sugar) is a synthetic chemical that was discovered in 1879 and was the first artificial sweetener. Two chemists at Johns Hopkins University discovered saccharine when a vessel boiled over in the lab where they were creating new chemical dyes from coal tar derivatives. One of the chemists forgot to wash his hands before eating and noticed that his fingers tasted sweet. Saccharin is 300 times sweeter than sugar and not metabolized by the body, so it has no calories.

Use

There are very few products that contain saccharin these days. Fountain Diet Coke^® and Pepsi^® use a blend of saccharin and aspartame, as does Tab^®. It's also still available as Sweet 'N Low^®, a tabletop sweetener in the familiar pink packet.

Controversy

Saccharin has had a very controversial past. The FDA tried to ban it in 1977 because some animal studies showed that it caused cancer (mainly bladder cancer, but also uterine, ovarian, skin, and others). Saccharin stayed on the market because of pressure from the diet food industry (and the dieters themselves). However, it carried a warning label that stated it had been shown to cause cancer in laboratory animals until the late 1990s. The Calorie Control Council argued that people don't develop bladder cancer in the same way that rats do, so the warning label should be removed.

In 2000, the National Cancer Institute (NCI) stated that people who used saccharin had no greater risk of bladder cancer than the population as a whole. People who were heavy saccharin users (six or more servings of saccharin or two or more 8-ounce servings of diet drink daily) had "some evidence of an increased risk of bladder cancer, particularly for those who heavily ingested the sweetener as a tabletop sweetener or through diet sodas." Because of this study and other research with laboratory animals, it was decided that saccharin was not a major risk factor for bladder cancer in humans. Saccharin was removed from the NIH's list of carcinogens and Congress agreed to remove the warning requirement from products containing it.

Next, we'll learn about aspartame, another controversial sweetener.

Basics

Aspartame (sold under the brand names Equal^®, NutraSweet^®, and NatraTaste^®) is derived from a combination of two amino acids: aspartic acid and phenylalanine. It was discovered in 1965 by chemist Jim Schlatter of the pharmaceutical company G. D. Searle & Co. (now a part of Pfizer). Schlatter licked his finger to pick up a piece of paper while testing a new anti-ulcer drug.

Aspartame is 180 to 200 times sweeter than sugar, so only very tiny amounts are necessary to sweeten a food or beverage. When digested, aspartame breaks down into three components: aspartic acid, phenylalanine, and methanol (wood alcohol).

People with the rare genetic disorder phenylketonuria (PKU) should avoid aspartame because their bodies are deficient in the enzyme that breaks down phenylalanine. If they consume foods or beverages containing significant amounts of phenylalanine, it can build up in their bodies and can cause mental impairment and possibly brain damage. Newborns are routinely checked for PKU.

Use

Because aspartame breaks down in heat, it is not generally used in baked or heated foods. According to the official aspartame Web site, it can be found in "more than 6,000 products including carbonated soft drinks, powdered soft drinks, chewing gum, confections, gelatins, dessert mixes, puddings and fillings, frozen desserts, yogurt, tabletop sweeteners, and some pharmaceuticals such as vitamins and sugar-free cough drops." Aspartame was approved as a food additive by the FDA in 1981.

Controversy

There appears to be more controversy over the safety of aspartame than any other artificial sweetener. Since its approval, 75 percent of all complaints reported to ARMS have been about aspartame. Only about one percent of people who experience a problem actually report it [ref].

While no officially recognized studies have shown problems with aspartame, many consumer groups and individuals are speaking out against it. Aspartame is blamed for a number of health problems, including headaches, seizures, chronic fatigue syndrome, memory loss, and dizziness. It has also been associated with an increase in multiple sclerosis, Alzheimer's disease, and cancer.

Critics of aspartame claim that although aspartame's two amino acids are a natural part of our diets, when they are consumed normally in food they appear with many other amino acids that cancel out any negative affects. When these amino acids are on their own, as they are in aspartame, the concern is that they enter the central nervous system in abnormally high concentrations.

A similar problem allegedly occurs with the methanol (wood alcohol) that aspartame breaks down into when digested. When it occurs naturally in fruit juices and alcoholic beverages, methanol is always accompanied by higher amounts of ethanol, which acts as an antidote for methanol toxicity. Ten percent of aspartame is absorbed into the bloodstream as methanol. The Environmental Protection Agency set a recommended limit of only 7.8 milligrams per day of methanol, while a one-liter aspartame-sweetened beverage contains about 56 milligrams, or eight times the recommended amount.

In 2005 the European Journal of Oncology published an article about a study of aspartame that showed that it caused lymphomas and leukemia in female rats. The lowest level of aspartame that was still found to increase these risks in adults was equal to about eight cans of aspartame-containing soda a day (two for children). Brain tumors were also found in 12 of 1500 animals that received aspartame, while the animals that received no aspartame had no brain tumors.

On the other hand, many groups have also performed studies that show aspartame is safe and causes no health problems.

Next we'll explore acesulfame, a lesser-known sweetener.

Basics

Acesulfame (also known as acesulfame potassium, and acesulfame K) is a synthetic chemical that is roughly 200 times sweeter than sugar. It was discovered in 1967 by Hoechst AG, a German life-sciences company that is now part of Aventis. Our bodies can't metabolize it, which is why it's considered low calorie. Acesulfame is made from a process involving acetoacetic acid and its combination with potassium.

Use

The FDA approved acesulfame in 1988 and it is found in more than 4,000 products around the world. In the United States, acesulfame potassium has been approved for use in candies, tabletop sweeteners, chewing gums, beverages, dessert and dairy product mixes, baked goods, alcoholic beverages, syrups, refrigerated and frozen desserts, and sweet sauces and toppings. It can be found under the brand names Sweet One^® and Sunett^®. Acesulfame is often blended with other artificial sweeteners to produce a more sugar-like taste.

Controversy

In August of 1988, the Center for Science in the Public Interestformally asked for a stay of acesulfame's approval by the FDA because of "significant doubt" about its safety. CSPI claimed that the studies were flawed and did not sufficiently prove that acesulfame did not cause cancer. According to the CSPI Web site, "...acetoacetamide, a breakdown product of acesulfame, has been shown to affect the thyroid in rats, rabbits, and dogs. Administration of 1 percent and 5 percent acetoacetamide in the diet for three months caused benign thyroid tumors in rats. The rapid appearance of tumors raises serious questions about the chemical's carcinogenic potency" [ref].

Next, we'll learn about one of the newest artificial sweeteners: sucralose.

Basics

To create sucralose, three of the hydrogen (H) and oxygen (O) groups in a sugar molecule are replaced with three chlorine (Cl) atoms. At that point it is no longer sugar -- it is an artificial sweetener that is 600 times sweeter than sugar.

Sucralose isn't metabolized by the body, so it has virtually no calories. The chlorine that prevents it from being absorbed by the body also gives it the ability to withstand enough heat to be used in baking. (Other sweeteners lose their sweetness if you try to bake with them.) It was approved by the FDA for use in foods and beverages in 1998.

Use

Sucralose, marketed as Splenda^®, is the fastest growing artificial sweetener on the market. It can be found in everything from frozen deserts, to sodas, to cookies, gum, and candies. Sucralose is sold in bulk for baking and is available in a small yellow packet for sweetening your coffee or tea.

Controversy

Sucralose isn't as controversial as aspartame. However, the Food and Drug Administration's 1998 report that gave approval for sucralose also stated that it is "weakly mutagenic in a mouse lymphoma mutation assay." This means it caused minor genetic damages in mouse cells. In addition, it stated that one of the substances sucralose breaks down into when digested is also "weakly mutagenic in the Ames test." The Ames test is the standard method used to detect possible carcinogens [ref].

The other controversy is over the way Sucralose is marketed as Splenda. Because of their tagline, "Splenda is made from sugar, so it tastes like sugar," many people believe that Splenda is a natural sweetener and therefore healthier, which isn't the case. Because there have been no long-term studies, no one really knows if sucralose is healthier then other artificial sweeteners.

Next, we'll discuss tagatose, another new artificial sweetener.

Basics

Tagatose (or Natrulose^®) is a new artificial sweetener manufactured from lactulose, or milk sugar. In one step, lactose is hydrolyzed (broken down into smaller molecules by using water) to glucose and galactose. In the second step, galactose is isomerized (changed to a molecule with the same chemical formula but a different atom arrangement) to D-tagatose by adding calcium hydroxide.

Tagatose was discovered when Gilbert Levin, founder of Spherix, wanted to find a new sweetener and thought a "left-handed" sugar might be the answer. In chemistry, a molecule can be chiral ("left-handed" or "right-handed") if it cannot be superimposed on its mirror image. For example, our hands are mirror images of one another and cannot be superimposed. Levin was accidentally sent D-tagatose, a "right-handed" molecule that structurally similar to L-fructose. It turned out to be just what he was looking for.

Tagatose has about 1.5 calories per gram, and does not significantly impact blood glucose or insulin levels. It can't be digested, so it passes through the body unabsorbed. It is equal in bulk and sweetness to sugar and can be combined with other artificial sweeteners to improve flavor and texture. The FDA accepted a Generally Recognized As Safe (GRAS) declaration submitted by the manufacturer of tagatose in 2001.

Use

Because it's so new, tagatose is not used in many products yet. Currently it is used in Diet Pepsi Slurpees^®sold at 7-Eleven^®, and Florida Gold^®'s new Light and Tangy frozen juice beverage concentrate. It can be used in breakfast cereals, diet soft drinks, health bars, frozen yogurt/nonfat ice cream, soft confectionaries, hard confectionaries, frosting, and chewing gum.

Controversy

Again, the newness of tagatose means that there isn't much controversy about it yet. It isn't absorbed well and can cause GI distress if consumed in large quantities.

Next, we'll discuss sugar alcohols.

Basics

Sugar alcohols are made from adding hydrogen atoms to sugars. They don't contain ethanol, so they're not related to alcoholic beverages. They can occur naturally in foods such as fruits and berries. Sugar alcohols have about one-half to one-third fewer calories than regular sugar, because they convert to glucose more slowly. They don't usually cause sudden increases in blood sugar, so can be used in moderation by diabetics. Some people with Type I diabetes have found that their blood sugars will rise if they consume sugar alcohols in large amounts.

The caloric content varies by specific sugar alcohol. Erythritol, for example, is not absorbed as easily as others, so it essentially has no calories. Some of the other sugar alcohols can have almost as many calories as sugar, so they're not necessarily used in "diet" foods, but in sugar-free gum.

Use

Sugar alcohols are found in many sugar-free processed foods, such as hard candies, cookies, chewing gums, soft drinks, throat lozenges, toothpaste, and mouthwash. Look on product labels for mannitol, sorbitol, xylitol, lactitol, isomalt, erythritol, maltitol, and hydrogenated starch hydrolysates (HSH).

Controversy

The FDA requires products that contain what would equate to a daily dose of 50 grams or sorbitol or 20 grams of mannitol to be labeled with a "laxative effect" warning. This is because higher levels of sugar alcohols unabsorbed in the intestines can cause bloating, gas, and diarrhea. According to the Center for Science in the Public Interest, only 10 grams of sorbitol can cause GI distress.

Check out the links on the next page for lots more information on artificial sweeteners and related topics.