Last week, I talked about the effects of artificial sweeteners on your mind: how these chemicals are feeding the American addiction to sweet foods. But how do they affect you physically? Now, let’s look at the science behind their toxicology.

Most academic sources cite that artificial sweeteners cause people to crave sweet tastes and overeat both sugary and savory foods. But proponents of sugar substitutes, including their manufacturers, may claim that the increased use of diet soda has not caused, but rather has been caused by, rising obesity rates in the American population. Yet even if the direction of this relationship may not be definitive, those who oppose the use of the chemicals in American products have another, stronger argument against their use: the most serious physiological threat of sugar substitutes is not their ability to induce overeating of other foods, but the consumption of the chemicals themselves.

The simple fact that artificial sweeteners are so drastically different from naturally occurring sugars should raise some red flags. In contrast to naturally occurring sugars such as those in fruit (fructose) and milk (lactose), sugar substitutes are added during preparation or processing and change the taste of the “natural” state of the food. Sugar substitute chemicals are also different from table sugar (sucrose), which is an organic compound found in some fruits like pineapple and apricot but more often chemically created from glucose and fructose. In fact, the sweet taste derived from these compounds is so different from that of sucrose that they are combined in complex mixtures just to produce a taste that is close enough to “naturally sweet.” Americans are not only becoming accustomed to the highly sweet tastes, but also to consuming foods that are increasingly far from their natural state.

But the compounds that make up the mixtures used in most artificially sweetened foods have individual toxicological effects as well. For example, the fruit juice sweetener cylamate — banned by the FDA in 1970 but still used in many parts of the world today — has been proven to cause bladder cancer in animal studies. Saccharin, the first artificial sweetener, found in Sweet’N Low, has been proven to cause cancer in rats, although by a mechanism not present in the human body. In light of this, the EPA approved the chemical for use in December 2010. Aspartame, which comprises Equal and NutraSweet, causes neurological and psychiatric side effects at levels of 40 milligrams of the sweetener per kilogram of body weight or greater, but the chemical was deemed safe for ingestion by the FAO and WHO because these levels are significantly higher than national averages. Sucralose, the sweetener used to make Splenda and Altern, is a chlorinated sugar, so it belongs to a class of carcinogens called “organochlorides.”

It is also important to note that the effects of these chemicals can change once they enter the human body; in vivo, they can morph into more highly dangerous compounds. Despite a 1980 petition from the FDA Board of Inquiry confirming that aspartame, a low-calorie sweetener used in over 5,000 American food products today, “might induce brain tumors,” the chemical was approved for commercial production in 1981. Since then, the FDA has justified its use by citing the manufacturer’s claims that aspartame is composed only of aspartic acid and phenylalanine — both relatively innocuous chemicals already produced naturally in the human body. But The Nutrasweet Company conveniently left out one ingredient that some argue must be added to this list; during human digestion, aspartame also breaks down into methanol, which is a toxic chemical causing blindness, vomiting, headaches and death. Did you that know you are drinking a compound found in antifreeze, gasoline and varnishes every time you have a can of Diet Coke?

Health effects alone aren’t the only significant chemical concern. Sweeteners used as food additives also change the structure of the goods they put in. The composition of high-intensity sweeteners can alter the texture of the food, and this requires the addition of even more chemicals to bring it back to taste “natural.” Bulking agents called maltodextrins must be added to all “diet” soft drinks to return the drinks to a “wet state.” So the Fresca beverage you just drank started out “dry” due to the sugar substitutes added, and this was rectified to improve the mouthful by adding yet another (although highly digestible) manufactured additive.

But selective benefits cannot be completely discounted. The sweeteners do technically facilitate weight loss in the short term and under very controlled use. Artificial sweeteners allow diabetics to limit their sugar intake and regulate their blood sugar levels. Reactive hypoglycemia patients can also avoid the intake of high-glycemic foods with the use of artificial sweeteners. Finally — take this economic trade-off for health as you will — artificial sweeteners often cost much less than sugar because they have a longer shelf life.

And, as with any consumer product, we must be aware of the political and social factors affecting science research; the booming industry for artificial sweeteners is inevitably subject to potential biases. From a pessimistic standpoint, we must consider who might be capable of delaying important research results. Splenda — which has the least amount of toxicological data released so far — is used in products of high-power companies such as Coca-Cola and Starbucks. Most controversy surrounding the sucralose compound used in Splenda is not on its human toxicology but rather on the commercial claim that it is derived directly from sugar. The company that markets this sweetener is McNeil Nutritionals, which is owned by Johnson & Johnson. While I would love to hope that all the toxicological data found has been released, I cannot help but wonder what executives at Johnson & Johnson would pay to keep Splenda’s influence on their stock increasing.

Rebecca Stern is a junior in Berkeley College.