Artificial sweeteners: are they truly as sweet as they taste?

Strange beginnings

It’s the number one rule in chemistry: don’t lick the science. When working with new or unknown molecules this is good advice, as any given substance has the potential to have toxic effects. But in a few instances, researchers have accidentally tasted their experiments, only to make some interesting discoveries.

In 1897, a grad student by the name of Constantine Fahlberg was trying to find ways to use coal tar, a waste product of coal processing. After a day of work, he noticed that his fingers tasted strangely sweet while eating his supper. The following day he tasted everything on his lab bench and traced the sugary flavour to a compound called saccharin. He ingested about 10 grams and waited. When nothing happened, he concluded that his discovery must be safe for human consumption, and brought saccharin to market under the name Sweet’n Low. During World War I, when sugar was scarce, saccharin rose to be a popular and inexpensive alternative. It’s still widely used today.

Thankfully, the same can’t be said of the first artificial sweetener: sugar of lead. This sweet-tasting salt, made by boiling lead in a mixture of vinegar and hydrogen peroxide, was first used by the ancient Romans as a sugar substitute in wine and food. It was used well into the 20th century, long after its toxic effects on humans and the environment had been recognized, until it could be replaced by new synthetic alternatives like saccharin.

In the past century, many other artificial sweeteners have been identified – some purposefully, some by scientists with poor lab practices. Aspartame, one of the most common options, is another product of the latter situation. In 1965, a researcher spilled a potential treatment for gastric ulcers on his hands, forgot, and licked his fingers. Luckily, the product wasn’t toxic and proved to be a widely used molecule with great commercial value. But sodium cyclamate, a third sweetener discovered by a forgetful chemist putting his hands in his mouth, was banned 32 years after its discovery due to potential cancerogenic properties. Sugar of lead and sodium cyclamate are not the only artificial sweeteners, either historically used or still available today, to have potential consequences to human health. The safety of aspartame, for example, remains a subject of debate. While this uncertainty is cause enough to better investigate the potential long-term health effects of artificial sweeteners, scientists are only just beginning to recognize that these molecules may have an effect on the environment too.

Artificial sweeteners today

Global use of artificial sweeteners now amounts to more than 159,000 metric tonnes per year, worth around $2 million (USD). They’re used in thousands of food products, including beverages, desserts, chewing gums, pastries, and breads. As they are low- or no-calorie and do not cause any glycemic effect (insulin reaction), they can be especially interesting to people looking to reduce their caloric intake or to those with conditions such as diabetes. Besides this, they’re practical additives to chewing gums or diet sodas as they aren’t linked to cavities in the way that sugar is. Artificial sweeteners are also found in pharmaceuticals and personal care products, such as toothpaste and cough syrup.

Not to be confused with natural low-calorie sweeteners, such as Stevia leaf extract, artificial sweeteners are made by chemically transforming other molecules. The starting materials in the production of these sweeteners can be anything from amino acids (aspartame), fossil fuel derivatives (saccharine), or sugar itself (sucralose). The resulting products are incredibly sweet, sometimes hundreds of times more than sugar, and incredibly persistent. Some sweeteners pass through the human body completely unaffected by the digestive system. As a result, they’ve been found in wastewater, both up and downstream of treatment facilities. In other words, artificial sweeteners can resist degradation or transformation in the human body and wastewater treatment facilities. Consequently, they’ve emerged as a new class of environmental pollutants, found in open waters, groundwater, and soils.

What is (and isn’t) known

If it can be argued that the potential health effects of artificial sweeteners are misunderstood, the case can certainly be made in regard to the environment. Despite the widespread use of artificial sweeteners over the past century, they’ve only been identified as an environmental contaminant in recent years. Their presence in marine and terrestrial environments has inevitably led to their unintentional appearance in human food and drinking water sources. As these molecules have generally been designed for human consumption, this may not prove to be that big of a problem. However, we don’t yet understand how they may affect other species or impact biogeochemical cycles. Scientists also don’t understand possible degradation mechanisms and what by-products might be generated as a consequence of artificial sweeteners accumulating in the environment.

Based on the current research, artificial sweeteners in their original form appear minimally harmful to aquatic environments. However, some can turn into metabolites that can be 99.5% more toxic, which is uncommon and alarming. It may be these by-products that have led to toxic effects being observed in certain bacteria, phytoplankton, and plants in a lab setting. Toxicity also manifests differently from one species to another, further complicating being able to gather conclusive evidence from preliminary studies.

The popularity of artificial sweeteners is enough reason for their complete and thorough investigation. As the market for this group of molecules is expected to keep growing, it’s important for scientists to research their precise effects on their target market (humans) and the environments in which they inevitably come to rest. Good chemistry should never be tasting unknown substances. But, if useful discoveries do arise from these unrecommended techniques, it’s important to completely understand a molecule’s behaviour before introducing it into many of the foods and beverages we consume. Add the emergence of artificial sweeteners as an environmental pollutant into the mix… Well, it’s high time to head back to the lab.