Every month, it seems like there's always a new diet drink or artificial sweetener popping up in our grocery aisles, claiming that it not only offers all the benefits of its nonfat predecessors, but it also comes with none of the downsides. Meanwhile, it’s hard to avoid the reports that claim to link various artificial sweeteners to weight gain, cancer, and other dangerous effects. So how can you separate fact from fiction?
The most common non-caloric artificial sweeteners (NAS) are substances with a very intense sweet taste. They’re used in small amounts to replace the sweetness of a much higher amount of sugar, or of other derivative substances.
You’ll probably recognize at least some of the following names of common artificial sweeteners:
But are any of these sweeteners really any better than the others --or perhaps, riskier? Let’s break down what the actual research has to say.
The main benefit of artificial sweeteners (or non-nutritive sweeteners) is to provide a zero-calorie alternative to foods and beverages, while still giving them a sweet taste. Replacing refined sugar with artificial sweeteners in your own diet can be an effective way to lower your calorie intake - which can allow you to bring in some healthier higher-calorie foods instead. Some studies have found that this kind of adjustment can help obesity, diabetes mellitus, and similar problems.
The truth is that only a few artificial sweeteners have been studied in-depth: aspartame, sucralose, acesulfame-K and saccharin. The majority of existing clinical and lab data only cover these sweeteners.
The FDA first approved aspartame in 1974, in light of a large amount of evidence - from labs and clinics in the United States, as well as from more than 90 other countries around the world - that demonstrated its safety for human consumption. So why did people get so paranoid about aspartame? Most likely because of a few studies on rodents, which have found that exposure to aspartame is associated with various cancers in rats and mice.
However, experiments have shown that the doses of aspartame required to pose danger to humans are far larger than what any normal person could consume in a day. The FDA has set the acceptable daily intake (ADI) for aspartame at 50 mg/kg of bodyweight - the equivalent of a whopping 18 to 19 cans of diet soda.
Rodent studies have shown a dose-dependent increase in lymphomas, leukemias, and transitional renal cell tumors in rats and mice who received doses of aspartame lower than the ADI - but while rodents and humans do share some metabolic similarities, there are many differences also. Mechanisms that our bodies use to process methanol, a byproduct of aspartame are quite different from those in rodents.  Thus, it is questionable whether the results of aspartame testing in rodent models can be readily applied to humans.
For people born with phenylketonuria (PKU), a rare inherited disease, aspartame can help create dangerously high levels of the naturally occurring essential amino acid phenylalanine - and there’s also some evidence pointing to a possible relationship between aspartame and migraine headaches. For most people, though, aspartame has always been perfectly safe at reasonable doses.
The human body doesn’t metabolize Ace-k at all, so it provides no calories - but it’s 200 times sweeter than table sugar. One breakdown product of ace-k is a chemical known as acetoacetamide, which is known to be toxic if consumed in very large doses - but the amounts of acetoacetamide found in spoonfuls of Ace-k are far below dangerous levels. Still, although plenty of research has found that Ace-k is safe for animals, human studies are still rare.
Although sucralose is made from sugar, the human body doesn’t recognize it as sugar, so it’s not metabolized - which means it provides no calories. Most of the sucralose we consume is excreted as waste - while another 11% to 27% of it gets absorbed into the bloodstream through the gastrointestinal tract, removed from the blood by the kidneys, and eliminated through our urine.
The acceptable daily intake (ADI) for sucralose is 5 mg/kg bodyweight per day, but the typical person’s estimated daily intake is a significantly lower 1.6 mg/kg per day. Human trials haven’t reported any significant dangerous effects for sucralose at all - but similarly to studies on aspartame, some research has found a relationship between sucralose intake and migraine headaches.
Among all the artificial sweeteners listed here, saccharine is the only one that deserves a stain on its reputation. The FDA tried to ban saccharin in 1977, in the wake of a series of animal studies that found close linkages between saccharin intake and the development of cancer in rodents. And while no study has ever shown a clear causal relationship between saccharin consumption and health risks in humans at normal doses, some studies do show a correlation between saccharine consumption and human cancer incidence.
More recently, researchers have found that saccharine can impair glucose metabolism in rodents. This has become a fairly controversial idea, though, and it’s probably the origin for the bad rap that all artificial sweeteners tend to catch.
A recent study by Suez et al. pooled evidence from animal studies to demonstrate several dangerous effects of saccharine - and those same authors also performed a study in which they administered high doses of saccharin to human subjects, then transplanted feces from two human subjects to two rodents. This transplant, the researchers found, caused some damage to the rats’ intestinal microbes, which in turn lowered their tolerance for glucose.
The news media grabbed the results of this single study and blew them out of all proportion to the facts, spawning outrageous headlines like “Diet Soda Causes Diabetes.” The truth is, a lot more research is needed to determine the effects of saccharin (and most other artificial sweeteners) on the human microbiome in vivo. For now, there’s no compelling evidence to suggest that normal doses of saccharin pose any harm to humans.
Aside from that, saccharin is nearly non-existent in today’s diet foods and beverages. Aspartame and sucralose are found all over the place - but saccharin is only found in Tab and a few other fountain drinks, and in the sweetener Sweet’N Low, where it’s present in tiny amounts. In order to match the dose that Suez et al. found to be dangerous for humans, you’d have to drink four cans of Tab, ten packets of Sweet’N Low, or fifty servings of a saccharin-containing fountain drink. So on the whole, even saccharine is a pretty low-risk sweetener.
What about the effects of artificial sweeteners on your weight-loss plans? Most short-term and long-term studies on humans have found that consuming artificial sweeteners doesn’t seem to decrease dieters’ energy intake - and randomized trials have found that people who use these sweeteners in place of refined sugar can successfully reduce both their weight and their body fat. Only been a few studies have examined the overall effects of artificial sweeteners on body weight - but every study has found  (reductions in weight and body fat in groups of people who use artificial sweeteners, as opposed to normal calorically dense ones).
So, should you be concerned? Maybe. Generally speaking, the only people who should be worried about artificial sweetener intake are children, pregnant women, nursing mothers, and those prone to seizures, headaches or migraines. If you don’t fall into one of those groups, then you probably shouldn’t be worried about opting for diet soda instead of regular soda.
- Species- and strain-dependent teratogenicity of methanol in rabbits and mice . Reprod Toxicol. (2011) Sweeting JN, et al.
- Sucrose compared with artificial sweeteners: different effects on ad libitum food intake and body weight after 10 wk of supplementation in overweight subjects . Am J Clin Nutr. (2002) Raben A, et al.