Last week, news broke of the latest study to claim that artificial, non-caloric sweeteners are dangerous. Unlike most of these articles or postings, which are nothing more than baseless rants, this one actually reports the results of a research study. But like most if not all previous research that has claimed non-caloric sweeteners are the strychnine of our day, this new study was conducted on lab animals, not humans. So before you drop that Diet Coke and run screaming to your Doctor to tell him you think you’ve been poisoned, let me reassure you that you should take the results of this study with a grain of salt. Let me explain why.

Groups of scientists and self-proclaimed scientists have been vilifying non-caloric sweeteners for at least 40 years and probably much longer. I have a particularly cynical and disparaging take on these efforts for a couple of reasons. First, when I was in my first year of graduate school, the eminent neuroscientist who was the director of the lab in which I was working called me into his office one day and told me he had an exciting research opportunity for me to consider: one of the largest sugar manufacturers wanted to invest a generous sum of money in our lab if we would demonstrate that artificial sweeteners caused brain damage. I refused immediately and transferred to another research advisor, one whose coffee break area sported the giant economy size bottle of saccharin! Second, over the years, I’ve reviewed the science behind the claims of harm caused by artificial sweeteners, and they’re all just badly flawed science.

Only a handful of studies of the possible dangers of these substances have ever been conducted on human participants. None of these studies has actually involved a trial, in which the participants were randomly assigned to receive either the sweetener, or a similar tasting and appearing placebo, with their assignment remaining unknown (and unknowable) to them and to the researchers until all the results were analyzed. This type of study design, the “Randomized Controlled Trial,” is considered the gold standard to test the safety and effectiveness of a substance.

Why don’t we do these kinds of studies? Because they’re virtually impossible to do in free-living people. In other words, people who are not confined to a clinical research center or some other setting where their access to food and beverages is completely controlled. If you wanted to do a randomized controlled trial to see if the contents of the little pink, blue, and yellow packets cause, say, cancer in humans, you would have to recruit a bunch of people, randomly divide them into two groups, make sure half ingested their daily dose of the experimental sweetener, make sure the other half ingested their daily dose of a placebo sweetener (presumably one proven to be safe, a challenge in itself!) and DIDN’T use any of that artificial sweetener, and make sure neither group knew which sweetener they were actually using (because knowing which sweetener you were getting could easily bias your reaction). As if that’s not impossible enough, they would also need to make sure nothing else changed in one group that might muddy the findings (like one group all going on a Mediterranean diet or giving up smoking or living near a polluted reservoir), and keep this up for 20 to 40 years!!! And if after all that time, you did see a difference, you would need to scrutinize every possible detail of the participants’ lives to make sure the difference couldn’t be attributed to something else. Consider the impracticality and expense!!!

Instead, the effects of artificial sweeteners have been guessed at, based on one or another kind of indirect observation. In one kind of indirect observational study, scientists “follow” groups of people over the course of months and years, asking them periodically about their use of artificial sweeteners or artificially sweetened foods and their recent health. How well do you recall what you ate yesterday? Last month? When you were 16? In the other type of observational study, which is even more likely to be biased, scientists will ask a bunch of people with a particular disease if they ever used artificial sweeteners! If you had just been diagnosed with a terrible disease, wouldn’t you be looking for something or someone to blame? Especially when Aunt Sally and Dr. “Google” know someone who swears she/he got the same terrible disease from using artificial sweeteners!

This is why scientists resort to studying lab animals—rats and mice—you can control what they eat and don’t eat. Furthermore, their life spans are short. A rat given a potentially known carcinogen (e.g., certain coal derivatives) will predictably develop tumors within a year at most.

The latest study showed that mice given artificial sweeteners developed resistance to the hormone insulin. Insulin is what allows our bodies to use the sugar found in food as a source of energy, so insulin resistance interferes with the body’s ability to use sugar, depriving cells, especially brain cells of much-needed energy. One of the hallmarks of Type 2 diabetes, the type of diabetes commonly diagnosed in overweight adults, is this insulin resistance and loss of the ability to absorb glucose. So does this mean artificial sweeteners cause diabetes? That’s what the researchers who did the study—and of course the media–would like us to conclude. But that would be a huge rush to judgement. Given the strength of this evidence, people with diabetes or pre-diabetes have far more to gain by using artificial sweeteners than by skipping them in favor of sugar!

Some other recent studies have shown that artificial sweeteners alter the balance of intestinal (gut) bacteria in mice. But, we need to keep in mind that many things alter the balance of bacteria in our intestines, including changing the foods we usually eat, traveling to another country (think “Traveler’s Diarrhea”!!), and taking antibiotics for an infection. So, it would actually be quite surprising if suddenly consuming large amounts of artificial sweeteners didn’t change a mouse’s gut bacteria, especially considering that unlike humans (and mice), these bacteria can actually live on artificial sweeteners! Interestingly, the researchers I described above whose mice developed insulin resistance after consuming artificial sweeteners found that feeding these mice antibiotics made the insulin resistance disappear—the mice went back to normal—perhaps because the antibiotics obliterated the strange new intestinal bacteria. What this means is anyone’s guess, and I’m not even going to head down that road!

But let me come back now to the general topic of animal studies. The problem with studies like these that use lab animals as “models” of human illnesses (not the Victoria’s Secret swimsuit kind of models, but animals in whom a health condition is induced as a means to replicate a human disease for the purpose of studying it) is that these models are never quite perfect: We really can’t calculate how much artificial sweetener would be comparable in a rodent’s overall diet to what the average human consumes. Rodents are tiny, they consume small amounts of food, and their bodies digest things differently than ours. In addition, their metabolic rates are much faster than ours, they mature at different rates than humans do, and their average lifespan is about 2 years. So, there really is some truth to that old joke that the amounts of artificial sweetener they give to lab animals might be equivalent to a person consuming 15 gallons of diet soda a day. Of a greater concern to me is that we have no idea whether the insulin resistance developed by the diet soda consuming mice is the same as—or even similar to—the insulin resistance people develop when they develop Type 2 diabetes. What I’m trying to say is that it’s difficult, if not impossible, to apply findings of most studies on rats and mice to humans. On top of that, rumors that the most widely used artificial sweetener, aspartame, causes cancer, migraine headaches, multiple sclerosis, or any other disease in rodents or humans have never been supported by research studies.

So what is a consumer to do regarding artificial sweeteners? I suggest not exceeding more than the equivalent of a couple of diet sodas a day. Keep in mind that any food labeled sugar-free probably contains artificial sweeteners, and that with the exception of artificially sweetened tea and soda, sugar-free foods are not free of CALORIES! Some of these foods contain more calories than their sugar-sweetened counterparts, and at least the same amount of total carbohydrates in order to make them taste good! These foods are highly processed and should play a minor role in your food selections, at most. Likewise, given that the foods that contain the most sugar (you’ve probably heard about the research that condemns sugar as well, but that’s for another blog) or artificial sweetener usually have relatively little nutritional value, most of us should be reducing the amount of sugar-sweetened foods we eat as well, satisfying our cravings for sweets with fruit! So, as usual, moderation reigns!