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Home » Scientific research says that aspartame (Nutrasweet) is safe

Scientific research says that aspartame (Nutrasweet) is safe

Last updated on April 6th, 2023 at 07:37 pm

Aspartame, the artificial sweetener known as Nutrasweet or Equal, is another target for those who love to push false narratives about substances in our foods. It’s the same for MSG, high fructose corn syrup, and so much else. As I wrote in a recent article about diet soda, the claims are not backed up by real science.

This article will look at aspartame as a “chemical,” and we know that any chemical scares people even though everything on the planet is made up of chemicals, and then we will look at the most current safety data from actual scientific research.

All about aspartame

Aspartame, which goes by the brand name Nutrasweet, although generic aspartame is also available, is a popular artificial sweetener, approximately 200 times sweeter than common table sugar or sucrose. Aspartame is a dipeptide of two natural amino acidsLaspartic acid and Lphenylalanine. Since amino acids are the basic building blocks of every protein in every organism on this planet, these two amino acids are consumed regularly whenever we eat any plant or animal. Aspartic acid and phenylalanine are not unusual or unique amino acids, they are, in fact, quite common.

So, let’s be clear, in case the above wasn’t. All amino acids in all life on this planet are the same. Whether those amino acids come from aspartame or your steak or your blueberry-kale smoothie is irrelevant to the body. There’s no magical difference between your “natural” food’s aspartic acid and phenylalanine and that found in Nutrasweet.

Time to get even more science in this article. When aspartame is ingested while drinking your Diet Coke, it is hydrolyzed (broken down by water molecules) into its constituent components — aspartate, phenylalanine, and methanol, in an approximate 4:5:1 ratio. No aspartame has been found in the bloodstream since it is so quickly hydrolyzed in the gut, and only the constituent components are absorbed by the digestive system. And there are probably no transport mechanisms that can transfer aspartame from the gut to the bloodstream.

Again, let’s be clear. Aspartame itself doesn’t get into the blood, only the constituent amino acids do. This is the first problem with many of the false claims about aspartame — it is broken down in the gut into simple amino acids that are absorbed by the body and then utilized to build new proteins that your body requires.

Setting aside the absolute safety of the amino acids (the body self-regulates amino acid production and usage), the one concern could be the methanol formed during the hydrolysis reaction in the gut. Except for the fact that most fruit juices, and the human body itself, produces much more methanol than can be consumed in many cans of diet soda.

The methanol produced by the metabolism of aspartame is absorbed and quickly converted into formaldehyde and then completely oxidized to formic acid. The methanol from aspartame is unlikely to be a safety concern. Moreover, methanol is not stored in the body, it is metabolized and then excreted. The only way for methanol to have a toxic effect is to ingest an amount so large that it temporarily cannot be cleared from the bloodstream and causes harm.

Here’s some math. A 12 US fluid ounce (355 ml) can of diet soda contains 180 milligrams (0.0063 oz) of aspartame. That means that a can of diet coke could produce 18 mg of methanol when digested, an amount substantially below the dose of 7 g of methanol that is considered harmful. It is around 0.26% of the dangerous dose. And remember, it is the dose that makes the poison.

Back to the amino acids. There just are no plausible pathways that small amounts of simple amino acids, substances that are prevalent throughout all food sources, and a tiny amount of methanol, a substance also found widely in fruits and vegetables, and is manufactured by the body as a byproduct of numerous metabolic processes, could have any effect on anyone. Those two amino acids will just be absorbed by humans and utilized to manufacture any of the thousands of proteins in the body.

I put Nutrasweet in my delicious cup of coffee. It’s that or a ton of sugar. Photo by Nathan Dumlao on Unsplash

Is aspartame dangerous?

Aspartame must be avoided by people with an extremely rare genetic mutation, called phenylketonuria, which leads to an inability to properly metabolize phenylalanine. But those with this disease not only must avoid aspartame, but also any protein that contains that amino acid. These individuals have a very restricted diet that only allows them to consume certain proteins.

Despite this overall lack of plausibility, aspartame dangers have been subject to pseudoscientific attacks almost from the day it launched. Internet hoaxes, government investigations, and unscientific studies have continued to make it appear there might be an issue with aspartame.

That’s why we have real science. The Scientific Opinion on the re-evaluation of aspartame (E 951) as a food additive (pdf), published by the European Food Safety Authority (EFSA), came to the following scientific consensus:

  • The amount of aspartame that is absorbed into the bloodstream is nonexistent in numerous human and animal studies. This supports the understanding that aspartame is hydrolyzed into its simple, widely consumed, and common constituent amino acids in the digestive tract.
  • Scientists have found no acute toxic effects of aspartame.
  • The available data did not indicate that aspartame had any genotoxic effect.
  • There were no aspartame-related increases in neoplasms and tumors in carcinogenicity studies.
  • They did recognize some studies indicated that aspartame should not be consumed in large quantities by pregnant women, not necessarily because of the aspartame itself, but possibly because of gastrointestinal disturbances and the quality of the overall diet. They established that the potentially harmful dose of aspartame is 1000 mg/kg/day, a few hundred cans of diet soda per day.
  • They noted that there was no epidemiological evidence for potential associations between the consumption of aspartame and cancers.
  • A large prospective cohort study in Denmark found no consistent association between the consumption of artificially sweetened beverages (but not with aspartame specifically) during pregnancy and the diagnosis of asthma or allergic rhinitis in children.
  • Data did not support the genotoxicity of the methanol metabolite of aspartame.

Those are the major points. The panel examined almost every claim about aspartame in detail, and reviewed all the scientific evidence–they found nothing. Aspartame is safe. They did recommend consuming less than 40 mg/kg body weight/day (less than the FDA’s recommended 50 mg/kg/day), that’s about 17 cans of diet soda every day. There are probably other issues to discuss if you’re at that consumption level of soda.

Links between aspartame and something

  • Aspartame and obesity. No evidence.
  • Aspartame and gut biome. The gut microbiome has become the conspiracy theory of nutrition — it is the claim that is made to prove that something is dangerous despite the utter lack of evidence. Almost all of the research on artificial sweeteners and the gut biome was on mice and rats. And as I have written many times, preclinical studies on rodents rarely, less than 1% of the time, lead to human clinical information. And if you take a bunch of mice or rats that are genetically similar, make sure they have no gut bacteria at the start of the study, and feed them different things, like artificial sweeteners, you will get dramatic results because there is no “noise” from the gut. In a living human gut, the biome is very complex, and a change in it would have to be powerful to show meaningful data.
  • Aspartame and glucose intolerance. Once again, the lack of evidence in human clinical studies is remarkably lacking. The belief that artificial sweeteners induce glucose intolerance is based on the same thing we just discussed — the infamous gut biome.
  • Aspartame and type 2 diabetes. You’ve probably heard that aspartame can lead to metabolic disorders like type 2 diabetes. However, a large meta-analysis, a type of study that’s considered to be at the pinnacle of the hierarchy of scientific research, clearly shows that there is no link between aspartame use and the signs of type 2 diabetes, like blood glucose levels.
  • Aspartame and cancer. Another meta-analysis shows that there is no link.
  • Aspartame and migraines. Now there is some, not high quality, evidence that aspartame is related to migraines and headaches. But much of that is based on anecdotes and one-off case studies. Some researchers propose that it is a placebo effect rather than a physiological one. It is possible that some people are sensitive to higher levels of phenylalanine. However, that would mean these people with this so-called sensitivity to phenylalanine would have to avoid all of these foods with high levels of the amino acid – soybeans, egg whites, shrimp, chicken breast, watercress, fish, nuts, crayfish, lobster, tuna, turkey, legumes, and low-fat cottage cheese. So if one is to claim that aspartame causes these headaches, it should also occur after a plate of shrimp cocktail and lobster.

Sometimes, you might find an analysis, such as this one, that concludes that non-nutritive sweeteners like aspartame have no actual benefit on overall health. That’s not the same as claiming that non-nutritive sweeteners are dangerous. My concern about these types of studies is they don’t account for the behaviors of people who use artificial sweeteners — the participants in the study might exchange a Diet Coke for a steak or extra slices of pizza, thereby causing bias in the analysis.

On the other hand, other systematic reviews (here and here) of clinical trials show that the use of non-nutritive sweeteners is linked to lower energy consumption (total calories consumed) and lower body weight.

A better study would create two groups, one with that consumed foods that replaced all sugars with artificial sweeteners compared to another that didn’t, and then examine the differences between the populations. Unfortunately, this is very difficult to do, since you can’t place each group in some sort of environment where they are not able to eat anything but controlled foods given to them by researchers.

This is the problem with all nutritional studies. They rely upon the memories and record keeping of the participants. And most effects of these sweeteners may take decades to observe. You cannot do a randomized, double-blind, well-controlled clinical trial to establish the safety and effectiveness of these sweeteners unfortunately. But what we do know is that most of the claims about the safety of aspartame aren’t supported by strong scientific evidence.


So the rumors and innuendo about aspartame dangers are swirling everywhere. But the real science says it’s safe, and it’s probably not related to any conditions that are claimed to be caused by aspartame. Sadly, some companies, like Pepsi, have bought into the unscientific claims about it and removed it from its drinks. Of course, they just switched from one non-nutritive sweetener to another, and that will probably bring on another list of false claims that I’ll have to debunk.

People demonize food ingredients all the time these days. Even scientifically minded individuals sometimes buy into the dramatic claims of pseudoscience, without actually reviewing the evidence. Sure, aspartame does taste different than good old-fashioned sugar, but that’s a personal preference and has little to do with the safety of the product.

Moreover, there’s a lack of critical thinking about the costs and benefits of an additive like aspartame. Maybe it does cause headaches in a small number of people (and the evidence for this is unconvincing at best). But for some people, say those who are diabetic or obese, the benefits far outweigh any potential risks of consuming it.

The non-existent dangers of aspartame are far outweighed by the benefits of lower caloric intake and lower body weight. And that’s just a basic analysis of the sweetener.

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Michael Simpson

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