People really love to hate on artificial sweeteners – particularly aspartame. But is it really the devil?

Let’s go on a little journey.

Aspartame was discovered in 1965. Chemist James Schlatter was working on an anti-ulcer drug at the time and unbeknown to him, he got a bit of the chemical mixture on his finger.

He later licked his finger to lift a piece of paper and discovered its sweet taste. This was how aspartame was discovered. A mere fluke.

Lucky really, that this man licking his contaminated finger in a chemistry lab discovered aspartame and not something more dangerous. You’d think that sort of reckless behaviour could kill you.

But had he been wearing gloves, we may never have taken the food science journey of the last 50 years. Imagine where we’d been without all the low-kcal sweet stuff making dieting to much easier.

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But for Schlatter there was no sudden death for reckless behaviour. Instead, his discovery spawned an entire industry, changing the face of food tech as we knew it.

Now, as you are probably aware, it’s not been smooth sailing for aspartame or for artificial sweeteners more generally. If you google “aspartame” there’s an avalanche of information on the pros and cons of the substance – with many of the cons claiming cancer, death and the end of days.

I remember adverts for food aimed at kids on the tele saying using the lack of aspartame as a selling point, because people were so worried of the consequences.

Is aspartame dangerous?

The short answer is no. There doesn’t seem to be much evidence that aspartame is going to kill you.

And if you’re not sure who you can trust, I often turn to the NHS for matters of Health. The NHS says aspartame and a number of other artificial sweeteners are safe and do not cause cancers.

Aspartame is one of a number of popular artificial sweeteners, used in many foods and drinks. Because it has zero calories, it provides an easy way for people to manage their caloric intake without necessarily having to make massive changes.

For instance, if you love drinking coke but you’re trying to lose weight, switching to diet coke is an easy win.

Aspartame is 200 times sweeter than table sugar, which means that the amount needed to make something taste sweet is tiny. This is why it’s considered calorie-free, because the amount of calories in the tiny amount of sweetner is negligible.

Aspartame has been approved for use in the UK, along with a bunch of other sweeteners including: saccharin, sorbitol and stevia, acesulfame K, sucralose, stevia and xylitol.

Interestingly, in a study released this year, the consumption of artificially sweetened drinks made other sweet foods seem less sweet, reducing a person’s desire for sweet drinks and food immediately after drinking it.

This means that not only are sweeteners helpful in terms of reducing overall calorie consumption, but they could also be helpful in curbing sweet cravings.

So why do people think aspartame is dangerous?

In 1996 there was a suspected link between aspartame and brain tumors. Credit: GraphicsMama
  • A 1996 report suggested a link between aspartame and brain tumors. But the study didn’t really have much scientific basis and later studies showed that it is in fact safe to consume.
  • The European Ramazzini Foundation of Oncology and Environmental Sciences published several studies in 2006 and 2007 linking aspartame to cancers. The US National Cancer Institute followed these with a massive study of nearly half a million people comparing those who drank aspartame with those who didn’t. They found drinking aspartame did not in fact increase the risk of cancer.
  • There’s an popular online conspiracy article entitled Most Dangerous Substance on the Market from an alternative medicine anti-vaxxer claiming aspartame is, well, the most dangerous substance on the market. According to, Dr Mercola (the guy ragging on sweeteners) is a bit of a con man. The US Food and Drug administration warned Mercola to stop making illegal claims regarding his products’ ability to detect, prevent and treat disease.

How much aspartame is safe?

One problem was that after the studies linking aspartame to cancer, the there was a media frenzy. One main problem when it comes to science communication is that journalists are not scientists and just take the press release they’re sent at face value.

This means that when bad science is presented to them, they can’t tell, and they run with it. The more outrageous something sounds, the more people will tune in, click or buy a paper, so the better for business.

Anything that causes cancer is big news, so there was big drama.

And people panicked. And that gives credence to the likes of Mercola who prey on people’s fears and insecurities to get them to buy his scam products.

The thing is, that 2006 study linking aspartame to cancer was done in rats.

We are considerably bigger than rats.

Studies in rats don’t always tell us what happens in humans. Credit: Sipa

The rats were given a ridiculous dose of aspartame, from 4mg/kg all the way up to 5,000mg/kg of bodyweight.

This means they were given between 1.6-2,000mg of aspartame. A 330ml can of diet coke has about 187mg of aspartame. That’s the equivalent of up to 10 cans of diet coke a day – but for the rat.

The average rat weighs about 0.4kg. Let’s apply these numbers to humans.

For a 60kg human, this would be the equivalent of up to 1,604 cans of diet coke a day.

This is me pretending I can draw. You’re welcome.

When is anybody ever going to drink that many cans of diet coke. Never, that was rhetorical. I don’t think it’s even possible.

And to be honest, if someone was drinking more than a couple of cans a day, I’d be more worried about their teeth than the cancer risk. The acid from the soda weakens the enamel on your teeth, making them more susceptible to cavities and dental erosion.

The acceptable daily intake of aspartame according to the ESFA (europe’s version of the FDA) is 40mg/kg. So that’s 12.8 cans of diet coke for a 60kg human. (In America, the FDA set the acceptable intake at 50mg/kg.)

Aspartame and the world

Aspartame has been approved for human consumption by regulatory agencies in more than 100 countries over the world. In a 2002 safety review in a peer-reviewed scientific jounal, researchers concluded:

[Aspartame has] received wide consumer acceptance with consumption by hundreds of millions of people over the past 20 years, representing billions of man-years of safe exposure.

2002 was 20 years ago, so that’s 40 years of in-life exposure. If aspartame was killing us, we’d probably know by now.

FDA officials describe aspartame as “one of the most thoroughly tested and studied food additives the agency has ever approved” and its safety as “clear cut.”

They add: “The agency says the more than 100 toxicological and clinical studies it has reviewed confirm that aspartame is safe for the general population.”

Aspartame and weight gain

Low calorie foods can play a helpful role in weight management. Food technology has provided us with artificial sweeteners, which provide tasty products for much lower calorie costs than once would have been the case.

So why do people think sweeteners cause weight gain?

One of the reasons based on observational studies which found correlation between artificial sweetener consumption and higher BMI. But I posit that that would have more to do with overweight and obese people being more likely to drink diet beverages as a means to lose/manage weight rather than the cause of the weight gain itself. Correlation doesn’t always equal causation.

In fact, most research disagrees with the idea that artificial sweeteners cause weight gain.

In one study, 41 overweight men and women were split into two groups.

The sucrose supplement group (the one with the calories) saw increases in energy intake, bodyweight, fat mass and blood pressure. This was not seen in the aspartame group.

In a 2012 six-month randomised control trial, participants swapped caloric beverages for non-caloric beverages – the people who swapped for the calorie-free drinks lost weight.

Another reason that people think aspartame causes weight gain, is because people don’t really understand calories. A lot of people see “healthy” or “calorie-free” or “protein” on a label and assume it means that they can eat as much of it as they want. This is known as the health halo effect.

And while you could have as much calorie-free drink as you want, it doesn’t mean you can then eat more food and still lose weight. The diet coke isn’t going to undo the KFC bucket or extra large pizza with sides.

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What about insulin?

There is still no evidence that aspartame spikes insulin levels in healthy or diabetic people.

In a 2018 study by Higgins et al, researchers assigned 100 lean adults to one of three groups for 12 weeks: 0mg aspartame/ day; 350mg/day; 1050mg/day.

That’s the equivalent of zero cans of diet coke; about 2 cans; and about 6 cans per day for 12 weeks.

The researchers concluded:

Aspartame ingested at 2 doses for 12 wk had no effect on glycemia, appetite, or body weight among healthy, lean adults. These data do not support the view that aspartame is problematic for the management of glycemia, appetite, or body weight.

This is something they’ve been looking at for YEARS. In this 1988 study, diabetics were found to have no spike in insulin after ingesting the sweeteners.

In fact, according to, the only study done to-date that does show sweeteners spiking insulin was done in rats.

As a little side-step, in a study that came out this year looking at the short-term consumption of sucralose, researchers found that consumption of sucralose combined with carbohydrates impairs insulin sensitivity – but sucralose did not have this effect when consumed in isolation.

Dalenberg et al 2020

In the study they found that consuming seven sucralose-sweetened beverages with maltodextrin over 10 days decreases insulin sensitivity in healthy humans.

Sucralose is not aspartame though. The study suggests that there could be knock-on effects to the metabolism when consuming sucralose and maltodextrin together. Sucralose and carbs are probably consumed together in real life scenarios fairly often, if you’re drinking a sugar-free beverage with a meal. The sample size in the study was really small, so it’s too early to say anything with too much certainty.

Something that improves insulin sensitivity is exercise, so if you’re worried about your weight or your insulin sensitivity and you’re drinking diet beverages, make sure you’re also doing exercise. Lift weights, go for walks, do short bursts of HIIT. Find something that you enjoy enough to work hard.

Moral of the story

  • Aspartame is not dangerous
  • Aspartame will not lead to weight gain – unless you overeat calories thinking you have a free pass
  • Drinking artificial sweeteners might reduce your desire for sweet things
  • You are not a rat

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