I have recently swapped out pretty much all my direct sugar intake for sweeteners. Instead of a Snickers, I reach for a sugar-free bar. Regular chocolate has made way for sugar-free sweets. Coke was traded in for Coke Zero long ago, and even ice cream — once the untouchable staple of life — has found its match in those little tubs boasting no sugar and a mere 100 calories.

On paper, it sounds like a brilliant deal. Except everything I consume is still suspiciously sweet — just now courtesy of sweeteners, ingredients that have spent years being accused of doing more harm than good.

So what have I actually swapped sugar for? Do sweeteners give us the best part of sugar minus the damage, or are we simply trading one villain for another? And is sugar really the villain we have made it out to be in the first place? Let’s look at what we actually know — and form our own view along the way.

You wake up and have your sweet coffee. You grab a sweet bar after lunch, then ice cream in the evening. Does any of it contain free sugar? Not necessarily. Sweeteners can give us much of the same sweetness for little or no energy — which sounds like a pretty good deal if you are counting calories.

So, does that deal actually work? If we look purely at calories, the answer seems pretty straightforward: yes. Replace sugar with a low- or no-calorie sweetener, and you cut calories — simple enough. More importantly, that obvious logic also holds up in controlled trials. A 2022 systematic review involving 1,733 adults with overweight or obesity found that replacing sugary drinks with low- or no-calorie sweetened alternatives led to an average 1.06 kg reduction in body weight over a median follow-up of 12 weeks.

There is one important catch: the benefit depends on what sweeteners are replacing. Swap regular Coke for Diet Coke, and you cut a meaningful amount of sugar and calories. Compare Diet Coke to water or tea, however, and that advantage largely disappears — water had no sugar or calories to begin with. So sweeteners seem most useful as a swap for sugar, rather than as a weight-loss tool in their own right.

The longer-term picture is less straightforward. Saving 100 calories on a drink doesn’t necessarily mean finishing the day 100 calories lighter. Outside a controlled experiment, we may consciously or unconsciously make some of those calories back elsewhere — something researchers call compensation.

And this brings us to WHO’s seemingly surprising 2023 recommendation not to rely on non-sugar sweeteners for long-term weight control. It wasn’t because WHO suddenly declared them dangerous. Rather, the evidence didn’t show a convincing long-term benefit in reducing body fat.

So, yes: replacing sugar with a sweetener can save calories and may help with weight. But the benefit seems to come mainly from cutting out sugar, rather than from sweeteners themselves.

How does our brain normally respond to sweetness? It tastes something sweet and essentially gets a signal: energy is coming. Sweeteners break that familiar pairing — the tongue says sweet, but very little, or sometimes virtually no, energy follows.

That has led to an interesting theory: could the brain feel somehow “unsatisfied” and go looking for those missing calories elsewhere? It sounds plausible, and probably explains headlines along the lines of “diet drinks make you crave sugar”.

The evidence, however, isn’t nearly as clear. Studies haven’t consistently shown that sweeteners make us hungrier or cause us to compensate by eating more. Sugar may sometimes make you feel fuller than sucralose, for example, but that isn’t the same as showing that sucralose actively makes you hungry.

And the opposite can happen too. In my case, replacing much of my usual sugary food with sweetened alternatives has actually reduced my cravings for sweets. One possible explanation is that a regular chocolate bar or ice cream isn’t rewarding simply because it contains sugar — it combines sweetness with fat, calories and texture. A sugar-free alternative can still satisfy the desire for something sweet without necessarily providing quite the same reward. You still get the familiar taste, so it doesn’t feel like complete restriction either.

So, can sweeteners make you crave more sweet food? Possibly. Can they help some people crave less? Possibly too. What we don’t have is good evidence that they systematically push our appetite in either direction.

Okay, whether sweeteners help you lose another kilo or two — or play around with your cravings — feels relatively minor once we get to the question people tend to worry about most: are they actually dangerous?

There is a slight problem with asking it that way. “Sweeteners” is a convenient umbrella term, but not a particularly useful one when we talk about safety. We are dealing with very different substances, and evidence about one doesn’t automatically tell us much about another.

Still, there are a few big concerns that come up again and again, so let’s start there and see how well the headlines hold up. We will save the sweetener-by-sweetener breakdown for the end — for those who make it through all this and still want one in their coffee (I still do!).

Claim 1: Sweeteners can cause cancer

Why do people believe this? In 2023, the International Agency for Research on Cancer (IARC) classified aspartame — one of the most common sweeteners — as “possibly carcinogenic to humans”. The decision came after studies suggested a possible link between aspartame and hepatocellular carcinoma, a type of liver cancer.

What is the other side? “Possibly carcinogenic” isn’t the same as “shown to cause cancer”. The evidence was limited, and IARC itself said other explanations couldn’t be ruled out. At the same time, JECFA looked at how much aspartame people can safely consume and kept the daily limit at 40 mg/kg — around 2,800 mg for a 70 kg adult. To put that into perspective, that is roughly the amount in 9 – 14 cans of diet soft drink.

The takeaway: the cancer concern didn’t come out of nowhere, but current evidence doesn’t show that consuming aspartame at normal levels causes cancer.

Claim 2: Sweeteners damage your gut microbiome

Why do people believe this? In a 2022 study published in Cell, researchers gave 120 healthy adults one of four sweeteners — saccharin, sucralose, aspartame or stevia — for two weeks. All four changed the composition of the participants’ gut microbiomes, while saccharin and sucralose also affected how their bodies responded to glucose.

What is the other side? A change in your microbiome doesn’t automatically mean damage. Our gut bacteria are constantly shifting in response to what we eat, our lifestyle and plenty of other factors. The study was also relatively small and short, and the effects differed considerably from person to person.

The takeaway: some sweeteners clearly can interact with our gut bacteria, and certain ones may also affect how we process glucose. What we still don’t know is whether these changes are actually harmful — particularly when it comes to long-term health.

Claim 3: Sweeteners can raise your blood sugar

Why do people believe this? In the same 2022 Cell study researchers found that saccharin and sucralose affected how some participants responded to glucose — which sounds particularly strange considering these sweeteners contain virtually no glucose themselves. One possible explanation is that changes in gut bacteria may influence the way our bodies process glucose.

What is the other side? Other human studies haven’t consistently found the same effect. And, just as with the microbiome, the response seems to depend on the type of sweetener, the amount consumed and the person taking it.

The takeaway: certain sweeteners might affect glucose regulation in some people. That is very different from saying that sweeteners raise your blood sugar across the board — or cause diabetes.

Claim 4: Sweeteners cause heart attacks

Why do people believe this? In 2023, a study published in Nature Medicine found that people with higher levels of erythritol in their blood were more likely to experience a heart attack, stroke or death over the following three years. The researchers also found evidence suggesting erythritol (another sweetener) could make blood platelets more likely to form clots.

What is the other side? The people in the study were already being assessed for cardiovascular problems, so they weren’t necessarily representative of the average healthy person. There is another complication too: our bodies naturally produce erythritol. That means higher levels in the blood may partly be a sign of someone’s existing metabolic health rather than simply a reflection of how much erythritol they eat.

The takeaway: high levels of erythritol in the blood have been linked to cardiovascular risk, and the findings deserve further research. What they don’t yet prove is that eating erythritol causes heart attacks in otherwise healthy people.

Okay, so none of this is quite as terrifying as the headlines suggest — though each comes with a few caveats worth keeping in mind, especially for the anxious among us. But if I am going to keep eating sweeteners anyway, which one should I actually choose?

One note before we rank them: these scores aren't scientific ratings. Think of them as my shorthand for navigating the evidence we have just gone through — based on the research, known caveats and how convincing the current concerns actually are.

1. Aspartame — 8/10. Extensively studied and considered safe within recommended limits, despite its rather spectacular reputation. The big exception: people with phenylketonuria (PKU) need to avoid it.

2. Sucralose — 8/10. Generally considered safe at approved intake levels, although the questions around glucose responses and the gut microbiome give it a couple of points to think about.

3. Stevia — 9/10. Approved high-purity steviol glycosides come with few major safety concerns. The bigger issue may simply be whether you can tolerate that distinctive bitter aftertaste.

4. Saccharin — 9/10. Its scary reputation mostly comes from old rat studies that turned out not to translate well to humans. These days, the metallic aftertaste may be a more convincing reason to avoid it than the cancer headlines.

5. Acesulfame potassium (Ace-K) — 9/10. Less famous, but widely used and considered safe within approved limits. So far, there is little compelling evidence to make it particularly alarming.

6. Erythritol — 7/10. The cardiovascular findings are interesting enough not to ignore, but nowhere near enough to prove that eating erythritol causes heart attacks or strokes. More prosaically, too much can leave you bloated, gassy or running to the loo.

7. Xylitol — 7/10. Similar cardiovascular question marks, similarly incomplete answers — plus the possibility of bloating, gas and diarrhoea at higher intakes. And if you have a dog, keep it well out of reach: xylitol is highly toxic to dogs.