What exactly are artificial sweeteners and how bad are they for our health?

A recent study has linked the widely used artificial sweetener erythritol to an increased risk of heart attacks and stroke. Do we need to look for alternatives? 

How much do we know about sweeteners, and the effect they have on our health?

According to the World Health Organisation (WHO), most of us consume the equivalent of about 14 teaspoons of sugar per day.

And with most of us more conscious than ever of our daily sugar intake, artificial sweeteners and sugar substitutes have become more commonplace - you might have seen the names on the labels of products at your local supermarket: Aspartame, Saccharin, Stevia, Xylitol, amongst others.

But a new WHO report has warned that these sweeteners are of little or no benefit as regards weight loss, and can potentially increase the risk of type 2 Diabetes or heart conditions.

Here, we answer some of your questions about them:

What are artificial sweeteners?

Most artificial sweeteners (also called nonnutritive sweeteners) are created from chemicals in a lab. These sweeteners don’t contain calories or sugar itself, but they also don’t have the beneficial nutrients of normal sugat like vitamins, fiber, minerals or antioxidants

In short, sweeteners promise to provide the sweet flavour we crave without the extra calories.

Varying in taste from 200 to 20,000 times as sweet as table sugar, they have, until recently, been considered helpful in combating the obesity epidemic. But some artificial sweeteners come with long-term health risks of their own. And they come in many different varieties. 

Let's take one example: Erythritol. 

Among the latest to fall under the spotlight in a new study published in journal is the sugar substitute erythritol, widely added to processed foods and fizzy drinks, which has been linked to an increased risk of heart attacks and strokes.

Marketed as a zero-calorie sweetener, erythritol is a type of sugar alcohol, that is found naturally in fruits including pears and grapes and is also an artificially made sweetener. In the newly published findings, blood samples of 1,157 patients being monitored for cardiovascular disease risk revealed that those with the highest blood concentration of erythritol were more likely to have a heart attack or stroke over three years. Analysis of other studies, one involving 2,000 people in the US and another 883 people in Europe, also suggested a similar risk associated with the sweetener.

The study had its weaknesses, says the dietitian Sarah Keogh. “We make some erythritol in our bodies and levels of it are raised in people with existing heart disease,” she says. “There is still no proven evidence that consuming it as an ingredient in food will increase the risk of heart problems.”

Still, there are other concerns about the widespread use of artificial sweeteners which crop up in everything from salad dressings and soups to yoghurt and toothpaste. Previous studies have suggested they can have a negative effect on metabolic health, blood sugar control, and appetite.

Keogh says that any sweeteners added to foods have been “rigorously tested over many years and have passed stringent safety tests set by the European Food Safety Authority”.

So how much do we know about sweeteners, and the effect they have on our health?

Are sweeteners good or bad for the gut?

The gut microbiome, the communities of bacteria, viruses, and fungi that live in the intestines, has a powerful impact on overall health and immunity. Whether some sweeteners harm gut bacteria balance has been questioned by scientists in recent years. When rats were fed an artificial sweetener containing sucralose for three months, levels of beneficial gut bacteria dwindled significantly by the end of the trial.

The same outcome may also be true in humans, with a study at the Weizmann Institute of Science in Israel last year suggesting that commonly used sweeteners could affect gut health in a way that causes blood sugar levels to rise. For their trial involving 120 adults, the team headed by immunologist and microbiome researcher Eran Elinav, provided some participants with sweeteners aspartame, saccharin, stevia, or sucralose in sachet form, while others acted as controls. Consumption of artificial sweeteners and sugar substitutes resulted in changes to the function and composition of their gut microbiomes in ways that were potentially damaging to their metabolic health. Why this happens is not clear — it might be that populations of harmful bacteria feed off sweeteners or that the products destroy some good gut bugs.

“To date, we don’t know whether these sweetening additives have a good, bad or neutral effect on the microbiome,” Keogh says. “More evidence is needed.”

Do sweeteners help with blood sugar control?

Too much sugar in the diet is known to play havoc with blood sugar control and insulin resistance, raising the risk of type 2 diabetes in the long term. Just one sugary drink a day has been linked to a 13% risk of Type 2 diabetes.

It makes sense to regard sugar alternatives as a better idea and yet evidence suggests that is not always the case.

In a 2019 review published in the , researchers said that small, short-term studies found artificial sweeteners improved fasting blood glucose levels, but some trials have shown that certain sweeteners disrupt the body’s ability to control blood sugar, eventually triggering metabolic changes that raise the risk of type 2 diabetes. Drinks sweetened with sucralose, for example, have been shown to hamper blood sugar regulation and in the study by Elinav, two other sweeteners — saccharin and stevia — had a similarly negative effect.

Not every participant’s ability to regulate blood sugar was affected in the same way, suggesting individual variations in the ways people respond to sugar alternatives in the diet.

“The general consensus from large review studies is that there is little impact on blood sugar control,” Keogh says. “And artificial sweeteners can be useful for people with Type 2 diabetes who occasionally want something sweet tasting.”

Are fake sugars responsible for hunger pangs?

Despite lowering our calorie intake at the time of consumption, could sweeteners make us feel hungrier in the long run? This has been suggested by some researchers who say when we consume sweet-tasting foods, the brain expects calories to be consumed. When those calories don’t appear from artificially sweetened foods, hunger pangs strike to ensure we eat more and make up any deficit. However, the jury is out on whether this is the case. While animal studies have suggested sweeteners can stimulate appetite in the brain, a large review of available studies found that artificial sweeteners don’t adversely affect calorie intake.

Do they help with weight loss?

According to a new WHO report, replacing normal sugar with non-sugar sweeteners "does not help with weight control in the long term."

"People need to consider other ways to reduce free sugars intake, such as consuming food with naturally occurring sugars, like fruit, or unsweetened food and beverages,” says Francesco Branca, WHO Director for Nutrition and Food Safety.

The WHO says such sweeteners are not essential dietary factors given they have no nutritional value. The WHO report recommends that people should "reduce the sweetness of the diet altogether, starting early in life, to improve their health."

So should we all avoid sweeteners entirely?

Artificial sweeteners are not risky when consumed in moderation and the Irish Nutrition and Dietetic Institute states that “all low-calorie sweeteners used in Ireland, including aspartame, sucralose, sorbitol and acesulfame K, have been tested and approved safe for human consumption”.

For a review in the BMJ researchers who looked at 35 observational studies and 21 controlled trials of sweetener consumption in children and adults found that while they probably offer no health benefits, they likely do no harm either.

“Even in studies looking at relatively high intakes, there is not enough scientific evidence to brand them bad for our health,” says Keogh. “In an ideal world, we would get sweetness from all-natural sources such as fruit, but in the real world these ingredients serve their purpose as long as consumed in moderation.”