IT WAS hard to believe I was eating a lemon. Earlier, I had let a tiny, tasteless tablet linger on my tongue, the dried powder of a fruit from the Synsepalum dulcificum shrub from West Africa known as the miracle berry. When I later bit on a slice of lemon, it was vivid sweetness rather than sourness that filled my mouth.
In Benin, the berry has long been used to sweeten tart foods, thanks to a protein in its pulp that temporarily activates sweet taste receptors in the mouth in the presence of acids. Now it could be destined for global greatness as a key player in our quest to find healthier ways to satisfy our sweet cravings.
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We all know that too much sugar is bad for us, driving an epidemic of obesity and type 2 diabetes. So, instead, many foods and drinks contain alternatives, such as aspartame, stevia and sucralose, to provide supposedly guilt-free sweetness. Increasingly, though, these products have been embroiled in controversy. In May, the and averting type 2 diabetes – things that they had previously been thought to help with.
Now we are gaining a clearer idea of exactly how these sweeteners affect our health, and the door has opened to a new wave of plant-derived alternatives. Sweeteners based on the miracle berry, a rare sugar from figs and a new kind of sugar crystal are all vying to take the top spot. Will they provide a healthy way to sate our cravings, or do we need to rethink our relationship with sweetness altogether?
Humans have a sweet tooth, and with good reason: our ancestors needed the energy that sugary foods provide in order to survive. Until relatively recently, however, our sugar hits mostly came from ripe fruits and perhaps a bit of honey. Fast-forward to today and our diets are laden with added sugars, the main culprit being table sugar – the sucrose extracted from sugar cane and beets.
Our inability to resist the stuff comes at a heavy price for our health, which is why the WHO recommends eating less than 25 grams per day (equivalent to six teaspoons) of added sugar in our food and drink. This can be challenging, given the almost ubiquitous presence of sugar in our diet. In the US, for instance, people . “It’s very important that we try to find a better alternative to sugar,” says at the University of Canberra in Australia.
To address this, food companies have long turned to non-sugar alternatives that activate the body’s sweet taste receptors but have few or no calories. The first artificial sweetener was the result of an , when a chemist called Constantin Fahlberg didn’t wash his hands after analysing coal tar – or so the story goes – and found that his dinner was unusually sweet. The substance responsible was , which is between 300 and 450 times sweeter than sugar.
Aspartame, sucralose and stevia
Many other artificial sweeteners have since been discovered, including in 1965 and in 1976, as well as natural ones such as extracts from the plant, used for centuries by people in South America and first commercialised in the 1970s. Most are no-calorie, although some, like aspartame, contain a few calories, and they are typically at least 100 times sweeter than the average apple or orange. There are also sweeteners derived from sugar alcohols, such as the naturally occurring and , which are roughly as sweet as table sugar but contain less than half the calories. Globally, , and these products must undergo stringent safety tests before approval by regulatory authorities.
“They’ve all got different properties in terms of aftertaste, how sweet they are and their chemical make-up,” says at Deakin University in Melbourne. “You can make different combinations of them to be appropriate for almost any food.”
Russell’s research has identified sugar substitutes in a diverse range of products, not just diet soda, chewing gum and sachets for adding to coffee, as you might expect, but also yogurts, cereals, ice cream, flavoured milks and kombucha drinks. This means it is very easy to consume low-calorie sweeteners without realising it, especially as they are often used in toothpaste and mouthwash (with good reason: to avoid the use of decay-promoting sugar). One study of people who said they didn’t consume low-calorie sweeteners found that , indicated by the presence of sucralose in their urine. Babies can even .
A 2022 survey of different foods and beverages worldwide conducted by Russell and her colleagues found that, as is their use in packaged foods in many countries. Usage was typically higher in countries with policies in place to reduce sugar intake.
Replacing sugar with these alternatives, however, is far from straightforward. Sugar not only contributes to the taste of food, but its texture. It prevents biscuits from crumbling and blends with egg white to yield the creamy mouthfeel of some sorbets. “Taking out just 10 per cent of the sugar and replacing it with something else causes all sorts of havoc with a biscuit,” says Naumovski. “It doesn’t colour up as well, and the texture doesn’t seem quite right.” Aspartame falls apart when heated and loses sweetness, cakes made with sucralose lack volume and stevia comes with a slightly bitter aftertaste that consumers can find unappealing. So, for all their sweetness, low-calorie sugar replacements have often had to settle for certain niches, such as flavouring diet drinks or chewing gum, or accompanying sugar rather than totally displacing it from food.
Things are equally complicated when it comes to the health impact of sweeteners. In theory, if they stop us ingesting so much sugar, they should be beneficial. However, this turns out to be a surprisingly contentious issue.
Health impact of sweeteners
Concerns have been raised over the years about the long-term safety of the consumption of certain sweeteners. The most recent was in July, when the International Agency for Research on Cancer, part of the WHO, , based on limited evidence that it might cause liver cancer. However, shortly afterwards, other health experts at the WHO that said .
Yet other long-term studies of large populations have also picked up links with cancer, although these don’t prove causation. In 2022, for instance, an , which encompasses more than a decade of dietary records from 102,865 adults in France, linked higher consumption of aspartame and another sweetener, acesulfame-K, to the incidence of cancer. This, together with other similar studies, “suggests signals regarding sweeteners and increased cancer risk in humans”, says , principal investigator of the NutriNet-Santé cohort.
Some studies also suggest that long-term consumption of sweeteners is associated with a risk of weight gain, and . One explanation is that the uncoupling of sweet taste and calories can interfere with the body’s physiological response to sugar. “The brain thinks that these sweeteners are like sugar and so produces the same amount of insulin, leading to excessive production,” says Touvier. “So, when we really need it, this insulin mechanism doesn’t work.” However, there are also suspicions that we are simply seeing reverse causation in these studies, whereby people already struggling with obesity and metabolic problems might consume more low-calorie beverages.
On the other hand, many studies, mainly in rodents, suggest that consumption of foods containing low-calorie sweeteners drives hunger and hence increased food intake. This fits with research on humans from 2019, led by at George Washington University in Washington DC, which found that the among US children and adolescents.
To complicate things further, a 2020 study found that sucralose-containing beverages . In other words, drinking a zero-calorie soda might only .
Some of the connection between sweeteners and the body’s glucose response may be due to the microbes in our gut. Key evidence for this comes from a randomised controlled trial last year on 120 people, led by at Johns Hopkins University in Maryland. This found that sucralose, saccharin, stevia and aspartame all significantly altered the types of bacteria in the gut and mouth as well as their activity, but only sucralose and saccharin resulted in significant blood glucose spikes.
Microbiome impact
When this altered microbiome was transferred to mice that lacked intestinal microbes, it elicited a similar glucose response, showing that the metabolic impact was being driven by changes in the microbiome. “A microbiome altered by exposure to sweeteners, when transplanted into mice who have no microbiome of their own… is sufficient to induce weight gain and disruption of glucose tolerance,” says Suez. “Our studies – and work by others – show that modulation of gut bacteria by sweeteners on its own is sufficient to disrupt metabolic health, independently of uncoupling sweet taste from calories.” Exactly how an altered microbiome disrupts metabolism is an open question, says Suez, who is currently investigating this.
The upshot is that sweeteners could be affecting our health in multiple ways, and we have yet to discover one with the same appeal as sugar but none of its downsides – if such a thing exists. But the hunt continues apace in the food industry. One promising place to look is among a group of from certain plants, the best known being allulose. Found in small quantities in figs and raisins, this has a similar taste and sweetness to table sugar, but just 10 per cent of the calories. It also , so in 2019 the US Food and Drug Administration . Already produced commercially, it has been used in some energy bars and condiments, yet is still relatively expensive to make. This may change in the future: a study last month showed that a genetically modified strain of the common bacteria E. coli can .
Another much-vaunted sugar alternative is , a concentrated powder produced by drying the juice from the berries of a vine that grows in remote regions of China. Used for centuries in Chinese traditional medicine, the extract’s sweetness comes from a substance called mogroside V, which is more than 200 times sweeter than sugar, but contains no calories. Finding a way to scale up the production of monk fruit extract has also been challenging, but the North Carolina “molecular farming” company Elo Life Systems has now developed a way to grow mogroside V directly in watermelons – with the idea being to generate it in much larger quantities.
Also emerging on the market is , which is made by “upcycling” the leftover parts of arable crops such as wheat straw, using enzymes to turn the carbohdyrates into a mix of sugars and fibres. This produces a high-fibre product that tastes similar to cane sugar and has similar properties when cooked, such as caramelisation, but with half the calories and generating a lower blood sugar response.
But perhaps we could one day get rid of sugar and its low-calorie mimics altogether, and still get a sweet hit. That is the promise of a range of sweet proteins found in the berries of various West African shrubs. These include brazzein, monellin and, the best known, miraculin, which comes from the berry that made my lemon sweet.
The miracle berry was disappearing from Benin’s national cuisine, says at the University of Abomey-Calavi in the country. One problem is that it is a slow-growing species that can take five years to fruit, he says. However, in 2019, he and his colleagues to just 18 months, with the aim of using the crop to help address surging rates of type 2 diabetes in Benin.
Sweet proteins
Food manufacturers elsewhere are attracted by the prospect of using miraculin or other sweet proteins in healthy but sour-tasting foods, such as plain Greek yogurt, to create the perception of sweetness. However, there are many hurdles to overcome, such as the short shelf-life of miraculin.
Genetic engineering may be one solution. Researchers at the University of Tsukuba in Japan have . Other researchers are attempting to produce proteins such as miraculin and brazzein through fermentation by that can then pump out these compounds, so there is no need to cultivate the berries.
Meanwhile, at the University of Naples in Italy, has been studying the sweet protein monellin, first isolated from the serendipity shrub in West Africa, and believes it has better commercial potential than miraculin. “It’s among the sweetest proteins, so you need just a very small amount as a sugar substitute,” she says. One drawback of monellin is that it disintegrates when exposed to heat, but in 2021 Picone and her colleagues so that it remains intact during cooking.
Although these substances are “generally recognised as safe” by regulatory authorities, watch this space, as research on the long-term health impacts of these newer products is in its infancy, so we don’t yet know if they will have similar disadvantages to more established sweeteners.
Meanwhile, researchers have been tinkering with sugar itself to reduce some of its downsides. The Israeli company Incredo has devised a way to restructure the sugar crystal by mixing it with tiny grains of silica, less than one-50th the diameter of a human hair, to make sugar dissolve faster on the tongue. This delivers an intense hit, allowing manufacturers to create lower-calorie sweet-tasting foods.
Too much sweetness
None of these developments, however, addresses the underlying problem that diets in modern high-income countries are simply too sweet, says Suez. “We’re consuming way more sweetness than our body evolved to handle, whether it’s caloric or non-caloric. This is why I think our number one goal, as we think about translating our research to the public, is helping people realise that we just need to consume less sweetness in general.”
Russell has similar concerns. There is a real harm from developing a very sweet palate “that makes us less likely to consume foods that we know are integral to a healthy diet – whole grains, fruits, vegetables, things like that that aren’t super-sweet in the way that a lot of manufactured products are”, she says. “That’s a huge problem for dietary patterns globally, especially for children. You get to the point where you just expect a massive sweet hit in almost everything.”
When it comes to sugariness without the sugar, it seems we still have a way to go before we hit the sweet spot.
David Cox is a freelance writer based in Brighton, UK
