Artificial city

The truth about artificial sweeteners – and what they really do to your body

We all know we need to eat less sugar, and sweeteners offer a compelling alternative. Since the introduction of the sugar tax in 2018, the global market for sugar substitutes has exploded and is expected to be worth around £7.5 billion by the end of 2026. These substitutes – saccharin has been produced for the first time in 1879 – are both artificial and natural extracts. They are used in a multitude of foods; nothing says “eat me” like a low sugar label.

But the big question has always been: do they actually help us lose weight? The debate rages on, but the conclusion tends to be – oddly enough, no. In fact, new research suggests that consuming sweeteners sends such mixed messages to our gut and brain that they may actually increase cravings and, ultimately, our food intake. Does that mean they are actually counterproductive?

A study last year at the University of Southern California asked 74 men and women to drink 300 ml of water, a sucralose drink or a sugar-flavored drink. Then they had an MRI scan that measured blood flow to the part of the brain responsible for appetite and cravings when shown pictures of high-calorie foods. They also measured how much food they ate at the buffet afterwards.

The results were surprising. Women and those who were obese showed increased craving activity in the brain after consuming sucralose compared to real sugar, and women drinking sucralose ate more from the buffet. The conclusion was that women and obese people could be encouraged to eat more by sucralose, and especially more than they would by consuming sugar. Experts suggest a number of reasons for this.

“When you consume sugar, the digestive system, including the mouth and gut, recognizes the sweetness and releases hormones – including insulin – in response to the anticipation of having sugar,” says the dietitian. consultant Sophie Medlin at City Dietitians. “If you consume sweeteners, it has been found that you can release a small amount of insulin. When the sugar doesn’t arrive, your blood sugar levels drop and you may feel hungrier.

She says we don’t know why women are generally more sensitive to sugar. “We know those who are overweight are probably more susceptible.” It is suggested that female hormones may play a role.

“It’s something that’s been talked about for years. Appetite is an incredibly complex signaling system; it’s not just on and off. We know that many hormones are released in the gut,” says British Dietetic Association Ursula Arens, Member and Nutrition Expert.

“When you consume a drink with sugar in it, the body recognizes it and triggers certain responses throughout the body,” she explains. “The brain tells the pancreas to secrete insulin to use as energy. The insulin response signals the brain that you have enough energy and recognizes that you have consumed calories.

But that’s not the case with a sweetener. “Your body hasn’t consumed any calories and you’re still feeling hungry,” says Arens. Sweeteners trigger the same dopamine receptors in the brain as sugar. “So your brain needs more sugar and your body is always hungry.

“There are a few studies showing that those who replace sugar don’t lose as much weight as they should. This may be because they are actually hungrier two hours later and therefore consume more.

“If you have something sweet that you know is light, you may feel you deserve more,” says Dr Duane Mellor, senior lecturer and member of the British Dietetic Association, head of nutrition at Aston Medical School . “You feel like you haven’t had the full reward, so it’s more of a behavioral response.”

Not all sweeteners are created equal. “Different sweeteners work differently in the gut,” says epidemiologist Professor Tim Spector, author of Spoon fed. “Some are absorbed quite early and others not at all. We know that the chemicals in sweeteners are considered foreign by gut microbes, so they are not metabolized,” he explains. “We think this means that microbes in the gut react and produce different chemicals that disrupt our normal metabolism.”

He says studies in mice have shown that sweeteners alter the function of microbes and reduce species diversity in the gut. “That explains why, when you do a lot of trials swapping cola for diet cola, people don’t lose weight and the only real benefit is to their teeth.”

In fact, a 2021 Israeli study found that three commonly used sweeteners – aspartame, saccharin and sucralose – can interfere with the communication between bacteria. According to the researchers, this suggests that they can disrupt gut bacteria and potentially cause digestion problems and increase the risk of obesity and type 2 diabetes.

A 2019 review of artificial and natural sugar alternatives, commissioned by the World Health Organization, showed conflicting evidence. On the plus side, they didn’t find the sweeteners to cause any harm. Some trials seemed to show improvements in blood sugar and another showed that those who didn’t try to lose weight actually did. But they didn’t seem to help those who were overweight and actively trying to lose weight.

“I would say it’s related to the insulin response — causing appetite dysregulation,” Medlin says. “Having excess body fat can lead to increased insulin sensitivity and further appetite dysregulation.”

“There might be a slight advantage over sugar,” Spector suggests, “but it doesn’t seem to make a huge difference. If you’re cutting 300 calories a day, you might be compensating in other ways. In some cases it may be because you feel like you gained extra nourishment from drinking a diet drink, in others it may be the extra craving.

Plus, he says sweeteners are hidden in many foods. “It was the sugar tax that started, and it’s amazing how many highly processed foods contain sweeteners, including many children’s products like yogurt. The craving for sugar or sweeteners lights up similar parts of the brain, so children crave sweet foods.

Those who have optimistically used foods containing sweeteners are certainly not always convinced that they help with weight loss.

Office manager Louise Cole Parker, 48, says: “I have dieted so much over the years and have included various drinks and slimming aids filled with sweeteners. Overall I felt deprived, very hungry, and definitely didn’t lose any weight! Eventually, my 11-year-old son said, “I don’t know why you bother, Mom,” and I gave in. Now she says she eats sensibly and tries to avoid processed foods. “I count calories but I’m not drastic and I take my time.”

However, no one is saying to ditch diet drinks and replace them with fully sugary drinks.

“Our view on sweeteners is that it’s a step,” says Mellor. “They have their place. Throwing out the sugar and replacing it with sweeteners is a start on the path to healthy eating.

He points out that some sugar substitutes can actually suppress your appetite a bit.

“A few studies suggest stevia might do this, but the effect will be weak. It’s not the one commonly used in soft drinks in the UK as it has a licorice aftertaste.

“They’re all manufactured and are either man-made or extracted from leaves,” says Mellor. “Those that you would probably consider artificial would be aspartame, saccharin and sucralose and those that are more natural extracts (but still go through an intense process) are stevia and xylitol.”

With food, you should always watch portion sizes, he suggests. “A large yogurt with sweetener will always have more calories than a small yogurt with sugar.” They are not perfect and are not a solution, he says. Use them but be aware of the limitations.

“There is a place for sweeteners,” agrees Professor Jack Winkler, a former professor of nutrition policy at London Metropolitan University. “The so-called war on sugar has spurred the search for alternative ingredients, and there are 18 categories of sweeteners, which are not only artificial and natural, but also new forms of sugar – Nestlé has patented a form of sugar where you scoop out the crystal and keep the shell, so there’s less sugar but the same taste.There’s even sweet protein and sugar fiber.

Spector disagrees. “We need to stop this sugar substitute campaign. We make it difficult to eat acidic or bitter foods – even fruits are sweeter than before. Substituting sugar for sweeteners is not going to end obesity.