Artificial sweeteners appeal to a lot of people as a magic bullet for weight loss, but – as researchers have found – they can cause havoc in the gut, making us susceptible to illnesses and even craving for sweets.
In 10 seconds? Research suggests that your sports drink or sugar replacement can be toxic for your gut bacteria, which regulate hunger and how we store fat. Crucially, the mix of these microbes also affects whether you develop diabetes or become obese. (Read the science)
Gosh, am I poisoning myself with that diet soda? Not yourself directly, but some of your tiny friends, depending on how much sweetener is in the drink. What happens is that by consuming certain artificial sweeteners, the fine balance of bacteria changes, as well as the compounds they produce. These are called metabolites and they play important roles keeping us healthy. (Read a review)
How did researchers work this out? Scientists made a vital, friendly bacterial species of E. coli “glow” in the lab whenever it encountered a toxic substance. The teams tested six different sweeteners on bacteria and found that even low concentrations of 1 mg/1 ml were causing toxicity. (Find out more)
What about evidence in humans? Well, one study found that those who drank 21 diet drinks per week were twice as likely to be overweight or obese than those who didn’t! Another study based on 6814 adults showed that people enjoying diet drinks daily were at 36% greater risk of metabolic syndromes and 67% increased risk for type 2 diabetes. (Read the details)
Well, can’t they just quit? Sure, but it might not be that easy, as one study suggests that artificial sugars might be addictive. Researchers exposed rats to cocaine, and then gave them a choice between cocaine or saccharin. 94% of rats chose saccharin, overriding their cocaine addiction! Breaking the habit, though, would be useful: foods and drinks with artificial sugars can cause a Catch-22 situation – making us crave and eat even more sweet foods. (More on the cocaine experiment with rats)
If artificial sugars are so dangerous, why are they marketed as safe? It depends on the definition of safe. While the US National Cancer Institute says that there is no scientific evidence linking artificial sweeteners to cancer, there is little research into how they affect other aspects on our long term health, such as their impact on gut microbes.
So back to real sugar? Obviously, eating too much sugar is not good. So it would be better to cut down on both real and artificial sugars, and eat unprocessed whole foods in which natural sugars come with more fibre and nutrients. As suggested by most healthcare providers, diets that are low in sodium, packed with fruits, vegetables and healthy oils are better for long term health and keep our little microbial friends in our guts happy. (More on how sugar conditions the gut microbiome).
Artificial sweeteners can pop up in unexpected places
Many of us make a conscious choice to cut down on sugar by dropping a packet of artificial sweetener into our morning coffee or quenching our thirst with a diet soda instead of a sugary fizzy drink.
But we also can consume artificial sweeteners inadvertently, by not expecting them in certain products and not reading the label. These can turn up in foods that are normally considered healthy, such as fruit juice and yogurts, or pop up in popcorn.
In fact, they can be detected in the breast milk of lactating women who reportedly did not consume artificial sugars, as they didn’t realise the contents of the foods they were eating.
One problem is that they can be labelled as “natural” sweeteners – for example in the US the federal regulatory authority, the FDA has no legal definition of “natural”.
Linda is a Postdoctoral Fellow, PhD in Pathology and Molecular Medicine, affiliated with Vanderbilt University, University of Cincinnati, Case Western Reserve University and Northwestern University.