High sucralose doses suppress immune system, research on mice shows

High doses of sucralose have an unexpected calming effect on the immune system, raising the prospect that the most widely used artificial sweetener will be able to treat some inflammatory diseases.

Scientists at the Francis Crick Institute in London said their findings of a study conducted on mice, reported in the journal Nature, should not raise safety concerns but suggested a possible therapeutic use for sucralose in treating diseases such as rheumatoid arthritis, type-1 diabetes and colitis.

The mice consumed sucralose — used as a low-calorie alternative to sugar in food and beverages such as cereals, chewing gum and fizzy drinks — at levels equivalent to the maximum daily intake for people recommended by US and European food safety authorities. The study showed that sucralose reduced the activity of T-cells, a component of the immune system that can trigger inflammatory conditions when overactive, in response to cancer or infections in the animals.

“If these initial findings hold up in people, they could one day offer a way to limit some of the harmful effects of autoimmune conditions,” said Karen Vousden, project leader. Such diseases develop when the immune system attacks the body’s own cells and tissues rather than infections.

Sucralose consumption reduced inflammation and improved symptoms of mice predisposed genetically to autoimmune disorders. It cut the proportion of susceptible animals that developed type-1 diabetes from 100 per cent to around 40 per cent.

“It has been clear for several years that a number of dietary sweeteners are far from inert and can have a range of effects,” said Danny Altmann, professor of immunology at Imperial College London, who was not involved in the research.

“This is the beginning of an interesting story — a route to reduced T-cell immunity which might be good news in the setting of an autoimmune disease such as multiple sclerosis or type-1 diabetes, but bad news when fighting infection or a tumour,” he added. A suppressed immune system is less effective at recognising and attacking pathogens or cancer cells.

Sucralose is made through a chemical transformation of sugar (sucrose), adding chlorine atoms to the natural compound. It is 600 times sweeter than real sugar and has almost no calories.

Developed by Tate & Lyle, the UK sugar company, sucralose was approved by the US Food and Drug Administration in 1998. Analysts at Research and Markets estimate that global sales of the sweetener — usually marketed as Splenda — will be $3.74bn in 2023.

The FDA regards sucralose as safe when consumed in quantities below the maximum acceptable daily intake (5 milligrams per kilogramme of body weight), though consumer groups have raised concerns about possible links to leukaemia, diabetes, liver inflammation and other conditions.

One recent concern is that the sweetener might significantly change the composition of the microbiome, the billions of beneficial bacteria that inhabit the gut. But the Crick study did not find such an effect in mice dosed with high levels of sucralose.

The scientists intend to work with clinicians to test whether sucralose would also modulate the immune system in humans whose T-cells are overactive. If so, it could be a much cheaper treatment than prescription drugs, with fewer side-effects. Or sucralose might be administered in combination with more potent immune-suppressing medicines such as methotrexate or antibody-based drugs to treat rheumatoid arthritis, Vousden said.

The study was part of broader research aiming to provide more personalised dietary advice, Vousden said, so that clinicians could eventually “advise on diets that are best suited to individual patients, or find elements of our diet that doctors can exploit for treatment”.