Artificial sweeteners increase the risk of obesity, diabetes, high blood pressure and heart disease, research suggests.

A wide-ranging review has found that long term use of the sweeteners – including aspartame, sucralose and stevia – may have negative effects on our metabolism and appetite, as well as our gut bacteria.

And contrary to expectation based on the belief cutting out sugar would prevent weight gain, evidence that taking artificial sweeteners reduces weight was mixed.

Researchers at the University of Manitoba's George & Fay Yee Centre for Healthcare Innovation reviewed 37 studies that followed over 400,000 people for an average of 10 years.

The researchers said there was no consistent weight loss seen in people who took artificial sweeteners.

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A wide-ranging review has found that long term use of the sweeteners may have negative effects on our metabolism and appetite, as well as our gut bacteria

Dr Ryan Zarychanski, Assistant Professor, Rady Faculty of Health Sciences, University of Manitoba said: 'Despite the fact that millions of individuals routinely consume artificial sweeteners, relatively few patients have been included in clinical trials of these products.

'We found that data from clinical trials do not clearly support the intended benefits of artificial sweeteners for weight management.'

'Caution is warranted'

His colleague and lead author Dr Meghan Azad added: 'Caution is warranted until the long-term health effects of artificial sweeteners are fully characterized.'

'Given the widespread and increasing use of artificial sweeteners, and the current epidemic of obesity and related diseases, more research is needed to determine the long-term risks and benefits of these products.'

It has been suggested that the use of artificial sweeteners may have a stimulating effect on appetite and, therefore, may play a role in weight gain and obesity.

Industry-funded studies

One problems with some of the artificial sweetener research is that it had been funded by industry.

The authors noted that the studies funded by industry showed a greater likelihood of subjects successfully controlling type 2 diabetes, which the researchers said suggested a possibility of bias in the results.

THEIR LINKS TO DEMENTIA Adults who have at least one diet drink a day are three times more at risk from a stroke or dementia, research showed in April. Scientists said they should no longer be regarded as the healthier alternative and urge the public to stick to water or milk. Their study of almost 4,400 adults also suggests diet drinks are more likely to cause strokes and dementia than those full of sugar. There was no link between sugary beverages and either of the illnesses - although the researchers aren't encouraging us to drink them either. The team of scientists from Boston University believe the artificial sweeteners including aspartame and saccharine maybe affecting the blood vessels, eventually triggering strokes and dementia. Advertisement

The authors noted that only seven of the 37 studies were randomised controlled trials – the gold standard in clinical research – involving 1,003 people followed for six months, on average.

Most of the other research were 'cohort studies' where the diet and health outcomes in large groups of people are followed over many years.

Another problem cited by the researchers of the current study is that many of the studies took place before 2004. Since then artificial sweetener use has increased greatly in many other foods.

Preventing tooth decay

One potential positive effect of artificial sweeteners – not mentioned in the study - is that they reduce the chances of tooth decay.

The European Food Safety Agency supports claims by artificial sweetener manufacturers that taking them benefits teeth, and can control blood sugar levels.

But they can act as laxatives

One potential negative effect of artificial sweeteners in some cases is that they can act as laxatives.

Five artificial sweeteners are permitted for use in the UK: aspartame, saccharin, acesulfame potassium (known as acesulfame K), cyclamate and sucralose.

The research was published in the Canadian Medical Association Journal.