Younger children should not be given any drinks containing artificial sweeteners, UK experts are now advising.
The Scientific Advisory Committee on Nutrition (SACN) recommendations apply to beverages such as sugar-free 'toothkind' squash that has ingredients such as aspartame, stevia, saccharin and sucralose.
It says preschool children should become accustomed to drinking water instead.
Sweeteners may help older children cut down on sugar though.
Eating too much sugar increases the risk of tooth decay and some long-term health conditions such as type 2 diabetes, obesity and cardiovascular disease.
Artificial sweeteners were developed as a substitute, providing a sweet taste with few or no calories.
All of the ones used in the UK are approved and have undergone rigorous safety tests.
But some are concerned that they enhance preferences for sweet tastes in children which can be hard to overcome.
After reviewing the available evidence, SACN says proof that sweeteners are cutting tooth decay is "poor", although a reduction in free sugars, alongside "other positive changes to diet", is likely to be beneficial to health overall.
It says there may be some value in using sweeteners to help reduce weight gain in the short to medium term, but "it is not essential and is not the only option."
And the SACN committee experts are concerned about "the gap in data" on UK population exposure to sweeteners.
They say there is currently "insufficient evidence" to carry out a full risk assessment and are asking goverment to gather more.
A Department of Health and Social Care spokesperson said government was committed to turning the tide on obesity, taking bold action to crack down on child-targeted junk food advertising on TV and online.
Prof Robin May, Chief Scientific Adviser at the Food Standards Agency, said: "We strongly support SACN's call for industry to make data on the quantity of these sweeteners in their ingredients publicly available to provide better information on how much people are consuming and to help inform our assessments of these ingredients."
Prof Graham Finlayson, Chair in Psychobiology, University of Leeds, said it was reasonable to be cautious, especially in children, but the evidence wasn't strong enough to dismiss non-sugar sweeteners as a tool for reducing sugar intake.
"With obesity and diabetes rates rising, knee-jerk policy changes could do more harm than good," he warned.
The International Sweeteners Association (ISA) said: "As part of an overall healthy diet and lifestyle, low/no calorie sweeteners can be used to further public health objectives on sugar intake reduction.
"ISA supports SACN's call for continued investment in high-quality, long-term research."
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