Some claims about the health benefits of Ribena Plus have been banned after the regulator found the brand exaggerated the effects of vitamins in the drink.
A page on the Ribena website promoting the Ribena Plus range said vitamin A "helps keep your vision in tip-top condition" and is "important for ... immunity too" and vitamin C "helps immunity" and is an antioxidant.
A visitor to the website challenged whether the statements were authorised on the EU Register of Nutrition and Health Claims.
GlaxoSmithKline acknowledged that some claims had been reworded to keep the language understandable and "more consumer-friendly" but believed they remained faithful to the authorised versions.
It believed the claim that vitamin A "helps keep your vision in tip-top condition" was consistent with the authorised version that it "contributes to the maintenance of normal vision".
The company said its claims about the effect of vitamin A and C on immunity were consistent with the wording of the authorised version that said each vitamin "contributes to the normal function of the immune system".
But the Advertising Standards Authority (ASA) said GSK's claim that vitamin A helps to keep vision in "tip-top condition" would be understood by consumers to mean "very best" or "optimum" vision rather than the "maintenance of normal vision".
The ASA said: "We considered the reworded claim therefore exaggerated the effects of the substance as stated in the authorised health claim."
Regarding the vitamin A and C immunity claim, the ASA said: "We considered that removing 'normal' from the authorised claim had changed the meaning of the claim by implying that vitamin A would optimise the immune system rather than contributing to its normal function."
Finally, it found that the claim that vitamin C was an antioxidant did not convey the full meaning of the authorised version that it "contributes to the protection of cells from oxidative stress".
The ASA said: "The claims must not appear again in their current form.
"We told GlaxoSmithKline to ensure they retained the meaning of, and did not exaggerate, any authorised health claims if they reworded them to aid consumer understanding."