A science project launched by two teenage students in New Zealand has cost a huge multinational more than $180,000 and forced it to launch a nationwide ad campaign to correct claims about vitamin C in the popular Ribena blackcurrant drink.

"It goes to show that consumer action really can make a difference — we hope it inspires other consumers to hold companies to the promises they make,"  Paula Rebstock, chair of New Zealand's commerce commission, said in a release Tuesday.

"It is very disappointing to see a major pharmaceutical and health-products company like [Ribena manufacturer] GlaxoSmithKline mislead the public in this way," she said.

"The company specifically promoted the vitamin C-related health benefits of Ribena for children, teenagers and pregnant women," yet some formulations of the drink contained no detectable level of vitamin C, contrary to the company's ads, she said.

Scientists at 14

Anna Devathasan and Jenny Suo were 14-year-old students at Pakuranga College near Auckland in 2004 when they tested the vitamin C content of Ribena and other drinks for a science fair.

They found Ribena did not contain the advertised level of vitamin C. GlaxoSmithKline didn't reply when the students approached the firm with their findings, so they took their results to a TV show.

Then the commerce commission got involved, leading GlaxoSmithKline to plead guilty to 15 advertising-related charges on Tuesday.

The company agreed to pay $227,500 NZ fine (more than $180,000 Cdn.) and take out ads in newspapers saying that some kinds of Ribena have virtually no vitamin C, the commission said.

The two girls said they were pleased with the sentence, but thought the company should have been ordered to run TV ads as well, they told the New Zealand Herald.

Kids and parents are more likely to see television ads, Suo said.

No detectable level

The commission tested claims that ready-to-drink Ribena contains seven milligrams of vitamin C per 100 millilitres, but found that there was "no detectable level" of the vitamin.

Five of the charges related to that claim. The other 10 were based on TV ads that said "the blackcurrants in Ribena have four times the vitamin C of oranges."

That is literally true, but if Ribena syrup is diluted as recommended, it only contains 1.5 times the vitamin C in orange juice. The company has accepted that the four-times claim was liable to mislead consumers, the commission said.