The letter from ministry chief executive Chai Chuah was disclosed yesterday at the Public Health Association Conference in Dunedin by Dr Rob Beaglehole, of Nelson, who started the push to rid health boards of sugary drinks.
Dr Beaglehole said he spoke to all 20 health board chief executives last week and about 13 had healthy drinks policies in place.
One, Hutt Valley, had gone further and also banned diet drinks.
Dr Beaglehole, principal dental officer at Nelson Marlborough District Health Board, said he pushed for a ban after seeing a Coca-Cola van parked on the property immediately after he had extracted 56 rotten teeth from four children.
He said 860 children in Auckland were waiting to be seen by a dentist to have rotten teeth removed under general anaesthetic.
Consumption of sugary drinks in New Zealand doubled between 2000 and 2006, he said.
Few people realised that a can of Coke contained three times the recommended daily intake of sugar for a child, he said.
There was also worrying evidence emerging about diet drinks, and their link to obesity and other problems.
He disclosed that Prof Sir Peter Gluckman, the Prime Minister's chief science adviser, had expressed concern to him about diet drinks' potential effect on gut flora.
Dr Beaglehole told the Otago Daily Times he was pleased with the ministry for showing decisiveness.
Green Party health spokesman Kevin Hague, who was at the conference, told the ODT the letter was significant because the ministry had not taken an active health promotion role under the National Government.
''This letter on sugary drinks is a marked change from that direction. This is the reverse of the direction they've been travelling in.''
When contacted, the ministry could not say how many health boards had implemented a healthy drinks policy, but said all were working towards the goal.
Long-term conditions chief adviser Dr Fran McGrath said the ministry would work with the boards that did not have policies yet to help them meet the September 30 deadline.
