The Heart Foundation says exaggerated claims are being made about the benefits of coconut oil and people should stick to unsaturated plant oils.
Coconut oil has gained popularity in New Zealand but the Heart Foundation has advised people not to switch to it as their main cooking aid.
It recently commissioned the country's leading specialist in oils and fats, Laurence Eyres, to prepare an academic paper called 'Coconut Oil and the Heart'.
Based on existing research, Dr Eyres has concluded that switching to coconut oil could potentially increase the risk of coronary heart disease, as it is extremely high in saturated fat.
The foundation's national nutrition advisor Delvina Gorton said the advice was not new, but people were being persuaded the oil was good for them.
"We're interested specifically in the claims about the heart, claims that it's a good choice for your heart. And I think it is really having an impact, we've seen an article recently that said 'if it says coconut it sells', so it is changing peoples choices," she said.
Coconut products gaining popularity
Coconutoilshop.co.nz started selling coconut oil online in 2009 and product manager Neil Smith said coconut products were definitely gaining in popularity.
He said he first got interested in the product when his family started using coconut oil to treat dry skin.
Mr Smith said while coconut oil was high in saturated fat, people should look at the bigger picture.
"What we see from history is that the people from India, Sri Lanka, in particular I'm thinking of, down to the Pacific Islands, Tonga and Samoa, those people in the past, history shows us didn't have the diseases that we're fighting today," he said.
But Dr Eyres said that was misconstruing the facts.
"It's actually quite true that indigenous populations who ate coconut, that's the whole flesh of the coconut and coconut milk and also in conjunction with their lifestyle and catching fish and eating vegetables, is perfectly okay," he said.
"But if you overlay coconut oil on a typical Western diet, which is already full of saturated fat, fizzy drinks and fast food, then that's not too good for you."
'It's OK as a small part of your overall diet'
Ms Gorton said in the past few years there had been a big rise in marketing around coconut oil, which she found frustrating.
"This is something we see with food a lot, that there are a lot of claims that make them sound really wonderful and, in our opinion, goes beyond what the evidence would say can be said about it," she said.
"There are definitely some very exaggerated claims being made."
Dr Eyres said coconut oil was fine in small amounts but should not be a major part of a diet.
"I've got nothing against coconut oil, personally. In fact, I used to manufacture it many years ago when I was in the edible oils business and it's OK as a small part of your overall diet.
"In a small amount, just like eating butter and cream and cheese in small amounts, it's fine for you. You wouldn't want to replace the healthy, unsaturated oils in your diet with coconut oil."