"We are getting all sorts of amazing testimonials, but the ones that are blowing us away the most at the moment are those taking it to help their kidney function,'' she said.
But when Mrs Frost and her husband Harry decided to plant blueberries 30 years ago that was the furthest thing from their minds. Even when they started producing the juice _ 100 per cent pure with no added sugar _ it was just because they liked the taste and thought a few people might like a non-alcoholic drink that was a little bit special.
The response took them by surprise.
"We found that people were buying it more than we thought they would ... They told me they were using it for health reasons,'' said Mrs Frost.
Three years ago Mamaku Blue commissioned a Massey University masters student to do her thesis on the health benefits of blueberries and the best way to optimise those.
"There are a number of reasons why our blueberry juice is so potent,'' said Mrs Frost.
"Firstly we grow our blueberries at 2000 feet above sea level on a volcanic ash soil. Secondly we are the only New Zealand company making juice from solely older highbush blueberry varieties that have high levels of anthocyanins and antioxidants. We also cellar the juice to protect the active components from heat and light.''
The Massey study is ongoing, one of many trying to scientifically prove what, if any, the health benefits of blueberries really are.
But Mrs Frost has no doubt there's something in it _ why else would customers keep returning to pay $30 for a litre bottle (or $330 for a dozen bottles).
"We'd love to say there is lots of scientific research on blueberries and kidney health, but there just isn't, all we know is what our customers are telling us.''
She said Mamaku Blue were restricted by the Commerce Commission as to how they advertised the product, which is why to date they have relied so heavily on testimonials from customers.
But Mrs Frost knows they need to up their marketing if they are to increase sales so is looking into ways of reaching the older population who may not be so internet savvy as well as upping their presence in Australia. She's also keen for locals to see what's right on their doorstep.
"We want to expand the best way we can.''