Glenn Cardwell is an Accredited Practising Dietitian with more than 30 years health nutrition experience, with a special interest in sweeteners. He gives us the low-down on the latest sweetener to pop up everywhere from garden centres to supermarket aisles stevia.

What is stevia?

Lately theres been a lot of interest in stevia, a little shrub originally from Paraguay whose leaf is a unique source of intense, natural sweetness. You might even have one in your backyard: if you pluck a leaf and chew it, you can taste the sweetness, and a slight aniseed aftertaste.

Apart from garden centres, it grows in the Amazon jungle on the border of Paraguay and Brazil, in South America, and in other parts of the world including Asia and Africa. The locals eat it raw or make a tea, or in their cooking. Sweeteners made from stevia leaves have a long history of use around the world including Paraguay and Japan.

Dietitian Glenn Cardwell has more than 30 years health nutrition experience and has keenly been watching the popularity of stevia grow. Stevia has a couple of very interesting properties. First, its incredibly sweet. You dont have to use a lot of it, because its 200 times sweeter than sugar. Secondly, it doesnt contain any calories, he says.

Is it safe to eat? 

Absolutely, says Glenn. South Americans have been using it for hundreds of years, and it has been used in Japan for more than 35 years without any problems. 

And its not just Paraguay and Japan. Stevia has been approved for use in many countries around the world, including Australia, where it was approved in 2008. 

Regulatory bodies dont approve a substance such as stevia until it has been well established as safe: by law, it must be tested scientifically. Because stevia was initially novel or different from what we would usually find in our food supply, it had to be first tested in laboratories to make sure it didnt cause any short or long-term problems, or problems in pregnant women or children.

It’s also worth mentioning that it is safe for people with diabetes and has been shown to be tooth-friendly,” says Glenn.

How can it be sweet, but have no calories?

Because stevia is incredibly sweet you only need a small amount to get the same sweetness as sugar, and thus provides no calories.

Several products contain stevia, but usually it comes in combination with some sugars; in other words, you need a sugar-stevia blend to achieve the best sweet taste profile, and these products may still have some calories.

Stevia is great if you are looking for fewer kilojoules but want a similar taste of a full-sugar soft drink, says Glenn.

What makes stevia taste sweet?

The sweet components of the stevia plant are Steviol glycosides which are extracted from the stevia plant.  They stimulate the taste receptors in your tongue that signal sweetness.

Glenn explains, We know this happens with sugars, but there are also other compounds that do that; there are amino acids in proteins that give rise to a sweet taste prawns are the best example. When you eat a prawn, theres a degree of sweetness, but it comes from protein not sugar.

How is stevia prepared?

Once stevia leaves reach their peak sweetness, they are harvested and dried. The dried stevia leaves are soaked in water to unlock the best-tasting, sweet substance found in the leaf. This extract is then filtered, purified, dried and crystalised.

Stevia producers emphasise that the plant is naturally occurring, making it more appealing to the consumer. 

In the end, it's all about great taste. We all know that it doesnt matter what you put on the label, if consumers dont like the flavour, they wont buy it again.