Stevia

Stevia is not one substance. What is extracted from the leaf of Stevia rebaudiana is a family of compounds called steviol glycosides, and which ones a manufacturer uses changes the taste considerably. Rebaudioside A is the common one; rebaudioside M is the newer one used to avoid the bitter aftertaste people complain about.

They are several hundred times sweeter than sugar, so the quantity in a product is tiny, which is why stevia is almost always blended with a bulking sweetener such as Erythritol to make up the volume.

The limit, and the application to raise it

Stevia is sold harder on being natural than almost anything else in this category, and that framing tends to imply there is no number attached. There is.

The acceptable daily intake is 4 mg per kilogram of body weight per day, “expressed as steviol equivalents”. It was set by applying a hundredfold uncertainty factor to the no observed adverse effect level from a two-year carcinogenicity study in rats, which is the ordinary way these numbers are built.

In 2024 an application asked to raise it to 6 or 16 mg per kilogram. The panel’s conclusion was direct: “there is insufficient justification to increase the current ADI for steviol glycosides (E960a-d) of 4 mg/kg bw per day”.

That is worth knowing not because 4 mg/kg is a difficult limit to stay under, for most people it is not, but because it is a regulator holding a line on a product marketed as though limits were beside the point. Being from a plant is not a regulatory category.

What happens to it in the body

More interesting than most, and it explains why the limit is expressed in steviol rather than in stevia.

Steviol glycosides “are not hydrolysed by digestive enzymes of the upper gastrointestinal tract”. They pass through intact, and in the colon the gut microbiota break them down, releasing steviol, which is then absorbed. Absorbed steviol is glucuronidated and excreted in urine and partly via bile.

So the sweetener you swallow is not the molecule your body deals with, which is why the intake limit counts steviol equivalents rather than grams of product.

For blood sugar

Steviol glycosides contribute effectively no carbohydrate and do not raise blood glucose, which is the reason they appear in products aimed at this reader.

The complication is what they are blended with. A stevia product bulked out with erythritol behaves like erythritol in quantity terms, and one bulked with maltodextrin or dextrose behaves like a carbohydrate. The front of the pack says stevia; the ingredient list says which. That distinction is the practical one and it is covered on the page for reading labels when you are watching blood sugar.

The taste problem, briefly

The bitter or liquorice aftertaste that puts people off stevia comes mostly from stevioside and less from the rebaudiosides, which is why product development in this area has been a steady march towards purer rebaudioside A and then M.

A label listing “steviol glycosides” without naming which one has told you the class and not the taste, and the two products can be quite different to drink.