If you have read what stevia actually is and want the chemistry behind it, this is the deep dive. As a Colombian beverage maker, we obsess over which steviol glycosides go into a drink — because the choice is the difference between "tastes like stevia" and "tastes clean." Here is the technical picture, in plain English.
What are steviol glycosides?
Steviol glycosides are the naturally sweet compounds found in the leaves of Stevia rebaudiana. Every one of them shares a common core called steviol — a diterpene molecule — with different combinations of glucose, rhamnose, or xylose sugar units attached at two points. Those attached sugars are why the molecules are called glycosides.
Because they all rest on the same steviol skeleton, the body handles them similarly: gut bacteria strip away the sugar units and release steviol, which is absorbed, processed by the liver, and excreted. None of them are metabolized for energy, which is why steviol glycosides deliver sweetness with zero calories and no impact on blood glucose. The differences between glycosides come down to how many sugar units they carry and where — and that small structural difference drives a big difference in taste.
How is Reb-A different from Reb-M and Reb-D?
The leaf naturally contains more than a dozen glycosides, but a few dominate the conversation:
- Stevioside — historically the most abundant glycoside in the leaf and the cheapest to extract, but the most bitter and licorice-like.
- Rebaudioside A (Reb-A) — the workhorse of most commercial stevia. Sweeter and cleaner than stevioside, but still prone to a lingering bitter aftertaste at higher doses.
- Rebaudioside D (Reb-D) and Rebaudioside M (Reb-M) — present only in tiny amounts in the leaf, these carry more glucose units. That extra structure makes them taste rounder, sweeter on first contact, and far cleaner on the finish, with little to none of the bitterness.
In short: the more glucose units a glycoside carries on its steviol core, the better it tends to taste. That is the central reason the industry has moved from stevioside, to Reb-A, and now toward Reb-M and Reb-D.
Why does Reb-A taste bitter while Reb-M tastes clean?
Taste is not only about the sweet receptor. Many steviol glycosides also activate bitter taste receptors on the tongue — and the degree to which they do depends on their exact shape. Stevioside and Reb-A trigger these bitter receptors more strongly, which is what produces the familiar metallic, licorice aftertaste.
Reb-M and Reb-D, with their additional sugar groups, bind the sweet receptor more favorably and the bitter receptors much less. The result is a sweetness that comes on faster, peaks higher, and disappears cleanly — much closer to the profile of sugar. The trade-off is supply: because the leaf makes so little Reb-M and Reb-D naturally, producing them at scale requires either careful extraction or modern bioconversion (using enzymes or fermentation to convert abundant glycosides into the rare, better-tasting ones).
How are steviol glycosides regulated?
Regulators do not approve "stevia" as a vague category — they approve high-purity steviol glycosides (typically 95%+ purity). In the United States, the FDA recognizes high-purity steviol glycosides as Generally Recognized as Safe (GRAS) for use in foods and beverages. Whole stevia leaf and crude extracts are not GRAS-approved; the purified glycosides are.
Globally, the safety benchmark is set by JECFA (the Joint FAO/WHO Expert Committee on Food Additives), which established an Acceptable Daily Intake (ADI) of up to 4 mg per kilogram of body weight per day, expressed as steviol equivalents. Expressing the limit in "steviol equivalents" is the clever part: because every glycoside breaks down to the same steviol core, regulators can pool all of them under one shared limit regardless of which specific glycoside you consume. The World Health Organization's broader guidance is to keep free sugars low — which is precisely the gap non-nutritive sweeteners like steviol glycosides are designed to fill. As always with intake questions, consult your doctor or a registered dietitian for advice specific to you.
How do the main steviol glycosides compare at a glance?
| Glycoside | Abundance in leaf | Sweetness vs sugar | Taste profile |
|---|---|---|---|
| Stevioside | High | ~150–200× | Bitter, licorice aftertaste |
| Rebaudioside A (Reb-A) | Moderate | ~200–300× | Sweet, mild lingering bitterness |
| Rebaudioside D (Reb-D) | Very low (rare) | ~200–250× | Clean, sugar-like |
| Rebaudioside M (Reb-M) | Very low (rare) | ~200–250× | Cleanest, closest to sugar |
This is the core reason the best-tasting stevia products lean on Reb-M and Reb-D rather than stevioside or Reb-A alone — and it is exactly the logic behind why we chose Reb-M and Reb-D for our drinks.
Frequently asked questions
Are steviol glycosides natural or artificial?
The glycosides themselves are natural compounds from the stevia leaf. High-purity extracts are produced by purifying those leaf compounds, and some rare glycosides like Reb-M are made by bioconversion of natural precursors. They are non-nutritive sweeteners, not synthetic ones like aspartame or sucralose.
Is Reb-M safer than Reb-A?
Safety is assessed for steviol glycosides as a group under one shared ADI, because they all break down to steviol. So Reb-M and Reb-A fall under the same safety umbrella — the difference between them is taste, not safety. For the full evidence picture, see the safety evidence.
Why do some stevia products still taste bitter?
Usually because they rely on cheaper, more abundant glycosides like stevioside or lower-grade Reb-A, which activate bitter receptors more strongly. Products formulated around Reb-M and Reb-D taste much cleaner because those molecules trigger little bitterness.
Do steviol glycosides affect blood sugar?
No. They are not metabolized for energy and contribute no calories or carbohydrates, so they do not raise blood glucose. If you manage diabetes, confirm any dietary change with your healthcare professional.
So which steviol glycoside should you look for?
Steviol glycosides are one molecule family with many members, and the member you choose decides whether stevia tastes harsh or clean. Reb-A is abundant and serviceable; Reb-M and Reb-D are rare and superior on the palate, which is where premium stevia is headed. If you want the basics first, go back to the stevia basics, or see how it all fits together in our complete guide to healthy drinks.
