Steviol Glycosides: A Deep Dive into Nature's High Intensity Sweetener

Matthew Caruana
Jul 2
11 min read

How a South American plant became one of the world's most widely used zero calorie sweeteners

By Matthew Caruana | Keto Chocolate Maker & Low Carb Sweetener Specialist

Over the last two decades stevia has become more and more popular as a healthier sugar substitute. Now it isn’t an obscure ingredient only found in health food shops - it’s found in food and drinks across many of the aisles in your average supermarket: Fizzy drinks, sports supplements, yoghurts, breakfast cereals, condiments, confectionery, sweeteners, and even Liqueurs.

But what exactly are steviol glycosides, where do they come from, and how do they work as a sweetener? This post explores the chemistry, cultivation, processing, and practical applications of one of the most intensely sweet naturally derived ingredients on Earth.

The Plant Behind the Sweetness

Steviol glycosides are the sweet tasting compounds extracted from Stevia rebaudiana Bertoni, a small perennial shrub native to the border regions of Paraguay and Brazil. The plant belongs to the Asteraceae family, along with Asters themselves, sunflowers and chrysanthemums (all of which are largely edible), and has been cultivated and used by the Guaraní people of the region for centuries, primarily to sweeten herbal teas and traditional medicines.

The stevia plant grows to roughly 60-80cm in height and thrives in semi humid subtropical climates, but you can actually buy them in most decent sized UK garden centres. It was formally documented by Swiss botanist Moisés Santiago Bertoni in 1899, who described it as having an extraordinarily sweet taste. Today, commercial cultivation has spread well beyond South America, with large scale growing operations established in China (the world's largest producer), India, Kenya, Paraguay, and the EU.

The leaves of the plant contain the sweet compounds, and the concentration of these glycosides varies with cultivar, growing conditions, and harvest timing. Leaves are typically harvested just before the plant flowers, when glycoside concentration is at its peak.

What Are Steviol Glycosides?

The term "steviol glycoside" refers to a family of over forty related molecules, not a single compound. They share a common structural backbone: the unique diterpene called Steviol, with glucose units attached in different configurations. It is this combination of a terpenoid core with several sugar chains that gives these molecules their distinctive high intensity sweet character.

The major steviol glycosides found in stevia leaves include:

Stevioside - the most common sweetener found within the leaf, typically making up 5-10% of dry leaf weight. It is 250 to 300 times sweeter than table sugar and has a bitter aftertaste.
Rebaudioside A (Reb A) - the second most abundant compound, and the one most widely used. It has a less bitter taste than stevioside, but certainly not no bitterness. The sweetness is more sugar like and is 200 to 400 times sweeter than sugar.
Rebaudioside C - present in smaller quantities. It is far less desirable due to a more intense bitterness.
Rebaudioside D - a minor glycoside with a taste profile considered by many to be superior to Reb A, with less of the characteristic stevia aftertaste.
Rebaudioside M (Reb M) - present in very small amounts in the leaf, often less than 1%, but commercially significant because it has the taste closest to sucrose and only a very low bitterness.
Dulcoside A - a minor component that contributes a pronounced bitterness with a sweetness only 30 to 50 times sweeter than normal sugar.

The variability in taste quality between these glycosides is a result of differences in the number and arrangement of glucose units attached to the steviol backbone. More glucose units generally mean a cleaner, less bitter, more sugar like taste - which is why Reb D and Reb M (which carry more glucose chains) are considered the best in terms of flavour. The reason they are not more widely seen in commercial products is entirely cost related.

Why Do They Taste So Sweet?

Steviol glycosides produce a sweet sensation due to their interaction with sweet taste receptors on the tongue.

Steviol glycosides bind to these receptors and trigger the same signals as sucrose, and produce the perception of sweetness in the brain. The steviol glycosides activate the receptors far more efficiently than normal sugar. This is because of the physical structure of the Steviol glycosides with their several attached glucose components that are able to activate several receptors at the same time, so only very small concentrations are needed to produce a strong sweet signal.

But the taste experience of steviol glycosides is not identical to sucrose. Sucrose produces a quick, clean onset of sweetness that fades relatively quickly – we call this sucrose’s sweetness curve.

Steviol glycosides, by contrast, tend to have:

A slower onset of sweetness
A longer lasting sweet sensation ("sweetness tail")
In many forms, a bitter or liquorice aftertaste, particularly at higher concentrations

These taste and flavour characteristics are the primary technical challenge that food manufacturers face when creating recipes with stevia. The aftertaste, which is most pronounced with stevioside, and least pronounced with Reb M, is a significant driver of recipe development decisions.

The Production Process

Commercial production of steviol glycosides involves several stages of processing to yield a purified, finished ingredient.

Modern commercial stevia growing operations have developed high glycoside varieties through conventional selective breeding, significantly increasing the yield of desirable glycosides per plant.

Leaves are harvested and then dried. The dried leaves are steeped in hot water in a process similar to making a cup of tea. The water soluble glycosides leach out of the dried leaf into the liquid. This leaves the insoluble leaf components behind, which are easily strained off and removed.

The liquid extract undergoes multiple purification steps, primarily several different types of ultrafiltration, to remove all the undesirable components and arrive at a liquid rich in steviol glycosides.

Fractional distillation can separate individual glycosides from each other.

The purified extract is typically spray dried or crystallised to yield a powder.

Commercial steviol glycoside ingredients are typically standardised to a defined minimum total glycoside content, which is why you will often find 100% stevia powder advertised as “95% steviol glycosides” – the other 5% is still dried stevia components, but they might be things like acids or proteins.

Modern bioconversion and fermentation

A more sophisticated approach is now widely used to produce specific glycosides at scale. Through enzymatic bioconversion and microbial fermentation, manufacturers can add extra glucose units to the steviol backbone, effectively converting common glycosides like Reb A into rarer, superior tasting ones like Reb M. This process allows for mass production of glycosides that occur only in tiny trace quantities in the natural leaf, making them commercially viable for the first time.

The ability to produce large volumes of Reb D and Reb M via fermentation is one of the reasons why the quality of UK keto chocolate has improved so dramatically in recent years.

Practical Use in Food and Beverages

Given their extreme sweetness intensity, steviol glycosides are used in very small quantities. Typically at concentrations measured in milligrams per 100g or per 100ml of the final product.

This creates a particular bulk and mouthfeel challenge. Sugar contributes not just sweetness but also texture, viscosity, and the physical sensation associated with a full bodied product. When sugar is replaced with steviol glycosides, recipe developers often compensate by using bulking sweeteners like erythritol, inulin, maltodextrin, or polydextrose, which may add negative health effects.

I have struggled with the bulk and mouthfeel issue myself when converting my erythritol sweetened couverture chocolate recipes to recipes sweetened with high intensity sweeteners including Steviol glycosides. At the time of writing this I have not managed to solve the textural issues this has caused.

Taste Modulation

The bitter aftertaste of many steviol glycosides is the most significant hurdle. Approaches to managing this include:

Selecting higher quality glycosides - Reb A, Reb D, and Reb M have progressively cleaner taste profiles.
Blending with other sweeteners such as erythritol, or other high intensity sweeteners to take advantage of synergistic effects.
Using masking agents or flavour modulators - certain flavour compounds, like salt and vanilla, can partially suppress bitterness perception.
Adjusting pH - the taste profile of steviol glycosides can vary with the pH of the product.

I have tried these techniques myself, eventually settling on Reb M. Earlier experiments included using salt to mask the bitterness, and a selection of acids to mask the “sweetness tail” but these combined techniques produced a bizarre flavour profile incompatible with sweet treats, and especially at odds with fine chocolate.

The most beneficial technique has been not to use stevia as the main sweetener, but instead to use it in a minor, supporting role, blended with a selection of other sweeteners.

Why steviol glycosides are perfect for keto

The ketogenic diet works by severely restricting carbohydrate intake, typically below 20–30g of net carbs per day, to maintain a metabolic state called ketosis, in which the body metabolises fat for fuel rather than glucose. Any sweetener that raises blood sugar or triggers an insulin response can disrupt this, which is why sweetener choice matters so much.

Steviol glycosides are massively useful for two key reasons:

They are not absorbed in the upper digestive tract

Unlike sugar and most starchy carbohydrates, steviol glycosides are not broken down or absorbed in the small intestine. They pass through to the large intestine largely intact, where gut bacteria convert them into steviol, which is then excreted in the urine. The body sees no change in blood glucose.

They have no effect on blood sugar or insulin

Multiple controlled studies confirm that steviol glycosides do not raise blood glucose or stimulate insulin secretion. Medical organisations working in the ketogenic diet space, including those supporting the use of therapeutic ketogenic diets in the UK, consistently list steviol glycosides in the "go ahead" category - sweeteners that can be used freely without concern about disrupting ketosis.

Steviol glycosides are fully keto compatible. They don’t contribute any net carbs or calories, and have no meaningful effect on blood sugar or ketosis. They are widely recommended by UK ketogenic diet specialists and dietitians.

The same is not true of many commercial stevia products, particularly granulated “table top sweetener” versions, that use bulking agents such as maltodextrin or dextrose to give the product a more sugar like texture and volume. These bulking agents do contain carbs and calories. Always check the full ingredients list, not just the front of pack claim.

How Healthy Is Stevia?

Stevia and steviol glycosides are widely considered a safe, zero calorie, plant based sugar substitute. Approved by food safety authorities like the Food Standards Agency, the European Food Standards Agency and the Food & Drug Administration in the US.

Key Health Benefits

Blood Sugar Control: Stevia does not raise blood glucose levels, making it suitable for people managing diabetes.
Weight Management: It allows you to reduce overall calorie consumption.

Potential Downsides & Side Effects

Sweet Cravings: Highly refined sweeteners may contribute to a psychological desire for sweet tasting foods.
Allergies: People with severe allergies to plants in the daisy (Asteraceae) family may occasionally experience adverse reactions.

According to the EU Commission Regulation, the acceptable daily intake for steviol equivalents is 4 milligrams per kilogram of body weight. Assuming a body weight of 70-90kg that would mean 0.28-0.36g of Steviol glycosides. In terms of my current chocolate recipes that would be somewhere between 3kg and 4kg of chocolate in a day.

We’ve known for quite a while now that stevia is an improvement on normal sugar and artificial sweeteners, but recent research has found some impressive health benefits: Laboratory and animal tests show that stevia can help fight viruses, support the immune system, and reduce inflammation.

Stevia helps improve how our bodies respond to insulin and acts as an antioxidant in our fat tissues and blood vessels. It’s also heart healthy, significantly lowering both systolic and diastolic blood pressure, while helping to stabilize and slow down the buildup of plaque in the arteries.

Cancer research lab studies have shown that derivatives of stevia can actually stop cancer cells from multiplying. They trigger a natural cell destruction process through the cell's mitochondria, which has shown promise against breast, prostate, stomach, and colon cancers.

That being said, it is not entirely without question marks. Over the last few decades, research has also looked into potential side effects: We know that how we process stevia depends heavily on our gut bacteria, which break down the glycosides into steviol which our bodies then absorb (and then excrete in our urine). Because of this relationship, scientists agree we still need to do more research to fully understand how stevia affects our overall gut microbiome.

As yet no definitive answer has been found to the question of how gut friendly stevia sweeteners are, but research is ongoing.

How Green Is Stevia?

Compared to sugar beet or sugar cane production, stevia cultivation requires considerably less land per unit of sweetness delivered, given the extreme sweetness potency of the glycosides. Estimates suggest that producing the equivalent sweetness from stevia requires a fraction of the agricultural land of traditional sugar crops.

Water use, fertiliser requirements, and the energy footprint of the extraction and purification process are all relevant to the overall environmental picture. Considering all the factors Steviol glycosides are significantly more environmentally friendly than normal sugar.

The Bitterness Problem

The biggest challenge with using steviol glycosides as the main sweetener in a recipe is the bitterness.

In higher concentrations the sweetness actually tops out and, as the Steviol levels increase, the bitterness increases exponentially while the sweetness remains the same.

This is due to the same structural idiosyncrasy that makes stevia derivatives so sweet. Steviol glycosides have a much higher affinity for your sweet receptors than your bitter ones. At low concentrations, they easily find and bind to the sweet receptors, so you mostly taste sweetness. At high concentrations, because the sweetness receptors are saturated by the many glucose components of the glycosides, the extra stevia added to the recipe can then activate the bitterness receptors in far higher quantities.

The Genetic Variance Issue

Some people find stevia completely unpalatable. This is because we have around 25 different bitter taste receptor genes. Human genetics is so varied and the way these 25 different genes could interact means that there are 25165824 different ways these genes can group together to form a combination that affects stevia perception. The consumer level effects of this variation mean that we all essentially experience taste and flavour in individual ways, so we all live in entirely different "sensory worlds." In terms of stevia experience, this includes not tasting any bitterness from stevia at all and tasting stevia as primarily bitter or even only bitter with no sweetness. Because of the molecular structural peculiarity that gives stevia its intense sweetness, the “bitterness super tasters” experience an equally intense bitterness, but also, because of the intensity of taste experience that stevia allows, it also means a wider range of consumer experiences compared to something like sucrose.

A "palate" is actually a mix of nature (your receptors) and nurture (your brain). So the brain can actually be reprogrammed to “improve” or “train” your palate, but there is a limit, as the receptors cannot be changed. So, unfortunately someone who experiences stevia as highly bitter is unlikely to be able to change that.

Around 10-15% of people are highly sensitive to stevia bitterness and will perceive it as predominantly bitter, metallic, or liquorice like, even in small doses.

So, if someone says stevia tastes disgusting it isn't an overreaction, it’s hardwired into their DNA.

Why Chocolate Is a Good Match for Steviol Glycosides

Cocoa already contains its own natural bitterness from theobromine and polyphenols, so we actually expect to experience some bitterness from chcoclate, especially dark chocolate. This actually works in the sugar free chocolate maker's favour: In a keto dark chocolate the slight bitterness of even the best steviol glycosides, like Reb M, is partially masked by the cocoa, and not out of place, while the sweetness comes through cleanly. So, a low carb dark chocolate made with Reb M can taste more convincingly like the real thing, while the same glycosides in a keto milk chocolate or white chocolate might still show some unexpected bitter aftertaste.

Summary

Steviol glycosides are a structurally diverse family of compounds extracted from Stevia rebaudiana, with a sweetness hundreds of times more intense than normal sugar. Different glycosides within the family vary significantly in taste quality, with Reb M and Reb D considered closest to sucrose. Commercial production involves extraction and purification from stevia leaf, with fermentation based routes increasingly used for rare, high quality glycosides. The ingredient is approved as a food additive in major markets worldwide and is applied across virtually every food and beverage category, with ongoing innovation focused on taste quality.

This article is intended as an overview of steviol glycosides for general interest, not to be taken as medical advice.

Steviol glycosides are approved as a food additive in the EU, UK, US (GRAS), Japan, and many other markets. As with any supplement or food additive, purchasing from reputable suppliers with transparent quality standards is advisable.

This article is for informational purposes only and does not constitute dietary or medical advice. Always consult an appropriate professional if you have specific health requirements or medical conditions.

By Matthew Caruana | Keto Chocolate Maker & Low Carb Sweetener Specialist

But what exactly are steviol glycosides, where do they come from, and how do they work as a sweetener? This post explores the chemistry, cultivation, processing, and practical applications of one of the most intensely sweet naturally derived ingredients on Earth.

The Plant Behind the Sweetness

The leaves of the plant contain the sweet compounds, and the concentration of these glycosides varies with cultivar, growing conditions, and harvest timing. Leaves are typically harvested just before the plant flowers, when glycoside concentration is at its peak.

What Are Steviol Glycosides?

The major steviol glycosides found in stevia leaves include:

Stevioside - the most common sweetener found within the leaf, typically making up 5-10% of dry leaf weight. It is 250 to 300 times sweeter than table sugar and has a bitter aftertaste.

Rebaudioside A (Reb A) - the second most abundant compound, and the one most widely used. It has a less bitter taste than stevioside, but certainly not no bitterness. The sweetness is more sugar like and is 200 to 400 times sweeter than sugar.

Rebaudioside C - present in smaller quantities. It is far less desirable due to a more intense bitterness.

Rebaudioside D - a minor glycoside with a taste profile considered by many to be superior to Reb A, with less of the characteristic stevia aftertaste.

Rebaudioside M (Reb M) - present in very small amounts in the leaf, often less than 1%, but commercially significant because it has the taste closest to sucrose and only a very low bitterness.

Dulcoside A - a minor component that contributes a pronounced bitterness with a sweetness only 30 to 50 times sweeter than normal sugar.

Why Do They Taste So Sweet?

Steviol glycosides produce a sweet sensation due to their interaction with sweet taste receptors on the tongue.

But the taste experience of steviol glycosides is not identical to sucrose. Sucrose produces a quick, clean onset of sweetness that fades relatively quickly – we call this sucrose’s sweetness curve.

Steviol glycosides, by contrast, tend to have:

A slower onset of sweetness

A longer lasting sweet sensation ("sweetness tail")

In many forms, a bitter or liquorice aftertaste, particularly at higher concentrations

These taste and flavour characteristics are the primary technical challenge that food manufacturers face when creating recipes with stevia. The aftertaste, which is most pronounced with stevioside, and least pronounced with Reb M, is a significant driver of recipe development decisions.

The Production Process

Commercial production of steviol glycosides involves several stages of processing to yield a purified, finished ingredient.

Modern commercial stevia growing operations have developed high glycoside varieties through conventional selective breeding, significantly increasing the yield of desirable glycosides per plant.

Leaves are harvested and then dried. The dried leaves are steeped in hot water in a process similar to making a cup of tea. The water soluble glycosides leach out of the dried leaf into the liquid. This leaves the insoluble leaf components behind, which are easily strained off and removed.

The liquid extract undergoes multiple purification steps, primarily several different types of ultrafiltration, to remove all the undesirable components and arrive at a liquid rich in steviol glycosides.

Fractional distillation can separate individual glycosides from each other.

The purified extract is typically spray dried or crystallised to yield a powder.

Modern bioconversion and fermentation

The ability to produce large volumes of Reb D and Reb M via fermentation is one of the reasons why the quality of UK keto chocolate has improved so dramatically in recent years.

Practical Use in Food and Beverages

Given their extreme sweetness intensity, steviol glycosides are used in very small quantities. Typically at concentrations measured in milligrams per 100g or per 100ml of the final product.

Taste Modulation

The bitter aftertaste of many steviol glycosides is the most significant hurdle. Approaches to managing this include:

Selecting higher quality glycosides - Reb A, Reb D, and Reb M have progressively cleaner taste profiles.

Blending with other sweeteners such as erythritol, or other high intensity sweeteners to take advantage of synergistic effects.

Using masking agents or flavour modulators - certain flavour compounds, like salt and vanilla, can partially suppress bitterness perception.

Adjusting pH - the taste profile of steviol glycosides can vary with the pH of the product.

The most beneficial technique has been not to use stevia as the main sweetener, but instead to use it in a minor, supporting role, blended with a selection of other sweeteners.

Why steviol glycosides are perfect for keto

Steviol glycosides are massively useful for two key reasons:

They are not absorbed in the upper digestive tract

They have no effect on blood sugar or insulin

Steviol glycosides are fully keto compatible. They don’t contribute any net carbs or calories, and have no meaningful effect on blood sugar or ketosis. They are widely recommended by UK ketogenic diet specialists and dietitians.

How Healthy Is Stevia?

Stevia and steviol glycosides are widely considered a safe, zero calorie, plant based sugar substitute. Approved by food safety authorities like the Food Standards Agency, the European Food Standards Agency and the Food & Drug Administration in the US.

Key Health Benefits

Blood Sugar Control: Stevia does not raise blood glucose levels, making it suitable for people managing diabetes.

Weight Management: It allows you to reduce overall calorie consumption.

Potential Downsides & Side Effects

Sweet Cravings: Highly refined sweeteners may contribute to a psychological desire for sweet tasting foods.

Allergies: People with severe allergies to plants in the daisy (Asteraceae) family may occasionally experience adverse reactions.

We’ve known for quite a while now that stevia is an improvement on normal sugar and artificial sweeteners, but recent research has found some impressive health benefits: Laboratory and animal tests show that stevia can help fight viruses, support the immune system, and reduce inflammation.

Stevia helps improve how our bodies respond to insulin and acts as an antioxidant in our fat tissues and blood vessels. It’s also heart healthy, significantly lowering both systolic and diastolic blood pressure, while helping to stabilize and slow down the buildup of plaque in the arteries.

Cancer research lab studies have shown that derivatives of stevia can actually stop cancer cells from multiplying. They trigger a natural cell destruction process through the cell's mitochondria, which has shown promise against breast, prostate, stomach, and colon cancers.

As yet no definitive answer has been found to the question of how gut friendly stevia sweeteners are, but research is ongoing.

How Green Is Stevia?

Water use, fertiliser requirements, and the energy footprint of the extraction and purification process are all relevant to the overall environmental picture. Considering all the factors Steviol glycosides are significantly more environmentally friendly than normal sugar.

The Bitterness Problem

The biggest challenge with using steviol glycosides as the main sweetener in a recipe is the bitterness.

In higher concentrations the sweetness actually tops out and, as the Steviol levels increase, the bitterness increases exponentially while the sweetness remains the same.

The Genetic Variance Issue

Around 10-15% of people are highly sensitive to stevia bitterness and will perceive it as predominantly bitter, metallic, or liquorice like, even in small doses.

So, if someone says stevia tastes disgusting it isn't an overreaction, it’s hardwired into their DNA.

Why Chocolate Is a Good Match for Steviol Glycosides

Summary

This article is intended as an overview of steviol glycosides for general interest, not to be taken as medical advice.

Steviol glycosides are approved as a food additive in the EU, UK, US (GRAS), Japan, and many other markets. As with any supplement or food additive, purchasing from reputable suppliers with transparent quality standards is advisable.

This article is for informational purposes only and does not constitute dietary or medical advice. Always consult an appropriate professional if you have specific health requirements or medical conditions.

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