Stevia

Stevia takes its common names, sweet leaf and sweet herb, from the intense sweetness of its leaves. The Guaraní people of South America called the plant Ka-a He-e, meaning sweet grass (Peteliuk et al., 2021). It was first recorded scientifically in Paraguay in 1899 and was classified in 1905 as Stevia rebaudiana, a member of the Asteraceae (sunflower) family. Japan was the first country to adopt stevia extract commercially, in the 1970s (Ashwell, 2015).

Stevia is a modern addition to Indian herbal practice and is not described in the classical Ayurvedic texts. For this reason, it has no classical classification by taste (rasa), potency (virya), post-digestive effect (vipaka), dosha action or gana and varga group. Its use in India rests mainly on its role as a sugar substitute, and its leaves are intensely sweet in taste.

Stevia is known by the following botanical, English, traditional and Indian names.

• Botanical name: Stevia rebaudiana Bertoni
• Hindi: Meethi Tulsi (sweet basil), Meethi Patti, Madhu Parni
• Tamil: Seeni Tulsi
• Telugu: Madhu Patri
• Marathi: Madhu Parani
• Punjabi: Madhu-Pattha
• Sanskrit: Madhu Patra
• Malayalam: Pancharakolli

Stevia leaves contain the following main compounds.

• Stevioside and rebaudioside A: The most abundant steviol glycosides in the leaf and the main source of its sweet taste (Peteliuk et al., 2021).
• Other steviol glycosides: Rebaudiosides B to F, dulcoside A, rubusoside, steviolmonoside and steviolbioside, which occur in smaller amounts (Gandhi et al., 2018; Peteliuk et al., 2021).
• Steviol: The common backbone of all steviol glycosides. Gut bacteria in the colon release steviol from the glycosides. It is then absorbed, processed in the liver and excreted mainly in the urine as steviol glucuronide (Ashwell, 2015).
• Phenolic compounds and flavonoids: Plant compounds that show antioxidant activity in laboratory tests (Peteliuk et al., 2021).
• Austroinulin and 6-O-acetyl-austroinulin: Diterpenoids that have shown anti-inflammatory activity in cell studies (Peteliuk et al., 2021).

Laboratory, animal and limited human studies have reported the following actions.

• Antioxidant: phenolic compounds in the leaf may help neutralise free radicals, which are unstable molecules that can damage cells, in laboratory tests.
• Anti-inflammatory: leaf extracts and stevioside are associated with reduced inflammatory signalling in cell studies.
• Antimicrobial: leaf extracts have inhibited some disease-causing bacteria, including bacteria linked to dental caries, in laboratory tests.
• Antihyperglycaemic: stevioside has been associated with a lower rise in blood glucose after a meal in one small human study, although results across different studies are not consistent.
• Immunomodulatory: stevioside is associated with changes in immune activity in animal and cell studies.

Most of this evidence comes from laboratory and animal work. Human trials are few in number, small and have produced inconsistent results. None of these actions has been shown to prevent or treat a disease (Peteliuk et al., 2021).

Stevia has the following potential benefits. Most relate to its use as a sugar substitute, and the strength of evidence is stated for each.

Calorie-Free Sweetness in Place of Sugar

Stevia provides sweetness without meaningful calories, because the body does not use steviol glycosides for energy. Replacing sugar with stevia therefore lowers the energy content of a drink or recipe (Ashwell, 2015). However, the World Health Organization (WHO, 2023) advises against using non-sugar sweeteners for long-term weight control.

Minimal Effect on Blood Glucose

Steviol glycosides are not expected to raise blood glucose in the same way as sugar. One small study found that stevioside lowered the glucose rise after a meal in adults with type 2 diabetes (Gregersen et al., 2004). A 16-week rebaudioside trial found no change in glucose control (Maki et al., 2008).

Lower Risk to Teeth Than Sugar

Mouth bacteria ferment sugar into acids that can damage tooth enamel. In a small randomised trial, stevia extracts did not lower plaque pH as sucrose did and were considered non-acidogenic. A review found stevioside and rebaudioside A were non-cariogenic in the studies reviewed (Ferrazzano et al., 2016).

Antioxidant Activity in Laboratory Studies

Stevia leaves contain phenolic compounds that neutralised free radicals in laboratory tests. Free radicals are unstable molecules that can damage cells through a process called oxidative stress. Studies in people are lacking, so a health benefit from this activity has not been established (Peteliuk et al., 2021).

Potential Effects on Blood Pressure

Certain steviol glycosides have been investigated for their possible effects on blood pressure. Some studies have suggested that particular compounds may influence blood vessel function, but clinical findings are inconsistent, and the overall evidence remains limited. Stevia should not be relied upon to lower blood pressure or used as a substitute for prescribed treatment (Onakpoya et al., 2014).

Important Note: Stevia is a sweetener and not a treatment for diabetes, high blood pressure, obesity or any other condition. People with a medical condition should follow their doctor's advice.

Stevia is used mainly to sweeten food and drinks. The usual settings are described below.

Sweetening Tea, Coffee and Other Drinks

Stevia tablets, powder and liquid drops are sold as tabletop sweeteners and are added to hot and cold drinks in place of sugar.

Reducing Sugar in Packaged Foods and Beverages

Manufacturers use purified steviol glycosides to reduce the sugar in products such as dairy-based drinks, dairy desserts and edible ices. In India, steviol glycosides (INS 960) are permitted only in the food categories listed by the Food Safety and Standards Authority of India (FSSAI), and they are not permitted in cocoa and chocolate products (FSSAI, 2023).

Cooking and Baking at Home

Stevia is far sweeter than sugar, so much smaller amounts are needed. Recipes therefore require adjustment, and the equivalent amount should be checked on the product label.

Traditional Leaf Use in South America

In South American tradition, dried leaves were used to sweeten bitter drinks such as mate (Peteliuk et al., 2021). This reflects traditional use as a sweetener and does not indicate a proven medicinal effect.

The following groups should take particular care when using stevia, especially in capsule or concentrated extract form.

• Pregnancy and breastfeeding: Regulatory reviews of purified steviol glycosides used within the acceptable daily intake found no harm to reproduction or to the developing child (EFSA, 2010). Data on concentrated stevia extracts and crude leaf products are limited, and some older studies in rats using crude extract reported reduced fertility (Peteliuk et al., 2021). Consult a doctor before using these products.
• Diabetes: People with diabetes should continue regular blood glucose monitoring when using stevia. Stevia must not replace prescribed treatment, and any change to a medicine dose should be decided by the treating doctor.
• Low blood pressure or blood pressure medicines: Stevioside capsules lowered blood pressure in adults with hypertension in clinical trials (Chan et al., 2000; Hsieh et al., 2003). People with low blood pressure, or who take blood pressure medicines, should consult a doctor before using stevia capsules or extracts.
• Heart or kidney disease: Steviol, the breakdown product of steviol glycosides, is processed in the liver and excreted in the urine (Ashwell, 2015). People with heart or kidney disease should consult a doctor before using stevia capsules or extracts.
• Allergy to Asteraceae plants: People allergic to ragweed, daisies or other plants of the Asteraceae family should avoid stevia leaf products and consult a doctor before using any other stevia product.
• Children: Safety data on stevia capsules and concentrated extracts in children are limited. These products should be given to children only on medical advice.
• Product quality: Products should state their steviol glycoside content and come from licensed manufacturers. In one laboratory study, three of six commercial stevia products were counterfeit and contained undeclared sodium cyclamate and sodium saccharin, as summarised in a review (Peteliuk et al., 2021).

The method of use depends on the form of stevia. The instructions printed on the product label should always be followed, because strengths differ between brands.

Adding Stevia Tablets to Drinks

1. Read the label to find how many tablets match the sweetness of one teaspoon of sugar and how many milligrams of steviol glycosides each tablet contains.
2. Drop one tablet into a drink and stir until it dissolves fully.
3. Taste the drink before adding a second tablet, because stevia is much sweeter than sugar.
4. Count all tablets used in a day and stay within the limit stated on the label.

Sweetening Food With Stevia Powder

1. Use only the measuring scoop or spoon supplied with the product, because the strength of powders varies.
2. Add a very small amount to the drink or food, mix thoroughly and taste.
3. Add more in small amounts only if needed.
4. When replacing sugar in a recipe, calculate the amount from the conversion chart on the label.

Measuring Stevia Liquid Drops

1. Check the label for the number of drops that equals the sweetness of one teaspoon of sugar.
2. Add the drops one at a time to the drink or food and mix well.
3. Taste before adding further drops.
4. Keep a count of the drops used in a day and stay within the limit stated on the label.

Taking Stevia Capsules

1. Use capsules only if a doctor has advised them, because no standard capsule dose has been established.
2. Check the label for the amount of steviol glycosides in each capsule.
3. Swallow the capsule whole with a glass of water, following the instructions provided by the doctor or product label.
4. Stop use and seek medical advice if dizziness, fainting, rash or swelling occurs.

The amount of stevia considered acceptable depends on body weight. The acceptable daily intake (ADI) for steviol glycosides is 4 mg per kg of body weight per day, expressed as steviol equivalents. It applies to adults and children (Ashwell, 2015; EFSA, 2010).

• Children (under 12 years): The ADI is up to 4 mg per kg per day. For a child weighing 20 kg, this is 80 mg of steviol equivalents. Stevia should be used only through food and drink products intended for general use. Capsules and concentrated extracts should be given only on a doctor's advice.
• Teenagers (12 to 17 years): The ADI is up to 4 mg per kg per day. For a teenager weighing 50 kg, this is 200 mg of steviol equivalents. Capsules and concentrated extracts should be used only on a doctor's advice.
• Adults (18 to 64 years): The ADI is up to 4 mg per kg per day. For an adult weighing 70 kg, this is 280 mg of steviol equivalents, or about 840 mg of high-purity steviol glycosides. Typical tabletop use is well below this limit (Ashwell, 2015).
• Elderly (65 years and above): The same weight-based limit applies. Older adults more often have diabetes, low blood pressure or kidney conditions and take regular medicines, so a doctor should be consulted before stevia capsules or extracts are used.
• Capsules and supplements (all ages): No standard dose has been established. Clinical trials gave stevioside at 750 mg per day (Chan et al., 2000) and 1,500 mg per day (Hsieh et al., 2003) under medical supervision. These are not doses for self-use, and the higher dose is above the acceptable daily intake for a 70 kg adult.

Important Note: These figures are general safety limits for sweetener use and not prescribed treatment doses. A doctor or pharmacist should be consulted before use by anyone with a medical condition or taking regular medicines.

Stevia is generally well tolerated within the acceptable daily intake, but the following effects can occur.

Allergic Reactions

People allergic to ragweed, daisies or other Asteraceae plants may react to stevia. Crude leaf extracts may carry a higher allergy risk than highly purified steviol glycosides (Peteliuk et al., 2021). Symptoms include rash, itching and swelling of the face or lips.

Low Blood Pressure and Dizziness

Stevioside capsules lowered blood pressure in adults with hypertension in clinical trials (Chan et al., 2000). In people already taking blood pressure medicines, this may cause dizziness or faintness. A doctor should be consulted if lightheadedness occurs.

Digestive Discomfort

Some people report bloating, a feeling of fullness or nausea after using stevia products. These symptoms may be mild. The amount used should be reduced or stopped, and a doctor should be consulted if symptoms persist.

When to Seek Medical Help

Urgent medical care is needed for swelling of the face, lips or throat, difficulty breathing, fainting or chest pain. A doctor should be consulted for persistent vomiting, severe abdominal pain or any symptom that does not settle after stevia is stopped.

Stevia has not been formally studied for drug interactions. The following interactions are possible based on findings from clinical trials.

Blood Pressure Medicines

Stevioside capsules lowered blood pressure in adults with hypertension in clinical trials (Chan et al., 2000; Hsieh et al., 2003). Taken with blood pressure medicines, an added effect is possible and could cause blood pressure to fall too far. People who use both should monitor their blood pressure and inform their doctor.

Diabetes Medicines

One small study reported that stevioside lowered the rise in blood glucose after a meal (Gregersen et al., 2004). With insulin or oral diabetes medicines, an added effect is possible, with a risk of low blood glucose (hypoglycaemia). A 16-week rebaudioside A trial found no change in glucose control (Maki et al., 2008), so the evidence is mixed. People who use both should monitor blood glucose and inform their doctor.

Other Medicines and Herbal Products

Other interactions have not been well studied. A doctor or pharmacist should be told about all medicines, vitamins and herbal or Ayurvedic products used together with stevia capsules or extracts.

Important Note: No medicine should be started, stopped or changed because of stevia use without a doctor's advice.

Storage of Stevia

Stevia tablets, powder, capsules and liquid drops should be kept in their original, tightly closed container in a cool, dry place away from direct sunlight and moisture. Any additional storage instructions printed on the label should be followed. All products should be kept out of the reach of children and should not be used after the expiry date.

• Stevia is a plant-derived sweetener made from the leaves of Stevia rebaudiana. It is a modern addition to Indian practice and is not described in the classical Ayurvedic texts.
• Steviol glycosides provide sweetness with virtually no calories and are not expected to raise blood glucose in the same way as sugar.
• The World Health Organization advises against using non-sugar sweeteners for long-term weight control.
• Antioxidant, anti-inflammatory and other actions are based mainly on laboratory and animal studies, and human evidence is limited.
• Regulators accept purified steviol glycosides up to 4 mg per kg of body weight per day. Safety data on crude leaf products and capsules are limited.
• Allergy to Asteraceae plants, low blood pressure, and medicines for blood pressure or diabetes call for caution. Pregnant or breastfeeding women should consult a doctor before using capsules or extracts.
• Stevia is not a treatment for any disease, and persistent or severe symptoms need medical assessment.