Stevia is a non-nutritive or zero-calorie sweetener made of steviol glycosides. These are compounds extracted and refined from the leaves of the Stevia rebaudiana plant.

Many people choose to replace sugar with stevia to reduce their calorie consumption. In this article, we look at the possible risks and side effects associated with this natural sweetener.

Stevia leaves are about 200 times sweeter than traditional white sugar and people have used them for centuries as a sweetener and herbal supplement.

However, the United States Food and Drug Administration (FDA) only consider high-purity steviol glycosides to be safe for human consumption currently.

Because the FDA have not approved crude stevia extracts and stevia leaves as a food additive, companies are not allowed to market them as sweetening products.

According to the FDA, the acceptable daily intake for steviol equivalents is 4 milligrams (mg) per kilogram of body weight. That equates to about 12 mg of high-purity stevia extracts per kilogram of body weight per day.

When used as a sweetener or to flavor foods, experts do not consider highly purified stevia to cause adverse side effects.

While several studies have identified potential side effects of stevia over the last few decades, most were done using laboratory animals, and many have since been disproved.

Potential side effects linked to stevia consumption include:

Kidney damage

Stevia is considered a diuretic, meaning that it increases the speed at which the body expels water and electrolytes from the body in urine. Because the kidney is responsible for filtering and creating urine, researchers initially thought that long-term consumption of stevia could damage the organ.

More recent studies, however, have concluded that stevia may help prevent kidney damage. A 2013 study carried out in a laboratory found that stevia reduced cyst growth in kidney cells.

Gastrointestinal symptoms

Some stevia products contain added sugar alcohols that may cause unpleasant symptoms in individuals that are very sensitive to the chemicals.

Although hypersensitivity to sugar alcohol is rare, its symptoms can include:

Several studies using rodent and human cell cultures have demonstrated the potential gastrointestinal benefits of steviol glycosides. Stevia use has been shown to help limit and reduce diarrhea and the symptoms of irritable bowel syndrome (IBS).

Allergic reaction

According to a 2015 review, there are very few reported cases of stevia allergy. Both the FDA and European Commission concluded that the number of individuals who are hypersensitive to stevia or at a risk of having an allergic response to it is low.

Hypoglycemia or low blood sugar

Although stevia may help control blood sugar in people with diabetes, it was also once thought that long-term or heavy stevia consumption might cause hypoglycemia or low blood sugar.

This has since been proven highly unlikely, except in individuals with abnormally low blood sugar levels.

Low blood pressure

Stevia is known to act as a vasodilator, causing the blood vessels to widen and lowering overall blood pressure. Currently, researchers have only explored the potentially positive aspects of this use.

Anything that actively lowers blood pressure can cause health complications with excessive, long-term use. People with chronic low blood pressure should speak to a doctor about prolonged stevia use.

Endocrine disruption

As a type of steroid, steviol glycosides can interfere with hormones controlled by the endocrine system. A 2016 study found that human sperm cells exposed to steviol experienced an increase in progesterone production.

Some people are at an increased risk of developing side effects from regular stevia use. This is because stevia can lower blood sugars and blood pressure, and act as a diuretic.

Stevia can also interact with certain medications, so it is important to discuss stevia with a doctor before consuming or purchasing the product.

Factors that may increase the risk of stevia side effects include:

  • blood pressure conditions and medications
  • liver conditions and medications
  • kidney conditions and medications
  • heart conditions and medications
  • hormone regulating medications
  • steroids
  • cancer medications

There are many different types of steviol glycoside found in stevia, classified into five major groups.

Although most of the existing research concerns the two major compounds in stevia — stevioside and rebaudioside A (reb A) — a 2016 study using human fecal samples concluded that all forms of the compound are probably safe for general use.

However, research supporting the safe use of less refined stevia compounds is still lacking. As a result, the FDA do not recognize stevia leaves and crude extracts as safe for consumption.

Increasingly, stevia supplements and extracts are being found to contain counterfeit ingredients, primarily artificial sweeteners that are linked to known health risks.

It is therefore important to buy products certified to contain at least 95 percent steviol glycoside, and that contain no artificial or synthetic sweeteners.

Common potentially harmful chemicals found in stevia products include:

  • maltodextrin
  • sodium saccharin
  • sodium cyclamate
  • aspartame

When consumed at low doses, purified stevia is generally not considered to pose health risks for pregnant people.

Studies using rat embryos have established that stevia did not affect pregnancy or fertility outcomes and was non-toxic to fetal tissues.

However, some of the common counterfeit ingredients found in stevia mixtures and formulas are linked to serious complications and may cause birth abnormalities. The most notable of these ingredients is saccharin.

High doses or heavy, long-term use of stevia may worsen common pregnancy symptoms by increasing the workload on organs such as the kidneys, bladder, and heart.

Potential complications with the overuse of stevia products during pregnancy include:

Researchers still do not understand the full range of risks associated with stevia. A 2017 review exploring health-outcomes and complications linked to zero-calorie sweeteners concluded that not enough studies had been done to make a judgment about stevia’s overall safety.

However, given the popularity of stevia, there are several large-scale, comprehensive studies working on the matter.

In a preliminary 2017 study, rats with diets comprised of up to 3.5 percent stevia for 90 days presented no clinical symptoms and experienced no change in blood chemistry, cellular function, compensation, or appearance.