What is Stevia?
Stevia was originally called Eupatorium rebaudiana bertoni in honor of Rebaudi, who was the first chemist to study the chemical characteristics of the plant’s extracts .
It was first used as a sweetener in herbal fusions by the Guarani people of South America, but Japan was the first country to market steviol glycosides in the food and drug industry.
Now, cultivation of the plant has expanded to other Asian regions like China, Malaysia, Singapore, South Korea, Taiwan, and Thailand. The plant is a long-lasting shrub that is over 100 to 300 times sweeter than table sugar and has no calories (2, 3).
Traditional Uses of Stevia
Indigenous people of South America, particularly in Paraguay and Brazil, have used stevia as a sweetener for hundreds of years. For example, the Gurani Indians of Paraguay have an age-old practice of using stevia to sweeten their Yerba Mate tea.
South American populations also have a long history of using stevia medicinally, as a tonic for heart problems, obesity, high blood pressure, and heartburn.
Stevia was first noticed by the outside world in the sixteenth century when Spaniards discovered the widespread use of stevia in South America.
In recent years, a growing need to find new, naturally sweet, calorie-free alternatives to sugar has led to greater interest in the “sweet herb” from nutritional researchers and commerce .
Health Benefits of Stevia
1) Stevia Helps Protect the Heart
Stevia Reduces High Blood Pressure (Hypertension)
Stevia has blood pressure lowering qualities.
A meta-analysis study found that steviol glycoside causes a considerable decrease in the diastolic blood pressure and fasting blood sugar (a determinative element of diabetes and prediabetes).
The blood pressure reduction due to steviol glycoside helps decrease the number of strokes one suffers and may be a preventive measure for managing hypertension and diabetes .
Systolic blood pressure is minimally affected by steviol glycoside compared to placebos. The results were most effective when observed over a long period of time.
A study conducted on women found that rebaudioside A caused no significant changes in systolic, diastolic blood pressure, or risks for heart problems. The blood pressure readings were monitored over a four-week period, during the morning, day, and night .
Stevia Inhibits Atherosclerotic Plaque Development
Atherosclerosis is also known as hardening of the arteries.
Stevioside is able to reduce the occurrence of hardening of the arteries through multiple mechanisms.
It has the ability to inhibit hardening of the arteries by reducing macrophages, oxidized low-density lipoprotein (ox-LDL), and fats. This reduces plaque.
Stevioside also proved to decrease the production of the inflammatory protein Nf-kB by increasing the production of Nfkbia .
2) Stevia Helps Lower Blood Sugar
Stevia contains bio-molecules that stimulate pancreatic cells to release insulin. This leads to the improvement of carbohydrate metabolizing enzymes, which lowers blood sugar levels.
Stevia also causes insulin secretion by increasing PPARy. This normalizes blood sugar levels and monitors insulin release from the pancreas.
Stevia also increases insulin sensitivity in animal models. For example, stevioside was found to increase insulin sensitivity in rats fed a high fructose diet .
Stevia glycosides also act like insulin in stimulating uptake of glucose into cells .
Steviosides cause an inhibition of glucagon release (in certain animal models), which lowers blood glucose. They also cause an increase in carnitine palmitoyltransferase 1 (CPT 1), which plays an important role in burning fatty acids in the mitochondria .
Steviol glycosides in stevia may help regulate blood sugar levels by increasing glucose transporter (GLUT).
3) Stevia Inhibits the Growth of Non-Human Rotavirus
Stevia has been proven to have an inhibitory effect against non-human rotavirus infection. This is due to stevia having a negatively charged ionic polysaccharide .
When using stevia in conjunction with Sophora flavescens, it enhances the inhibitory ability against rotavirus replication.
Studies have shown that the combination causes a decrease in the average concentration of Sophora flavescens needed to get a result of 50 percent replication inhibition.
However, the combination only fights against replication, not attachment. The combination of Sophora flavescens and stevia cures severe diarrhea and intestinal lesions, caused by rotavirus, better than sophora flavescens by itself .
4) Stevia Inhibits Tumor Growth and May Prevent Cancer
Stevia Inhibits the Formations of Skin Tumors Induced By Chemicals
Steviol, stevioside, and isosteviol were found to inhibit the formation of benign tumors (papillomas) caused by cancer-causing and tumor-causing elements such as DMBA (12-dimethylbenz[a]anthracene) and TPA (12-o-tetradecanoyl phorbol-13-acetate).
The three stevia extracts suppress the promotion stage of tumor production (tumorigenesis), caused by DMBA, by reducing the rapid accumulation of abnormal growth cells that can turn cancerous.
The three extracts also suppress the initiation stage of tumorigenesis induced by peroxynitrite, an oxidant, and nitrating element.
Steviol also has the ability to inhibit the activation of an Epstein-Barr virus early antigen, which is a herpesvirus partly responsible for the infection of mononucleosis (a.k.a. mono) .
Studies conducted on F344 mice concluded that stevia extracts such as rebaudioside A and C, stevioside, and dulcoside have inhibited inflammation caused by TPA (12-O-tetradecanoyl phorbol-13-acetate).
Rebaudioside A and C and dulcoside A have anti-inflammatory promoting abilities that are comparable to the function of hydrocortisone. Stevioside was more effective than an anti-inflammatory drug called indomethacin.
Rebaudioside C prevented 50 percent of swelling with doses 10 times less than indomethacin and 100 times less than quercetin (an anti-tumor promoting agent).
Concentrations of stevioside were also found to have similar activity to the components: triterpenoids, heliantriol C, pachymic acid, 3-O-acetyl-16a-hydroxytrametenolic acid, and poricoic acid.
These are the most effective naturally occurring elements from plants and fungi that have anti-tumor promoting effects. Tests performed on mice found that utilizing a stevioside mixture reduced the formation of tumors caused by TPA and DMBA (7,12-dimethylbenz[a]anthracene) by approximately 73 to 96 percent.
The effects depend on the concentration of stevioside used. The mixture also delayed the formation of tumors in the mice .
Stevia May Help Treat Breast Cancer
Studies show that stevia lowers the presence of benign tumors (adenomas) in the breasts of mice compared to mice not treated with stevioside concentrations. These changes are linked to the reduction in body weight due to caloric restriction .
Stevioside also has strong inhibitory effects on MCF-7 breast cancer cells. It generates reactive oxygen species within MCF-7 cells, which promote cell transmission and balance.
Free radicals are also generated by the treatment of stevioside, which accelerate cell death by damaging cellular components such as DNA, proteins, and fat membrane .
5) Stevia May Be Used to Treat Acute Lung Injuries
Treatments with stevioside may be utilized as therapy for acute lung injury.
Stevioside can lessen the lung damage caused by lipopolysaccharides by decreasing the wet-to-dry ratio in the lungs, pro-inflammatory cytokine production, and inflammatory cell migration into the lungs.
Acute lung injury is linked to inflated productions of iNOS (inducible nitric oxide synthase). Stevioside reduces the presence of nitrate and nitrite and also inhibits the production of iNOS in the lungs.
Stevioside also has protective anti-inflammatory effects by decreasing the production of proteins (cytokines) .
6) Stevia Helps Prevent Fatty Liver
Stevioside, rebaudioside A, and steviol has an effect on the metabolic pathways that involve high-fat levels (lipotoxicity) such as deterioration (steatosis), hepatitis, and liver disease (steatohepatitis).
Obese and insulin-resistant mice were treated with stevioside, rebaudioside A, and steviol, and the results exhibited a significant decrease in liver steatosis levels.
Liver steatosis occurs when liver cells are invaded with fat. The reduction in liver steatosis levels is due to the improvement of sugar energy production, fat breakdown, bile acid energy production, and fat storage and transport by all three steviol compounds.
Stevia derivatives also protect from the toxic effects of abnormal placement of fat build up in the liver which contributes to obesity .
7) Stevia May Help Reduce Kidney Damage
Concentrations of stevioside have been used to reduce the severity of chronic kidney disease (nephropathy).
According to one study in streptozocin-induced diabetic rats, stevia leaves could reduce the risk of oxidative stress and thus reduce kidney damage .
In another study, Stevia leaves were more effective than I-NNA (N-nitro-L-arginine) in managing diabetes-induced kidney disorders in rats .
8) Effects of Stevia on Fertility
Many studies have been conducted regarding the effects of stevia on fertility. Tukey and Mann-Whitney tests were used to determine how stevia impacts male reproductive organs.
It found that the cauda epididymis, seminal vesicle, and testis of male mice (treated with high concentrations of stevia) decreased in relative weight. The cauda epididymis also experienced a large decrease in spermatozoa.
These effects were believed to be caused by a reduction of blood levels of androgen receptors (steroid hormones that promote certain male sex characteristics) .
However, other studies have found contrasting results. For instance, a more recent study proved that stevia has no effect on male reproduction by replicating the Tukey and Mann-Whitney tests that were previously used.
An extremely high concentration of stevia was used in the experiment; the amount is comparative to approximately 50 percent of the mice’s body weight.
Experiments were also performed on chicken embryos because they are highly susceptible to toxins. Broiler eggs were injected with stevioside, then evaluated at hatch day and a week after.
Dosage and Safety
Based on the published research, independent scientific experts in both the U.S and globally have concluded that stevia sweeteners are safe for people of all ages and an acceptable daily intake (ADI) of 4mg/Kg body weight has been established .
The natural, whole stevia leaf has mostly been shown to be non-toxic and safe. Studies indicate that stevioside, the primary chemical that gives stevia its sweetness, cannot cause cellular changes or affect fertility [29, 30].
Similarly, Stevioside was found to be non-toxic in rats fed with doses as high as 2,000 mg/kg.
However, there was one study on male rats that found that consumption of a water extract of the stevia leaf lowered testosterone levels and sperm count .
Fortunately, this result seems to be anomalous and probably due to the high levels of stevia used in the study.
Another study gave stevia extracts to 500 rats for two years, with stevia totaling 1 percent of their diet. The researchers found that there was no dose-related change in growth, organ health, appearance or other health parameters .
Some commentators have suggested that certain components of stevia are converted by the body into compounds that cause DNA mutations and cancer.
However, researchers found that the potential of steviol glycosides to cause DNA mutation is 3,000 times less than common compounds like diesel smoke or burnt meat.
While stevia has recently become widely used in many countries without indications of toxicity surfacing, until certain aspects of distribution and energy production have been properly investigated in humans, any assumption of safety appears premature. This explains why the FDA has not approved crude or whole-leaf stevia as a safe food additive.
One piece of research discovered that 16 percent of infants with nasal allergies, 34 percent of infants with bronchial asthma, and 64 percent of infants with atopic eczema were allergic to stevia.
If you have an allergy to plants in the Compositae or Asteraceae families – such as chrysanthemums, marigolds, ragweed or daisies – then it’s entirely possible that you will have an allergic response to stevia.
Symptoms include swelling and itching of the oral area, hives, GI pain, nausea, and vomiting.
Constituents of Stevia
It is now known as Stevia rebaudiana or stevia, for short. The best known natural products derived from stevia rebaudiana are glycosides such as stevioside (9.1%), rebaudioside A (3.8%), rebaudioside C (0.6%), steviolbioside (a.k.a. steviol), dihydroisosteviol (a.k.a. isosteviol), rubusoside, and dulcoside (0.3%).
Stevia consists of approximately 80 – 85% percent water, protein, fiber, fats, monosaccharides, essential oils, vitamin c, β-carotene, vitamin B2, and vitamin B1.
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