The leaves of this plant are very sweet, yet they do not contain sugar. They are non-caloric, just as many other leaves of plants. Stevia has been consumed by native people in South and Central America for thousands of years – it even features in the ancient Mayan text, the Popol Vuh (i). Stevia has been used commercially in food products in numerous countries such as Japan since the 1970s and the US and Europe since the 2000s. In addition to eating it directly, it is used to make sweet tea and as a medicinal plant for those with high blood pressure, pre-diabetes, and diabetes as it helps to regulate blood pressure and blood glucose. Given its medicinal applications, there has been a large amount of research (>1,000 studies) conducted on it for food and medical applications (ii, iii, iv, v). In addition to the thousands of years of human consumption, the research evidence on this plant has only further confirmed its helpful effects (vi).
HOW MUCH IS MEDICINAL?
Stevia leaf extract is 300x as sweet as sugar, so if you eat or drink a stevia-sweetened product, you will most likely get 50-170mg per food/drink that is sweetened with stevia leaf extract (labelled usually as steviol glycosides, the scientific name for the plant’s sweet molecules). It is important to remember that some studies on stevia’s health benefits use higher doses than this. However, there are still benefits of smaller doses according to the scientific literature.
Stevia IMPROVES METABOLISM and REDUCES BLOOD GLUCOSE
After oral intake, steviol glycosides are broken down by gut microbiota. Free steviol is absorbed and transformed into steviol glucuronide, which goes to peripheral blood and is excreted by the kidneys (vii, viii). In non-obese, Type 2 diabetes, stevioside (the main steviol glycoside) significantly reduces blood glucose spikes by 30% (incremental area under the curve), by improving insulin secretion and sensitivity, and suppressing glucagon (v). Interestingly, stevia seems to behave in an adaptogenic medicinal way, as stevioside does not cause hypoglycemia (excess blood glucose lowering) in non-diabetic (metabolically ‘normal’) controls (v, ix). Stevia appears to act directly on both taste receptor cells and pancreatic β cells to appropriately modulate glucose-induced insulin secretion, preventing diabetic hyperglycemia (x). In both animal and human trials, depending on the dose, stevia improves insulin sensitivity and fasting blood glucose.
Stevia IMPROVES MUSCLE CELL INSULIN SENSITIVITY and ENHANCES MUSCLE GLYCOGEN REPLENSHIMENT
Muscle cell insulin resistance and impaired muscle glycogen synthesis are among the earliest biomarkers of metabolic syndrome, hyperglycemia, and Type 2 diabetes (xi, xii). Research indicates that stevioside enhances glucose transport in insulin resistant skeletal muscle cells (in both lean and obese animal models), directly ameliorating this early dysfunction in the pathogenesis of insulin resistance (xiii). While muscle glycogen replenishment function is often impaired in Type 2 diabetes, research demonstrates that physiological levels of stevioside increase glycogen replenishment by 35% compared to controls, which is remarkable and relevant for muscle maintenance and athletic performance, in addition to enhancing and maintaining metabolic health generally (xiv).
Stevia helps in Losing and Maintaining Weight
In a 12-week animal study in female rats, comparing a standard diet (Negative control) with the same diet plus sucrose dissolved in water (Positive control: 500mg/kg/day, c. 30g of sugar for an average adult human), and compared to 4 groups with various doses of stevia, demonstrated that the stevia groups consumed less calories and lost weight vs. both control groups that gained weight (xix).
Stevia can PROTECT AGAINST ATHEROSCLEROSIS (Cardiovascular Disease) and has IMMUNOREGULATORY EFFECTS
Multiple studies have demonstrated stevia’s powerful antioxidant impacts, including boosting levels of our own body’s major antioxidants such as superoxide dismutase (SOD). Research has demonstrated that stevioside treatment significantly improved insulin signaling in adipose tissue, reduced oxidized low-density lipoprotein (oxLDL), reduced macrophages and lipids in atherosclerotic plaque and increased smooth muscle cells that promote more stable plaque in the aorta. Stevioside also has a direct anti-inflammatory effect, by lowering expression of genes that increase inflammation and that recruit monocytes to the blood vessel wall.
How can STEVIA TASTE GREAT? You may have tried products with stevia and found they tasted unpleasant or bitter.
The problem is that food ingredients companies use chemicals to extract the sweet molecules from the leaves, changing their biochemical structure and taste (for the worse). This process creates bitter and unpleasant aftertastes. How you process food makes a big difference to how it tastes! We know this in the kitchen, yet we take it for granted when buying what we think are ‘standardized’ ingredients. There are some commodities that taste similar wherever they come from, no matter how they are produced, including sugar. Whether from sugar beets or sugar-cane, sugar tastes the same. However, most foods taste very different, depending on how they are grown or extracted.
References
(i) Tedlock, D. (Revised ed. 1996) ‘Popol Vuh: The Definitive Edition of the Mayan Book of the Dawn of Life and the Glories of Gods and Kings’, Touchstone
(ii) Wölwer-Rieck, U. (2012) ‘The Leaves of Stevia rebaudiana (Bertoni), Their Constituents and the Analyses Thereof: A Review’, Journal of Agricultural and Food Chemistry, 60(4)