The sweetest of herbs.
Discover for yourself how sweet it is. The taste of stevia is not identical to that of sugar, but it is pleasing with a wide variety of foods. Here are some nutritious and satisfying treats that owe their sweet taste to stevia.
From the highlands of Paraguay comes a sweet little secret: Stevia rebaudiana, whose leaves are the sweetest natural product known. Far sweeter than sugar, stevia has virtually no calories, and unlike sugar, it doesn’t raise blood-sugar levels or promote tooth decay. In the United States, after bitter controversy in recent years, the plant is now becoming more widely available, but people in other parts of the world have long appreciated its extraordinary sweetness.
S. rebaudiana, a member of the aster family (Compositae), is a small perennial shrub native to Paraguay, Brazil, and Argentina. Indians of the Guarani tribe appear to have used the leaves as a sweetener since pre-Columbian times, but it was not until 1887 that a South American natural scientist “discovered” it.
Originally placed in the genus Eupatorium, the plant was reassigned to Stevia in 1905. More than 80 species of stevia are known to grow wild in North America and another 200 in South America, but of these, only S. rebaudiana and another species, now extinct, have possessed the intense natural sweetness.
The sweet secret of stevia lies in a white crystalline compound called stevioside, a glycoside composed of glucose, sophorose, and steviol. Stevia leaves are 10 to 15 times as sweet as table sugar, but stevioside extracts may range from 100 to 300 times as sweet as sugar.
Why is stevia such a secret? Is it safe? How can we use it when cooking and preparing food?
In Paraguay, Indians have long used stevia to sweeten bitter beverages, particularly maté. By the turn of the century, this “sweet herb” or “honeyleaf” was being widely used by herbalists throughout Paraguay as a tea sweetener.
Research to unravel the secret of stevia began in 1931 when two French chemists isolated a constituent they named stevioside. They found it to be 300 times as sweet as sugar and apparently nontoxic to laboratory animals.
In 1941, because of the scarcity of sugar and other sweeteners in England due to the German submarine blockade, the British sought a substitute sweetener that could be cultivated in the British Isles. Research commissioned by the director of the Royal Botanical Gardens at Kew showed that stevia had potential for sweetening beer and other beverages, as well as food for diabetics. Furthermore, the dried leaves could be kept indefinitely and added whole or powdered to tea or coffee, and powdered leaves could be used for sweetening stewed fruit and other dishes.
Within the year, seeds from Paraguay were planted in Cornwall and Devon, where test plots yielded the equivalent of two tons of sugar per acre. For unknown reasons, however, the project was set aside and largely forgotten in the aftermath of the war.
In 1952, researchers at the National Institute of Arthritis and Metabolic Diseases, a branch of the U.S. Public Health Service in Bethesda, Maryland, began investigating stevia. They determined the chemical composition of the large and complex stevioside molecule and used an improved extraction procedure to increase its yield. In addition, they confirmed that stevioside is the sweetest natural product yet found.
The Japanese began to grow stevia in hothouses in 1954. When the Japanese government banned certain artificial sweeteners due to health concerns in the late sixties, stevia use increased dramatically. Consumer concerns about sugar-related tooth decay, obesity, and diabetes also contributed to this increase. Besides consuming it directly as a tabletop sweetener, they now use it extensively to sweeten pickles, dried seafoods, fish and meat products, and soy sauce, as well as fruit juices and soft drinks, yogurt, baked goods and cereals, frozen desserts, gum, and low-calorie foods.
During the 1970s, Chinese researchers used a nonchemical method of extraction recorded in herbal manuscripts of the Chinese emperors to remove both the undesirable color and bitter aftertaste from stevia leaves.
Today, stevia and stevioside have become major export products, with stevia cultivated in more than a dozen countries worldwide, including South America, Japan, Korea, the Philippines, Southeast Asia, Israel, California, and southern Ontario. The largest user of stevia remains Japan, where by 1988, stevia extracts had captured 41 percent of the value of the high-potency sweetener market. Stevia and stevioside are also widely used in North and South Korea, China, Taiwan, Israel, Brazil, Paraguay, and Malaysia.
Stevia’s pharmacological activity has been investigated, with contradictory results, for its effects on diabetes, blood pressure, contraception, and bacterial growth, and as a source of plant growth hormones and flavonoid glycosides. Herbalists in Brazil have used decoctions or extracts of stevia to regulate blood-sugar levels for at least forty years, and some scientific studies have confirmed that stevia may help regulate blood-sugar levels in normal adults. Stevioside has been the sweetener of choice in toothpastes, mouthwashes, and gums intended to decrease the incidence of tooth decay and retard the growth of plaque. Although further research on its medical benefits is indicated, no studies to date have reported any toxicity or harm caused by stevia or its sweet constituents.
Stevia plants are spindly, with many branches bearing simple paired leaves. In the wild, they may grow 24 inches tall; cultivated varieties may reach 36 inches. The root system consists of fine roots that spread near the surface of the soil and thicker roots that delve deeper.
Wild stevia grows primarily in the infertile acidic sands and mucks that border marshes and in grasslands with shallow water tables, yet stevia has shown itself to be adaptable to a variety of soil conditions. Its native climate is semihumid and subtropical with an average temperature of 75°F and a range of 25° to 110°F (Zone 9). Rainfall averaging 55 inches per year keeps the coarse-textured soil continuously moist but not subject to prolonged inundation.
Stevia reproduces in the wild by seed, crown division, or the rooting of branches that lodge in the soil or are trampled by cattle. Grazing and overharvesting have diminished much of its native range, however.
Seeds should be sown indoors and the seedlings transplanted outdoors as early in the spring as possible for maximum growth and yield. Because seed germination is erratic, however, most commercial stevia is grown from cuttings. Seedlings or rooted cuttings typically blossom in the late summer and early fall. When planting out, site in full sun and space the plants closely so that they support each other; thin them the following year when the stems are woodier. Keep the soil constantly moist. Stevia is harvested as it begins to flower, when the leaf weight is the greatest and the stevioside content at its peak.
Stevioside yields of 6 to 12 percent have been commonly noted in cultivated stevia leaves. One study showed a yield of 220 pounds per acre, equivalent in sweetening power to about 28 tons of sugar.
In the United States, stevia was widely used during the eighties to sweeten herbal teas, but in 1991, the Food and Drug Administration (FDA) issued an import ban that blocked sales of stevia in this country. The American Herbal Products Association was unsuccessful in petitioning the FDA to lift the ban.
Passage of the Dietary Supplement Health and Education Act of 1994 effectively nullified the ban, however, and in September 1995, the FDA allowed stevia and stevioside into the country—but only if labeled as dietary supplements. Stevia and its extracts have not been approved as food additives nor recognized as safe; the FDA has stated that the available toxicological information on stevia is inadequate to demonstrate its safety.
What does this tell us about the safety of stevia? Not much. A look at the scientific research on stevia since 1887, its record of use over the past two centuries by Guarani Indians in Paraguay, as well as its widespread modern use worldwide leaves little doubt in my mind that stevia’s safety is unquestionable. Even its most skeptical critics admit that there hasn’t been a single reported case of stevia toxicity to humans in the past forty years. Despite the FDA’s stance, the rest of the world agrees that stevia has been shown to be a safe, natural product.
Stevia is available at most health-food stores and from many mail-order suppliers, including the following:
• Frontier Cooperative Herbs, PO Box 118, Norway, IA 52318-0118. Catalog free. Powder and cut–and–sifted.
• Fruitful Yield, 2111 Bloomingdale Rd., Glendale Heights, IL 60139. Powder and liquid extract.
• Mulberry Creek’s Herb Farm, 3312 Bogart Rd., Huron, OH 44839. Catalog free. Plants.
• Richter’s, Goodwood, ON, Canada L0C 1A0. Catalog free. Plants.
• Well-Sweep Herb Farm, 317 Mt. Bethel Rd., Port Murray, NJ 07865. Catalog $2. Plants.
David Richard is an herb enthusiast and a health writer/publisher who lives in a wooded area outside of Chicago. This article is adapted from his book Stevia Rebaudiana: Nature’s Sweet Secret (Blue Heron Press, 1997).