Sugar Leaf - A new breed of 'sweetener'
by Ashraf Tanvir, Director Scientific Information, NARC Islamabad
Published in "The News" Rawalpindi / Islamabad, Lahore and Karachi on May 24, 2005
Commonly known as sugar leaf, honey leaf or sweet leaf of Paraguay, the plant seed was introduced by scientists of National Agricultural Research Centre (NARC), Islamabad - the premier research establishment of PARC. In 2003, it was sown for the first time in Pakistan at different climatic sites including shade, semi-shade and full sunlight for testing its viability in the local environment.
Stevia rebaudiana or sugar leaf
is a perennial shrub that grows up to 1 m tall and has 2-3 cm long leaves used
as sweetener. It belongs to the Aster family, which is indigenous to the
northern regions of South America. Stevia is still found growing wild in the
highlands of Amambay and Lguacu districts (a border area between Brazil and
Paraguay). It is estimated that as many as 200 species of Stevia are native to
South America, however, no other Stevia plants have exhibited the same intensity
of sweetness as Stevia rebaudiana. It is grown commercially in many parts of
Brazil, Paraguay, Uruguay, Central America, Israel, Thailand and China.
Its germination has been recorded very well at NARC, Islamabad and now the plants are under observation with respect to acclimatisation. These plants have attained a height of one foot and are expected to bloom this year. When these plants attain the height of one meter, the experiment will be considered as successful according to the climatic conditions of Pakistan.
After their successful acclimatisation, the plant will be sent to different units of the Horticulture Research Institute of NARC situated at different locations i.e. Sariab (Quetta), Tandojam (Sindh), Tarnab (NWFP) and Faisalabad (Punjab) for Uniform Yield Trials and other relevant studies on its various biological effects.
In Pakistan, the sugar leaf plant was first exhibited at the 13th national citrus and winter vegetables expo and it remained the main attraction. A large number of visitors appreciated the efforts of NARC scientists and evinced their deep interest in this plant. Sugar leaf plant was among the rarities that crowned this year's winter show being visited by a large number of visitors as reported in one of the national newspapers on 16th January 2005.
For hundreds of years, people in Brazil and Paraguay have used the leaves of stevia as a sweetener. The Guarani Indians of Paraguay call it "kaa jhee" and have used it to sweeten their yerba mate tea for centuries. They have also used stevia to sweeten other teas and foods and have used it medicinally as a cardiotonic, for obesity, hypertension and heartburn, and to help lower uric acid levels.
In addition to being a sweetener, stevia is considered (in Brazilian herbal medicine) to be hypoglycemic, hypotensive, diuretic, cardiotonic and tonic. The leaf is used for diabetes, obesity, cavities, hypertension, fatigue, depression, sweet cravings, and infections. The leaf is employed in traditional medical systems in Paraguay and Brazil.
Europeans first learned about stevia in the 16th century, when conquistadors sent word to Spain that the natives of South America were using the plant to sweeten herbal tea. Since then, stevia has been used widely throughout Europe and Asia. In the United States, herbalists use the leaf for diabetes, high blood pressure, infections, and as a sweetening agent. In Japan and Brazil, stevia is approved as a food additive and sugar substitute.
Western interest in stevia began around the turn of the 9th century, when researchers in Brazil started hearing about a plant with leaves so sweet that just one leaf would sweeten a whole gourd full of bitter yerba mate tea. It was first studied in 1899 by Paraguayan botanist Moises S. Bertoni, who wrote some of the earliest articles on stevia in the early 1900s.
Brazilian scientists recorded steviosside's ability to lower systemic blood pressure in rats in 1991. Then in 2000, a double-blind, placebo-controlled study was undertaken with 106 Chinese hypertensive men and women. Sixty subjects were given capsules containing stevioside (250 mg) or placebo thrice daily and followed up at monthly intervals for one year. After three months, the systolic and diastolic blood pressure of the stevioside group decreased significantly and the effect persisted over the whole year.
Stevia's effects and uses as a heart tonic to normalise blood pressure levels, to regulate heartbeat, and for other cardiopulmonary indications were first reported in rat studies in 1978. Following these studies, a crude extract of stevia demonstrated hypotensive activity in a 1996 clinical study with rats, showing that "... at dosages higher than used for sweetening purposes, [stevia extract] is a vasodilator agent in normo- and hypertensive animals." In humans, a hot water extract of the leaf has been shown to lower both systolic and diastolic blood pressure. Several earlier studies on both stevia extracts, as well as its isolated glycosides, demonstrated this hypotensive action.
In other research, stevia has demonstrated antimicrobial, antibacterial, antiviral, and antiyeast activity. Additionally, a U.S. patent was filed in 1993 on an extract of stevia that claimed it to have vasodilatory activity and deemed it effective for various skin diseases (acne, heat rash, pruritis) and diseases caused by blood circulation insufficiency.
For nearly 20 years, millions of consumers in Japan and Brazil, where stevia is approved as a food additive, have been using stevia extracts as safe, natural, non-caloric sweeteners. Japan is the largest consumer of stevia leaves and extracts in the world, and there it is used to sweeten everything from soy sauce to pickles, confectionery and soft drinks. Even multinational giants like Coca-Cola and Beatrice Foods use stevia extracts to sweeten foods (as a replacement for NutraSweet and saccharin) for sale in Japan, Brazil, and other countries where it is approved as a food additive.
In the U.S. stevia is mostly employed as a sugar substitute. About 1/4 teaspoon of the natural ground leaves (or one whole leaf) is the equivalent of about one teaspoon of sugar. In South America, a standard infusion is sometimes used as a natural aid for diabetes and hypertension; one cup is taken 2-3 times daily. It contains stevisoid, a natural sweetener. It is 300 times as sweet as sugar, yet it is not absorbed by the body and contains hardly any calories.
In Rio de Janeiro, studies on Stevia are continuing and it is considered to be the sweetener of the future. Stevia is grown in the interior of Sao Paulo. In the city of Birigui the plant is so popular that the tea made from it is sold at almost all bars and restaurants. Milkshakes, juices and coffee are sweetened with stevia. The inhabitants in this little town speak of the wonders of stevia and the positive results it has given in cases of diabetes, hypertension and infections. Stevia is considered to be a great help in weight loss programmes because it is very low in calories and its sweetness is so concentrated. Chewing a few leaves of Stevia will satisfy anyone's sweet tooth, and the shredded leaves are an excellent substitute for sugar in cooking.