Stevia’s scientific name is Stevia Rebaudiana, and in addition to the name ‘stevia’, it is also called sweetleaf and sugarleaf. The genus is a large collection, over two hundred species, of plants from the sunflower family. Where is Stevia From? Stevia is native to tropical and subtropical of South and Central America. Some species are also found in certain areas of North America, in Texas and Arizona for example. The plant has been grown by indigenous groups in South America for over 1500 years. Traditional uses include sweetening teas and as a medicine. What is Stevia? Stevia is used as a sugar substitute and sweetener. Fresh stevia leaves have over thirty times the sweetness of sucrose and their taste has a slower onset and duration. How does it work? Although the plant had been used by indigenous people for over one thousand years it was only described to Western science in 1899, by a Swiss botanist. In 1931, the glycosides which give the plant its sweet taste were isolated by French chemists, they were called rebaudioside and stevioside. These glycosides are almost 300 times as sweet as sucrose and non-fermentable. In addition, they are pH and heat stable. These highly sweet glycosides can have a bitter aftertaste. Of them, rebaudioside A is the least bitter and as such is often the target of commercial production. This involves extracting the rebaudioside from dried stevia leaves, first by water extraction and then cyrstallization which separates the glycoside molecules. The result is pure rebaudioside A. The tongue reacts to the glucose in the glycosides. As rebaudiosides have more glucose than steviosides these taste sweeter to us. Glycosides also contain aglycones, non-sugar substances, and these can activate some of the tongue’s bitter receptors. After injesting rebaudioside, it is metabolised into stevioside which in turn is broken down into steviol and glucose. The glucose is not absorbed into the blood stream but is used by the bacteria in our gut, and steviol is simply passed from the digestive system as waste. Commercial Usage of Stevia Stevia extracts, steviol glycosides, were first made commercially available by a Japanese company in the early 1970s. These can have up to 300 times the sweetness of sugar. This, combined with the fact that stevia has no measurable effect on blood glucose, mean that stevia has drawn wide interest as a natural alternative to sugar for people on sugar and carbohydrate controlled diets. Japan leads the way when it comes to the use of stevia as a sweetener with around 40% of the sweetener market being made up of stevia products. In Japan, stevia is found in soft drinks and food, as well as being available for table use. This reliance on stevia developed as a result of concerns over other sweeteners, e.g. saccharin, being carcinogenic. Stevia is grown and used in food products in many east Asian countries, as well as in much of South America. It’s usage in America and the EU is a recent development due to previous concerns over safety (see next section). In the USA, Coca-Cola developed a stevia-derived sweetener called rebiana, marketed at Truvia, which was approved as a food additive in 2008. With stevia also being approved in the EU from 2011 we’re sure to see it becoming more widely available over the next few years. It is Stevia Safe? Although widely available in parts of Asia and South America for more than thirty years, there has been some controversy over stevia’s usage in the USA and the EU. A study (1) in the 1980s reported that steviol acts as a mutagen in rats liver. The findings were criticized as flawed and further studies (2) went on to find that steviol did not produce harmful effects. The World Health Organization performed their own investigation (3) of stevioside and rebaudioside finding them not toxic, and indeed finding that steviol’s toxicity is not expressed in vivo. They went on to find no evidence of carcinogenic properties, something that has been a concern for other sweeteners, and noted the possible benefits of stevia for those with hypertension and type-2 diabetes (see next section). The World Health Organization conducted a follow-up study (4) which approves daily intake of steviol glycoside at a maximum of 4mg/kg body weight. This means that all food and beverages containing stevia extracts are subject to maximum levels. The American Food Standards Agency recognised rebaudioside A as safe in 2009. Secondary Health Benefits of Stevia The primary usage for stevia is as an alternative to sugar. However, some studies have found some further interesting benefits. For example, a study (5) conducted in 2009 found that stevioside has anti-imflammatory, anti-tumour, anti-hypertensive, anti-diarrheal and anti-hyperglycemic properties. Stevia’s effect on diabetes has also been investigated. In rats stevia has been shown to improve sensitivity to insulin. (6) Stevia can also revitalise the β-cells of the pancreas and may also promote insulin production. Eating stevia before meals can reduce insulin levels following the meal when compared to other sweeteners. A study in 2011 (7) concluded that stevia would therefore benefit diabetic individuals. Where to Buy Stevia and How to Use It With evidence stacking up in favour of stevia as a viable alternative to sugar you’ll probably want to know where you can get hold of some, the different forms it comes in and how you use it in everyday life. There are a multitude of websites now selling stevia products. You can buy stevia in liquid, powder and tablet form. Tablets and the liquid form are easily dissolved in drinks while the powder is best used in cooking. A 25g shaker of stevia powder contains 1000 servings, this means 1/3 teaspoon is about the equivalent of one cup of sugar. Final Words Marketers of stevia tout it as a ‘natural’ alternative to sugar, but unless you’re using the actual plants this isn’t strictly true. However, when you consider stevia extracts in comparison to the aspartame and saccharin products that are also widely available, and the controversy that often surrounds these additives, I think you’ll agree that stevia makes for a pretty sweet alternative
Posted on: Thu, 12 Sep 2013 04:13:40 +0000
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