By Jenny Lee WIRED Korea

In Korea, a new type of fruit is making its way into homes, satisfying sugar cravings of many people: sugar-tasting tomatoes.

These tomatoes are widely known in Korea as either “tomango,” a compound word of tomato and mango, or “danmato,” of dan, a Korean word for sweet, and tomato.

Their popularity is growing as a number of public figures including fashion stylist Han Hye-yeon are touting them as their secret to weight loss and staying fit; Han says she lost a whopping 12.5 kilograms by consuming just these tomatoes for a period.

So what makes tomangoes and danmatoes so sweet yet nutritious? The answer lies in stevia, a natural, zero-calorie intense sweetener that is estimated to be 200 to 300 times sweeter than regular table sugar. Written on the packaging of these tomatoes that are currently sold in major markets across the country is a description that they contain about 0.01 percent of “enzyme-treated stevia” or “stevioside.”

A Healthful Alternative to Sugar

Stevia is a concentrated extract from the leaves of the stevia plant, a member of the chrysanthemum family that grows wild as a small shrub in Paraguay, Brazil and other parts of Southeast Asia and is cultivated in some countries such as Japan and China.

Rebaudioside and stevioside, both steviol glycosides present in the plant, are what give stevia leaves their sweet flavor, and they have been used as a substitute to added sugar in many beverages and foods for hundreds of years.

Although stevia is currently available around the world, it was once designated as “unsafe” by the U.S. Food and Drug Administration (FDA). In 1991, the FDA banned the importation of stevia and its use based on early reports that the natural sweetener may cause cancer.

As later studies refuted these claims, the FDA lifted the ban in 1995 and allowed stevia to be imported into the U.S., but only as a dietary supplement. It was in 2008 that high-purity glycoside extracts were categorized as “Generally Recognized as Safe” (GRAS) and were allowed in food products. The use of stevia leaf and crude extracts are still forbidden due to “inadequate toxicological information.”

Multiple studies have proven that using stevia as a sweetener can bring considerable health benefits including weight loss and improved diabetes control. As stevia contains no sugar and very few, if any, calories and has no effect on blood glucose or insulin response, if used as a sugar substitute, it can help people on a diet minimize energy intake without sacrificing taste, while allowing those with diabetes to enjoy a wider range of foods.

Stevia however can be harmful, especially to those with chronic hypotension or hypoglycemia, if consumed in large amounts -- more than the recommended daily intake, which is less than 4 milligrams per kilogram of body weight.

Korean Farmers Chase Sweeter Crops Using Stevia

The stevia plant was first introduced in Korea in the early 1970s, with efforts being made by the Rural Development Administration, under the Ministry of Agriculture, Food and Rural Affairs, to develop different breeds, according to Kang Kyeong-hun of Korea Stevia Co., Ltd, a supplier of stevia concentrates, based in Jeongeup, North Jeolla Province.

“Since the late 1980s, the stevia plant cultivation has spread slowly, but not to a great extent,” says Kang, deputy director of Korea Stevia’s research and development center, which has been making efforts to grow new breeds of the stevia plant. “Stevia extracts are now being used across a wide range of applications, including agriculture, food, medicine, cosmetics, and others.”

Stevia use has become much more sophisticated in Korea recently, as farmers begin to raise their crops with help from this all-natural ingredient.

Known as stevia farming technique, it involves spraying a concentrate made from chemically-untreated stevia leaves and stems onto crops or on the soil as fertilizers, from the time of seeding to harvesting. This method, which started in Japan and was later introduced in Korea, is being adopted by a growing number of fruit and vegetable growers to enrich the soil, prolong the freshness of their produce and improve their sugar content, Kang says.

Farmer Chang Won-man says he started incorporating stevia extracts into his farming practice 15 years ago and he has been reaping the rewards ever since.

“It's been maintained for 15 years, which proves that it is effective,” says Chang, head of an agricultural corporation based in Yeongcheon, North Gyeongsang Province. “We use stevia for sweetness in the case of fruits and for freshness in vegetables.”

Chang says he grew a wide variety of crops using this method, from plums, grapes and peaches to lettuces, onions and potatoes. He uses brix, a measure of sugar, to determine the sweetness of his fruit and vegetable products.

“Most watermelons, when fully ripe, are about 12 brix, grapes about 15 brix and apples about 13 to 14 brix, but what we produce is often 18 brix or above,” Chang says. “Increasing just 1 brix is extremely difficult and if done would create enormous added value.”

Tomango Production in Veil

But tomangoes and danmatoes are of different sorts; the farmer explains they are remotely similar to his agricultural products where stevia was used as an all-natural fertilizer.

When asked about the stevia tomatoes, Kang of Korea Stevia says they are “manufactured” by injecting stevioside into already-produced tomatoes, not an agricultural practice but an artificial mechanism to increase their sweetness.

This not only raises safety concerns but also has negative effects on the lifespan of these tomatoes, Kang says. While the shelf life of regular tomatoes past their date purchased is approximately one to two weeks, stevia tomatoes can only last three to four days.

“The reason why such a method is used only on tomatoes is that they have thicker skin compared to other fruits and therefore can hold the injected stevioside inside intact,” Chang says. “If it was possible to manufacture other types of fruits in such a way, they would have been making headlines in the news already.”

Tomangoes and danmatoes, which have been available since April of last year, are being advertised on YouTube and other social media channels as well as on television or radio programs, with the actual production process mostly under wraps.

Udeumji Farm, the biggest stevia tomato producer in the country declined WIRED Korea’s request for comment.