Yacon (scientific name: Polymnia sanchifolia) is an herbaceous plant that belongs to the Compositae family (sunflower family). But unlike its better known cousin, the sunflower, it is grown mainly for its tubers and not its seeds.
The yacon plant is native to the Andes mountains of South America, the longest mountain range in the world. It grows wild at medium altitudes (2,000-7,000 ft. above sea level) from Columbia to Argentina, but can be cultivated even at sea level.
The yacon plant is now being grown and its tubers sold in some parts of the Philippines, notably the Cordillera region and Baguio. I just don’t know if it is already available in Metro Manila.
In his article which was printed in the Philippine Panorama magazine last Nov. 6, Nestor Cuartero said that Region 2 Tourism director Blessida Diwa informed him that the plant was introduced to the Philippines in 2000 by a Japanese national and is presently being grown extensively in the highland Vizcaya towns of Santa Fe and Dupax del Norte where cool temperature is considered ideal in growing the crop.
The yacon plant can reach six feet in height. Its leaves are dark green and its stems are hairy. Its root system consists of four to 20 fleshy tubers each of which can reach 25 cm in length and 10 cm in diameter. The tubers, as you yourself have noted, look like sweet potatoes (camote), but they are slightly softer and bigger. The skin is brownish, but the meat is white to yellowish.
The stems and leaves of the yacon plant are cooked and eaten as vegetables. The tubers are usually eaten raw, like a fruit, after peeling the skin; but they can also be boiled or baked. When fresh, they have the consistency and crispness of turnips (sinkamas), but are much sweeter. The tubers can also be added to green salads and can substitute for "ubod" in "lumpia." They can likewise be squeezed to make a sweet drink. In Peru, they are even made into candies.
The yacon tuber is a very poor source of nutrients. Analysis of fresh tubers has revealed that they consist mainly of water (69-83 percent). Their protein content is minimal (0.4-2.2 percent).
Carbohydrates (sugars) comprise up to 20 percent of the tubers, but the sugars stored in the tubers include only minimal amounts of glucose, they consist mainly of fructose, sucrose, some oligosaccharides and inulin — sugars that are poorly absorbed in the gastro-intestinal tract of humans.
Despite its poor nutritional value, the yacon plant has been cultivated by the indigenous people of the Andes to add variety to their diet and for its supposed medicinal properties.
Andean lore attributes several medicinal properties to yacon. It supposedly controls blood sugar among diabetics. In Brazil, the dried leaves are used to prepare a medicinal tea for diabetics. It allegedly also cures kidney and digestive problems, and rejuvenates the skin.
To date, however, the medicinal properties attributed to yacon remain unsubstantiated. Very few scientific studies have been conducted on the matter, although some have yielded encouraging results. For example, in an animal experiment where rats with induced diabetes were fed with water extracts of dried yacon leaves, some hypoglycemic (blood sugar-lowering) activity has been demonstrated.
Inulin, one of the carbohydrates found in yacon tubers, has been the subject of much scientific interest lately. It reportedly stimulates the body’s immune system when injected; but inulin is not absorbed in the gastrointestinal tract and therefore its immuno-stimulant effects have never been observed with oral use.
Inulin has likewise been demonstrated to stimulate the growth of friendly bacteria (lactobacilli) in the large intestine. In a study where subjects were given 15 grams of inulin a day for 15 days, the population of Lactobacillus bifidobacteria increased by 10 percent, while at the same time, the population of disease-causing bacteria decreased.
A recent animal research also showed that inulin prevents precancerous changes in the colon.
All said, the medicinal properties ascribed to yacon are unproven. Even if the plant contains substances that have medicinal uses, these substances probably need to be extracted, purified and concentrated before they can become potent enough to be beneficial.
Realistically, the yacon tuber should be simply regarded as a food product that can serve as a sweet and refreshing treat that diabetics can enjoy without fear of increasing their blood sugar levels, and as a filling yet low caloric food that can help dieters lose weight by sating their appetite.
