Brown coated tubers and yams
Almost all brown vegetables comprise tubers and yams that grow underground. Yams or ‘ala’ in Sinhala are basically edible tuberous roots. Many of these vegetables are made up of complex carbohydrates generally known as ‘good carbs’ the major components being starch and dietary fibre as well as some vitamins and minerals.
It is best to eat these tubers and yams with non-starchy food for a balanced intake. The dietary fibre adds bulk to stools, allowing them to easily pass through the digestive system. Getting enough fibre also helps prevent constipation, bloating, cramping and indigestion. Further, the dietary fibre helps regulate insulin and glucose levels and prevents blood sugar from spiking while also contributing towards decreasing bad (LDL) cholesterol levels.
The protein content in most of these vegetables is low. While they are a good source of energy and can be part of a healthy diet, it is important for someone with diabetes to eat them in moderation as they can cause blood glucose levels to rise. They are also high in calories and can cause weight gain so weight watchers should not eat in excess.
The vitamins and minerals in the tubers and yams vary from source to source. Commonly present vitamins are the B complex group that mediates various metabolic functions in the body, and vitamin C that plays an important role in anti-aging, immune function, wound healing, and bone growth. Body-beneficial minerals present include, copper which produces healthy red blood cells, calcium vital for bone health, potassium essential for maintaining cardiovascular function and keeping blood pressure in check, iron, an important component of haemoglobin, manganese that supports bone mineral density and phosphorus a major contributor to the formation of bones and teeth. Each of these vegetables also has their own specific advantages.
Potatoes
Potato, Solanum tuberosum in the family Solanaceae is more energy-packed than any other popular vegetable and has even more potassium than a banana when cooked with the skin. How healthful a potato is in the diet depends to some extent on what is added or how it is cooked. Oil, sour cream, and butter all add calories, but the plain potato itself is relatively low in calories and also provides important nutrients, such as vitamin C, vitamin B6, and various minerals.Quercetin, a flavonoid found in potato skin has an anti-inflammatory and antioxidant effect that protects the body’s cells from damage by free radicals. The vitamin, mineral, and fibre content of potato are mostly in the skin,so it is best to eat them with the skin left on.
Manioc
Manioc (Cassava), Manihot esculenta in the family Euphorbiaceae comes loaded with carbohydrates especially the beneficial dietary fibres and is perhaps one of the highest value calorie foods for any tropical starch-rich tubers and roots.Manioc also contains significant levels of magnesium and copper. The folate abundant in cassava reduces the risk of complications during pregnancy. Cassava tubers contain toxic cyanogenic glucosides that convert to poisonous hydrocyanic acid when the cells are ruptured. The cyanide content is substantially higher in the peel and thus peeling followed by cooking ensures them safe for consumption. Always boil in an open pot and throw away the water. Incorrect preparation of the tubers can lead to cyanide poisoning signs of which include headache, convulsions and in extreme cases even death.
Kohila
The Kohila tuber, Lasia spinosa, in the family Araceae comes from a spinous herb which grows abundantly in Sri Lankan marshlands. This can be considered as a valuable functional food from the viewpoint of its antioxidant and dietary fibre content. Taken as a vegetable, kohila reduces unnecessary toxins in the intestines and is effective for other intestinal disorders. The tuber reduces bleeding and is given after indigestion and diarrhoea (not during). Eaten as a food, it increases appetite and body weight, reduces urine output and burning sensation in the body. It also expels worms and is used widely, both as a food and a medicine, by those suffering from piles.
Gahala
Gahala, Colocasiaesculenta in the family Araceae stands out as the root crop with a very high fibre content which is said to be three times that of whole potato. It is also a good source of potassium. The antioxidants cryptoxanthin and beta-carotene present in the tubers contributes to improving vision health.
Innala
Innala, also known as ratala, Solenostemon rotundi folius in the Lamiaceae (mint family) is richer in nutrients as compared with other root and tuber crops. Innala has relatively lower starch content in comparison to manioc and sweet potato and as such will contribute less to the fattening effect. It is a richer source of iron and calcium than other tubers.
Kiriala
Kiriala, Xanthosomasagitti folium in the family Araceae has a slightly milky taste when cooked, hence the name kiriala in Sinhalese. It is rich in vitamin B6, copper, potassium and iron and is considered as the lowest allergenic food which makes it a good diet for the people who experience various food allergic situations.
Other yams
The other common yams such as Purple yam (rajala) Dioscoreaalata and Sweet Potatoes (bathala), Ipomeabatatas have already been covered in the article on purple vegetables.
There are several other edible yam types even though not very commonly used.
- Hingurala, Acacia caesia is known to be good for pregnant women and those aspiring to be pregnant and also known to be good for problems such as diarrhoea and indigestion.
- Hulankeeriya(arrowroot) Maranta arundinacea has high protein content and is known to be beneficial in preventing and alleviating illnesses related to the digestive tract.
- Kidaran (elephant foot yam) Amorphophallus paeonii folius has three different varieties and only the white variety can be consumed. It is known to be good for haemorrhoids as well as for curing and prevention of stomach ulcers.
- Udala (Air potato) Dioscorea bulbifera has a taste which is very similar to potatoes. The udala creeper produces smaller tuber-like rhizomes on its surface as well.