Dioscorea, a pan-continental genus of over 600 species/taxa of family Dioscoreaceae is mainly found in Africa, India, Southeast Asia, Australia, and tropical America. About only 12 out of 600 species are considered edible. Its name comes from ancient Greek physician and botanist Dioscorides. It’s a tuberous herbaceous perennial climber 2-12m or taller, slightly brown in colour, odourless, bitter in taste, with alternate, broad heart-shaped leaves and soft, horizontally arranged rhizomes. It consists of greenish – yellow, six petaled, mostly dioceious, rarely monoeicious flowers.
Also known by the names Rheumatism root, colic root, yam. The word yam is derived from African word for root/tuber ‘nyami’. Different species are known by different yam names i.e Chinese yam (D.opposita), Air yam/potato (D.bulbifera), wild yam (D.villosa), bitter yam (D.dumetorum), lesser yam (D.esculenta), water yam (D.alata), cush-cush yam (D.trifida), white yam (D.rotundata) etc.
A yam is not, contrary to belief in the US and UK a sweet potato. Yams are starchier and drier as compared to sweet potatoes.
The edible part used in yam is tuber whereas it’s storage roots in case of sweet potatoes. Yams taste more like potatoes (starchy) than sweet potatoes (sweet).
What makes Dioscorea beneficial?
Plant parts used are rhizomes, tuber, and roots. It gives around 110 Kcal per 100g serving. Dioscorea rhizomes contain 75% starch. It constitutes approximately 2% protein, not a good source of essential amino acids. It contains high amount of phenylalanine and threonine but limited amount of sulphur amino acids, cystine, methionine and tryptophan. Therefore Africans who consume yam have a high risk of kwashiorkor. It is rich in Potassium (17%), Manganese, dietary fiber (4.1g/100g), Vitamin B6 (23%), Vitamin C (21%) and low in saturated fat and sodium.
The main active component of dioscorea is diosgenin, a steroidal sapogenin (4-6%) which is a hydrolytic product of saponin dioscin, alkaloids (dioscorin), gylcosides (smilagenin, epismilagenin) and yammogenin.
Apart from potassium, manganese and sodium, yam contains minerals including calcium, chloride, copper, iron, magnesium, phosphorus, zinc and selenium.
Health Benefits of Dioscorea
Some key health benefits of Dioscorea are as follows:
Rich source of steroidal sapogenin, diosgenin : The root and bulb parts of the plant are used as a source of diosgenin which is then prepared as “extract” which is a primary preparation then further used in other processes.
Anti-Rheumatic agent and as expectorant : It’s used in the treatment of acute phase of rheumatic arthritis in case of intense inflammation.
Estrogen replacement therapy : Wild yam due to its estrogen-like activity is used as ‘natural alterative’ to estrogen therapy.
Used in synthesis of corticosteroids, sex-hormones, oral contraceptive : Due to the presence of diosgenin which is steroidal in nature, used as a precursor in commercial synthesis of corticosteroids(cortisone, pregnenolone, prednisone, hydrocortisone), sex-hormones (progesterone), androgen(testosterone) and birth control pills.
PMS and Menstrual disorders : It eases menstrual cramps, ovarian neuralgia and PMS (premenstrual syndrome). It’s also indicated for threatened miscarriage, dysmenorrhoea, vaginal dryness in older women, increasing energy and sexual drive in men and women owing to the presence of steroidal sapogenin, diosgenin which has estrogen-like activity and structure similar to sex-hormone (progesterone). It’s not proved but evidences from research have showed that Benefits in PMS might be due to the presence of high amount of Vitamin B-complex and Vitamin B6.
Gall-bladder problems and Gall stone colic : As its name suggest, colic root, is used in various forms of colic with spasmodic contractions, bilious colic, gall-bladder colic, intestinal colic and it also promotes the flow of bile.
Natural DHEA : Diosgenin has structural similarity to adrenal hormone DHEA (dehydroepiandrosterone) and shows DHEA-like effects in the body. Therefore it has a balancing effect which can be helped to overcome the negative effects of declining levels of DHEA with aging thereby also modifies serum lipid levels.
Antioxidant and anti-spasmodic agent : Dioscorea contains an alkaloid dioscorin which plays the role of antioxidant. It also acts as anti-spasmodic agent. It relieves spasm in circular muscles of GIT.
Treat osteoporosis : It maintains a good potassium-sodium balance as it is high in potassium and low in sodium thereby prevents osteoporosis (weak bones) and risk of heart diseases.
Usage and Storage of Dioscorea
It’s a versatile herb. It can be boiled, baked, roasted, smoked, barbecued, fried, grilled and can be made into dessert recipes by grating it. But it should be remembered that not all dioscorea species are edible, only 12 are edible ones. If the toxic ones are consumed, it can prove fatal and hazardous to health.
Store dioscorea at temperature between 14-16 degrees Celcius ( 57.2 – 60.8 degrees F) away from direct sunlight and rain after providing proper curing. Remove any rotting or damaged pieces.
When not to use it Dioscorea
- Avoid use during pregnancy and breast feeding.
- Do not use in hormone sensitive conditions like ovarian cancer, breast cancer, uterine cancer, endometriosis, uterine fibroids as it might act like estrogen and worsen the condition.
- If you are suffering from protein S Deficiency should avoid dioscorea use as there’s an increased risk of clot formation due to its estrogen-like activity.
The consumption of edible dioscorea can serve delicious as well as healthy treat which can be eaten in many forms- boiled, baked, roasted, smoked, barbecued, fried, grilled and can be made into dessert recipes by grating it.