Yam: benefits, dosage, contraindications
Other name(s)
Wild yam, Chinese yam, Chinese yam
Scientific name(s)
Dioscorea oppositifolia, Dioscorea villosa
Family or group:
Plants
Active ingredients:
Diosgenin
Dioscorine
Indications
Scoring methodology
EFSA approval.
Menopause ✪✪✪✪✪
Diosgenin, the saponin extracted from yam, does not bind to the human estrogen or progesterone receptors in vitro and cannot be converted into progesterone in the human body. Yam could theoretically be given to women who have been treated for breast cancer, but safety data are needed. When administered as a cream, the effect on menopausal symptoms is not statistically significant compared with placebo. A study in which 22 women received 390 g of Chinese yam per day for 30 days found that urinary concentrations of the genotoxic estrogen metabolite, 16-alpha-hydroxyestrone, decreased significantly by 37%, suggesting the possibility of reducing breast cancer risk, but again clinical trial data are required. Another study of postmenopausal Taiwanese women concluded that the Diascorea alata variety significantly reduced psychological symptoms, particularly anxiety, after 12 months of consumption.
Posologie
Oral: root, rhizome
50 - 390 mg
12 months
standardized extract, dry extract
Estrogenic Effects of the Extracts From the Chinese Yam (Dioscorea Opposite Thunb.) and Its Effective Compounds in Vitro and in Vivo
Effects of wild yam extract on menopausal symptoms, lipids and sex hormones in healthy menopausal women.
Comparative Analysis of Proteins With Stimulating Activity on Ovarian Estradiol Biosynthesis From Four Different Dioscorea Species in Vitro Using Both Phenotypic and Target-based Approaches: Implication for Treating Menopause
Research and Development of Proteins and Peptides With Therapeutic Potential From Yam Tubers
Estrogenic Effect of Yam Ingestion in Healthy Postmenopausal Women
Cognitive performance ✪✪✪✪✪
Preliminary clinical research shows that taking a specific wild yam extract at 50 mg per day for 12 weeks slightly improves overall measures of cognitive function and semantic fluency compared with placebo in healthy adults.
Posologie
Oral: root, rhizome
50 - 250 mg
12 - weeks
standardized extract, dry extract
Healthy aging ✪✪✪✪✪
The steroidal saponins contained in yam may exert estrogenic effects and counteract symptoms related to declines in estrogen levels due to aging. Several studies have described the pharmacological effects of diosgenin and its derivatives against various diseases such as cancer, diabetes, osteoporosis, Alzheimer's disease and stroke. Increasing experimental evidence has shown that diosgenin and its derivatives have promising therapeutic potential in several neurodegenerative and neurological disorders.
Posologie
Oral: root, rhizome
50 - 250 mg
standardized extract, dry extract
Osteoporosis ✪✪✪✪✪
Because of its estrogenic activity, yam may be beneficial in osteoporosis. It was found that yam increased bone mineral density in ovariectomized rats, but human studies are lacking. nn
Posologie
Oral: root, rhizome
50 - 250 mg
standardized extract
Diarrhea ✪✪✪✪✪
Huai Shan Yao (Chinese yam), a common staple food in China, has been used for more than 2,000 years in TCM to treat various systemic disorders. It is also used to strengthen stomach function, relieve anorexia, and treat diarrhea.nn
Posologie
Oral: root, rhizome
50 - 250 mg
powder
Properties
Estrogenic action
The chemical conversion of diosgenin, a constituent of wild yam, into estrogen, progesterone, or other steroid compounds does not occur in the human body. However, wild yam appears to have some estrogenic properties, although these properties vary by species. A wild yam extract enhances the binding of estradiol to estrogen receptors and induces transcriptional activity in estrogen-sensitive cells. In laboratory studies, evaluation of four Dioscorea species, including D. oppositifolia (Chinese yam), D. alata, D. collettii var. hypoglaucau and D. zingiberensis, found that only Dioscorea oppositifolia exhibits estrogenic effects on ovarian cells. In animal research, extract of Dioscorea oppositifolia increases levels of estradiol and follicle-stimulating hormone (FSH), and regulates the expression of estrogen receptors in the uterus. Adenosine and arbutin are thought to be the constituents responsible for these estrogenic effects. Postmenopausal women who replace 390 grams per day of wild yam (Dioscorea alata) with another staple food such as rice for 30 days show significant increases in serum estrone, sex hormone-binding globulin (SHBG), and possibly serum estradiol levels.
Usages associés
Hormone metabolism
One of the steroid saponins, diosgenin, was isolated from wild yam. Diosgenin has been commercially used to produce steroid hormones such as cortisone, estrogen, and progesterone by chemical modification in vitro. Although it has been assumed that wild yam extract is converted into DHEA (dehydroepiandrosterone) in humans, this hypothesis has not been demonstrated in humans. A small clinical study showed that diosgenin does not induce steroidogenesis resulting in increased DHEA or cholesterol. The chemical conversion of diosgenin, a constituent of wild yam, into estrogen, progesterone, or other steroid compounds would not occur in the human body. However, wild yam appears to have some estrogenic properties, although these properties vary by species. A wild yam extract enhances estradiol binding to estrogen receptors and induces transcriptional activity in estrogen-responsive cells. In animal research, extract of Dioscorea oppositifolia increases estradiol and follicle-stimulating hormone (FSH) levels and regulates the expression of estrogen receptors in the uterus. Adenosine and arbutin are thought to be the constituents responsible for these estrogenic effects.
Usages associés
Anticancer
Components of Chinese yam have shown tumoricidal activity against certain cancer cell lines, including MCF7 breast cancer cells, HepG2 hepatoma cells, CNE2 nasopharyngeal carcinoma cells, and B16 melanoma cancer cell lines. In an in vitro comparative study, wild yam root (Dioscorea villosa) was found to be the plant extract with the most potent tumoricidal activity among 374 other plant extracts.
Neurological
In animal studies, diosgenin, a constituent of yam, improves memory deficits and object recognition memory. In early clinical research, wild yam extract standardized to diosgenin slightly improved cognitive function in healthy adults.nnMany studies have shown that diosgenin and its derivatives have preventive and therapeutic effects against various neurological disorders. Animal experiments have shown that diosgenin is active in the treatment of nervous system diseases such as Parkinson's disease and Alzheimer's disease.nn
Usages associés
Gastroprotective
The 40% ethanol extract of Chinese yam has shown an ability to inhibit gastric acid secretion and to improve intestinal functions, observed by gastrointestinal transit and the presence of lactose-fermenting bacteria in the stool. nnChinese yam appears to positively influence the composition of the gut flora. Studies in rats have shown that consumption of yam powder fermented with Lactobacillus acidophilus reduced gastric lesions. Moreover, yam fermented with Lactobacillus bulgaricus showed increased protection against gastric lesions, suggesting its usefulness in yogurt production.nn
Cholagogue
Studies suggest that wild yam, particularly its component diosgenin, may have a beneficial effect on bile. Diosgenin increases the secretion of cholesterol into bile and prevents the reduction of bile flow caused by estrogens in rats. nnIt also contributes to the elimination of indomethacin and reduces the intestinal inflammation that it can cause.nn
Safe dosage
Adults 18 years and older: 50 mg - 390 mg (standardized extract)
- Decoction of dried root: 2-4 g three times a day.nn- Tincture (1:5): 2-10 mL three times a day.nn
Interactions
Médicaments
Estrogens: moderate interaction
Because yam has estrogenic properties, concurrent use with estrogens could produce additive effects.
Precautions
Hormone-sensitive disease: avoid
In vitro evidence suggests that wild yam has estrogenic and anti-estrogenic effects; however, it does not appear to affect hormone levels when used topically. nnWomen with hormone-sensitive conditions should avoid wild yam. Hormone-sensitive conditions include breast cancer, uterine cancer, ovarian cancer, endometriosis, and uterine fibroidsnn
Protein S deficiency: avoid
Patients with Protein S deficiency have an increased risk of thrombosis. Wild yam could increase the risk of thrombosis in these patients due to the potential estrogenic activity of wild yam. nn
Pregnant women: avoid
Not enough data.nn
Breastfeeding: avoid
Not enough data.nn
