Bitter yam

The Bitter yam, botanically known as Dioscorea dumetorum, belongs to the yam family (Dioscoreaceae) and is native to West Africa. It has been used for centuries in traditional African medicine, where various potent properties are attributed to it, particularly for the treatment of diabetes and neurological disorders.

What benefits does the Bitter yam offer?

Dioscorea dumetorum is used in traditional medicine for a wide variety of health concerns. Studies conducted on the plant's effects partly confirm the attributed effects; however, the studies are as always to be viewed critically and are not readily transferable.

  • Blood-sugar-lowering effects: The Bitter yam is traditionally used to lower blood sugar levels in diabetics. Studies show that it can have insulin-like effects and positively influence glucose metabolism (1, 2,3).
  • Neurological effects: Active compounds in the plant show properties that can affect neurons (4).
  • Antioxidant effects: The plant contains powerful antioxidants that can protect cells from oxidative stress and damage (2,3,4,5,6).
  • Antimicrobial effects: The tubers of the yam are possible sources of antimicrobial and antioxidant compounds, as they are rich in phenols (5,7)
  • Cholesterol-lowering effects: Studies have shown that the extract of the Bitter yam could help in controlling hypercholesterolemia, hyperlipidemia, and hyperketonemia (8)

How does the Bitter yam work?

The effects of the Bitter yam are based on various bioactive constituents, including, for example:

  • Dioscoretine: A principal alkaloid that has blood-sugar-lowering properties and supports the body's insulin balance (9,10).
  • Saponins and flavonoids: These compounds contribute to the plant's antioxidant effects (6,11,12).

Side effects and risks

Despite the health benefits, side effects can occur:

  • Toxicity: In its raw state, the plant contains toxic alkaloids that can lead to poisoning (13).
  • Gastrointestinal complaints: Excessive consumption can lead to nausea, vomiting, or diarrhea.
  • Pregnancy and breastfeeding: Use is not recommended during these phases, as there are potential risks for mother and child.

Conclusion

Dioscorea dumetorum is an interesting medicinal plant with promising effects, particularly in blood sugar regulation. Due to its potential toxicity and the still very thin body of research, however, it should only be used under medical supervision, in properly prepared form, and in appropriate doses.

Sources:

  1. Price EJ, Wilkin P, Sarasan V and Fraser PD. (2016). Metabolite profiling of Dioscorea (yam) species reveals underutilised biodiversity and renewable sources for high-value compounds. Scientific Reports. 6: 29136.
  2. Malviya N, Jain S and Malviya S. (2010). Antidiabetic potential of medicinal plants. Acta Poloniae Pharmaceutica – Drug Research. 67: 113–118
  3. Aiyedun, P. O., Sonibare, M. A., Ajiboye, C. O., Gueye, B., Paliwal, R., Albach, D. C., Nchiozem-Ngnitedem, V.-A., & Schmidt, B. (2024). Phytoecdysteroids from Dioscorea dumetorum (Kunth) Pax. and their antioxidant and antidiabetic activities. Fitoterapia, 177, 106103. https://doi.org/10.1016/j.fitote.2024.106103
  4. Celestine, U., Onoja, S., & Maxwell, E. (2015). Experimental evaluation of analgesic and antioxidant effects of hydromethanolic extract of Dioscorea dumetorum tuber. Journal of Advances in Medical and Pharmaceutical Sciences, 3(3), 131-137. https://doi.org/10.9734/JAMPS/2015/18117
  5. Sonibare MA and Abegunde RB. (2012). In vitro antimicrobial and antioxidant analysis of Dioscorea dumetorum (Kunth) Pax and Dioscorea hirtiflora (Linn.) and their bioactive metabolites fromNigeria. Journal of Applied Biosciences. 51: 3583–3590.
  6. Ukom AN, Ojimelukwe PC, Ezeama CF, Ortiz DO and Aragon I. (2014). Phenolic content and antioxidant activity of some under-utilized Nigerian yam (Dioscorea spp.) and cocoyam (Xanthosoma maffa (scoth)) tubers. IOSR Journal of Environmental Science, Toxicology and Food Technology. 8: 104–111.
  7. Kumar S and Jena PK. (2017). Tools from Biodiversity: Wild Nutraceutical Plants. Ed: James N Furze et al.: Identifying Frontier Research Integrating Mathematic Approaches to Diverse Systems / Sustainability. Springer, Switzerland. DOI: 10.1007/978-3-319-43901-3-9.
  8. Mckoy, M.-L., Thomas-Brown, P.-G., Asemota, H., Omoruyi, F., & Simon, O. (2014). Effects of Jamaican bitter yam (Dioscorea polygonoides) and diosgenin on blood and fecal cholesterol in rats. Journal of Medicinal Food, 17(9), 976–982. https://doi.org/10.1089/jmf.2013.0140
  9. Price EJ, Wilkin P, Sarasan V and Fraser PD. (2016). Metabolite profiling of Dioscorea (yam) species reveals underutilised biodiversity and renewable sources for high-value compounds. Scientific Reports. 6: 29136.
  10. Sonibare MA and Abegunde RB. (2012). In vitro antimicrobial and antioxidant analysis of Dioscorea dumetorum (Kunth) Pax and Dioscorea hirtiflora (Linn.) and their bioactive metabolites from Nigeria. Journal of Applied Biosciences. 51: 3583–3590
  11. Chan, K. W., Iqbal, S., Khong, N. M. H., Ooi, D.-J., & Ismail, M. (2014). Antioxidant activity of phenolics–saponins rich fraction prepared from defatted kenaf seed meal. LWT - Food Science and Technology, 56(1), 181–186. https://doi.org/10.1016/j.lwt.2013.10.028
  12. Mohammadi, N., dos Santos Lima, A., Azevedo, L., & Granato, D. (2024). Bridging the gap in antioxidant activity of flavonoids: Correlating the oxidation of human plasma with chemical and cellular assays. Current Research in Food Science, 8, 100714. https://doi.org/10.1016/j.crfs.2024.100714
  13. Joob, B., & Wiwanitkit, V. (2014). Asiatic bitter yam intoxication. Asian Pacific journal of tropical biomedicine, 4(Suppl 1), S42. https://doi.org/10.12980/APJTB.4.2014C429