The popular zobo drink made from the calyx (flower part) of roselle (Hibiscus sabdariffa) has been successfully used in traditional medicine to treat various diseases such as cough, hypertension, stomach disorders, loss of appetite, upper respiratory congestion, nerve and heart disorders and menstrual difficulties. But recent studies suggest that although it could be used to reduce the risk of kidney damage in diabetics, high doses could lead to kidney damage. CHUKWUMA MUANYA writes.
CAN drinking high doses of the popular zobo drink lead to kidney damage? Results of a recent study suggest that aqueous extract of Hibiscus sabdariffa (HSE) has no harmful effect on the liver but when consumed in high doses could be harmful to the kidney. “Further research aimed at identifying the chemical composition and potential toxic agent(s) in HS is recommended,” the researchers wrote.
Commonly called zobo or roselle in Nigeria, Hibiscus sabdariffa belongs to the plant family malvaceae.
The study titled: “Toxicilogical effects of aqueous extract of Hibiscus Sabdariffa on the liver and kidney,” was published in Journal of College of Medicine.
The aim of the study is to show the effect of graded doses of aqueous extract of HS on major excretory organs (liver and kidney) of albino Wistar rats. This may be helpful in determining the safety or otherwise of its consumption at different concentrations.
The researchers wrote: “There were no significant changes in the histology of the liver throughout the period of HS administration in all the groups. However, there were significant histological changes in the kidney, which were more pronounced at higher doses (80 and 160mg/kg). There was shrinkage of glomerular tuft, increase in urinary pole, increase in size of tubular lumen and tubular damage. These effects were more marked as the duration of administration of the extract progressed with greatest effect observed at 12th week.”
Another study found that Hibiscus sabdariffa might help treat kidney stones via uricosuric activity. The study titled: “Uricosuric effect of Roselle (Hibiscus sabdariffa) in normal and renal-stone former subjects,” was published in Journal of Ethnopharmacology.
Uricosuric agents are used to lower the uric acid level in the blood and to prevent the formation of uric acid crystals in the joints and kidneys. These drugs are often used to treat gout, a disease in which uric acid crystals deposit in joints and cause pain. By decreasing plasma uric acid levels, these drugs decrease the deposition of crystals in joints, eventually decreasing inflammation and thereby reducing the pain of gout.
Researchers from Thailand conducted a study with nine subjects with no history of kidney stones and nine with a history of kidney stones. A cup of tea made from 1.5 grams of dry roselle was provided to subjects twice daily (morning and evening) for 15 days.
After taking the tea, both groups showed increases in oxalate and citrate. In the non-kidney stone group, increases in uric acid excretion and clearance were observed. In the patients with kidney stones, both uric acid excretion and clearance were significantly increased.
The study authors concluded that roselle has a uricosuric effect and they suggested that the chemical constituents exerting this effect should be identified.
Also, researchers have shown that aqueous (water) extracts of HSE is capable of reducing lipid peroxidation, increasing catalase and glutathione activities significantly in diabetic kidney, and decreasing the plasma levels of triglyceride, low-density lipoprotein (LDL) and increasing high-density lipoprotein (HDL) value.
