A new study found that roselle (Hibiscus sabdariffa) may help treat kidney stones via uricosuric activity.
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.
Kidney stones, also called renal calculi, urolithiasis or nephrolithiasis, usually develop when the urine becomes too concentrated. As a result, minerals and other substances in the urine form hard crystals in the kidneys. Over time, these crystals may combine to form a small, hard mass or stone.
There are four types of kidney stones that can develop: calcium oxalate stones, struvite stones, uric acid stones and cystine stones.
Calcium stones are the most common type of kidney stones, accounting for 80 percent of cases. They develop when there are high levels of calcium and oxalate in the blood. Patients who consume excessive amounts of vitamin D or who have overactive thyroids may have high levels of calcium in the blood. Patients who consume large amounts of oxalic acid or undergo intestinal bypass surgery may have high levels of oxalate in the blood.
Struvite stones are usually caused by chronic urinary tract infections. The bacteria that cause these infections release enzymes that increase the amount of ammonia in the urine. This excess ammonia may form large, sharp stones that may damage the kidneys.
Uric acid is a byproduct of protein metabolism. Uric acid stones are usually caused by a cancer treatment called chemotherapy. They may also develop in patients who eat high-protein diets. Some patients are genetically predisposed to develop uric acid stones.
Cystine stones develop in patients who have an inherited disorder called cystinuria. This disorder causes the kidneys to release too many amino acids. The excess amino acids then form stones.
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.