They found that BP drugs helpfully accelerate loss of fluids, but also deplete important chemicals, including potassium, so that those who take them are generally advised to eat bananas and other potassium-rich foods to counteract the effect.
"Previous studies have told us that when patients take diuretic thiazides, potassium levels drop and the risk of diabetes climbs to 50 percent," said lead researcher Tariq Shafi, M.H.S., of the Department of Nephrology at Johns Hopkins University School of Medicine.
"Now, for the first time, we think we have concrete information connecting the dots," he added.
During the study, the researchers examined the data from 3,790 nondiabetic participants in the Systolic Hypertension in Elderly Program (SHEP).
Half of the subjects were treated with chlorthalidone and half with a fake drug.
They found that for each 0.5 milliequivalent-per-liter (MEq/L) decrease in serum potassium, there was a 45 percent increased risk of diabetes.
"This study shows us that as long as physicians monitor and regulate potassium levels, thiazides could be used safely, saving patients thousands of dollars a year," said Shafi.
"It could be as simple as increasing the consumption of potassium-rich foods like bananas and oranges and/or reducing salt intake, both of which will keep potassium from dropping," he added.
The study is published online in the journal Hypertension.