Untitled Document
The toxicity itself seems to occur in mice and rats in a similar idea as the blood pressure reducing effects in humans, as in they occur reliably although the dose required to induce toxicity and what exactly occurs seems to vary from one study to another. This may be related to the exact molecules mediating toxicity not being known right now. For the majority of toxic effects, the lowest they have occurred is 200mg/kg in rats (2.2g dried calyx for a 150lb human). Human studies have used this dose or above with no apparent side effects though. The toxicity of these doses of Roselle need to be evaluated more.
One concern that does exist is testicular toxicity, which occurs fairly reliably at 200mg/kg or above in animals but has not been investigated in humans. Roselle appears to be anti-fertility in men, inducing abnormal sperm morphology. In females, there was a series of studies suggesting Roselle could cause abnormal (higher) birth weights in offspring with a delay of pubertal onset; for the most part these are attributed to the appetite suppressing effect causing maternal malnutrition, with no per se mechanisms harming the pup (via lactation) currently known.
Although these toxic effects can possibly be avoided by adhering to proper dosing, the amount of safety information in humans is not as expansive as would be desired; the therapeutic threshold (degree of 'safety buffer' between the active dose and toxic dose) is also lower than desirable, so possible toxic effects with overdosing Roselle is probably more relevant than other supplements.
Higher doses of Roselle do exert toxic effects, although none of these toxic effects have been reported in humans (that being said, they have not conclusively been disproven either). It would be prudent to avoid taking too much Roselle, especially since many benefits of Roselle are not dose-dependent above the lowest observable toxic dose of 2.2g/150lb human. *
