Red clover (Trifolium pratense), is indeed a phytoestrogen.
It is useful for prostate problems, as any estrogen would be for that purpose.
Red clover was traditionally used to treat asthma, pertussis, cancer, and gout. Results are mixed and totally anecdotal.
"Clinical" results are not a firm basis for belief in- or usage of any drug. Time related trials and years of actual observation in a clinical node are required for any derived results to hold accuracy. Such clinical results are qualified by only needing two or more observed results, and in short are not likely the whole results necessary for the efficacy or usefulness of a drug, essence or therapeutic.
In modern times, isoflavone extracts of red clover are most often used to treat menopausal symptoms, as an alternative hormone replacement therapy, for high cholesterol, or to prevent osteoporosis.
However, at this time, there are no high-quality human studies supporting the use of red clover for any medical condition.
Here's a real caveat, however.....
Based on laboratory studies, red clover may interfere with the way the liver processes some drugs using an enzyme called cytochrome P450 3A4. This is the SAME reaction by the liver caused by grapefruit!
As a result, the levels of these drugs may be increased in the blood, and may cause increased effects or potentially serious adverse reactions. Patients using any medications should check the package insert and speak with a healthcare professional or pharmacist about possible interactions.
First-pass filtering of drugs are part of the prescribed values to most drugs, and if the liver has been turned OFF, then the first-pass results are not enacted and severe overdoes of the prescribed (and un-prescribed too!) may occur.
Be careful!
Just thought you'd like to know.