What it is
Promensil is a dietary supplement containing standardized red clover (Trifolium pratense) isoflavones. The isoflavones in red clover include genistein, daidzein, formononetin, and biochanin A. These compounds are phytoestrogens, meaning they bind weakly to estrogen receptors. This activity resembles a phyto-SERM, though the effect is weaker than prescription SERMs or the fermented soy extract in Femarelle. Novogen (now PharmaCare) manufactures it, and it is sold over the counter under DSHEA.
How well it works
The evidence for red clover isoflavones is mixed. A meta-analysis of 8 randomized controlled trials found a statistically significant reduction in daily hot flush incidence of 1.73 hot flushes per day compared to placebo (95% CI -3.28 to -0.18, p=0.029; PMID 33920485). An earlier RCT of 30 women with 5 or more hot flushes per day found a 44% reduction in hot flush frequency in the isoflavone group, with no further reduction in placebo (PMID 12161042). A crossover RCT of 109 postmenopausal women found significant reductions in depressive and anxiety symptoms (PMID 19948385). However, some individual RCTs show no significant benefit over placebo, so the evidence is less consistent than for rhapontic rhubarb (Estroven Complete) or prescription options.
Side effects and cautions
Promensil was generally well tolerated in studies, with mild gastrointestinal symptoms possible. Because red clover isoflavones bind to estrogen receptors, talk to your doctor before using it if you have a history of estrogen-dependent cancer or take prescription hormone therapy. It is a dietary supplement, not an FDA-approved drug, so it has not gone through the same safety and efficacy review as prescription medications.
Where to get it
You can buy Promensil over the counter at pharmacies, health food stores, and online without a prescription. It comes in 30 count packs. Availability is stronger in the UK and Australia than in the United States, where it may require online purchase.