AARM Reference Review
Pueraria mirifica is a Leguminoseae family herb that thrives in warm moist climates around the world. Pueraria mirifica is indigenous to Thailand, where it known by the name Kwao Kruea Khao. It has been the subject of numerous recent clinical investigations for possible benefits to menopausal women.
Pueraria mirifica contains the isoflavones puerarin and daidzein and the related phytoestrogen miroestrol. Miroestrol and deoxymiroestrol, like other phytoestrogens, act as Selective Estrogen Receptor Modulators (SERMs). As such, these compounds selectively bind to estrogen receptors and act as agonists or antagonists depending on the tissue and the physiologic circumstances. For instance, miroestrol competes with estrogen and blocks the excessive stimulation of estrogen receptors often seen with breast or endometrial cancer. On the other hand, these phytoestrogens act as estrogen agonists to support bone density, promote cardiovascular health, and to alleviate menopausal symptoms.1
Pueraria root extract is typically recommended in the treatment of menopause-related hot flashes, at a dose range of 200 mg containing 150 mcg Miroestrol twice per day. Symptom resolution of hot flashes often occurs within a few weeks of therapy.
Pueraria root extract has no known side effects at commonly prescribed doses. There are no confirmed drug interactions found in any clinical trial or quantitative systematic review.
PUERARIA SPECIES CONTAIN THE ISOFLAVONE PUERARIN
Pueraria, among other legumes, contains isoflavones known to support bone density2 and the vascular system.3 Puerarin, the major isoflavone in Pueraria, has been shown to be readily absorbed and quickly eliminated. Accordingly, dosing this herb three or more times daily might be advised, to perpetuate blood levels and maintain constant physiologic support of hormonal functions.4 In contrast to phytoestrogens such as genistein and daidzein, which may stimulate estrogen receptors in cells that are already over-expressing estrogen receptors (e.g. in estrogen-dependent cancers), puerarin has been shown to decrease estrogen receptor over-expression.5 Puerarin may thus be considered a safer option in the treatment of estrogen dependant conditions and estrogen dependent cancers.
PUERARIA ALLEVIATES MENOPAUSAL SYMPTOMS
Pueraria mirifica has been shown to alleviate vasomotor and other menopausal symptoms.6 The herb reduces FSH and LH levels in menopausal monkeys suggesting that an estrogen-like effect exerts negative feedback to pituitary gonadotrophin release.7 FSH and LH levels returned to pretreatment levels upon cessation of the Pueraria supplementation. Pueraria mirifica has also been found to decrease serum parathyroid hormone and calcium levels in aged monkeys suggesting reduced bone loss.8 Flavones from Pueraria roots were found to prevent uterine atrophy and prevent increases in total cholesterol and triglycerides that typically follow rapid declines in system-wide estrogen levels.9 This study also showed that Pueraria limits the increase in abdominal fat stores that occur in ovariectomized menopause animal models.9 A human clinical study demonstrated that Pueraria lobata, a close but less potent relative of Pueraria mirifica,10 improves cognitive parameters and attention span compared to placebo11.
PUERARIA MAY SUPPORT GENITOURINARY INTEGRITY
Loss of integrity of the vaginal and uroepithelial mucosal membranes is a common occurrence in and after menopause and can lead to vaginal dryness, dyspareunia, and an increased tendency to bladder infections and urinary incontinence. Since pharmaceutical grade hormones often have tremendous side effects on the entire body including increased risk for breast and endometrial cancer, as well as damaging effects on vasculature,12 there is an ongoing search for herbal, nutritional, and other alternative medications that maintain urinary and vaginal epithelium. Animal studies have shown Pueraria mirifica to have a supportive effect on the urinary and vaginal mucosal tissues in a manner similar to, but less powerful than estradiol.13 Pueraria has been shown to have beneficial effects on the vaginal mucosa, improving vaginal pH, dryness, and dyspareunia as well as achieving measurable estrogen-like effects on atrophic vaginal epithelia.14
PUERARIA MAY IMPROVE BLOOD LIPIDS
Menopause negatively impacts lipid metabolism as evidenced by increased occurrence of cardiovascular disease and worsening lipid profiles.15,16 Prior to menopause, women display less heart disease compared to men, but postmenopausally there is a marked change and women and men display nearly equal incidence of atherosclerosis and other cardiovascular diseases. Blood pressure, insulin resistance, and lipid profiles quickly alter to equal that seen in the male population.17 Soy isoflavones and other plants in the legume family have been reported in numerous studies to offer a protective effect on the vasculature and slow the detrimental changes to lipids and metabolism seen post-menopause.9,18
Postmenopausal women given Pueraria mirifica for two months had improved lipid profiles compared to a placebo control group. HDL increased 34% while LDL decreased 17% in the group receiving the Pueraria.19 Individual phytoestrogens were examined and miroestrol and coumestrol were both reported to act on both alpha and beta estrogen receptors while daidzein and genistein were more active on beta estrogen receptors. The researchers proposed that Pueraria phytosterol constituents enabled gene transcription in a manner that benefited lipid metabolism. Other studies have not been able to demonstrate improved blood lipids with the use of Pueraria3,11 and further investigations are warranted.
CLINICAL TRIALS SHOW PUERARIA OFFERS HORMONAL SUPPORT WITHOUT OVER-STIMULATING THE BREASTS AND ENDOMETRIAL LINNG
Another double-blind, placebo controlled human clinical trial administered several dosage strengths of Pueraria versus a placebo medication to postmenopausal women aged 45 to 60 and measured the effects on blood lipids, bone alkaline phosphatase, endometrial thickness, and breast parameters. Liver and renal blood parameters were also assessed to rule out any possible organ toxicity caused by the herb. After 24 weeks the groups receiving the Pueraria showed a significant decrease in bone alkaline phosphatase suggesting a reduction in bone resorption and turnover. No measurable changes were seen in the breasts or the endometrium in any group, suggesting that Pueraria does not have a proliferating effect on the uterine lining or breast tissue as do pharmaceutical grade estrogens.20
Another clinical pilot study found that Pueraria mirifica at either 50 mg or 100 mg a day for six months reduced perimenopausal symptoms of hot flashes and night sweats. Serum estradiol increased slightly with no detectable changes in FSH or LH levels.21 A larger follow up clinical trial compared the effects of Pueraria mirifica to conjugated equine estrogen, with and without medroxyprogesterone. There were no significant differences between treatment groups with respect to climacteric symptoms, and all participants reported some relief of vasomotor, urogenital, and psychological symptoms. There were no significant differences in FSH, LH, or serum estradiol levels between the groups, indicating that Pueraria was as effective as conventional pharmaceutical therapy.22
PUERARIA AS A SAFE ALTERNATIVE HORMONE REPLACEMENT THERAPY
Due to its numerous benefits Pueraria mirifica is considered a safe alternative to improve bone density, genitourinary epithelium, blood lipids, inflammatory markers, and general menopausal symptoms. Pueraria may be considered an effective alternative to pharmaceutical hormone replacement therapy. Furthermore, research is suggesting the safe application of Pueraria in cases of hormonal excess, hormone-dependent cancers and genetic over-expression of estrogen receptors (Fig 1), lending the plant wide utility in the general population.
References and Original Article
Please see the original journal article available here in PDF format for references: