The roots of Pueraria mirifica are cherished in Thailand for their alleged anti-aging and antioxidant properties. People take it for menopausal complaints, cognitive effects, and heart and bone health. However, limited evidence supports most of this herb’s traditional uses. Read on to find out more about the purported benefits and side effects of Pueraria mirifica.
What is Pueraria mirifica?
Also known as White Kwao Krua, Pueraria mirifica is a medicinal plant that originates in Thailand. People in Thailand have thought that this herb has anti-aging properties for centuries 
Pueraria mirifica is a woody plant that climbs as it grows. The real interest is in the roots, which are large tubular structures that contain many starch granules and are white on the inside .
However, Pueraria mirifica supplements have not been approved by the FDA for medical use. Supplements generally lack solid clinical research. Regulations set manufacturing standards for them but don’t guarantee that they’re safe or effective. Speak with your doctor before supplementing.
The roots contain phytoestrogens, which are plant compounds that mimic the female hormone estrogen. At least 17 phytoestrogens have been identified, which can be categorized into isoflavonoids, coumestans, and chromenes. The most common phytoestrogen in Pueraria mirifica is miroestrol .
The exact phytoestrogen content of the plant depends on its location and variety .
The phytoestrogen content also depends on the age of the plant. Older plants have more consistent and substantial phytoestrogen content. One study determined plants that were 3 years old were best for use as supplements .
Also, plants harvested in the summer had a much higher phytoestrogen content than in the rainy and winter seasons .
In Pueraria mirifica herbs, phytoestrogens are found in the leaves, stems, and roots. However, the phytoestrogen content is much larger in the roots .
Mechanism of Action
Scientists hypothesize that the phytoestrogen content of Pueraria mirifica mimics the effects of the hormone estrogen .
Purported Health Benefits of Pueraria mirifica
There is insufficient evidence to support the use of Pueraria mirifica for any of the below listed uses.
Remember to speak with a doctor before taking Pueraria mirifica supplements. Pueraria mirifica should never be used as a replacement for approved medical therapies.
1) Menopausal Symptoms
In a small clinical trial of 5 volunteers, an oral supplement of P. mirifica reduced symptoms of menopause. Patients received a 200 mg daily dose for 4 months, followed by 200 mg every 2 days. These patients showed decreases in menopausal symptoms, including :
- Hot flashes
- Sleep disorders
- Skin dryness
- High blood cholesterol levels
- Absent Periods
- Irregular periods
In one study (DB-RCT) of 71 healthy postmenopausal women, the women received either a placebo or 20 mg, 30 mg, or 50 mg of Pueraria mirifica supplement. Pueraria mirifica was effective at decreasing vaginal dryness .
Despite these promising findings, large-scale clinical trials are needed to confirm the effectiveness and safety of this plant for menopausal symptoms.
2) Bone Health
Limited evidence supports the use of Pueraria mirifica for bone health in humans.
We identified only one clinical trial (DB-RCT) of 71 postmenopausal women. In this study, 24 weeks of P. mirifica supplements improved bone structure. The phytoestrogens in the plant are hypothesized to slow bone deterioration .
Additional research is needed.
3) Heart Health
According to some theories, postmenopausal women have a decreased ability to process fats. This can lead to fat deposits in arteries and veins, which increase heart disease risk. In a study (DB-RCT) of 19 postmenopausal women, oral ingestion of Pueraria mirifica powder improved heart function. After 2 months of treatment, the women had a better ability to processing fats and improved heart function .
In rabbits, P. mirifica improved heart function and reduced heart disease risk .
We can’t draw any conclusions from a single clinical study that had a very small sample size. Further studies are needed.
4) Antioxidant Activity
In mice, miroestrol extracts from Pueraria mirifica improved antioxidant activity and had beneficial effects on the antioxidant activities in the liver. Pueraria mirifica may be beneficial as a replacement for hormone therapy to increase antioxidant activities .
The antioxidant effects of this herb have not been investigated in humans yet.
Effects on Brain Function
Though people traditionally take P. mirifica to improve memory, the effects of this plant on brain function in humans is completely unknown.
In rats, Pueraria mirifica supplementation increased the strength of signals sent between neurons. This means that it can increase the effectiveness and efficiency of brain function .
In another rat study, early treatment with P. mirifica decreased brain function impairment .
In mice, pretreatment of a high dose of P. mirifica 4 weeks before treatment of a tumor decreased tumor development. Another rat study suggested that pretreatment of P. mirifica prevented the development of breast cancer .
In cells, purified phytoestrogens of Pueraria mirifica killed breast cancer cells and stopped them from spreading. However, phytoestrogens are toxic to cells. When given a carcinogen, high levels of this plant promoted breast cancer in rats [17, 18].
Proper safety trials on this plant are lacking. Its effects on cancer risk in humans are completely unknown.
Using Pueraria mirifica
Pueraria mirifica is most commonly taken orally, usually in pill form. Traditionally, pills are made of finely ground root powder, but some commercial brands use the root extract .
In mice, P. mirifica did not have toxic effects when the supplement was given to them in a powder form. When treated with a proportional dose to ones taken by humans, no abnormalities were found. But, when the dose was substantially increased, they found abnormalities in the blood .
Limitations and Caveats
Few human clinical trials have been conducted. The efficacy and long-term safety of Pueraria mirifica are unknown.
One user said she had a quick decrease in her menopausal symptoms.
Many users have claimed that Pueraria mirifica has enlarged their breasts.
One user said that after taking Pueraria mirifica they began to shake and felt weak as if they needed to eat something.
Another user said that after taking a Pueraria mirifica supplement, they felt weak and their heart hurt.
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