Menopause is a natural part of the healthy aging process in women and typically starts around the age of 50. Unfortunately, menopause is often associated with unwanted complaints that can impact a woman’s quality of life, such as hot flashes. Emerging research suggests that plant compounds called phytoestrogens may support estrogen homeostasis and help diminish mild hot flashes caused by menopause. 

Hot flashes are characterized by a sudden sensation of warmth across the chest, neck, and face, accompanied by flushing and sweating. Hot flashes affect an estimated 85% of menopausal women and can last for months or even years. It is estimated that 65% of women complain of hot flashes for more than two years and 36% for more than five years. 

The exact pathophysiology of hot flashes is still being investigated. However, the primary cause is believed to be a dysfunction of the central thermoregulatory centers due to decreased estrogen status during menopause. The withdrawal of estrogen, rather than low circulating estrogen levels, is associated with hot flashes. 

Phytoestrogens can be found in plant-based foods like flaxseeds, beans, berries, broccoli, and garlic. Phytoestrogens, such as genistein and lignans, are structurally similar to the endogenous estrogen 17β-estradiol, allowing them to bind to estrogen receptor (ER) transcription factors in the body and modulate their activation (with a higher affinity for ERβ receptors). It is important to note that phytoestrogens are 100 to 1,000 times weaker in potency and activation of ERs compared to endogenous estradiol. They can potentially help promote estrogen homeostasis by acting as either agonists or antagonists depending on factors like target tissue, ER type, and endogenous estrogen concentration.

Genistein, an isoflavone phytoestrogen, has demonstrated the potential to diminish mild hot flashes caused by menopause. In a 12-month, prospective, randomized, double-blind, placebo-controlled study, postmenopausal women (n = 247) who were supplemented with 27 mg of genistein twice daily experienced a 56.4% reduction in the mean number of hot flashes and approximately a 40% reduction in the severity of hot flashes. Another study (n = 84) observed that women who consumed genistein (30 mg/day for 12 weeks) experienced a  statistically significant 51% reduction in the number of hot flashes compared to a 30% decrease in the placebo group.

Spruce lignans are phytoestrogens derived from the knot wood extract of Norwegian spruce (Picea abies) that may promote estrogen homeostasis. Postmenopausal women (n = 22) administered 72 mg/day of spruce lignans (as HMRlignan®) for eight weeks experienced a statistically significant 50% reduction in the weekly mean number of hot flashes at week eight compared to baseline. Additionally, when assessing the frequency of severe hot flashes, the women demonstrated a statistically significant reduction of 79% at week four and 80% at week eight compared to baseline. 

Estrogen status undergoes fluctuations during menopause and eventually declines and stabilizes post-menopause. This pattern is associated with mild hot flashes during the menopausal transition. While more research is needed, phytoestrogens have the potential to support menopausal women who are experiencing mild hot flashes by promoting estrogen homeostasis.

By Danielle Moyer, MS, CNS, LDN