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New research suggests that a low fat, plant-based diet rich in soy may help reduce hot flash symptoms and promote weight loss. Kelvin Murray/Getty Images
  • A new study suggests that a low fat, plant-based diet rich in soy is as effective as hormone replacement therapy (HRT) for reducing hot flashes.
  • The 12-week trial found that a plant-rich diet reduced moderate to severe hot flashes by 88%.
  • The diet may have also helped women lose 8 pounds on average and improved their quality of life.
  • Some experts say the study isn’t robust enough and that HRT is still the best option for reducing severe hot flashes.
  • More research is needed to determine the impact of diet on reducing menopausal symptoms like hot flashes.

A recent study reported that a plant-based, soy-rich diet could alleviate menopausal symptoms with the same effectiveness as hormone replacement therapy (HRT).

The Women’s Study for the Alleviation of Vasomotor Symptoms (WAVS) trial found that this food-based approach reduced moderate to severe hot flashes by 88%. HRT has been shown to improve these symptoms by 70%–90%.

Moreover, trial participants lost an average of 8 pounds during the 12-week study.

Lead researcher Dr. Neal Barnard, president of the Physicians Committee for Responsible Medicine and adjunct professor at the George Washington University School of Medicine, said in a news release:

“We do not fully understand yet why this combination works but it seems that these three elements are key— avoiding animal products, reducing fat, and adding a serving of soybeans. Our results mirror the diets of places in the world, like pre-Westernized Japan and modern-day Yucatán Peninsula, where a low fat, plant-based diet including soybeans is more prevalent and where postmenopausal women experience fewer symptoms.”

These findings were recently published in Menopause: The Journal of the North American Menopause Society.

Vasomotor symptoms include recurrent hot flashes, night sweats, and blood pressure fluctuations.

Medical News Today discussed this study with Dr. G. Thomas Ruiz, the obstetrics and gynecology lead at MemorialCare Orange Coast Medical Center in Fountain Valley, CA. He was not involved in this research.

Dr. Ruiz explained that vasomotor symptoms arise primarily from changes in the hypothalamic-pituitary-ovarian axis, which regulates sex hormone secretions.

The hypothalamus, located in the center of the brain, helps control the internal thermostat.

Fluctuating and decreasing hormone levels during menopause cause disruption in the hypothalamus. Hot flashes happen as the brain area is trying to reset its temperature, Dr. Ruiz shared.

Dr. Barnard and his research team recruited postmenopausal women ages 40 to 65 years for a parallel-design study in September 2020 and February 2021.

Out of 1,662 respondents, 71 remained for the final data analysis.

An intervention group followed a low fat, vegan diet with half a cup of cooked, nongenetically modified soybeans a day for 12 weeks. A control group made no dietary changes.

Both groups took a vitamin B12 supplement daily and were asked not to take any other supplements, change medications, or exercise regimens.

A mobile application recorded the frequency and severity of hot flashes.

Participants completed the Menopause-Specific Quality of Life survey to record vasomotor, physical, psychosocial, and sexual symptoms.

Why limit healthy fats?

The study’s recommended diet was partially inspired by a traditional Japanese diet emphasizing plant-based foods, soy products, and low amounts of oils.

MNT asked Dr. Barnard about limiting even “healthy” oils and fats, such as nuts and avocados:

“The fat in nuts and avocados is healthier than the fat in dairy products and meat. The former are low in saturated fat, and the latter are loaded with it. But we often reduce fat of all kinds in our research studies. Oils and fats — ‘good’ or ‘bad’ — tend to interfere with weight loss [and] loss of excess weight seems to help with hot flashes.”

“Oils and fats modify estrogen activity. During the study, we did find that those women who carefully avoided oily foods seemed to have faster benefits,” Dr. Barnard added.

The intervention diet may have resulted in significantly reduced menopausal symptoms.

The total hot flash frequency in the fall cohort (September 2020) dropped by 78% in the intervention group and decreased by 39% in the control group.

Moderate to severe hot flashes in the spring cohort (February 2021) intervention group fell by 88%, while the control saw a decrease of 34%.

Women with seven or more hot flashes per day at the start of the study experienced a 93% reduction in symptoms in the intervention group. The control group had 36% fewer symptoms at the end of the study.

The researchers found that reducing fat consumption and increasing fiber intake correlated with reduced severe hot flashes.

The intervention group members lost an average of 7.93 pounds, while the control group participants lost one-half a pound on average.

Dr. Ruiz saw the cohort study design as a disadvantage. He argued that a double-blind study is “really the only way to come up with an observation that may be medically meaningful.”

“A healthy diet will help you overall because it will make [you] feel better in general,” Dr. Ruiz said, adding that people who regularly eat healthily are also more likely to exercise as well.

Dr. Ruiz added that the study’s small sample increased the possibility of a “huge placebo effect.”

The study’s authors did admit that placebo effects could not be ruled out. It should also be noted that several of the study’s co-authors received compensation from the Physicians Committee for Responsible Medicine for their contributions.

“When the results are very strong and consistent, a smaller sample can prove the effect,” Dr. Barnard said.

“In this case, the 88% drop in moderate-to-severe hot flashes is enormous, and statistically, there is less than 1 [in] 1000 that this is due to chance. Our sample of 84 women was more than double the size needed to prove the effect.”

Dr. Barnard hopes that future investigations will assess this study’s dietary approach for other conditions that cause hot flashes.

For instance, he said that people with breast cancer or prostate cancer deal with hot flashes. To date, they have limited options for relief.

“In both cases, a low fat vegan diet, plus soybeans, would be exactly the diet they should have clinically,” Dr. Barnard said.

Dr. Ruiz has observed that most women experience mild to moderate hot flashes, and some individuals don’t have symptoms at all.

According to Dr. Ruiz, HRT is still the best treatment for women with severe vasomotor symptoms.

“The FDA-authorized prescribing information for any HRT preparation lists serious risks,” Dr. Ruiz said.

“For estrogen alone, the listed risks include endometrial cancer, stroke, deep vein thrombosis, and dementia. For estrogen and progestin combinations, the risks include breast cancer, stroke, deep vein thrombosis, dementia, and myocardial infarction. A low fat vegan diet plus soybeans is safe and effective, and all the ‘side-effects’ are good ones [such as] weight loss and lower cholesterol.”

– Dr. Ruiz, OB-GYN