According to Dr. Hana Kahleova, director of clinical research at the Physicians Committee for Responsible Medicine and lead author of this study, one of the reasons she wanted to study the effect of a vegan diet on hot flashes is because obesity is a risk factor for hot flashes.

“Research, including our own, shows that a vegan diet promotes weight loss and can help fight obesity,” Dr. Kahleova told Medical News Today. “A vegan diet also avoids meat and dairy products, which are high in saturated fat and compounds called advanced glycation end-products, both of which cause inflammation that can contribute to hot flashes.”

“Also, some research shows that women who have hot flashes may be at increased risk of heart disease and breast cancer, and a vegan diet can help lower the risk of both,” she added.

Although estrogen and estrogen-progestin medications can be used to treat hot flashes, Dr. Kahleova said they have been shown to increase the risk of breast cancer and cardiovascular problems.

“Vegan diets, on the other hand, can reduce these risks, and research shows that soy products are associated with a reduction in breast cancer risk,” she added.

For this study, Dr. Kahleova and her team used data from 84 postmenopausal women participating in the Women’s Study for the Alleviation of Vasomotor Symptoms (WAVS) trial. The participants reported having two or more moderate to severe hot flashes every day.

Study participants were randomly asked to either follow a low-fat vegan diet that included a half-cup of cooked soybeans a day, or to just continue with their normal diet for 12 weeks.

A subset of 11 participants were asked to provide stool samples for a gut microbiome analysis both before the start of the study and after being on a vegan diet for 12 weeks.

Scientists found changes in the species of bacteria in the gut microbiome of participants who followed the vegan diet.

For example, more of the bacteria Porphyromonas and Prevotella corporis were found in those who followed the vegan diet, and these were linked to a reduction in severe hot flashes, including after adjustment for body mass index (BMI), a calculation that infers adiposity.

At the same time, researchers found a decline in the number of the bacteria Clostridium asparagiforme in the gut microbiome, which was associated with a decrease in total severe and severe night hot flashes.

Dr. Kahleova explained:

All told, researchers found that study participants who consumed the low-fat vegan diet with added soy decreased their overall hot flashes by 95% compared to those who continued their usual diet.

Researchers also reported the vegan diet led to a 96% decrease in moderate to severe hot flashes, as well as a reduction in daytime hot flashes by 96% and nighttime hot flashes by 94%.

And study participants following the vegan diet also lost an average of 6.4 pounds (lbs) over the 12 weeks.

“Based on what we already know about the benefits of a low-fat vegan diet, we expected that it would change the composition of gut bacteria and help decrease hot flashes,” Dr. Kahleova said. “In addition to confirming our expectations, our study is the first, to our knowledge, to find that reductions in the abundance of the bacteria Porphyromonas, Prevotella corporis, and Clostridium asparagiforme may help reduce severe hot flashes.”

“These findings are the latest example of how eating a vegan diet plays a pivotal role in fighting diet-related conditions and diseases and maintaining good health as we age,” she added.

MNT also spoke with Monique Richard, a registered dietitian nutritionist, owner of Nutrition-In-Sight, and national media spokesperson for the Academy of Nutrition Dietetics, about this study.

Richard commented that because only 11 participants’ stools were analyzed during the study, it is a very small sample even though the percentage of hot flash frequency was significant at 95%.

“It is a very small sample size to pull from and make a conclusive statement/headline,” she noted. “It would be important to see this study replicated in larger sample sizes. Looking at vegans, vegetarians, and omnivores each as a population, measuring fiber in each group, or possibly seeing if simply adding the 1/2 cup soy a day to each sample size would elicit the same type of outcomes and similar microbiome profiles would be interesting.”

Richard said previous research shows isoflavones in soy may contribute to a reduction in hot flashes possibly from the estrogen-like constituents of the plant, but they are not able to ascertain direct cause and effect and some of the studies are inconsistent and inconclusive.

“What we do know is that soybeans are a great source of protein, fiber, phytochemicals, and beneficial nutrients that also feed our ‘good’ gut bugs and provide many protective benefits,” she continued.

“Literally feeding the gut microbiome with a plant-centric diet of whole foods tends to be beneficial in numerous ways and also alters the gut microbiome configuration and how those bacteria interact with hormones, enzymes, proteins, and metabolic reactions. This in turn affects our general well-being, tolerance, and symptomatic consequences of menses, illness, disease management and so much more.”

– Monique Richard

When it comes to using diet to help reduce menopausal hot flashes, Richard said because each individual has unique needs and these specific transitional times in a woman’s life bring additional factors to consider, it is important to meet with a registered dietitian nutritionist to assess overall dietary needs, nutrient needs, possible supplement recommendations, and lifestyle modifications.

“Overall, adequate sources of lean protein, fiber — both soluble and insoluble — omega-3 fatty acids, possibly a reduction in saturated fats, caffeine, alcohol, refined carbohydrates, and added sugars may also be beneficial to preserving bone mass, staving off common symptoms and supporting energy, mood and managing weight fluctuations,” she detailed.

“In addition to a diverse, colorful, varied diet with fruits, nuts, vegetables, legumes, fermented foods, seeds, and healthy fats, weight resistance training, sleep hygiene, and hydration status should be assessed and modified as necessary,” Richard continued. “Working with a registered dietitian nutritionist and healthcare team may help an individual mitigate and alleviate some of the uncomfortable and inconvenient symptoms during this season of life.”