Plant-Based Diets and Menopausal Hot Flashes
By Rebecca H. Allen, MD, MPH
Associate Professor, Department of Obstetrics and Gynecology, Warren Alpert Medical School of Brown University, Women & Infants Hospital, Providence, RI
SYNOPSIS: In this clinical trial, women randomized to a low-fat, vegan diet including one-half cup of cooked whole soybeans daily experienced a reduction in total hot flashes of 79% vs. 49% in the control group over 12 weeks of observation.
SOURCE: Barnard ND, Kahleova H, Holtz DN, et al. The Women’s Study for the Alleviation of Vasomotor Symptoms (WAVS): A randomized, controlled trial of a plant-based diet and whole soybeans for postmenopausal women. Menopause 2021;28:1150-1156.
This study was conducted to evaluate the effectiveness of whole soybeans and a plant-based vegan diet in reducing the frequency and severity of menopausal hot flashes. Previous studies have revealed some indication that soy (phytoestrogen) supplements can modestly reduce hot flashes, although data are limited.1 This was a randomized, controlled trial performed over 12 weeks among women with postmenopausal hot flashes. Inclusion criteria were women age 40 to 65 years, moderate to severe hot flashes at least twice a day, last menses within the preceding 10 years, and no menses in the preceding 12 months. Exclusion criteria were use of hormonal medications in the previous two months, smoking, substance abuse, history of an eating disorder, use of weight loss medications in the past six months, attempting to lose weight, body mass index (BMI) of < 18.5 kg/m2, soy allergy, and current diet already matching the study diet.
The intervention group followed a low-fat vegan diet, including consuming one-half cup of soybeans daily. Intervention participants attended weekly one-hour group sessions, received information on meal planning and food preparation (a pressure cooker was provided for the soybeans), and answered weekly questions about diet adherence. Control group participants followed their usual diet, also used a pressure cooker, and attended four one-hour group sessions. For both groups, alcohol was limited to one drink per day. Data collection was performed at baseline and at 12 weeks and included three-day dietary intake record, body weight and height, health status, medication use, physical activity, menopausal symptoms (hot flashes), and the Menopause-Specific Quality of Life (MENQOL) questionnaire.
The authors considered this a pilot study and aimed to enroll 40 participants. Women were recruited through social media and screened by phone. Ultimately, 38 women were randomized. There was no significant difference between the two groups in terms of age, race, and BMI. Mean body weight decreased by 3.5 kg in the vegan diet group vs. a 0.8-kg gain in the control group (P = 0.002). Total hot flashes decreased by 79% in the intervention group (6.2 vs. 1.3 events per seven days) compared to 49% in the control group (4.9 vs. 2.5 events per seven days; P = 0.01). Moderate-to-severe hot flashes decreased 84% in the intervention group vs. 42% in the control group (P = 0.013). From 0 to 12 weeks, 59% of intervention-group participants reported becoming free of moderate-to-severe hot flashes compared to no change in the control group (P = 0.0003). The MENQOL questionnaire showed significant reductions in all the vasomotor, psychosocial, physical, and sexual domains vs. the control group.
COMMENTARY
Hot flashes are common in the perimenopausal transition and menopause. The most effective treatment for hot flashes is systemic estrogen therapy. For women who do not want to use hormones, there are a few nonhormonal medications that have proven effective: selective serotonin reuptake inhibitors, selective serotonin-norepinephrine reuptake inhibitors, clonidine, and gabapentin.2 However, the goal of this study was to evaluate the usefulness of whole soybeans because many women are seeking nonhormonal and nonpharmacological options to treat menopausal symptoms. Phytoestrogens are plant-derived substances with estrogenic biologic activity. Examples include the isoflavones genistein and daidzein, which are found in high amounts in soybeans, soy products, and red clover. Previous studies have shown soy products may be modestly useful in treating menopausal hot flashes.1 However, current evidence has not been strong enough to recommend soy products on a routine basis.2
Barnard et al showed a vegan diet with whole soybeans reduced hot flashes significantly and almost eliminated moderate-to-severe hot flashes. The control group also experienced a decrease in hot flashes. The authors speculated this was because the control group also was aware of the vegan diet in the intervention group and possibly followed it. However, the study was limited by the small sample size and short duration. But the findings were dramatic and deserve further study. Certainly, there may be other health benefits to a plant-based vegan diet, and there is no downside to eating soybeans. Therefore, this may be an option for patients who do not want to use medications and do not find enough benefit from regular lifestyle changes, such as layering clothing, lowering ambient temperatures, and consuming cool drinks.
REFERENCES
- Franco OH, Chowdhury R, Troup J, et al. Use of plant-based therapies and menopausal symptoms: A systematic review and meta-analysis. JAMA 2016;315:2554-2563.
- The American College of Obstetricians and Gynecologists. Management of menopausal symptoms. Practice Bulletin Number 141. Published January 2014.
Women randomized to a low-fat, vegan diet including one-half cup of cooked whole soybeans daily experienced a reduction in total hot flashes of 79% vs. 49% in the control group over 12 weeks of observation.
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