By Rebecca H. Allen, MD, MPH, Editor
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% compared to 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; Jul 12. doi: 10.1097/GME.0000000000001812. [Online ahead of print].
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 found some indication that soy (phytoestrogen) supplements can modestly reduce hot flashes, although data are limited.1 This is a randomized controlled trial performed over 12 weeks among women with postmenopausal hot flashes. Inclusion criteria were women 40 to 65 years of age, 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) < 18.5 kg/m2, soy allergy, and current diet already consisting of the study diet. The intervention group followed a low-fat vegan diet and was provided with soybeans to consume one-half cup per day. Intervention participants attended weekly one-hour group sessions and were given information on meal planning and food preparation (a pressure cooker was provided for the soybeans) and were asked weekly about adherence to the diet. Control group participants followed their usual diet, also were given 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 a total of 40 participants. Women were recruited through social media and screened by telephone. 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 compared to 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 compared to 42% in the control group (P = 0.013). From 0 to 12 weeks, 59% (10/17) 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 compared to the control group.
COMMENTARY
Vasomotor symptoms, or 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.
This study was sponsored by the Physicians Committee for Responsible Medicine, a nonprofit organization that promotes plant-based diets for preventive medicine and conducts clinical research in this area. 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 that 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
This study showed that a vegan diet with whole soybeans (one-half cup per day) 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 also 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 eating soybeans does not have a downside. 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. https://www.acog.org/clinical/clinical-guidance/practice-bulletin/articles/2014/01/management-of-menopausal-symptoms
