By Michaela Carrick, BSc Human Nutrition
What are hot flashes?
Vasomotor symptoms, better known as hot flashes and night sweats, are sudden feelings of warmth in the body, usually experienced most intensely in the face, neck, or chest. Hot flashes are one of the most common symptoms of menopause with up to 40% of menopausal women experiencing them (1). Hot flashes are caused by the change in hormones during menopause. Diet may be able to reduce their frequency or severity.
How can diet affect hot flashes?
Back in the 1980s, women living in Japan reported hot flashes less commonly than women living in Western countries (2). The traditional Japanese diet was mainly plant-based, with rice, vegetables, and soy-based products eaten regularly. As the Japanese diet became more Westernised, reporting of hot flashes doubled (3)! This increase suggested diet may play a role in the occurrence of hot flashes.
How might soy help?
- Soy products contain isoflavones which have a similar chemical structure to the human hormone oestrogen. Isoflavones cannot replace the oestrogen that is decreased during menopause but may help reduce menopausal symptoms like hot flashes.
- In some women, bacteria in the gut can metabolise certain types of isoflavones, increasing their effects. The soy isoflavone daidzein can be metabolised into a compound called equol which can bind to oestrogen receptors. This binding produces an oestrogen-like effect, reducing the frequency of hot flashes. Therefore, having a healthy microbiota may help enhance the benefits of soy (4). In general, a more diverse gut microbiota is a healthier one. As plant-based diets can quickly change the gut microbiota and increase the bacterial diversity, this type of diet may reduce symptoms of menopause like hot flashes (5).
New Research Alert: Women’s Study for the Alleviation of Vasomotor Symptoms (WAVS)
In an exciting study just published, (the WAVS study), researchers investigated if a low-fat plant-based diet with soybeans could affect the frequency and severity of hot flashes in menopausal women (6). Thirty-eight women experiencing hot flashes were prescribed a low-fat vegan diet including ½ cup (86g) of cooked soybeans daily, or assigned to a control group that made no diet changes. For 12 weeks women recorded their hot flashes and other menopausal symptoms.
The frequency and severity of hot flashes decreased in women following the low-fat plant-based diet with soybeans. By the end of the 12-week period, 59% of women reported becoming free of moderate and severe hot flashes! Psychological, physical, and sexual symptoms also decreased.
While this study adds to the evidence of a role of diet in menopausal symptoms, it does not confirm that soybeans or any other specific food alone can reduce hot flashes. We need to remember that this trial was done alongside a low-fat, plant-based diet.
So how much soy would you need to eat to make a difference?
Eating about 50mg of soy isoflavones daily could reduce the frequency and severity of hot flashes (7). You can reach this 50mg amount by eating two servings of soy products a day.
If you would like to include more soy in your diet, here are some tips
- Swap the meat or chicken in stir-frys with cubes of tofu. Marinating tofu before cooking can help it become more flavourful.
- Order edamame (soy beans) or miso soup with tofu as a starter when eating at Asian restaurants.
- Use soy milk in teas/coffees and with breakfast cereals. Check food labels on soy milk to be sure they have added calcium and vitamin D.
- Blend silken tofu into smoothies or desserts like cheesecakes or puddings.
- Add soybeans to salads or main dishes like chilli, stews, or casseroles.
References
1. Sussman M, Trocio J, Best C, Mirkin S, Bushmakin AG, Yood R, Friedman M, Menzin J, Louie M. (2015). Prevalence of menopausal symptoms among mid-life women: findings from electronic medical records. BMC Womens Health.
2. Lock M. Menopause: lessons from anthropology. Psychosom Med 1998;60:410-419.
3. Melby MK. Vasomotor symptom prevalence and language of menopause in Japan. Menopause 2005;12:250-257.
4. Setchell KD, Cole SJ. Method of defining equol-producer status and its frequency among vegetarians. J Nutr 2006;136:2188-2193.
5. Kahleova H, Rembert E, Alwarith J, et al. Effects of a low-fat vegan diet on gut microbiota in overweight individuals and relationships with body weight, body composition, and insulin sensitivity. A randomized clinical trial. Nutrients 2020;12:2917.
6. Barnard ND, Kahleova H, Holtz DN, Del Aguila F, Neola M, Crosby LM & Holubkov R. (2021). 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.
7. Taku K, Melby MK, Kronenberg F, Kurzer MS, & Messina M. (2012). Extracted or synthesized soybean isoflavones reduce menopausal hot flash frequency and severity: systematic review and meta-analysis of randomized controlled trials. Menopause, 19(7), 776-790.
