Randomised trial, 2005
Do soy isoflavones reduce premenstrual syndrome symptoms?
Soy isoflavones reduced specific PMS symptoms like headache, breast tenderness, cramps, and swelling better than placebo. However, overall PMS improved on both soy and placebo, showing the placebo effect is strong. The true benefit of soy beyond placebo is modest.
What they did
Double-blind, placebo-controlled, crossover study over 7 menstrual cycles. 23 women aged 18-35 with confirmed PMS consumed isolated soya protein containing 68 mg per day of soy isoflavones for two menstrual cycles, then switched to milk protein placebo for two cycles. Symptoms were measured throughout.
What they found
Overall PMS severity and physical symptoms improved on both soy isoflavones and placebo compared to baseline. Specific symptoms improved more with soy than placebo: headache, breast tenderness, cramps, and swelling were all significantly reduced with soy. Blood levels of genistein and daidzein increased following soy isoflavone consumption.
What it means for you
Soy isoflavones may help specific PMS symptoms, particularly pain-related symptoms and fluid retention. However, since placebo was also effective, the extra benefit of soy beyond placebo appears modest. The supplement appears to work through natural hormone-related mechanisms.
23
women in study
68 mg/day
soy isoflavones dose
7
menstrual cycles, study duration
About the study
- Original title
- Effect of consumption of soy isoflavones on behavioural, somatic and affective symptoms in women with premenstrual syndrome
- Authors
- Bryant M, Cassidy A, Hill C et al.
- Journal
- The British journal of nutrition
- Year
- 2005
- Study design
- Randomised trial
- What was tested
- Isolated soya protein with 68 mg per day soy isoflavones versus milk protein placebo
- Open access
- Yes
- Read the paper
- doi.org/10.1079/bjn20041396
Topics
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