Alleged benefits experienced after the consumption of soy in Asian countries have been attributed to the isoflavone content of soy products. Amongst other benefits, isoflavones are believed to relieve menopausal symptoms and are therefore often consumed in supplement form in Western countries. These supplements contain relatively high amounts of isoflavones and are on the market in different compositions. The question is whether supplements with different compositions exert similar effects or whether the effects differ substantially.

Intervention study with two substudies; each substudy is a double blind placebo controlled crossover intervention study. The first substudy has two groups: 'high daidzein' supplement versus placebo (n=18) and vice versa (n=18); the second substudy also has two groups 'high genistein' versus placebo (n=18) and vice versa (n=18).

Inclusion Criteria:

• Female
• 50-70 years
• menstrual cycle absent for more than 1 year

Exclusion Criteria:

• current use of contraceptives containing hormones
• current use of hormone replacement therapy
• regular soy product use (more than once a week)
• regular isoflavone supplement use (more than once a week)
• current use of medication containing sexhormones or sexhormone-triggering compounds
• current use of anti-inflammatory medicines
• use of antibiotics in the past 3 months
• severe heart disease
• diabetes
• thyroid disorders --> use of medicines for thyroid disorders
• removed thyroid gland
• complete ovarectomy
• prior diagnosis of cancer
• alcohol and drug abuse
• current smoker
• BMI >35 kg/m2
• allergy to soy (products)