Phytoestrogens have modest positive effects on bone tissue and on the development of osteoporosis in experimental animals. However, more well-designed human studies are needed before making general recommendations. So concludes the recently completed European-funded project Venus.
Based on a database on phytoestrogens (PEs) within European diets compiled by the Venus team, led by Prof Francesco Branca at the Istituto Nazionale di Ricerca per gli Alimenti e la Nutrizione (INRAN) in Rome, Italy, PE intake in Europe is estimated to be less than 1 mg/day, compared to an intake of 20-100 mg/day in Asia and to the expected range for physiological effect, 60-100 mg/day.
Bioavailability studies confirmed that most PEs are readily absorbed by humans, but large subject variability was found, possibly due to variability in gut microflora, diet and metabolism, suggest the researchers.
They add that because isoflavones are mostly found in soy products, which are not extensively used in Europe, an adequate intake in European diets may be difficult. For this reason, the team worked out a number of menus containing soy fractions which would significantly contribute to an increased PE intake.
Phytoestrogens, mostly found in soybeans, other beans, nuts and some cereals, are compounds in plant foods which in the human body are converted into compounds with oestrogen-like effects. PEs considered for the Venus study included isoflavones (genistein and daidzein), coumestrol, formononetin, biochanin A, and lignans.
Missing links identified by the Venus project will be taken up by the recently launched European project called Phytos. The major objective of the new project is to provide clear scientific evidence about the effects of soy isoflavones on markers of osteoporosis in postmenopausal women.