LIGNANS AND ISOFLAVONOIDS IN PLASMA AND PROSTATIC FLUID IN MEN - SAMPLES FROM PORTUGAL, HONG-KONG, AND THE UNITED-KINGDOM

BACKGROUND. Chinese men have lower incidences of prostate cancer compa red to men from Europe and North America. Asians consume large quantit ies of soya, a rich source of isoflavanoids phyto-oestrogens and have high plasma and urinary levels of these compounds. The mammalian ligna ns, enterolactone and enterodiol, are another group of weak plant oest rogens and are derived from seeds, cereals and grains. Vegetarians hav e high plasma and urinary concentrations of lignans. METHODS. The conc entrations lignans and isoflavonic phyto-oestrogens were determined by gas chromatography-mass spectrometry (GC-MS) in plasma and prostatic fluid from Portuguese, Chinese and British men consuming their traditi onal diets. RESULTS. in prostatic fluid the mean concentrations of ent erolactone were 31, 162 and 20.3ng/ml for Hong Kong, Portugal and Brit ain respectively. Very high levels of enterolactone (>600ng/ml) were o bserved in the prostatic fluid of some of the men from Portugal. High concentrations of equol (3270 ng/ml) and daidzein (532 ng/ml) were fou nd in a sample of prostatic fluid from Hong Kong. Higher mean levels o f daidzein were observed in prostatic fluid from Hong Kong at 70ng/ml, compared to 4.6 and 11.3ng/ml in samples from Portugal and Britain re spectively. Mean levels of daidzein were higher in the plasma samples from Hong Kong (31.3ng/ml) compared to those from Portugal (1.3ng/ml) and Britain (8.2ng/ml). In general, the mean plasma concentrations of enterolactone from the three centres were similar, at 6.2, 3.9 and 3.9 ng/ml in samples from Hong Kong, Portugal and Britain respectively. CO NCLUSIONS. Higher concentrations of the isoflavanoid phyto-oestrogens, daidzein and equol, were found in the plasma and prostatic fluid of m en from Hong Kong, compared to those from Britain and Portugal. Howeve r, the levels of the lignan, enterolactone, were very much higher in p rostatic fluid of Portuguese men. Isoflavanoids and lignans have many interesting properties and may, in part, be responsible for lower inci dences of prostate cancer in men from Asia and also some Mediterranean countries. The isoflavanoids from soya, which are present in high con centrations in the prostatic fluid of Asian men, may be protective aga inst prostate disease. (C) 1997 Wiley-Liss, Inc.