The lack of effect of isoflavones on high-density lipoprotein cholesterol concentrations in adolescent boys: a 6-week randomised trial

<jats:title>Abstract</jats:title><jats:sec id="S1368980007000869_abs1" sec-type="general"><jats:title>Background</jats:title><jats:p>A substantial fall in high-density lipoprotein cholesterol (HDL-C) during puberty in boys, but not girls, has been reported in Western populations. The fall in boys is believed to be due to hormonal changes – androgens have been shown to be associated with lower HDL-C, whereas oestrogens are associated with higher HDL-C. The fall in HDL-C during puberty was not observed, however, in a study of Moslem boys in Israel, nor in a group of Japanese boys. A diet high in phyto-oestrogens may account for the lack of a fall in HDL-C in these populations.</jats:p></jats:sec><jats:sec id="S1368980007000869_abs2" sec-type="general"><jats:title>Objective</jats:title><jats:p>To examine the effect of dietary supplementation with phyto-oestrogens on the HDL-C concentration of adolescent boys from a Western population. We hypothesised that dietary supplementation of 50 mg of the isoflavones daidzein and genistein would produce a 12% higher HDL-C concentration than in controls at the end of a 6-week intervention period.</jats:p></jats:sec><jats:sec id="S1368980007000869_abs3" sec-type="general"><jats:title>Design</jats:title><jats:p>A randomised controlled trial.</jats:p></jats:sec><jats:sec id="S1368980007000869_abs4" sec-type="general"><jats:title>Setting</jats:title><jats:p>Hellyer College in Burnie (Tasmania, Australia).</jats:p></jats:sec><jats:sec id="S1368980007000869_abs5" sec-type="subjects"><jats:title>Subjects</jats:title><jats:p>Adolescent boys (aged 16–18 years) were recruited through a letter sent to parents. A total of 132 eligible participants enrolled and five subjects withdrew from the trial.</jats:p></jats:sec><jats:sec id="S1368980007000869_abs6" sec-type="results"><jats:title>Results</jats:title><jats:p>No significant increase in HDL-C was observed in the treatment group (–0.02 mmol l<jats:sup>–1</jats:sup>, standard error (SE)=0.03, <jats:italic>P</jats:italic> = 0.53) or the placebo group (0.05 mmol l<jats:sup>–1</jats:sup>, SE = 0.03, <jats:italic>P</jats:italic> = 0.11).</jats:p></jats:sec><jats:sec id="S1368980007000869_abs7" sec-type="conclusion"><jats:title>Conclusions</jats:title><jats:p>Factors other than isolated dietary isoflavones may be responsible for the lack of fall in HDL-C during puberty in Japanese and Moslem boys.</jats:p></jats:sec>