To observe the effects of short-term soybean consumption on cognitive spatial abilities and changes in sex endocrine net in both genders.
Short-term prospective intervention study.
Academic medical center.
Fifty-four healthy females and 32 healthy males (18 - 25 y of age).
Volunteers were asked to eat 2 g/kg per day of soybeans during 1 week. Saliva and plasma samples were taken, and psychometric tests were performed on the 1st (before soybean intake), 7th (after soybean intake), and 14th days (after washout period) of the study.
Salivary T and plasma E(2) were measured. Mental rotation (MR) and spatial visualization (SV) tests were performed on the days of sampling.
Soybean intake did not change salivary T and plasma E(2) levels in men. During the washout period, both parameters have shown a tendency to rise. The effect of soybean intake on hormonal parameters in men was, however, dependent on the basal T levels. In women, salivary T as well as plasma E(2) levels showed a tendency toward a decline after soybean intake (the decrease in E(2) was statistically significant) and to increase back toward basal levels during the washout period. Both males and females statistically significantly improved in MR and SV after soybean intake. During the washout period, both genders further improved their results in MR but not in SV.
Short-term soybean consumption alters the concentrations of salivary T and plasma E(2) in both men and women. Spatial abilities appear to be improved by short-term soybean intake, but the exact mechanisms require further study.
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[Show abstract][Hide abstract] ABSTRACT: Recent follow-up analyses of the previous findings from the Women's Health Initiative and the Women's Health Initiative Memory Study confirmed some health benefits of estrogen-containing hormone therapy (HT) in women within 10 years from the onset of menopause. However, the potential risks associated with long-term administration of HT, such as breast cancer and stroke, remain a concern for therapy recipients, underlying the need for an alternative treatment that is functionally equivalent but with a greater safety profile. Owing to their structural and functional resemblance to mammalian estrogens and lack of evident adverse effects, research interest in plant-derived phytoestrogens has increased in the past decade. While multiple health-promoting benefits of phytoestrogens have been proposed from basic science, the clinical data remain inconclusive. This review provides a comparative analysis of human studies on the effects of soy-based isoflavones on cognition. Of the eight studies published in 2000-2007, seven were conducted in postmenopausal women, four of which revealed a positive impact of isoflavones on cognitive function. Multiple factors could have contributed to the discrepant outcomes across studies, such as variation in the composition of phytoestrogen interventions and the heterogeneous characteristics of the study population. Thus, a well-designed clinical study based on a standardized stable formulation in a well-characterized study population is required in order to reach a clinical consensus. A formulation composed of select estrogen receptor beta-selective phytoestrogens with a rationally designed composition would avoid the potential antagonism present in a mixture and thus enhance therapeutic efficacy. In addition, inclusion of equol in a study formulation offers a potential synergistic effect from equol in both equol-producing and nonproducing individuals, as well as added benefits for men. With respect to the design of study population, a clinically consistent effect could potentially be achieved by stratifying populations based on genotype, age, hormonal history and even diets. Development of an effective phytoestrogen formulation would benefit both women and men to prevent or treat hormone-dependent conditions and, most of all, to improve neurological health and reduce the risk of Alzheimer's disease.
[Show abstract][Hide abstract] ABSTRACT: It is well known that men outperform women in tests of spatial cognition, such as mental rotation, and that performance in these tasks is influenced by sexual hormones. Phytoestrogens are plant substances chemically similar to estradiol, capable of binding estrogen receptors. In a previous study, one-week phytoestrogen-rich diet improved performance in mental rotation in women, but it remained unclear whether this was due to direct binding of phytoestrogens to estrogen receptors or by modulating testosterone blood levels.
We investigated whether one week consumption of phytoestrogens will equally affect performance in mental rotation in women and men. We expected improved performance in women, but unchanged skill in men, if the effects were mediated by changes of testosterone level. On the other hand, direct modulation of estrogen receptors should yield comparable improvement in both genders.
Thirty-six healthy adult young volunteers (16 females) were divided into the control and soy groups. During 7 consecutive days, in addition to their usual diet, subjects in the soy group consumed a daily dose of 2 g of soybeans per kilogram body weight (about 170 mg/kg of isoflavones). The control group members stayed on their usual diet. The subjects were tested on mental rotation of letters and digits at the baseline and after 7 days of soy consumption.
Consumption of soy had no influence on performance in the mental rotation task. For the intermediate stimulus rotation angle (60 deg), irrespective of soy intake, improvement of response latencies was greater in women than in men.
The results indicate that soy phytoestrogens have little impact on mental rotation skill. The findings also suggest that women, in contrast to men, more readily engage memory mechanisms to solve the mental rotation task.
[Show abstract][Hide abstract] ABSTRACT: Females perform better in certain memory-related tasks than males. Sex differences in cognitive performance may be attributable to differences in circulating oestrogen acting on oestrogen beta receptors (ERbeta) which are prevalent in brain regions such as the hippocampus, frontal lobe and cortex that mediate cognitive functions. Since soya isoflavones are known to activate ERbeta, chronic isoflavone supplementation in males may improve cognitive performance in memory-related tasks. A 12-week double-blind, placebo-controlled cross-over trial was conducted in thirty-four healthy men to investigate the effect of isoflavone supplementation on cognitive function. Volunteers were randomised to take four capsules/d containing soya isoflavones (116 mg isoflavone equivalents/d: 68 mg daidzein, 12 mg genistein, 36 mg glycitin) or placebo for 6 weeks, and the alternate treatment during the following 6 weeks. Assessments of memory (verbal episodic, auditory and working), executive function (planning, attention, mental flexibility) and visual-spatial processing were performed at baseline and after each treatment period. Isoflavone supplementation significantly improved spatial working memory (P = 0.01), a test in which females consistently perform better than males. Compared with placebo supplementation, there were 18 % fewer attempts (P = 0.01), 23 % fewer errors (P = 0.02) and 17 % less time (P = 0.03) required to correctly identify the requisite information. Isoflavones did not affect auditory and episodic memory (Paired Associate Learning, Rey's Auditory Verbal Learning Task, Backward Digit Span and Letter-Number Sequencing), executive function (Trail Making and Initial Letter Fluency Task) or visual-spatial processing (Mental Rotation Task). Isoflavone supplementation in healthy males may enhance cognitive processes which appear dependent on oestrogen activation.
The British journal of nutrition 07/2009; 102(9):1348-54. DOI:10.1017/S0007114509990201 · 3.45 Impact Factor