Soy intake and cognitive function: results from clinical trials

摘要

Cognitive function is an umbrella term used to encompass a range of mental functions, such as attention, learning, memory, mental flexibility and planning. Many drugs, dietary insufficiency and physiological factors, such as sleep deprivation, can impair cognitive function. With increasing interest in potential health benefits of soy, a crucial question is whether there might be cognitive benefits following soy administration. Three recent studies of soy administration from 3-6 months provide some evidence that this might be the case (File et al, 2001; Duffy et al, 2003; Kritz-Silverstein et al, 2003) and the results of our latest study (File et al., 2004) suggest that the onset of benefit may be as soon as 6 weeks. Two important questions arise with respect to the effects of soy. Firstly, and most importantly, is whether the reported benefits are reliable, or whether they could have occurred by chance. Secondly, are the benefits specific to particular cognitive processes, or are they rather non-specific in nature. One important confounding factor to exclude is any possible mood changes, since, for example, if one group was more depressed than the other, this could result in different performance levels in the cognitive tests. None of the studieson the effects of soy found any mood changes and hence this indirect influence on cognition can be ruled out. All the studies on soy also took care to match the two groups for IQ and educational level, again factors that can have an important influence on cognitive performance. It is also possible to see a non-specific improvement in performance of cognitive tasks through an action to reduce reaction times. However, there is no evidence from any of the studies that administration of soy has a general effect of speeding up reaction times.