**3. Impact of flavonoids on cognition**

The common medicine has focused on symptoms and treatment but the majority of chronical diseases are the result of unhealthy habits. The lifestyle medicine has focused on prevention, which means an increase in life quality, well-being, and avoids morbidity conditions [16]. Habitual consumption of dietary flavonoids has been consistently linked with improving cognitive functions [17–19]. For this reason, the flavonoids have been described as a class promised to maintain cognition functions and/or to delay in the progression of age-related cognitive. Despite a growing body of animal studies demonstrating positive effects in learning and memory after flavonoid intake (discussed in the next session), the human clinical trials are somewhat scarcer.

The neurobehavioral effects of phytoestrogens have been the limited data that exist regarding the influence of soy-derived dietary isoflavones on brain structure and function [20]. Clinical trial studies showed the efficacy of isoflavones on cognitive function in postmenopausal women. For example, Long term soy-isoflavonebased supplement (110 mg/d) for 6 months showed better verbal memory than the placebo control group [21]. Similarly, in women aged 50–65 found that intake of 60 mg/d for 3 months resulted in cognitive improvement in several categories related to frontal cortical functions [22]. Another study, involving younger postmenopausal women receiving 160 mg/d isoflavones for 6 months, and results showed an improvement cognitive flexibility [23].

With respect to anthocyanins, blueberry flavonoids supplement (579 mg/d) for 7 days induce cognitive improvements in young and aged adults [24]. Similar results were found after 3 months (long-term supplementation) with blueberry juice in older adults with cognitive impairment in working memory [25]. Some studies address the cognitive impact of a single dose of a blueberry juice in children (8–10 years old) [26]. This study showed for the first time a cognitive benefit for acute flavonoid intervention in children. Another study with 30 g of lyophilized anthocyanins, equivalent to 240 g or 1½ cups of fresh blueberries, demonstrated beneficial cognitive effects on memory and attention, not extending reading ability, in healthy children of 7–10 years of age. These findings increase the growing body of evidence that flavonoids are beneficial to healthy brain function [27].

Finally, precise estimation of nutrient intake is essential for establishing a relationship between diet and cognitive function. However, estimations of dietary flavonoid intake need to take into account their complexity and variability. More recently, a review reported wide range for mean total flavonoid intakes between 209 and 1017 mg/d (mean 435 mg/d) in European, US, and Australian adult populations [28]. In Brazil, the estimate is between 60 and 106 mg/d [29]. There are substantial variations in population estimates of dietary flavonoid intake, which may be associated to true differences in dietary patterns, such as differences in the food supply and cultural eating patterns between countries. Further studies are required to address and to detect effects of dietary interventions on human cognitive functions.
