Brain Food: I Eat, Therefore I Think

Thinking requires lots of energy, and energy requires food. This ties the brain and its cognitive function to the diet in a co-dependent relationship. Fernando Gómez-Pinilla, Ph.D., a researcher from UCLA, recently published a comprehensive review, "Brain Foods: the effects of nutrients on brain function," in the July 2008 issue of Nature: Neuroscience Reviews, detailing the effect food and dietary nutrients can have on cognitive processes and emotions.

Gómez-Pinilla noted paleontological evidence has suggested a direct link between access to food and brain size, with larger brains associated with development of better survival skills. He further discussed the important role docosahexaenoic acid (DHA) has been theorized to play in the cognitive development of humans as a species, noting encephalization (increased brain/body-mass ratio) seemed to occur after humans adapted to a fish or "shore" diet. Considering this, he theorized the increased consumption of saturated fats, linoleic acid and trans fatty acids, coupled with decreased omega-3 intake, in Western civilization could be a possible cause of the growing incidence of depression.

The link between omega-3s and both cognition and depression is not new to those in the natural products industry. Gómez-Pinilla reiterated the research showing omega-3s support cognitive processes in humans, as well as upregulate genes important for synaptic function and plasticity, at least in animal trials. On the contrary, he said science suggests diets higher in saturated fats reduce substrates that support cognitive function and increase risk of neurological dysfunction.

He noted, however, that the link between food and cognition goes beyond just omega-3s, as vagal nerves connecting the belly to the brain go beyond managing digestion and into affecting mood, including depression. In fact, research into vagal nerve stimulation (VNS) and depression have shown improvements to memory and depression (long-term VNS), indicating information carried to the brain via the vagus nerve might influence higher-order cognitive processing.

Furthermore, the hormones in the gut that regulate digestion—leptin, ghrelin, glucagon-like peptide-1 (GLP1) and insulin—have been found to impact emotion and cognition. Leptin spurs expression of brain-derived neurotrophic factor (BDNF), which supports the survival of existing neurons while stimulating growth and differentiation of new neurons and synapses. Ghrelin helps to reorganize synaptic terminals in the hypothalamus and synaptic formation in dendric spines and long-term potentiation (LTP) in the hippocappus regions of the brain, possibly aiding spatial learning and memory formation. For its part, GLP1 infusion into the brain, to receptors on hypothalamus neurons, has led to improved associative and spatial memory in animal trials. Insulin can also enter the brain, where it interacts with signal transduction receptors in "discrete" regions of the brain, possibly can help modulate cognitive processes.

Gómez-Pinilla delves into the interplay of energy metabolism and cognition, ending up with two major relationships: insulin growth factor-1 (IGF1) and synaptic plasticity, and BDNF deficiency and numerous diseases including depression, diabetes type II and schizophrenia.

On specific nutrients, he reviews some of the research findings on omega-3s, including the effects of deficiency on cognitive impairment in children and adults, which is reversed by supplementation. He also discusses flavonols in fruits, cocoa and herbs like Ginkgo biloba, specifically noting quercetin and (-)epicatechin have fairly well-documented mechanisms in support of memory formation. Also singled-out is folate and its parent foods such as spinach, orange juice and yeast. Adequate levels of folate are required for optimal brain function, with deficiency of the vitamin linked to neurological disorders and cognitive impairment. He noted positive results on supplementing with folate in such cases were tempered only by concern over managing any possible side effects.

Other food and herbal ingredients covered include: curcumin, for inhibiting cognitive decline in Alzheimer's disease (AD); vitamin D, for preserving cognitive ability in the elderly; vitamin E, for limiting damage and decline from brain trauma; choline, for theorize link to cognition and for preserving memory after seizures; and various minerals, the serum levels for which are linked to various swings in cognitive function.

Overall, Gómez-Pinilla points out the probable benefit of antioxidant foods, given the high-susceptibility of the brain to oxidative damage. He highlighted the science on antioxidant-rich berries and both cognition and plasticity, probably due to protecting membranes from lipid peroxidation. To this end, he also talks about alpha lipoic acid (ALA) from meats, spinach, broccoli and potatoes, for its ability to improve memory.

Beyond specific nutrients, how much food is eaten comes into question, as some studies suggest excess caloric intake can reduce synaptic plasticity and leave brain cells more vulnerable to damage at the hands of free radicals. Therefore, calorie restriction can reverse these risks, possibly even raising levels of the beneficial BDNF.

"We are beginning to uncover the basic principles that are involved in the actions of food on the brain," Gómez-Pinilla concludes, adding science now knows particular nutrients influence cognition by acting on molecular systems for cellular processes that are vital for maintaining cognitive function. "This raises the exciting possibility that dietary manipulation are a viable strategy for enhancing cognitive abilities and protecting the brain from damage, promoting repair and counteracting the effects of aging."