Food For Thought: Nutrition's Effect on Cognition

Jan. 30, 2014
The human brain demands energy at a prodigious rate, so it's natural to consider the effect of nutrition on cognition.

Cognition is defined as the mental processes that include the long-term memory needed for comprehending language and for learning, reasoning, problem-solving and decision-making. Fully 20 percent of our resting energy is used by the brain. That’s a lot of activity concentrated into a small space, requiring not only fuel but the micronutrients — such as vitamins and minerals, including all of the B vitamins — to process that fuel into energy.

The byproducts of all that oxygen-requiring activity are damaging oxygen radicals -- from which membranes require antioxidant protection. Essential components of these membranes include the omega-3 fatty acids referred to as DHA (docosahexaenoic acid). These fatty acids are important during brain development and highly susceptible to oxidative damage.

Although not definitive, some research suggests that supplementing the diets of elderly people with DHA could help prevent cognitive decline. What is definitive is that DHA is vital to the developing brain.

The primary consideration when it comes to cognition is fuel, and that fuel is glucose. The brain, unlike muscles, will not use fat for energy. Only when carbohydrates are severely limited will ketones, a byproduct of fatty acid oxidation, be recruited as emergency fuel.

As brain activity increases, glucose decreases and must be constantly supplied. The recent argument that sugar causes cognitive decline is based only on studies that link insulin resistance and diabetes to cognitive decline, conditions in which blood glucose is elevated. Far from a successful indictment of carbohydrates, these observations serve only to reinforce the abundant research showing obesity, insulin resistance and diabetes are related to high-fat, highly refined-carbohydrate westernized diets. Traditional diets rich in staple carbohydrates (grains, beans and potatoes and other tubers), such as Asian diets and Mediterranean-style diets, are not associated with cognitive decline, obesity or type 2 diabetes.

The true relationship between glucose and cognition may be by way of glycogen stores in the brain. Glycogen in the brain is a necessary source of fuel. A 2011 animal study published in the research journal Cell suggested that long-term memory also is associated with glycogen stored in the brain cells called astrocytes.

Glycogen, a storage form of glucose, is converted to lactate via glucose and delivered to neurons. When this chain of reactions going from glycogen to lactate was prevented in favor of one supplying glucose alone to produce lactate, long-term memory was impaired.

Preventing cognitive decline might also be a matter of reducing the oxidative stress associated with the Western-style diet. Increasing the total antioxidant capacity (which would include antioxidant vitamins and many phytochemicals) as a means of reducing cognitive decline has been the object of a number of studies. For example, animals that consumed antioxidant-rich foods like spinach or a variety of berries or vegetable extracts have shown a decrease or even a reversal of age-related deficits in cognition.

To a lesser extent, supplemental vitamin E produced similar results. Vitamin E is an important fat-soluble antioxidant capable of preventing membrane damage. However, vitamin E requires the co-enzyme CoQ-10 in order work most efficiently. For this reason, CoQ-10 has seen an increase in popularity and even has been included in some supplement-infused beverages and bars.

Enhancing cognition via certain plant extracts is reputed to have positive mood-altering effects that benefit cognition. The succulent herb Sceletium tortuosum, sometimes called the “African happy plant,” has been prepared by fermentation and chewed for its mood-altering effects by South African farmers and hunter-gatherers for hundreds of years. It has also been made into teas and tinctures.

A pure extract of this plant marketed under the name Zembrin by P.L. Thomas Inc., Morristown, N.J., was recently released in 2012 following years of research. Traditionally, the plant also has been used as a means of reducing stress and anxiety and promoting relaxation. The mechanism of action is that of serotonin reuptake inhibitor and a phosphodiesterase inhibitor.

Other cognition ingredients attracting interest include extracts from the Bacopa plant (also provided by P.L. Thomas); gamma-aminobutyrate (GABA); phosphatidyl serine (such as Lipogen PS Plus, by Lipogen Ltd.); and extracts of green tea, such as epigallocatechin gallate (EGCG), provided by Blue California Inc. 

Enhancing cognition and preventing cognitive decline are becoming increasingly important, especially as the spread of obesity and type 2 diabetes continue in an aging population. Strategies and products that assure brain energetics and relieve oxidative stress will continue to demand shelf space.

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