Topic of the Month

Micronutrients and mental performance

February 1, 2011

The human brain monitors and regulates the body’s actions and reactions. It continuously receives sensory information, rapidly analyzes this data and then responds, controlling bodily actions and functions. While one part of the brain controls processes that are independent of conscious brain functions (e.g., breathing and heart rate), others are responsible for the coordination of movement or complex thinking processes such as learning and memory.  

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As the most metabolically active part of the body, the brain demands nutrients to support its essential work. Filling the brain’s nutritional needs is an important part of using the mind to its fullest potential. The human brain begins to form very early in prenatal life, but in many ways, brain development is a lifelong project. Thus, an adequate micronutrient intake can support cognition and mental performance from gestation through to old age. 

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The brain

The brain is made up of billions of cells, of which two types are the most common: neurons and glia cells. Neurons are the specialized nerve cells that are responsible for brain functions like thinking. The brain can be seen as a network of neurons, which are nourished, protected and supported by glia cells. All physical and mental functioning depends on the establishment and maintenance of neural networks. A person’s habits and skills become embedded within the brain in frequently activated neural connections.

The thought processes are actually electrical impulses: an impulse at one end of a neuron triggers the production of neurotransmitters, which are released at the other end into a space shared by other neurons. Neurons communicate not only with thousands of other neurons, but also with other tissues such as muscles, skin and digestive organs. Part of the high metabolic needs of the brain is from the energy needed to keep the electrical impulses firing.

Different brain functions are localized into specific sections of the brain. The largest part (“cerebrum”) controls language, speech, emotions, voluntary movement, and is the place where memories are stored and processed as well as where calculations are done. In addition, it comprehends sounds and images, and generates music and art. The “brain stem” connects the cerebrum with the spinal cord. It regulates critical body functions like breathing, swallowing, blood pressure, heartbeat and pulse rate, digestion and posture. Movement and coordination start in the “cerebellum,” which also stores memories of practiced movements. Memory formation occurs in the “hippocampus.” This part of the brain continues to produce nerve cells even during adulthood.

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Pregnancy

Brain development starts very early in life: by three weeks after conception, the brain cells begin to form at the tip of the embryo. It begins as a tube that expands and matures to form the spinal cord. After that, the tube forms the brain. The neurons get developed in a slow process and begin to make contacts with one another. Some 100 billion neurons are formed during just the first five months of gestation. After 6 months, the brain development of the fetus is almost complete. Almost all the neurons that are needed for a human life are present in the fetal brain at this point.

Brain development is most sensitive to a baby’s nutrition between mid-gestation and two years of age. Pregnant women need to be careful that they are getting the right micronutrients, the ones that support their baby’s brain development, because the fetus relies entirely on its mother’s supply of nutrients. A critical time in brain development is around three to four weeks after conception when the neural tube closes and the initial brain structures form. The B-vitamin folate/folic acid (vitamin B9) helps reduce the risk of neural tube defects (1, 2), thus women of childbearing age should ensure that they have adequate intake of this essential nutrient (3).

The long-chain polyunsaturated fatty acids docosohexaenoic acid (DHA) and arachidonic acid (ARA) concentrate in the fetal brain throughout pregnancy, with the greatest transfer from mother to unborn baby in the third trimester (4). Intakes of these should be adequate throughout pregnancy. DHA and ARA can be formed from common precursors in the diet. The intake of the omega-6 fatty acid ARA and its main precursor linoleic acid is normally sufficient. The consumption of the omega-3 fatty acid DHA may not be adequate due to high demands during pregnancy, low intakes of common food sources and poor conversion (5); therefore, supplementation can be useful.

Choline, an essential nutrient which is usually grouped among the B-complex vitamins, is important as a building block for many vital compounds in the brain (6). Choline is needed for structural integrity and the signaling roles of cell membranes as well as the transmission of information between neurons. Circulating choline levels are high in the developing fetus and newborn babies (7). Studies indicate that it seems to be particularly important for pregnant women to get enough choline, since low choline intake may raise the rate of neural tube defects in infants (8).

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Infants

Although all of the neurons in the brain are produced before birth, they are poorly connected. In spite of the great number of neurons present at birth, brain size itself increases more gradually: A newborn’s brain is only about one-quarter the size of an adult’s. It grows to about 80% of adult size by three years of age. This growth is largely due to changes in individual neurons as they gradually sprout hundreds of long, branching dendrites, which serve as the receiving point for synaptic input from other neurons. Between the first and the second year, brain connections expand to about twice the density of the adult brain, since the toddler brain is 2 ½ times as active as the adult one.

After birth, brain growth depends critically on the quality of a child’s nutrition. Newborn babies also need docosohexaenoic acid (DHA) and arachidonic acid (ARA) after birth. A steady supply of DHA and ARA either from breast milk or formula supports growing brains. Women with higher intakes of long-chain omega-3 fatty acids produce higher levels in their milk. Also supplements have been shown to support mental development in infants (9-11).

There is some evidence that choline is important for normal brain development, particularly in areas related to the child’s memory (12). Recent analysis of an US nutrition survey revealed that for older children and pregnant women mean choline intakes are far below the adequate levels (6). As the consumption of food high in choline (e.g., beef liver) is low in large parts of the population, dietary supplements, such as lecithin derived from soy or egg yolks, can balance out insufficient intake.

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School children and students

By the age of 5 the brain is 90% of its adult weight. Between infancy and the early grade school years, the brain actually produces an abundance of neural connections that is greater than that of an adult’s. During this critical period, a child’s sensory, motoric, emotional, and intellectual experience determines which of the synapses will be preserved. The least useful connections are pruned away as the child grows. In other words, the number of synapses in the brain peaks within the first few years of life, but then declines by about one third between early childhood and adolescence.

School children and students lacking essential micronutrients may have difficulties reaching their mental and cognitive potential (13). A number of studies have shown that nutrition can enhance mental performance in school-aged children. The key micronutrients that play an important role in brain performance and learning include the vitamins B1B2 and B6iron (14) and essential fatty acids, particularly eicosapentaenoic acid (EPA) and docosohexaenoic acid (DHA) (15). These nutrients provide the building blocks for cells and enzymes that are important in the brain. An adequate micronutrient intake has been shown to support academic performance in school-aged children (14).

Attention deficit hyperactivity disorder is very common, found in 5 – 10% of school-aged children (16). Children with this condition showed improvements in mood, learning capacity and behavior when EPA and DHA intake was increased, in combination with other essential fatty acids (17-19). In a randomized controlled trial, six months of treatment with fatty acid supplements among 102 dyslexic school aged children significantly improved reading scores on standardized tests of single word reading (20).

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Adults

Neurons of the adult brain do not generally undergo cell division, and usually cannot be replaced after being lost, although there are a few known exceptions (e.g., self-renewing neural stem cells). However, the adult brain continues to develop throughout the entire life. As an adult, the most important trait of the brain is its plasticity, the ability of the brain to make new neural connections and to adapt in response to new experiences (outside stimuli).

Research consistently demonstrates that a balanced diet can benefit the adult brain. The importance of nutrition is highlighted by the role of breakfast in improving mental performance (21). The B-vitamins are needed for proper energy metabolism in the body and brain. Adequate intakes of folate/folic acid (vitamin B9), vitamin B6 and B12 support cognitive function throughout life (22, 23). These three vitamins help maintain healthy homocysteine levels, which may protect the delicate blood vessels in the brain (24).

Zinc is highly concentrated in a particular type of neuron found in the forebrain, at the site where neurotransmitters are released (25). An adequate intake is needed for normal cognitive function.

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Seniors

The human brain is able to continually adapt and rewire itself. Even in old age, it can grow new neural connections. Severe mental decline is usually caused by disease, whereas most age-related losses in memory or motor skills simply result from inactivity and a lack of mental exercise and stimulation (“use it or lose it”).

Nutrition can help maintain mental performance in aging populations. Vitamin B1 deficiency is related to some neurological conditions (26-28). An adequate intake has been shown to enhance quality of life in subjects with a poor vitamin B1 status (29), which is particularly relevant in elderly populations that may suffer a lack (30, 31). Vitamin B5 is needed to help brain and nerve cells function and assists in their regular metabolism (32), contributing to normal mental performance.

Higher consumption of omega-3 fatty acids has been linked to lower rates of cognitive disorders (33). Supplementation with docosohexaenoic acid and eicosapentaenoic acid has been shown to improve cognition in older adults (34).

In a study of older adults, long-term beta-carotene supplementation has been linked to improvements in general cognition and verbal memory (35) and may contribute to preventing cognitive decline (36). Verbal fluency increased after lutein supplementation in a medium-term trial in older women (34).

Vitamin D receptors are found in the hippocampus and outer layer of the cerebrum, key areas of cognition (37). Low vitamin D serumlevels have been associated with decreased cognitive functioning in older adults (38-40). The mood-depressing effects of seasonal affection disorder seem to be linked to vitamin D deficiency (41, 42).

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