Nutrition and the Aging Brain

As we age, changes occur throughout our bodies. Generally speaking, people reach the peak of their physical capacities in their twenties. After that levels of hormones such as DHEA, growth hormone, melatonin, estrogen and testosterone decline. Arteries clog; blood pressure rises; we no longer regulate blood sugar as precisely.

Many of these changes affect the brain, but contrary to popular perception, they don't lead to a wholesale downward slide. Wisdom-the ability to make executive decisions based on accumulated knowledge-increases throughout our lives. Given sufficient time, an older person can complete a complex task as competently or better than someone fifty years younger.

What does tend to decline is mental quickness and agility. Short-term memory deteriorates as does the ability to multitask and adapt to novel situations. A study published in the Journal of Cognitive Neuroscience indicates that older adults use both hemispheres of the brain to remember what younger adults can using only one hemisphere. In older adults unexpected regions of the brain are activated for verbal and spatial memory tasks. When younger adults use short term memory (like memorizing a phone number) they activate a network of brain regions involved in speech and short term verbal storage. Older adults activate these areas too, but also activate a frontal cortex. The more complex the task presented, the more parts of the brain the older adults used, the slower the problem-solving process became.

But even these changes need not be inevitable.

Hypertension causes a decline in cognitive function. Vascular dementia (the most common cause of dementia next to Alzheimer's) is the most dramatic form, but in all age groups hypertension decreases ability to react and respond to novel information and can lead to permanent brain damage over time. Regular monitoring of blood pressure is essential. While people's individual propensities to hypertension differ, generally speaking a diet relatively low in sodium and high in calcium, potassium, and magnesium helps. Sometimes medication is necessary.

Fatty acids build and maintain integrity of the myelin sheaths which protect the neurons, or nerve cells. While the majority of neuronal connections form before the age of three, new connections do continue to form throughout our live. The best source of fatty acids for the under-three set is breast milk; after that oily fishes such as mackerel, salmon, swordfish, fresh tuna and sardines take over. The oils in these fish also improve circulation to the brain. Unfortunately these healthful fatty acids also may contain potentially toxic levels of mercury thanks to their propensity to uptake heavy metal toxins like dioxins and PCBs. The consensus at this time is that women of childbearing years should limit themselves to 1-2 servings of oily fish per week, while men and older women can safely eat up to four servings a week.

Antioxidants protect against free radical damage in the brain. These antioxidants include vitamins C and E, carotene, certain minerals, and phytochemicals, of which anthocyanins (responsible for the blueness of blueberries) have gotten the most publicity.

A large study in Switzerland of people showed that people over sixty with the highest intake levels of vitamin C and carotene (from food, not supplements) scored highest on memory tests. Not only is carotene an antioxidant, is the precursor to vitamin A. When mature neurons make new connections, vitamin A is one of the substances they call upon.

In a recent study, Japanese researchers showed that vitamin E helped preserve the integrity of the hippocampus, the part of the brain most responsible for memory. In another study published in the American Journal of Epidemiology, involving 4800 people, showed a significant association between poor memory in the elderly and low blood levels of vitamin E.

Low levels of magnesium and zinc have been correlated with Attention Deficit Syndrome (ADD). Low zinc status has been linked to depression, nervousness, and anorexia. Selenium appears to balance moods. Iron is critical to red blood cells and oxygen delivery throughout the body. Low iron levels impact attention span and cognitive skills.

And what about those blueberries? A rash of studies pointed to surprisingly beneficial effects from these little fruits. When fed to rats, the "birth rate" of cells in the hippocampus increased, and the rats performed better in memory tests. Blueberries also improved balance and coordination. But its not necessary to gorge yourself on blueberries. Lots of other fresh fruits and vegetables pack in the anthocyanins and other beneficial phytochemicals too, most notably strawberries, raspberries, spinach, kale, plums, blackberries, and, yes, red wine.

All B vitamins improve brain function. Low levels of B vitamins correlate with high blood levels of homocysteine, which is affiliated with heart disease. So low B levels could impair cognitive abilities by clogging arteries. A study presented at the American Dietetic Association indicated that the B complex slowed memory loss. But of all the B vitamins, B12 and folate are the most critical for the brain.

Malabsorption of vitamin B12 is a common problem in older adults. It results from atrophic gastritis, a condition where people lack sufficient stomach acid to cleave B12 from the protein by which it's attached to the food. Deficiencies can lead to irreversible neurological damage in as little as three years. People with atrophic gastritis must take a B12 supplement or get B12 shots. Since vitamin B12 is found only in animal products, vegans can develop B12 deficiency also, but that deficiency takes longer to develop and is usually not as devastating.

Folate aids in the production and growth of new cells, including new neurons. Studies show that people with higher blood levels of folate have better memories. Folate deficiency in women of childbearing years increases the danger of neurological birth defects such as spina bifida.

Our growing understanding of the importance of nutrition in brain function has spawned a plethora of nutritional supplements. Few of these are harmful, but the best source of these nutrients remains whole, unprocessed foods. Nutrients are frequently better absorbed by the body when taken in food, and the interactions between nutrients cannot be duplicated in a pill.

One should also keep in mind that food is only one part of the total picture.

Physical activity is crucial. In one study, sedentary adults (ages 58-78) started a walking program. After three months, MRIs showed increased brain activity and significant improvement on tests measuring decision-making. Interestingly, weight and flexibility training helps cognitive function too. The exact mechanism is unclear, but presumably physical activity increases blood flow to the brain. Learning new physical skills (such as dance steps or yoga positions) forces neurons to make new connections, keeping the brain flexible.

Mental exercise is also essential, especially activities that force the brain to learn new patterns, such as mastering a foreign language, knitting and crocheting, playing a musical instrument, or engaging in word games such as crossword puzzles.