Why do we lose memory as we age?

As we grow older, the rate of “brain aging” varies from person to person. Some will start becoming forgetful in their 40s, others will develop Alzheimer disease, and still others will become hypertensive (develop high blood pressure) and may have a stroke. Each of  these conditions impacts how our brain is functioning at any particular instant in time. Many other factors play a role. Some of us, the lucky ones, are blessed with fine mental function well into our 90s.

What determines where we fall in this spectrum? From a global perspective the best way to understand what occurs is to consider several overlapping processes. We start out as a single cell in the womb. The brain and other organs develop and enlarge as pregnancy progresses. Our genes and the availability of the proper nutritional building blocks underlie the construction of the brain much like a blueprint and the necessary amounts of concrete, stone, steel and glass enable tall buildings to be erected.

After birth, new nerve cells (called neurons) are constantly being produced throughout the brain. They form connections with surrounding neurons. Each neuron has the capacity to form up to 100,000 connections with surrounding neurons. The key is not necessarily which connections or how many are formed, but which survive. It is akin to the survival of the fittest. In this case, the “fittest” connections are the ones that are used most frequently. A term used by neuroscientists to describe this process of changing connectivity is plasticity.  Just remember the rhyme, “neurons that fire together, wire together.” When one neuron is triggered and “talks” to its neighbor, that physical interaction strengthens the point of contact between the two (called a synapse). As this happens repeatedly, connections develop and become stronger. Simultaneously, connections with neighboring neurons that are not being used as routinely wither and may even disappear. That is how nerves form networks with one another. The process is driven by brain activity in response to both the external world and internal thoughts. The greater the depth and breadth of experiential interactions processed by the brain, the more dense the networks of contacts are and the better the function. These processes determine how good a brain you are building.

After a great brain has been sculpted, keeping it functioning optimally and making it as resistant as possible to the dents and dings associated with the aging process is important. A combination of continued mental stimulation, a proper diet, stress avoidance, adequate sleep, social interaction and all types of physical exercise will help assure a healthy brain well into later life.

What is the best diet for ensuring a healthy brain?

The answer to that question is unknown. What we can say, though, is that what we eat has changed dramatically from the diet with which our genes evolved. Much of this change has occurred over the past 10,000 years. Such a short time frame has not allowed our genes to adapt to the profound dietary alterations. Hence, our genes and diet are currently “out of sync.” The diet to which humans have become adapted over millions of years has now become maladaptive. This means that until our genetic makeup changes, the gene-diet dissonance will create health problems. Some of these will adversely impact the brain.

We have all heard that “the brain burns glucose.” Glucose is the sugar that is measured in the blood stream when blood tests are performed. It is what becomes elevated when diabetics lose blood sugar control. They inject the hormone insulin to keep blood glucose levels properly regulated. Glucose differs from table sugar, which consists of sucrose, a combination of one molecule of glucose and one of fructose joined together.  (Fructose is also called fruit sugar and occurs naturally in grapes, for example.)  When a molecule of table sugar is digested, it produces one molecule of glucose and one of fructose. Starch consists of long, branched chains of glucose molecules hooked together end to end.  It is digested by enzymes in the intestine that break these connections, thus producing millions of individual glucose molecules thus allowing their absorption into the blood. When digested, a potato produces half a cup of sugar (glucose). Even though a potato is a naturally-occurring vegetable, it is digested rapidly, flooding the blood with glucose at a rate much faster than can be used. Hence, blood sugar rises, and, sensing this change, the body releases high amounts of insulin to help control the blood sugar level.

Although the brain requires enough glucose to function normally, too much at one time can cause spikes of blood glucose and insulin. The frequent repetition of this process, as happens regularly on our modern “Western type diet,” is detrimental to brain health. This is easily seen by noting that people with diabetes (too much glucose in their blood) have a fourfold risk of developing memory problems and Alzheimer disease. Pre-diabetes is associated with triple the incidence of these problems and a condition called insulin-resistance (meaning your blood sugar level is normal, but to keep it there your body needs to use much higher amounts of insulin) is linked to a doubling of Alzheimer disease.

Observations like these reveal how dietary alterations can adversely impact brain function and brain aging. Therefore, some preliminary recommendations can be made regarding a brain-healthy diet. Any rapidly digested carbohydrates (such as bread, cakes, cookies, soda, starchy fruits and vegetables, candy and sweeteners containing sucrose (table sugar) or HFCS (high fructose corn syrup) should be avoided. Lean protein, especially fish, is to be encouraged. Berries, non-starchy veggies, nuts, seeds, and eggs are all good brain foods. One other caveat is that controlling your weight is also very important because new research is showing that weight gain is linked to loss of brain function.

What are considered good exercises for brain health?

To be a flexible thinking machine, the brain needs to be stimulated. When we get bored, our mind wanders, we become easily distracted and fail to concentrate. There are fascinating brain scans called PET scans (Positron Emission Tomography) and fMRI scans (functional Magnetic Resonance Imaging) that show how the brain responds to various mental challenges. They reveal how much of the brain is activated by various mental tasks. When stimulated with a novel task, large brain regions get involved in the “thinking process.” If a task involves some mundane process, minimal regions of brain activation are revealed. This tells brain researchers that the optimal mental exercises are those that are new, different, novel and require thinking “outside the box.”

This mentally challenging thinking pattern is engaged during stimulating occupational pursuits or school projects and during leisure activities such as solving complex mental problems, while learning a new language, learning how to play a musical instrument, reading or writing, discussing your response to a recent op-ed piece…really anything that forces you to become actively mentally engaged and to look at and evaluate things from many perspectives. A physical exercise analogy may be appropriate here. Flexing and contracting your pinkie finger repeatedly isn’t considered very good exercise. However, swimming, getting on an elliptical machine at the gym or playing tennis are all great forms of exercise because they activate many muscle groups. The same applies for brain activities. You want to choose mentally challenging, novel activities for maximal impact.

What effect does physical activity have on brain health?

My opinion is that physical exercise is the new frontier for the brain. New studies that  demonstrate why physical activity is great for the brain are being published weekly. This is true at all ages and even during pregnancy. But how much and what types are necessary?  Before starting any exercise program you should get permission from your health care professional to make sure it is safe. Remember to begin slowly and work your way up in intensity. Exercise with a friend. Establish a schedule. Vary your routine.

That having been said, aerobic exercise (meaning exercise that elevates your heart rate for an extended period of time) carries more blood throughout the body, including the brain. This supplies more oxygen and necessary nutrients to the brain. It also acts directly on the neurons by elevating specific chemicals called neurotrophins. They go by many different names such as BDNF (Brain-Derived Neurotrophic Factor) and NGF (Nerve Growth Factor). These compounds facilitate the production of increased connections between neurons and make them more resistant to the myriad insults to which they are routinely exposed. Resistance exercise, meaning weight training, that we all know is good for bone health, is also good for the brain due to its impact on the same neurotrophins. Other types of exercise that engage many brain regions are activities that involve balance, coordination and agility such as ping-pong, trampoline, juggling, balance beam, standing on one foot, jumping rope and sports like skiing or skating. My recommendation is to cross-train the brain by including a mix of exercises from each category on a regular basis. If you can work up to 30 minutes on most days, I guarantee that you will see a difference in several weeks. Go safely so you won’t get injured. And enjoy!