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Friday, May 28, 2010

Magnesium: a mineral you need and may lack

The only time I ever thought about magnesium,  before I became a scientist, was the summer I swept magnesium shavings off the floor at the Kaiser helicopter-engine factory. When I went to college, I learned that magnesium was an essential mineral in human and animal bodies. As a veterinary medical student, I learned that a magnesium deficiency caused "grass tetany" in cattle that ate lush, heavily fertilized grass growing especially in soils high in potassium or aluminum; these conditions reduce availability of magnesium.

Recently, a MIT scientist, Inna Slutsky reported a five year study showing that magnesium improved learning abilities, working memory and both short- and long-term memory in rats. The improvements were produced in both young and old rats. They fed rats a synthetic magnesium supplement, magnesium-L-threonate (MgT), which improved the ability of magnesium to get across the blood-brain barrier and into nerve cells.

How magnesium benefits brain function is probably related to the fact that magnesium is a cofactor for enzymes that convert adenosine triphosphate (ATP) to adenosine pyrophosphoric acid (ADP), with the subsequent release of energy. The brain is a real energy hog.

How much MgT would humans need to take is not known, but presumably somebody is working on that. The recommended daily amount of magnesium is 400 milligrams for men and 310 milligrams for women. It is estimated that only 32% of Americans get this amount in their diet. Primary food sources are green veggies, fruits, and certain nuts.  Traditional nutritional supplements are not a solution. The researchers found that the magnesium in common dietary supplements does not readily enter the brain.

A commercial product, when it becomes available, may not have been tested for safety (nutritional supplements are not government regulated), On the other hand, healthy kidneys are pretty good at getting rid of excess blood magnesium. The possibility of excess magnesium in the brain from use of MgT has not been investigated.

Slutsky, I. et al. 2009. Enhancement of learning and  memory by elevating brain magnesium. Neuron. 65 (2): 165-177.

Copyright, 2010, W.  R. Klemm

Monday, May 10, 2010

Can Exercise Help Kids Do Better in School?

Even when I was a kid, people said that being physically active could help you perform better in school. But this was mostly anecdotal, with very little research evidence. Now there is some evidence.

Charles Hillman and colleagues at the University of Illinois recently reported a study on the eff
ects of exercise on cognitive function of 20 preadolescent children aged 9 to 10. They administered some stimulus discrimination tests and academic tests for reading, spelling and math. On one day, students were tested following a 20-minute resting period; on another day, students walked on a treadmill before testing. The exercise consisted of 20 min of treadmill exercise at 60% of estimated maximum heart rate. Mental function was then tested once heart rate returned to within 10% of pre-exercise levels. Results indicated improved performance on the tests following aerobic exercise relative to the resting session. Recordings of brain responses to stimuli suggested that the difference was attributable to improved attentiveness after exercise.

Note that this is just from a single aerobic exercise experience. How can that be beneficial? The most obvious explanation is that exercise generates more blood supply to the brain, but I don't know that this has been documented with MRI studies, for example. Actually, what is known is that exercise diverts blood to the muscles. The generally accepted view is that the body tightly regulates blood flow to the brain and that the brain always gets what it needs. Another possibility is that exercise relieves anxiety and stress, which are known to disrupt attentiveness and learning. Maybe the repetitive discipline of exercises like treadmill walking help entrain the brain into a more attentive mode. We need a study that compares tradmill walking with a different kind of exercise regimen (like a vigorous and competitive basketball game, for example).

As for what goes on in a typical school recess, I doubt that such activities as shooting marbles, gossiping, or whatever else goes on these days with kids at recess, really helps school work. Gym class might be another matter, but unfortunately many schools do not provide a meaningful gym class. Some of the authors' suggestions don't
seem to be supported by this particular research. For example, they advocate:

• scheduling outdoor recess as a part of each school day (recess does not typically provide aerobic levels of exercise)

• offering formal physical education 150 minutes per week at the elementary level, 225 minutes at the secondary level (again, the beneficial effects likely come from aerobic
levels of exercise, not just any exercise)

• encouraging classroom teachers to integrate physical activity into learning (this almost certainly will not be at aerobic levels of exercise.)

There is the also the issue of a continuing aerobic exercise program, which presumably could produce long-lasting beneficial effects in young children. My own prejudice is that schools and parents ought to get serious about requiring an aerobic exercise program for kids. It should not only improve the quality of school work but also help combat the epidemic of obesity and diabetes. One caveat: running to achieve aerobic levels of exercise may not be advisable in children. My own exp
erience with jogging, for example, might have been great for my heart and brain, but I now have two artificial kness to show for it.

If exercise is so good for academic performance, why do varsity athletes generally make poorer grades than their classmates? Well, there are many other factors, of course. One prevailing attitude among athletes is that academics are less important to them than their sport. Their peers idolize athletic stars. Students who make all As are not considered heroes; they are considered nerds or otherwise abnormal. Athletes devote their time and energy to their sport, not school work.


Hillman, C. H., et al. 2009. The effect of acute treadmill walking on cognitive control and academic achievement in preadolescent children. Neuroscience. 31;159(3):1044-54.