Thursday, June 23, 2011

DrMirkin's eZine: Food for hot-weather exercise, near-sightedness, more . . .

Dr. Gabe Mirkin's Fitness and Health E-Zine
June 26, 2011

What to Eat During Hot-Weather Competition and Exercise

To be able to exercise intensely in hot weather, you have to
maintain water, sugar and salt in your body for the entire time
you exercise. How fast you can ride, run, or exercise is limited
by the time it takes to bring oxygen into your muscles. If you
can increase the oxygen supplied, or decrease the oxygen needed,
you can move faster. Since sugar requires less oxygen to power
your muscles than fat or protein, anything that allows your
muscles to burn more sugar and less fat will help you to move
Taking extra sugar during a competition or intense exercise
lasting more than two hours is far more important than what you
eat before your event. The limiting factor to how fast and
intensely you can exercise in events requiring endurance depends
on how quickly you can get sugar into muscles during exercise. You
can markedly improve performance in endurance sports by starting
to eat and drink soon after you start exercising.
START YOUR COMPETITION. When you eat sugar and your muscles are
not contracting, you get a high rise in blood sugar that causes
the pancreas to release large amounts of insulin. This can cause
a drop in blood sugar levels that can tire you. On the other
hand, exercising muscles draw sugar rapidly from the bloodstream
without needing insulin. So taking sugar during exercise usually
does not cause the high rise in blood sugar levels that causes
your pancreas to release large amounts of insulin.
The energy for your brain comes almost exclusively from the
sugar in your bloodstream. When blood sugar levels drop, so do
brain levels, and you feel tired and have difficulty coordinating
your muscles.
Another reason why you have to take sugar during intense
exercise is that there is only enough sugar in your bloodstream to
last three minutes at rest. To maintain blood sugar levels, your
liver constantly releases sugar into your bloodstream, but your
liver holds only enough sugar to last about twelve hours at rest
and far less than that when you exercise. When muscles run out of
their stored sugar supply, it hurts to exercise and the muscles
become difficult to control.
DON'T WAIT TO FEEL HUNGRY: Hunger during exercise is a very
late sign of not getting enough calories. By the time you feel
hungry, your body will be so depleted of sugar that you will have
to eat large amounts of carbohydrate-rich food just to restore
your sugar supplies.
WHAT TO EAT AND DRINK: All carbohydrates are single sugars,
or sugars bound together in twos, up to thousands and millions.
Before any carbohydrate can be absorbed into your bloodstream, it
must first be broken down into single sugars. Human intestines do
not permit combination sugars to pass into the bloodstream, so the
most effective way to increase endurance is to take sugar-
containing foods and drinks during prolonged exercise.
CAFFEINE increases sugar absorption from the gut. Taking
caffeine when you eat carbohydrate-containing foods and drinks can
double your rise in blood sugar (Journal of Caffeine Research,
April 16, 2011). A high rise in blood sugar causes all the side
effects of diabetes: blindness, deafness, heart attacks, strokes
and so forth. However, during exercise, caffeine can increase
endurance (Medicine & Science in Sports & Exercise, July, 2010) by
increasing the absorption of sugar from your intestines and by
increasing the uptake of sugar by your exercising muscles by as
much as 26 percent (Journal of Applied Physiology, June 2006).
Caffeine is found in coffee, tea, chocolate, cocoa and
caffeinated soft drinks.
CAUTION! Take caffeinated sugared drinks only during
prolonged, intense exercise. Taking sugared drinks, with or
without caffeine, when you are not exercising causes higher rises
in blood sugars that increase risk for diabetes and cell damage.
Read my comprehensive report on what to eat and drink before
and during hot-weather competition at


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Dear Dr. Mirkin: How can I prevent my child from becoming as
nearsighted as I am?

Take him outside often. From 1970 to 2000, the incidence of
nearsightedness has almost doubled, probably because growing
children spend too much time indoors (Archives of Ophthalmology,
June and December 2009). Nearsightedness is not caused by reading
at a young age. It appears to be caused at least in part by not
getting enough sunlight.
As an infant grows, the eyes adjust to the amount of
available light. Sunlight sets the normal distance between the
lens and the eye nerve called the retina. However, when a child
spends most of his time under artificial lights, the eye
accommodates to this decrease in light by extending the distance
between the lens and the retina. This makes far away objects
appear blurred and a person becomes nearsighted.


Update on colon cancer and red meat:

The World Cancer Research Fund (WCRF) reviewed 263 research
papers associating lifestyle factors with colon cancer and issued
an 850-page report advising people to limit their intake of red
meats such as beef, pork and lamb, and to avoid processed meat
such as ham and salami. These meats have been associated with
increased risk for colon cancer (PLoS ONE, June 6, 2011)
Other factors associated with increased risk for colon
cancer include: taking more than too drinks of alcohol per day,
lack of exercise, being overweight, and not eating enough fruits
and vegetables.


Recipe of the Week:

Golden Lentil Soup

You'll find lots of recipes and helpful tips in
The Good Food Book


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Gabe Mirkin, M.D.
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