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Q: Should I avoid taking my calcium supplement with my morning
coffee? I heard that caffeine interferes with calcium absorption.
A: Don’t worry
about the timing. Caffeine slightly reduces calcium absorption,
but this is not a problem if you get adequate
calcium, according to Dr. Robert Heaney, a noted calcium researcher
at Creighton University in Nebraska. As little as one to two tablespoons
of milk is enough, he says, to offset any potential effects of
the caffeine.
Though a few studies have linked caffeine-containing
beverages to reduced bone density and increased fractures, this
is seen mainly
in people with low calcium intake. That is, the combination of
high caffeine and low calcium seems to be harmful to bones, not
caffeine alone.
Rather than worry about calcium-caffeine interactions,
just be sure to get enough calcium from food and/or supplements:
1,000
milligrams a day for people age 19 to 50, and 1,200 milligrams
for those over 50. (And get enough vitamin D, which works with
calcium—we advise 800 to 1,000 IU for most people.) Keep
in mind that many substances interfere with the absorption of nutrients
in general, and dietary recommendations take such factors into
account.

Q: Can FRS, the energy drink endorsed by Lance Armstrong,
improve my athletic performance?
A: Its main ingredient,
the antioxidant quercetin, looks
promising in some studies. But there’s
little evidence to support claims that FRS enhances exercise/work
performance, reduces recovery time, fights fatigue, or neutralizes
free radicals produced by exercise.
FRS (for Free Radical Scavenger)
contains 325 milligrams of quercetin (the average diet provides
25 to 50 milligrams a day), plus green
tea catechins (also antioxidants), B vitamins, C, and E (said to
enhance the effectiveness of quercetin), and a little caffeine.
The recommended “dose” is two 11.5-ounce cans (or four
soft chews) a day. Besides Lance Armstrong, who is on the board
of the company, a score of well-known athletes and coaches have
endorsed the product.
In small studies by Dr. David Nieman, a sports
nutrition researcher at Appalachian State University in North Carolina,
high doses of
quercetin reduced infections and boosted vigilance in athletes,
even though no changes were seen in immune markers, inflammation,
or free radical damage.
But, says Dr. Nieman, the claims made for
FRS are based more on speculation than science. Only one study
on the actual product
has been published. It found that two cans of FRS a day for six
weeks improved performance in a small group of elite cyclists—though
a formulation without quercetin resulted in some improvements too.
If you’re a recreational exerciser, any effect of FRS is
likely to be insignificant. Besides being unproven, it costs about
$2 a can and has 140 calories (though low-calorie versions are
available). If you’re looking for quercetin and other antioxidants,
eat more fruits and vegetables. Good quercetin sources include
apples, onions, broccoli, blueberries, red grapes, red wine, and
tea.

Q: In
August you said that maté has been linked
to esophageal cancer, possibly because of the hot temperature at
which
the herbal
tea is consumed. What about coffee and other hot drinks?
A: Studies dating to
the 1930s have linked scalding-hot beverages (and foods) to both
esophageal cancer and pre-cancerous lesions.
Chronic exposure of the esophagus to very high temperature can
damage tissue in the lining, setting the stage for cellular changes.
But this doesn’t mean you should give up coffee or tea. Here’s
why:
Most evidence comes from observations of large populations
in Asia and South America, where people regularly drink beverages
near
boiling temperature. Other factors likely play a role as well,
such as tobacco and alcohol use. Associations between hot beverages
and esophageal cancer are stronger in people who smoke and drink
a lot. In addition, something specific to certain beverages or
foods (potential cancer-causing compounds in maté, for example,
or the high salt content of hot soup) may increase the cancer risk.
The amount consumed may also matter more than temperature
alone. In a study from Uruguay in 2003, people who drank more than
a liter
a day of very hot maté had three times the risk of squamous-cell
esophageal cancer as those who drank less than a half-liter at
a warm or hot temperature.
Most people in the U.S. don’t
drink large amounts of very hot beverages. Moreover, the few studies
done in the West have
been inconsistent; one in 2001 in the British Journal of Cancer
found no link between very hot beverages and esophageal cancer.
Keep in mind that some hot beverages, like green tea, have been
linked to cancer protection in some (but not all) studies.
To be
on the safe side: Don’t make a habit of consuming beverages
(and foods) at scalding-hot temperatures—let them cool a
little first. The greatest risk factors for esophageal cancer are
alcohol and tobacco, so the best way to avoid this disease is to
not smoke and to drink moderately, if at all.

Q: My
family prefers broccoli stalks to the “flowers.” Which
is better for you?
A: All parts of broccoli
are good for you. Broccoli is one of the most nutritious vegetables,
providing vitamin C (a day’s
worth in a cup, chopped), potassium, B vitamins (including folate),
even some calcium and iron. Ounce for ounce, the florets and stalks
deliver equal amounts of these nutrients, according to the USDA.
Broccoli (and other cruciferous vegetables) also contains sulforaphane
and other compounds that may protect against certain cancers.
The
florets, however, outshine the stalks in beta carotene. And a study
in 2006 found that the florets had nearly twice as much
sulforaphane. The stalks, on the other hand, have more fiber. Eating
all parts of broccoli—even the leaves—is thus a good
idea.
Look for broccoli with dark green or purplish (not
yellowing) florets. To preserve nutrients, don’t overcook.
UC Berkeley Wellness
Letter, September 2008

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