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50 to 3,000 liters of wine per day. In studies of whole
wine, benefits could not be determined in light of the
confounding effects of alcohol consumption.
BEET JUICE
Beets are a great source of nitrates, which the body
can change into NO. Some studies have found that
NO can promote improvement in FMD, lowered
blood pressure, decreased oxygen needs for the same
level of exercise and enhanced exercise performance.
Mechanisms for such enhancements at the cellular and
muscular tissue levels, however, were not found. Other
studies contradict these findings and claim no effect of
nitrate supplementation on exercise performance or
other physiological functions.
Researchers studied the use of NO supplements in
divers with the rationale that NO may be involved in
bubble formation and the endothelial damage caused
by bubbles. In one study, nitroglycerin (an NO donor)
was given
intravenously
to animals 30
minutes before
decompression
from a three-
hour, 130-foot
(40-m) dive.
The amount
of venous gas bubbles after decompression was 10
times less in experimental animals than in controls.
Researchers also tested nitroglycerin in open-water scuba
divers to 100 feet (30 m) for 30 minutes and in hyperbaric
chamber dives to 60 feet (18 m) for 80 minutes. The
same divers did each dive twice. Thirty minutes before
the second dive in the same conditions, divers received
nitroglycerine by oral spray. The postdive amount of
venous gas bubbles detected in divers was smaller
when they received nitroglycerine before the dive.
These findings seemed promising at the time, but the
evidence was not sufficient to consider recommendation
of nitroglycerine to divers — the potential benefit
was demonstrated in experiments involving extreme
exposures not common in recreational diving.
Since that study, no other research has reproduced
these results or moved further toward a possible
practical application. Nitroglycerin is a powerful drug
that should not be used without a prescription. It can
cause side effects when taken alone or in interaction
with other drugs or supplements and thus should not
be taken for diving.
Supplements with L-arginine (another NO donor)
may help to lower blood pressure, and people who
take it should be aware of possible interactions with
any medications they are using. Beet juice, on the
other hand, may be added to your diet without much
cause for concern. Just remember that neither of these
products has been proven to offer specific protective
effects for divers.
TO SUPPLEMENT OR NOT TO SUPPLEMENT
Consuming dietary supplements and certain foods
may change the availability of substances such as NO
that participate in basic physiological processes. It may
even cause measurable but temporary changes in some
functions such as FMD. In experimental settings it may
affect the amount of venous gas bubbles present after
dives. But these effects are not so pronounced as to
suggest, for example, that an antioxidant will decrease
the risk of DCS in real-life diving or that without
these supplements diving would lead to long-term
health problems.
The U.S. Preventive Services Task Force, which regularly
reviews evidence and provides recommendations, found
that vitamin C, vitamin E and some other minerals and
supplements
studied provide
no benefit to
healthy subjects
with regard to
heart disease,
cancer and
mortality.
1
Many
other supplements on the market make various health
claims with little or no supporting evidence. A healthy
and balanced diet will provide all the micronutrients
you need. If you like chocolate, beware of excess sugar.
If you drink wine, enjoy it in moderation, and do not
drink before diving. Remember, your safety underwater
depends on your dive behaviors and good judgment, not
the foods you eat.
AD
Reference
1. Fortmann SP, Burda BU, Senger CA, Lin J, Beil T, O’Connor E, Whitlock EP. Vitamin, Mineral, and Multivitamin Supplements for the Primary
Prevention of Cardiovascular Disease and Cancer: A Systematic Evidence Review for the U.S. Preventive Services Task Force. Evidence Report
No. 108. AHRQ Publication No. 14-05199-EF-1. Rockville, Md.: Agency for Healthcare Research and Quality; 2013.
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