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SPRING 2016
D
ietary supplements are
popular among health- and
fitness-conscious people,
including recreational divers.
Divers often ask about the
possible benefits and adverse
effects of supplements, used
for either general wellness
or protection from certain diving injuries. Dietary
supplements are clearly helpful to people with a chronic
deficit of specific nutrients such as vitamin C (scurvy) or
vitamin D (rickets), but effects of supplements in healthy
people who eat a balanced diet are less obvious. The large
number of supplements available today far exceeds our
cumulative scientific capacity to study them all, and so use
of supplements grows beyond evidence of their benefits.
OXIDATIVE DAMAGE
Antioxidants are molecules found in cells throughout the
body where they help control the free radicals that result
from oxidative metabolism. Free radicals are reactive
oxygen species (ROS): chemically reactive oxygen-
containing molecules that may damage cells and tissues.
Most ROS are successfully contained by antioxidants.
Some oxidative damage to cells occurs all the time, but
most is repaired. Sustained damage, however, may cause
genetic changes, various diseases and faster aging.
Breathing hyperoxic gas mixes — those containing
more than 21 percent oxygen — for prolonged periods
causes oxidative damage in divers. This can affect the
eyes (causing myopia), the lungs (causing difficulty
breathing) and/or the central nervous system (causing
various symptoms, including convulsions). After
decades of research we have not managed to prolong
the time of symptom-free diving with hyperoxic
breathing gases; instead we have learned there are
limits on oxygen exposure that divers must obey.
In addition to hyperoxic breathing gas, factors such
as immersion, cold, hypoxia and exertion may increase
oxidative stress. Accumulation of low-level oxidative
damage over time may damage DNA and possibly
reduce longevity.
One manifestation of oxygen damage is loss of
arteries’ self-regulatory capacity, also known as
endothelial dysfunction. The endothelium, the inner
layer of the arteries in contact with the blood, releases
nitric oxide (NO), which relaxes the smooth muscles in
the arterial walls to increase their diameter and change
their tone. These mechanisms increase blood flow and/
or reduce blood pressure.
B Y P E T A R D E NOB L E , M . D . , D . S c .
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Dietary
Supplements
and Healthy
Foods for
Divers
RONSTIK/ISTOCKPHOTO.COM