Is Too Much Iron
Dangerous for Divers?
An interesting personal anecdotal report by
NASA researchers recently quantified a number of physiological changes,
previously detected in astronauts in outer space, in divers in an
underwater habitat off the coast of Florida. In the underwater habitat
during the nearly 2 week saturation dive at a depth of 19 meters,
researchers detected a decrease in hemoglobin and hematocrit and an
increase in body iron storage in divers. They also detected and
measured, perhaps for the first time, an increase in serum iron levels.
NASA scientists hypothesize exposure to increased oxygen pressure
during the dive indirectly caused neocytolysis or destruction of newly
formed circulating red blood cells (you will recall from biology
courses that hemoglobin protein binds to iron and transports oxygen in
red blood cells). Implicationsof neocytolysis include a potential for
increased release of iron into free form from the lysed RBC. Their
results, published in a leading journal, are of concern to divers
because excess iron in free form causes the formation of free radicals,
which damage DNA and proteins. The health implications of increased
body iron stores are well documented in medical literature and include
liver cirrhosis, liver cancer, cardiomyopathy, diabetes and cataracts.
Fortunately, I became aware of this study, Body Iron Stores and
Oxidative Damage in Humans Increased during and after a 10 to 12 Day
Undersea Dive, published in The Journal of Nutrition, but not before
some experienced anxious moments. I had just returned to USA from
Palau, where I had been captain/dive master on a live-aboard for 7
months, and went for a routine medical checkup. I requested an iron
test be conducted along with the usual blood tests to check for anemia
since I had recently cut red meat out of my diet. A few days later the
lab results came back normal except for serum iron levels, which were
quite elevated. My doctor informed me that iron overload produces
nearly the same symptoms as anemia or low iron. He suggested the cause
was most likely the primary hereditary disorder in Caucasians of
northern European descent, hereditary hemochromatosis, which affects 1
in 200 of that group. Since I am Caucasian and do have northern
European heritage, the likely culprit of iron overload was apparently
something I had little control over, or so I thought at the time.
Google searches yielded the above mentioned NASA study of divers and a
previous study with similar results detected in astronauts in outer
space. Since I had not been in outer space recently, there was a chance
the 3-4 daily dives in Palau could account for my iron overload.
Immediately, I contacted Diver’s Alert Network (DAN) and was put
directly through to the chief medical officer’s voice mail. The
following day, DAN's Dr. Nick Bird called to discuss my health issue
and disclosed DAN medical staff were unaware of any correlation between
iron overload and scuba diving. After that initial blood test, I
continued to have my serum iron as well as serum ferritin (body iron
stores), transferrin protein and alpha-fetoprotein (to rule out liver
cancer or cirrhosis) levels checked on a monthly basis.
In addition, I became proactive and initiated steps to mitigate the
effects of excess iron and to reduce iron intake. I donated blood to
remove iron, avoided vitamin C supplements, which help the gut absorb
iron, avoided multi-vitamins with iron, took the natural herb milk
thistle, continued with a no red meat diet and suspended scuba
activities. All tests returned normal except for the serum iron levels
and those levels began to drop 14% each month between June and August
and by September levels were down 40% from August and well within a
normal range. At that time, I contacted the lead researcher in the NASA
study to thank her and her colleagues for publishing their findings.
That information alone had encouraged me there could be another cause
for my iron overload other than an hereditary disorder, which
apparently is managed primarily by phlebotomy treatments.
At the end of the day, based on the length of time required for iron
levels of subjects in a followup NASA study to return to normal
(results related but not yet published) and the length of time it took
for my own iron levels to return to normal, the only countermeasure may
be to sit on the sideline for 3 months or just snorkel. Hopefully this
topic will be researched further and divers who make multiple daily
dives over an extended period of time will be made aware of the
potential risks and consequences of iron overload and will be
encouraged to have iron levels checked during their next physical.
Martin Kirk is a PADI Dive Master who developed iron overload after
logging 315 dives in 7 months