Is Too Much Iron Dangerous for Divers?
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