IRON STATUS MEASUREMENTS IN ELITES A glance at the title of a research article abstract, “Incidence of Iron Deficiency and Iron Deficient Anemia in Elite Athletes and Triathletes” led me to believe the results were going to be somewhat predictable. Women would likely show lower values in lab tests that measured iron status than men, due to their periodic blood loss from menstruation.
However, research from the University of Guelph in Ontario revealed that triathletes and runners of both genders had a HIGHER incidence of having at least one episode of iron deficiency (low serum iron value) than what had previously been reported in the scientific literature for endurance athletes.
Surprisingly, it was MALE elite triathletes and runners who had a higher incidence of iron deficiency anemia (low blood hemoglobin levels) than their female counterparts. About 88% of male triathletes had at least one low blood hemoglobin value compared with about 33% of male runners, 20% of female triathletes, and 0% female runners. According to the data, “although the athletes were appropriately treated with oral iron there was no observed correlation between iron intake” and the blood test levels.
Before discussing more results let’s first learn a little more about iron deficiency (ID) and iron deficiency anemia (IDA) as defined in this research study, and the methods employed.
Elemental iron in the body is bound to proteins, mostly found within certain cells and tissues. In red blood cells (RBCs), it is held within hemoglobin molecules, in skeletal muscle cells within myoglobin, and in the spleen stored as hemosiderin. A very small amount of iron circulates in the blood serum bound to a protein called transferrin.
Iron deficiency (ID) in this study was identified by the finding of a low blood serum iron level. Iron deficiency anemia (IDA) was identified by finding a low blood serum iron level PLUS a low hemoglobin level, reflecting a low number of RBCs, within a SINGLE (the same) blood test.
The article explains, “Iron is an important element that makes up the ‘heme’ molecules of hemoglobin within red blood cells” allowing them to bind and transport oxygen to tissues for use. In anemia, defined as too few RBCs, there is too little oxygen-carrying hemoglobin and therefore not enough capacity to deliver oxygen to the tissues. This can have an adverse effect on athletic performance*. To make matters worse, “endurance athletes are often thought to be at increased risk of ID and IDA”, the authors tell us, through several possible mechanisms**.
Methods: In this study, the four groups of subjects included a total of 38 elite runners (25) and triathletes (13), between the ages of 21 and 36 years of age, who had had blood drawn between spring 2009 and fall 2015. They were male (16) and female runners (9), and male (8) and female triathletes (5). All athletes resided in Canada, were affiliated with elite training centers there, and had “competed minimally at a national level (3) and the majority competed internationally (35)”
No race/ethnicity information was provided. The total number of serum iron and hemoglobin lab tests performed for each group was identified, but there was no information on the frequency of testing or the number of tests per individual subject (did each person have one or multiple draws, how often, and for what reasons?).
Athletes completed a written questionnaire about oral iron supplementation after the collection of blood data. Reports were collected about iron infusions or injections.
Results and discussion: In addition to the findings that pertain to ID and IDA in the four groups of athletes, it was found that “most athletes maintained weekly iron supplements over time.” As stated above, the research paper did not find that iron supplementation correlated with serum iron or hemoglobin levels; there was no evidence that taking supplements improved iron test results!
The scientists thought it was possible that oral iron dosages were too high, and that the larger amount taken daily may have had the effect of decreasing intestinal absorption rates (a natural response that protects the body from harmful iron overload). The recommended allowance for iron is quoted as 18mg/d for women and 8mg/d for men, with an upper limit set at 45mg/d. Athletes in the study were taking from 2 to 158 mg/d (on average, 80mg/d).
Scientists in this study cited evidence from other research that suggested taking lower doses (40-60 mg/d), may be one way to help increase absorption of supplemental iron. Another potentially beneficial tactic, they proposed, would be to take supplements in the morning before workouts. Their thinking is that greater “training volume or multiple high intensity workouts within the same day" might be blocking iron absorption.
There are more complicated details that won’t be discussed here. Like nearly every research study, this one's design has ‘limitations’ which also means there are limits to what we can conclude about the findings.
The authors mention that the retrospective nature of the work did not provide them with specific quantifiable information in such areas as dietary intake, training loads/performance, and menstrual/health history in women. For example, we don’t know from this study if there were differences in lab results between red meat-eaters and those who obtain iron mostly from plant sources or supplements.
The main message, in my opinion, is that non-elite athletes who repeatedly train for and compete in endurance events, especially triathlons, might wish to check measures of iron status as part of an annual physical. Iron deficiency and iron deficiency anemia may be more common than previously demonstrated. Men might consider themselves at equal or greater risk for this nutritional problem, for uncertain reasons. An unexplained decrease in performance, or undue fatigue or tiredness in training could be worthy of investigation.
Also, we are reminded that supplementation may not be the answer to all nutritional needs, and that more is not necessarily better. In the words of the researchers, “Ensuring sufficient dietary intake of heme iron, as well as adequate calories from a NUTRIENT RICH DIET to ensure energy balance as often as possible, is likely the BEST FORM OF PREVENTION”.
MORE SCIENCE for those who crave it:
*Anemia has the opposite effect on athletic performance as the drug EPO. Erythropoietin (EPO) is a naturally-occurring body hormone that stimulates the production of RBCs as needed to keep levels within the normal range. In the world of competitive sports, artificially manufactured EPO is considered to be a performance-enhancing drug, banned from use by athletes. It can boost the number of RBCs carrying oxygen to muscles, thereby improving aerobic capacity. Taking the drug EPO is a medical form of illegal blood doping. Thus, iron deficiency anemia represents the nearly opposite condition, red blood cell depletion.
**Mechanisms for increased risk of ID and IDA in endurance athletes proposed in the article include: 1) destruction of RBCs within very small blood vessels due to repeated foot-strike trauma, 2) poor blood flow in body organs, 3) bleeding from stomach lesions caused by frequent use of non-steroidal anti-inflammatory medications, NSAIDS, 4) loss of iron through urine related to poor blood flow in the kidneys, and 5) iron losses in sweat
"Incidence of Iron Deficiency and Iron Deficiency Anemia in Elite Runners and Triathletes". Coates, Alexandra BSc; MountJoy Margo MD PhD; Burr, Jamie PhD
Clin J Sport Med. 2017 Sep;27(5):493-498
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EARNED RUNS is edited and authored by me, runner and founder. I began participating in road races before 5Ks were common. I've been a dietitian, practiced and taught clinical pathology, and been involved with research that utilized pathology. I am fascinated with understanding the origins of disease as well as health.
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