Iron Metabolism and Supplementation for Ultrarunners with Dr. Alannah McKay #192
Episode overview:
Alannah McKay completed a Bachelor of Science (Exercise, Health and Sports Science) at the University of Western Australia in 2014. Subsequently, Alannah completed a post-graduate position within the Physiology department at the Australian Institute of Sport, where she was involved in the preparation of many Australian athletes prior to the 2016 Rio Olympic and Paralympic games. Since, Alannah has submitted her PhD titled “The Effect of Dietary Manipulation on Iron Metabolism and the Immune System in Elite Athletes”, which was undertaken in partnership with the Australian Institute of Sport, Western Australian Institute of Sport and the University of Western Australia. Alannah joined Australian Catholic University as a Postdoctoral Research Fellow in 2020. Her research will continue to explore the impact of diet and exercise on a range of health outcomes in athletes, with a specific interest in iron metabolism.
Episode highlights:
(20:48) Iron metabolism and low-carb diets: 3 week ketogenic intervention followed by <24 hours of carbohydrate intake, low carb diets decrease hepcidin, the acute carb intervention did not restore hepcidin, low carb states are when you are at greater risk for iron deficiency
(39:40) What iron supplements to use: ferrous sulfate, 100mg of elemental iron, maltofer, deficiency versus topping off, tailor frequency and dosing, avoid multivitamins
(47:39) Frequency of supplementation: absolute and relative absorption, the more iron you consume the more you absorb, alternate day dosing is well supported, mechanistic reasoning
Our conversation:
(0:00) Introduction: the problematic, impactful, and confusing areas of iron status and iron supplementation, introducing Dr. Alannah McKay’s background as a researcher and practitioner
(2:42) Alannah’s background: a glowing start to her career, working at the Australian Institute of Sport, current work with Louise Burke around iron metabolism, carbohydrate metabolism, and female athletes
(4:59) You can’t do much with alphabet soup: interdisciplinary and practical research
(6:42) The iron metabolic pathway: iron cannot be produced by the body, it is absorbed with 2-35% efficiency at the level of the gut, non-heme iron (vegetarian sources) are harder to absorb, combining heme and non-heme sources is ideal
(9:02) Uses of iron in the body: hemoglobin in red blood cells, iron is stored in ferritin, use in the spleen, liver, and other tissues
(10:15) Hepcidin: a regulatory hormone, when iron levels decrease hepcidin also decreases, prompting more iron to be absorbed, hepcidin can also block iron absorption when you have too much
(12:09) IL-6 and timing iron intake: IL-6 correlates with hepcidin, post-exercise IL-6 and hepcidin increase, decreasing iron absorption, setup for timing iron supplementation
(14:26) Exercise duration and iron absorption: examples, duration of exercise is the greatest predictor of IL-6 because muscle glycogen stores deplete, IL-6 is released to increase glucose, thus iron absorption is impaired
(17:14) IL-6 study: is IL-6 released due to low energy or low glucose, methods, manipulating total energy and carbohydrate levels in endurance racewalkers, results, carbohydrate level is more essential than total energy for signaling of IL-6, study by Ida Heikura
(20:48) Iron metabolism and low-carb diets: 3 week ketogenic intervention followed by <24 hours of carbohydrate intake, low carb diets decrease hepcidin, the acute carb intervention did not restore hepcidin, low carb states are when you are at greater risk for iron deficiency
(22:49) Restoring carbohydrate levels post-keto: 2-3 days to replenish glucose stores, iron metabolism could take weeks
(24:14) Ferritin cutoffs: previous KoopCast episode on live high-train low, should there be a ferritin cutoff for large training volumes, the impact of training load on iron levels in racewalkers, overview of iron utilization mechanisms, preloading might be dangerous
(27:30) Supplementing iron in training: when to avoid supplementation, monitoring athlete iron status, individual genetic and personal variation, supplementing for female athletes especially during training camps might be useful
(28:47) Iron for altitude training: 2-3 weeks prior is sufficient, upcoming paper with iron metabolism at altitude, at altitude you absorb 2.5x more iron, this can be a benefit or a drawback
(30:08) Avoiding intensified training when iron levels are low: Koop’s process, correcting low hematological levels before starting hard training, Alannah’s ultramarathon athlete, reducing training load to correct iron deficiency, RED-S and iron deficiency
(33:24) Iron supplementation: check out Alannah’s approachable 10-minute article, link in the show notes, considering type of iron supplementation, timing, and dosing
(35:27) Complications with iron supplementation: 100mg of elemental iron / day is the standard, but every athlete needs to be tested against the standard to identify what works for them, this takes time, oral iron supplements take 8-12 weeks
(37:09) Iron formulation: ferrous salts are a good affordable option, athletes will have to supplement frequently so cost is crucial, the state of research on slow-release capsules, salts are a good place to start, examples
(39:40) What iron supplements to use: ferrous sulfate, 100mg of elemental iron, maltofer, deficiency versus topping off, tailor frequency and dosing, avoid multivitamins
(43:35) Timing of supplementation: morning is best, example of research with dancers, nighttime intake is fine, iron intake may be enhanced 30 minutes pre- or post-exercise, >90min post-exercise will be inhibited from hepcidin, pre-exercise may be best for ultrarunners
(47:39) Frequency of supplementation: absolute and relative absorption, the more iron you consume the more you absorb, alternate day dosing is well supported, mechanistic reasoning
(51:36) Everything and the kitchen sink: examples of athlete strategies for maximizing iron, iron infusions have minor risks compared to oral supplementation but are a good option if needed
(53:22) Doping control: make sure your supplements are NSF certified, iron and vitamin C are okay, other ingredients in iron supplements are suspect for doping violations
(54:04) Wrap-up: giving thanks, check out links in the show notes, where to find Alannah
(55:53) Outro: additional resources, commitment to no sponsorship, check out Research Essentials for Ultrarunning, Research Essentials discussion of how ultramarathons affect iron metabolism, a sneak peak of future KoopCasts
Additional resources:
Papers discussed-
CONTEMPORARY APPROACHES TO THE IDENTIFICATION AND TREATMENT OF IRON DEFICIENCY IN ATHLETES
Chronic Adherence to a Ketogenic Diet Modifies Iron Metabolism in Elite Athletes
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