Iron Metabolism: Interactions with Energy and Carbohydrate Availability

Abstract

The provision or restriction of select nutrients in an athlete’s diet can elicit a variety of changes in fuel utilization, training adaptation, and performance outcomes. Furthermore, nutrient availability can also influence athlete health, with one key system of interest being iron metabolism. The aim of this review was to synthesize the current evidence examining the impact of dietary manipulations on the iron regulatory response to exercise. Specifically, we assessed the impact of both acute and chronic carbohydrate (CHO) restriction on iron metabolism, with relevance to contemporary sports nutrition approaches, including models of periodized CHO availability and ketogenic low CHO high fat diets. Additionally, we reviewed the current evidence linking poor iron status and altered hepcidin activity with low energy availability in athletes. A cohesive understanding of these interactions guides nutritional recommendations for athletes struggling to maintain healthy iron stores, and highlights future directions and knowledge gaps specific to elite athletes.

The Hepcidin-25/Ferritin Ratio Is Increased in University Rugby Players with Lower Fat Mass

“…However, normal hepcidin levels among athletes remain a topic of debate [ 11 , 12 ]; while one study shows that the levels are higher in athletes [ 11 ], another reports that the levels are not elevated [ 12 ]. This discrepancy is partly ascribed to the fact that lean athletes have low ferritin levels, and resting hepcidin levels are generally regulated by the ferritin level [ 13 , 14 , 15 , 16 ]; however, in some cases, the hepcidin level is independent of the ferritin level. For instance, acute exercise increases the hepcidin level without changing the ferritin level due to exercise-induced inflammation caused by elevated interleukin-6 (IL-6) levels [ 14 , 15 , 16 ].…”

“…This discrepancy is partly ascribed to the fact that lean athletes have low ferritin levels, and resting hepcidin levels are generally regulated by the ferritin level [ 13 , 14 , 15 , 16 ]; however, in some cases, the hepcidin level is independent of the ferritin level. For instance, acute exercise increases the hepcidin level without changing the ferritin level due to exercise-induced inflammation caused by elevated interleukin-6 (IL-6) levels [ 14 , 15 , 16 ]. This higher hepcidin level can remain sustained for 2–3 days while the IL-6 level is in the normal range soon after the exercise [ 16 , 17 , 18 ].…”

“…For instance, acute exercise increases the hepcidin level without changing the ferritin level due to exercise-induced inflammation caused by elevated interleukin-6 (IL-6) levels [ 14 , 15 , 16 ]. This higher hepcidin level can remain sustained for 2–3 days while the IL-6 level is in the normal range soon after the exercise [ 16 , 17 , 18 ]. In addition, the hepcidin level is higher during an intensified training period than during a regular training period, independent of the ferritin level [ 19 ].…”

Current and Novel Reviews in Sports Nutrition

“…For this Special Issue, research leaders in sports nutrition were approached and invited to submit current reviews in their areas of expertise [ 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 ]. The topics are novel and wide-ranging, and include updates and insights on protein [ 11 , 12 ], dietary patterns and nutritional interventions to support sleep, older athletes, and sports performance [ 13 , 14 , 15 ], pre-exercise nutrition [ 16 ], supplementation with betaine, iron, and creatine [ 17 , 18 , 19 ], and sports nutrition research methodologies for body composition and muscle glycogen analysis [ 20 , 21 ]. A major emphasis in all of the papers was a focus on strengths and weaknesses for various sports nutrition strategies, and insights for future research.…”

“…Low carbohydrate and energy intake can negatively influence iron status in athletes and is often mediated by hepcidin expression. The comprehensive narrative review by McKay et al [ 18 ] recommended that athletes shorten the duration of low carbohydrate training periods to minimize potential effects on hepcidin and iron regulation. Creatine is one of the most popular sports nutrition supplements on the market, and Arzi et al [ 19 ] presented emerging evidence that creatine supplements may play a role in countering exercise-induced oxidative stress.…”