Beef Protein and Iron Status in Endurance Athletes

Endurance athletes are often subjected to high training loads, which increases their energy needs. These needs must be met by consuming the necessary macro and micronutrients to protect their health and support their performance. Among the micronutrients that athletes need is iron, a trace mineral that has a direct relationship with many proteins and enzymes, as it is an essential component of them, facilitating their transport and storage. Iron plays a critical role in the athletic performance of endurance athletes, as it is involved in the synthesis of hemoglobin and in oxygen transport, so maintaining adequate iron levels in the blood can lead to an increase in oxygen consumption (1), mainly in athletes who have a deficiency of this mineral.

Various studies indicate that endurance athletes have a higher tendency to develop iron deficiency and depletion compared to the general population (2, 3), which over time can become anemia. This deficiency is usually caused by a combination of factors, including:

• A poor contribution of nutrients in the diet.
• An increase in the demand for iron, due to the need for an increase in hemoglobin levels.
• An increase in iron loss due to possible gastrointestinal bleeding during running, through losses from sweat and urine, and due to menstruation, in women of reproductive age.
• Intravascular hemolysis, consisting of the destruction of erythrocytes due to the increased speed in blood circulation during running, the compression of the capillaries in the sole of the foot, the increase in body temperature, and the fragility of the blood cell membrane due to an increase in adrenaline levels.
• An increase in hepcidin levels, a peptide hormone that is a central regulator of iron metabolism in humans and that possesses antimicrobial properties (4, 5).

• A factor that, in our opinion, should not be included as a cause of iron deficiency is the increase in plasma volume. This factor can cause low hematological values in endurance athletes, but in most cases, these are accompanied by normal blood iron levels (serum iron). For this reason, the most reliable indicators of a possible iron deficiency in athletes are ferritin (a protein that stores iron in the body and releases it in a controlled manner), serum iron (the amount of iron present in the blood), and the transferrin saturation index (measured through total iron-binding capacity and serum iron value), using hemoglobin (an oxygen-carrying protein) as an indirect value.

The rate of depletion of iron stores depends on a balanced relationship between the loss of body iron and the intake of both heme iron (the organic form of iron derived from animals) and non-heme iron (the inorganic form of iron derived from vegetables and grains). We must take into account that not all the intake of heme and non-heme iron from the diet is absorbed by the body, so an imbalance between iron needs and its absorption (bioavailability) is what will lead to a deficiency of this mineral, or even to anemia.

When planning the diet of our athletes, we must take into account that both milk-derived proteins, such as casein and whey protein, as well as eggs and albumin, inhibit iron absorption. Soy protein also presents limitations in iron absorption due to its phytic acid content (6). On the other hand, heme iron absorption is increased by the co-administration of animal proteins, which are a source of iron, zinc, vitamin B12, and essential fatty acids (2, 7).

In this regard, in a recent study conducted at the University of Greenwich (8), the effects of intake of hydrolyzed meat protein (Crown Sport Nutrition), whey protein, and carbohydrates (maltodextrin) were compared on aerobic performance, body composition, muscle thickness, ferritin concentration, and blood health parameters. In this study, 30 male triathletes between 35 and 60 years old were analyzed, who followed a training control and nutritional control program, lasting 10 weeks.The results showed that only hydrolyzed meat protein produced an increase in dietary heme iron and a significant rise in blood ferritin concentration, in addition to other positive effects for sports performance such as the reduction of body composition and the maintenance or increase of muscle mass.

Conclusions

• The ideal source of iron for athletes should come from a complete and balanced diet.
• Iron supplementation (oral or intravenous) should only be used when the diet is insufficient to cover an athlete's iron-deficient states and they present with iron deficiency or anemia.
• Consuming foods with a high density of micronutrients in the diet is the best method to optimize physical adaptations, speed up recovery processes, and prevent nutritional deficiencies, preserving iron stores in endurance athletes.
• The consumption of iron in the form of high-quality hydrolyzed meat protein within the diet can be a valid alternative in the prevention of iron deficiencies in endurance athletes.

References

1. Friedmann B, Weller E, Mairbaurl H, Bärtsch P. (2001). Effects of iron repletion on blood volume and performance capacity in young athletes. Medicine and Science in Sports and Exercise, 33(5):741-746.
2. Lombardi G, Lippi G, Banfi G. (2014). Iron requirements and iron status of athletes. In: Maughan R, editor. Sports Nutrition. West Sussex: International Olympic Committee. p. 229–241.
3. Clénin G, Cordes M, Huber A, Schumacher YO, Noack P, Scales J, Kriemler S. (2015). Iron deficiency in sports – definition, influence on performance and therapy. Swiss Medical Weekly, 145:w14196
4. Sim M, Dawson B, Landers G, Swinkels DW, Tjalsma H, Trinder D, et al. (2013). Effect of exercise modality and intensity on post-exercise interleukin-6 and hepcidin levels. Int J Sport Nutr Exerc Metab, 23:178–186.
5. Ishibashi A, Maeda N, Sumi D, Goto K. (2017). Elevated Serum Hepcidin Levels during an Intensified Training Period in Well-Trained Female Long-Distance Runners. Nutrients, 9:277.
6. Jenkinson DM, Harbert AJ. (2008). Supplements and sports. American Family Physician, 78:1039–1046.
7. Phillips SM. (2012). Nutrient-rich meat proteins in offsetting age-related muscle loss. Meat Science, 92:174–178.
8. Naclerio F, Seijo M, Larumbe-Zabala E, Ashrafi N, Christides T, Karsten B, Nielsen BV. (2017). Effects of Supplementation with Beef or Whey Protein Versus Carbohydrate in Master Triathletes. J Am Coll Nutr, 19.

AUTORES

Dr. Marcos Seijo, MSc. Dunia Pantoja