Hematological status of male runners in relation to the extent of physical training

Professional Female Athletes Are at a Heightened Risk of Iron-Deficient Erythropoiesis Compared With Nonathletes

This study primarily aimed to quantify and compare iron status in professional female athletes and nonathletes. Furthermore, this study also aimed to identify differences in iron status according to sporting discipline and explore the relationship between ferritin concentration and weekly training volume in professional athletes. A total of 152 participants were included in this study, including 85 athletes who were members of senior teams (handball, n = 24; volleyball, n = 36; soccer, n = 19; and judo, n = 6) involved at the highest level of competition and 67 nonathletes. A significantly greater proportion (p = .05) of athletes (27%) demonstrated iron-deficient erythropoiesis (IDE) compared with nonathletes (13%). There were nonsignificant differences (p > .05) in the prevalence of iron deficiency (ID; 49% vs. 46%) and iron deficiency anemia (IDA; 2% vs. 4%) between athletes and nonathletes. Similarly, the prevalence of ID, IDE, and IDA was not significantly different between sports (p > .05). Furthermore, training volume was negatively correlated with ferritin concentration in athletes (r: −.464, moderate, p < .001). Professional female athletes are at a heightened risk of IDE compared with nonathletes; therefore, they should be periodically screened for ID to reduce the deleterious effects on training and performance. The similar prevalence of ID, IDE, and IDA found across athletes competing in different sports suggests that overlaps exist between handball, volleyball, soccer, and judo athletes regarding risk of disturbance in iron metabolism.

Iron Deficiency in Athletes

Adequate body stores of iron are necessary for optimal endurance exercise performance. Severe iron depletion resulting in overt iron-deficiency anemia clearly depresses endurance fitness, but it is not clear if milder degrees of iron deficiency (low serum ferritin with normal hemoglobin levels) impair physical capacity. The question is an important one for athletes, particularly females, who are particularly prone to iron deficiency without anemia. This review examines research data, in both animals and humans, which have addressed this issue. Constructing guidelines based on this often-conflicting body of information is difficult. Routine screening is advocated for at-risk athletes, particularly elite-level female competitors in distance sports, and, although controversial, many authorities recommend iron treatment for athletes with hypoferritemia (ferritin <12-20 ng/mL), even without overt anemia. However, “blind” supplementation with oral iron by athletes is not recommended.

Energy needs of athletes

Each athlete has unique energy requirements, which underpin their ability to meet total nutritional goals. For everyday dietary planning and evaluation, energy requirements can be predicted via estimations of RMR and activity levels. Research methods such as indirect calorimetry and DLW allow energy requirements to be measured, and may be useful to confirm situations in which an athlete has a true energy balance anomaly. There is some evidence that individual athletes may have reduced energy requirements, although this occurs less frequently than is reported. Most self-reports of food intake substantially under-estimate energy intake, due to under-reporting or under-eating during the period of record keeping. Many athletes are over-focused on reducing body mass and body fat below levels that are consistent with long-term health and performance. Restrained eating can cause significant detrimental outcomes to body function. Leptin may be involved in modulating or mediating some of these changes. Athletes should use their energy budget to choose foods that provide macronutrient and micronutrient needs for optimal health and performance. Practical advice may help athletes to achieve energy intake challenges.

Guidelines for daily carbohydrate intake: do athletes achieve them?

Official dietary guidelines for athletes are unanimous in their recommendation of high carbohydrate (CHO) intakes in routine or training diets. These guidelines have been criticised on the basis of a lack of scientific support for superior training adaptations and performance, and the apparent failure of successful athletes to achieve such dietary practices. Part of the problem rests with the expression of CHO intake guidelines in terms of percentage of dietary energy. It is preferable to provide recommendations for routine CHO intake in grams (relative to the body mass of the athlete) and allow flexibility for the athlete to meet these targets within the context of their energy needs and other dietary goals. CHO intake ranges of 5 to 7 g/kg/day for general training needs and 7 to 10 g/kg/day for the increased needs of endurance athletes are suggested. The limitations of dietary survey techniques should be recognised when assessing the adequacy of the dietary practices of athletes. In particular, the errors caused by under-reporting or undereating during the period of the dietary survey must be taken into account. A review of the current dietary survey literature of athletes shows that a typical male athlete achieves CHO intake within the recommended range (on a g/kg basis). Individual athletes may need nutritional education or dietary counselling to fine-tune their eating habits to meet specific CHO intake targets. Female athletes, particularly endurance athletes, are less likely to achieve these CHO intake guidelines. This is due to chronic or periodic restriction of total energy intake in order to achieve or maintain low levels of body fat. With professional counselling, female athletes may be helped to find a balance between bodyweight control issues and fuel intake goals. Although we look to the top athletes as role models, it is understandable that many do not achieve optimal nutrition practices. The real or apparent failure of these athletes to achieve the daily CHO intakes recommended by sports nutritionists does not necessarily invalidate the benefits of meeting such guidelines. Further longitudinal studies of training adaptation and performance are needed to determine differences in the outcomes of high versus moderate CHO intakes. In the meantime, the recommendations of sports nutritionists are based on plentiful evidence that increased CHO availability enhances endurance and performance during single exercise sessions.

Micronutrients: interaction between physical activity, intakes and requirements

The present literature review examines the following questions: (a) What is the evidence that micronutrient requirements are increased in physically active people? (b) Is there an association between physical activity and micronutrient intake? (c) Are there any significant differences between indices of micronutrient status between physically active and inactive people? The available data suggest that micronutrient requirements are increased in physically active people because of increased losses through sweat, urine and faeces, and an increased need for defence against free radicals. However the evidence is controversial, and it is not possible to make any quantitative estimations. Micronutrient requirements in moderately active people are not likely to be very much above the levels recommended for the general population. The intake of micronutrients increases with increasing energy intake. Therefore, physically highly active people (athletes) have higher micronutrient intakes than untrained subjects. However, moderate physical activity does not necessarily affect daily micronutrient intake. The available indices of micronutrient status do not support the belief that micronutrient status is compromised in highly trained athletes, even without use of dietary supplements. Hence, there are no reasons to believe that the situation would be different in people who are only moderately active. The results suggest that micronutrient status is adequate for health and functional performance in physically active people who follow a normal, mixed Western diet.

Indicators of vitamin and mineral status in athletes' blood: a review

This review examines the hypothesis that vitamin and mineral status in athletes is inadequate for optimal sports performance. The review is based on indicators determined from blood and on studies published since 1980. Most of the studies did not find micronutrient status in athletes to be different from untrained controls. The serum ferritin concentration in females was lower than in males (27 vs. 78 micrograms.L-1), and the prevalence of low serum ferritin concentration was higher in female athletes than in untrained female controls (37 vs. 23%). Supplementation of water-soluble vitamins and iron was associated with an improvement in the corresponding indicators. Excluding a few studies with mildly anemic subjects, improvements in indicators of micronutrient status were not associated with enhanced athletic performance. Consequently, the levels of indicators of micronutrient status seen in athletes' blood were apparently compatible with optimal physical performance.

Effects of high volume and/or intense exercise on selected blood chemistry parameters

The goal of athletic training is to provide the body with a stimulus to adapt, increasing the capacity of the various systems to perform increased work loads. However, the magnitude of the stress must be large enough to induce the synthesis of new enzymes, tissues, and yet not so large that the biochemical and physiological processes of recovery are depressed. As each individual undergoes this process at a different rate, objective evaluation of the level of fatigue and adaptation is of enormous value in directing the training program of an athlete. The role of iron in the body is such that this element can be used as a marker of both adaptation to training and as an indicator of an acute inflammatory response to exercise. The various clinical measurements of iron in transport, storage, and in hematological parameters are discussed in this paper, relative to athletic populations. In addition expected changes in the level of the acute inflammatory protein, alpha 1-antitrypsin are also discussed relative to acute and chronic training protocols. Data is presented indicating that measurement of serum iron, transferrin, serum ferritin, and alpha 1-antitrypsin can be used to differentiate between an inflammatory response to tissue damage and infection. These parameters can also provide information as to the state of recovery, or lack thereof, experienced by an athlete to both acute and chronic training programs. The use of biochemical markers can help to avoid an overstress situation.