Nutritional problems and measures in elite and amateur athletes

Nutrient Adequacy in Endurance Athletes

Proper nutrition is critical for optimal performance in endurance athletes. However, it is unclear if endurance athletes are meeting all their energy and nutrient needs. We examined if endurance athletes are meeting their nutritional requirements and if this differed by sex. Ninety-five endurance athletes (n = 95; 50.5% men; 34.9 ± 12.9 y) participated in the study. Dietary intake was evaluated using the 24 h dietary recall method. Energy and nutrient intakes were calculated using the ESHA Food Processor Diet Analysis Software and compared against reference nutrient intakes. Endurance athletes did not consume the recommended amount of energy (76.8% of athletes), carbohydrates (95.8%), linoleic acid (75.8%), α-linolenic acid (ALA) (77.9%), eicosatetraenoic and docosahexaenoic acid (96.8%), dietary fiber (49.5%), vitamins D (93.7%), E (71.6%), and K (54.7%), folate (54.7%), pantothenic acid (70.5%), biotin (83.2%), manganese (58.9%), magnesium (56.8%), chromium (91.6%), molybdenum (93.7%), choline (85.3%), and potassium (56.8%), and consumed too much saturated fat (50.5%) and sodium (94.7%) than recommended. Fisher's Exact test showed that the requirements for dietary fiber (70.8% vs. 27.7%), ALA (87.5% vs. 68.1%), and total water (70.8% vs. 44.7%) were not met by more men versus women (p < 0.05). The needs for protein (70.2% vs. 25%) and vitamin B12 (46.8% vs. 22.9%) were not met by more women compared to men (p < 0.05). These findings need to be confirmed by a larger study.

Dietary Acid-Base Balance in High-Performance Athletes

Physical exercise leads to metabolic changes that affect the acid-base balance in skeletal muscles and other tissues. Nutrition is one of the factors that may influence the acid-base balance in the body. Keeping alkaline circumstances in the body is important not only for health and athletic performance in training but also during competition in many sport events. This is especially significant for athletes who practice in sport at the highest level of competition. The aim of the study was to determine the dietary acid-base balance in competitive Lithuanian high-performance athletes, and to evaluate the effect of actual diets of athletes on NEAP (net endogenous acid production), muscle mass and body mineral content during a four-year Olympic cycle. The research participants were 18.1 ± 3.3-year-old Lithuanian high performance athletes (n = 323). The actual diet was investigated using the 24 h recall dietary survey method. The measurements of body composition were performed using BIA (bioelectrical impedance analysis). The potential renal acid load of the diets of athletes (dietary PRAL) and NEAP were calculated. In 10.2% of athletes, NEAP exceeds 100 mEq · day-1 and is on average 126.1 ± 32.7 mEq · day-1. Higher NEAP in athletes is associated with lower muscle mass (β -1.2% of body weight, p < 0.001) but has no effect on the amount of minerals in the body (β 0.01% of body weight, p = 0.073). Overall, 25-30% of Lithuanian high-performance athletes use high-protein diets (2.0-4.8 g · kg-1 · day-1) leading to a dietary acid-base imbalance as well as an excessive production of endogenous acids in the body. Athletes are recommended to consume higher amounts of potassium and magnesium. An increase in calcium intake up to 1500 mg per day is recommended. In exceptional cases, periodised nutrition for athletes may involve diets complemented with bicarbonate and/or beta-alanine supplements.

Macronutrient Intakes in 553 Dutch Elite and Sub-Elite Endurance, Team, and Strength Athletes: Does Intake Differ between Sport Disciplines?

Web-based 24-h dietary recalls and questionnaires were obtained from 553 Dutch well-trained athletes. The total energy and macronutrient intake was compared between discipline-categories (endurance, team, and strength) within gender, and dietary inadequacy, i.e., too low or high intakes, according to selected recommendations and guidelines, was evaluated by applying a probability approach. On average, 2.83 days per person were reported with a mean energy intake of 2566-2985 kcal and 1997-2457 kcal per day, for men and women, respectively. Between disciplines, small differences in the mean intake of energy and macronutrients were seen for both men and women. Overall, 80% of the athletes met the suggested lower-limit sport nutrition recommendation of 1.2 g·kg^-1 of protein per day. The carbohydrate intake of 50%-80% of athletes was between 3 and 5 g·kg^-1 bodyweight, irrespective of the category of their discipline. This can be considered as low to moderate, in view of their daily total exercise load (athletes reported on average ~100 minutes per day). In conclusion, only small differences in the mean energy and macronutrient intake between elite endurance, strength, and team sport athletes, were found. The majority of the athletes were able to meet the generally accepted protein recommendation for athletes, of 1.2 g·kg^-1. However, for most athletes, the carbohydrate intake was lower than generally recommended in the existing consensus guidelines on sport nutrition. This suggests that athletes could either optimize their carbohydrate intake, or that average carbohydrate requirements merit a re-evaluation.

Unique aspects of competitive weightlifting: performance, training and physiology

Weightlifting is a dynamic strength and power sport in which two, multijoint, whole-body lifts are performed in competition; the snatch and clean and jerk. During the performance of these lifts, weightlifters have achieved some of the highest absolute and relative peak power outputs reported in the literature. The training structure of competitive weightlifters is characterized by the frequent use of high-intensity resistance exercise movements. Varied coaching and training philosophies currently exist around the world and further research is required to substantiate the best type of training programme for male and female weightlifters of various age groups. As competitive weightlifting is contested over eight male and seven female body weight categories, the anthropometric characteristics of the athletes widely ranges. The body compositions of weightlifters are similar to that of athletes of comparable body mass in other strength and power sports. However, the shorter height and limb lengths of weightlifters provide mechanical advantages when lifting heavy loads by reducing the mechanical torque and the vertical distance that the barbell must be displaced. Furthermore, the shorter body dimensions coincide with a greater mean skeletal muscle cross-sectional area that is advantageous to weightlifting performance. Weightlifting training induces a high metabolic cost. Although dietary records demonstrate that weightlifters typically meet their required daily energy intake, weightlifters have been shown to over consume protein and fat at the expense of adequate carbohydrate. The resulting macronutrient imbalance may not yield optimal performance gains. Cross-sectional data suggest that weightlifting training induces type IIX to IIA fibre-type transformation. Furthermore, weightlifters exhibit hypertrophy of type II fibres that is advantageous to weightlifting performance and maximal force production. As such, the isometric peak force and contractile rate of force development of weightlifters is ~15-20% and ~13-16% greater, respectively, than in other strength and power athletes. In addition, weightlifting training has been shown to reduce the typical sex-related difference in the expression of neuromuscular strength and power. However, this apparent sex-related difference appears to be augmented with increasing adult age demonstrating that women undergo a greater age-related decline in muscle shortening velocity and peak power when compared with men. Weightlifting training and competition has been shown to induce significant structural and functional adaptations of the cardiovascular system. The collective evidence shows that these adaptations are physiological as opposed to pathological. Finally, the acute exercise-induced testosterone, cortisol and growth hormone responses of weightlifters have similarities to that of following conventional strength and hypertrophy protocols involving large muscle mass exercises. The routine assessment of the basal testosterone : cortisol ratio may be beneficial when attempting to quantify the adaptive responses to weightlifting training. As competitive weightlifting is becoming increasingly popular around the world, further research addressing the physiological responses and adaptations of female weightlifters and younger (i.e. ≤17 years of age) and older (i.e. ≥35 years of age) weightlifters of both sexes is required.

Micronutrient deficiency and cognitive and physical performance in Indian children

Several micronutrient deficiencies affect functional, particularly cognition and physical performance of children. Identifying and preventing sub-clinical deficiencies may be important so that adverse effects on functional performance by these deficiencies, particularly of iron and the B vitamins, are prevented. There is also the potential for childhood micronutrient deficiencies to have long-term effects that affect health and productivity in adulthood. This is especially relevant in a developing country such as India, which faces the dual burden of malnutrition and where the prevalence of these deficiencies is high. This review highlights the extent of micronutrient deficiencies in Indian children and focuses on the effect of deficiencies of the B vitamins and iron on cognitive and physical performance in children. Most studies on multiple micronutrient supplementation or fortification in Indian school children show modest effects on cognitive and physical performance, and it is relevant to point out that these studies have largely been conducted on urban children with mild deficiency at most; children with moderate or severe deficiency have not been studied. However, diets of rural children indicate large deficits in micronutrient intake, particularly of folic acid, riboflavin and iron, and their consequences have not been studied. With the limited evidence available, a short term but economical solution to ensure adequate micronutrient intakes could be through the fortification of staple cereals taken throughout the day. As increasing household incomes translate into an increase in food expenditure and diet diversification, it may become necessary to define upper limits of intake for nutrients in India, particularly as many commercial foods are fortified.

Unique aspects of competitive weightlifting: performance, training and physiology

Weightlifting is a dynamic strength and power sport in which two, multijoint, whole-body lifts are performed in competition; the snatch and clean and jerk. During the performance of these lifts, weightlifters have achieved some of the highest absolute and relative peak power outputs reported in the literature. The training structure of competitive weightlifters is characterized by the frequent use of high-intensity resistance exercise movements. Varied coaching and training philosophies currently exist around the world and further research is required to substantiate the best type of training programme for male and female weightlifters of various age groups. As competitive weightlifting is contested over eight male and seven female body weight categories, the anthropometric characteristics of the athletes widely ranges. The body compositions of weightlifters are similar to that of athletes of comparable body mass in other strength and power sports. However, the shorter height and limb lengths of weightlifters provide mechanical advantages when lifting heavy loads by reducing the mechanical torque and the vertical distance that the barbell must be displaced. Furthermore, the shorter body dimensions coincide with a greater mean skeletal muscle cross-sectional area that is advantageous to weightlifting performance. Weightlifting training induces a high metabolic cost. Although dietary records demonstrate that weightlifters typically meet their required daily energy intake, weightlifters have been shown to over consume protein and fat at the expense of adequate carbohydrate. The resulting macronutrient imbalance may not yield optimal performance gains. Cross-sectional data suggest that weightlifting training induces type IIX to IIA fibre-type transformation. Furthermore, weightlifters exhibit hypertrophy of type II fibres that is advantageous to weightlifting performance and maximal force production. As such, the isometric peak force and contractile rate of force development of weightlifters is ~15-20% and ~13-16% greater, respectively, than in other strength and power athletes. In addition, weightlifting training has been shown to reduce the typical sex-related difference in the expression of neuromuscular strength and power. However, this apparent sex-related difference appears to be augmented with increasing adult age demonstrating that women undergo a greater age-related decline in muscle shortening velocity and peak power when compared with men. Weightlifting training and competition has been shown to induce significant structural and functional adaptations of the cardiovascular system. The collective evidence shows that these adaptations are physiological as opposed to pathological. Finally, the acute exercise-induced testosterone, cortisol and growth hormone responses of weightlifters have similarities to that of following conventional strength and hypertrophy protocols involving large muscle mass exercises. The routine assessment of the basal testosterone : cortisol ratio may be beneficial when attempting to quantify the adaptive responses to weightlifting training. As competitive weightlifting is becoming increasingly popular around the world, further research addressing the physiological responses and adaptations of female weightlifters and younger (i.e. ≤17 years of age) and older (i.e. ≥35 years of age) weightlifters of both sexes is required.

Multiple micronutrient-fortified rice affects physical performance and plasma vitamin B-12 and homocysteine concentrations of Indian school children

Fortifying rice with multiple micronutrients could be a promising strategy for combat micronutrient deficiencies in developing countries. We determined the efficacy of extruded rice grains fortified with multiple micronutrients on the prevalence of anemia, micronutrient status, and physical and cognitive performance in 6- to 12-y-old, low-income school children in Bangalore, India. In a randomized, double-blind, controlled trial, 258 children were assigned to 1 of 3 intervention groups to receive rice-based lunch meals fortified with multiple micronutrients with either low-iron (6.25 mg) or high-iron (12.5 mg) concentrations or identical meals with unfortified rice. The meals were provided 6 d/wk for 6 mo. Anthropometric, biochemical, physical performance, and cognitive assessments were taken at baseline and endpoint. At baseline, study groups were comparable, with 61% of the children being anemic. However, only <10% were deficient in iron, vitamin A, and zinc. After 6 mo, plasma vitamin B-12 and homocysteine concentrations (both P < 0.001) as well as physical performance (P < 0.05) significantly improved in the intervention arms. No between-group differences were observed in hemoglobin concentration, anemia, and deficiencies of other micronutrients or cognitive function after 6 mo, but paired analyses revealed a small reduction in anemia prevalence in children in the low-iron group. The fortified rice was efficacious in improving vitamin B-12 status and physical performance in Indian school children.

Anthropometric characteristics and nutritional profile of young amateur swimmers

The aim of this study was to evaluate nutritional and anthropometric profiles of young swimmers belonging to semiprofessional teams. Thirty-six caucasian adolescent swimmers (22 boys and 14 girls) participated voluntarily in the study. Anthropometric data, dietary intake, and blood parameters were determined. Female swimmers had greater values of triceps, suprailiac, and abdominal skinfolds. Endomorphic somatotype was twofold greater in girls compared with in boys. Energy intake and protein intake per kilogram of body weight were significantly greater in boys compared to in girls. On the other hand, girls had significantly greater polyunsaturated fatty acid intake compared that of boys. Energy intake of boys and girls was below their requirements. In contrast, protein intake doubled the requirements of the study population. Furthermore, inadequate intake of carotenes, vitamin A, vitamin E, vitamin D, and folic acid was found in both boys and girls; girls also had inadequate intake of iron and calcium. Plasma levels of iron, vitamins C and E, and carotenes were similar in male and females swimmers, and they were within the normal range. In conclusion, young swimmers participating in the present study had differences between sexes in somatotypes. Adolescent swimmers had low average total energy intakes, excessive protein intake, and lower intake of several micronutrients in both sexes.

Nutrition guidelines for strength sports: sprinting, weightlifting, throwing events, and bodybuilding

Strength and power athletes are primarily interested in enhancing power relative to body weight and thus almost all undertake some form of resistance training. While athletes may periodically attempt to promote skeletal muscle hypertrophy, key nutritional issues are broader than those pertinent to hypertrophy and include an appreciation of the sports supplement industry, the strategic timing of nutrient intake to maximize fuelling and recovery objectives, plus achievement of pre-competition body mass requirements. Total energy and macronutrient intakes of strength-power athletes are generally high but intakes tend to be unremarkable when expressed relative to body mass. Greater insight into optimization of dietary intake to achieve nutrition-related goals would be achieved from assessment of nutrient distribution over the day, especially intake before, during, and after exercise. This information is not readily available on strength-power athletes and research is warranted. There is a general void of scientific investigation relating specifically to this unique group of athletes. Until this is resolved, sports nutrition recommendations for strength-power athletes should be directed at the individual athlete, focusing on their specific nutrition-related goals, with an emphasis on the nutritional support of training.

Athletes' dietary intake was closer to French RDA's than those of young sedentary counterparts

It has been demonstrated that athletes' dietary intake was relatively well-balanced according to the recommended dietary allowances (RDAs). In contrast, other studies have shown that athletes may have low energy intake or imbalance of protein and fat and insufficient minerals and vitamins. Nonetheless, we hypothesized that practicing a sport may allow young adults to have a nutritional status closer to recommended values. The purpose of this experiment was to study the nutritional status of young French adults, particularly to compare the nutritional status of trained young male and female athletes to those of young sedentary control subjects, and to national RDAs. A total of 85 young adults were recruited and filled a 4-day food and physical activity record. Dietary intake, energy expenditure, energy balance, carbohydrate, protein, fat, water, vitamins, and minerals were recorded. Data were analyzed with a software Nutrilog and statistics with Sigma Stat. Energy intake values were 9874 +/- 3050 kJ for the athletes and 7506 +/- 1845 kJ for control subjects. Athletes' nutritional status was closer to French RDAs than those of sedentary subjects who present a lower energy intake, a greater percentage of the energy intake from fat and lower values for minerals and vitamins. In conclusion, practicing a sport may allow athletes to balance their energy intake and expenditure and could be a good way to have a nutritional status closer to RDAs. Educational programs for students on proper food selection, eating habits and physical activity are needed to improve the nutritional status of these young French adults, particularly in sedentary students.

Diet, body composition, and bone mass in well-trained cyclists

Cycling is believed to be associated with low bone mass. In this study, we investigate food intake, body composition, and bone mass in well-trained young adult cyclists compared with those in sedentary controls. Four-day estimated diet records were used to study dietary intake in 31 cyclists and 28 sedentary controls (all male, 24yr old on average), together with maximal oxygen uptake (VO(2max)), body composition, and bone mass measurements (dual-energy X-ray absorptiometry). The VO(2max) values were twice as high as those in the cyclists, whereas no significant difference in bone mass was observed between cyclists and controls. A total of 10 cyclists and 9 controls had low bone mass. Total-body lean mass and appendicular skeletal muscle mass were higher in cyclists (p<0.001), whereas percentage of body fat was lower (p<0.001) compared with that of the controls. Energy and macro- and micronutrient intake was higher in the cyclists than in the controls (p<0.01). Energy consumption was considered adequate in the cyclists, whereas lipid and protein intake was higher than the American College of Sports Medicine recommendation. Lipid consumption negatively correlated with bone mass in the athletes. Our results demonstrate that cycling was associated with greater aerobic conditioning and lean mass without significant association with bone mass compared with sedentary controls.

Diagnóstico do estado nutricional dos atletas da Equipe Olímpica Permanente de Levantamento de Peso do Comitê Olímpico Brasileiro (COB)

Objetivou-se neste estudo diagnosticar o estado nutricional da Equipe Olímpica Permanente de Levantamento de Peso do Comitê Olímpico Brasileiro (COB). A amostra foi composta por 24 atletas, na faixa etária entre 16 e 23 anos, sendo 12 do sexo masculino (19,7 ± 2,4 anos) e 12 do feminino (19,2 ± 1,8 ano). Realizou-se o seguinte procedimento para o diagnóstico do estado nutricional: análise da adequação da ingestão de energia e dos macronutrientes - carboidratos (CHO), lipídios (LIP) e proteínas (PRO) -, por meio dos métodos Recordatório de 24 horas e Questionário de Freqüência de Consumo Alimentar, além da caracterização do perfil antropométrico. Os resultados da avaliação dietética indicaram que a distribuição energética entre os macronutrientes encontra-se adequada sendo de 54 ± 6,8% (CHO); 28,5 ± 5,9% (LIP); e 14,5 ± 3,4% (PRO) para os homens e 56,3 ± 4,7% (CHO); 28,6 ± 4,6% (LIP); e 13,7 ± 2,4% (PRO) para a equipe feminina. Entretanto, quanto ao consumo energético total, 83% dos atletas estavam com ingestão energética abaixo dos valores recomendados, considerando o alto nível de atividade física, promovendo deficiência calórica diária. O percentual de gordura corporal dos atletas do sexo masculino (3,6 ± 0,7%) indicou que todos estavam abaixo do padrão de referência, enquanto 58% dos esportistas do sexo feminino apresentavam excesso de gordura (17,9 ± 5,8%). Tem-se, como conclusão, que, apesar de os desportistas avaliados terem realizado distribuição energética adequada entre os macronutrientes, esta ainda não foi suficiente para suprir as exigências energéticas da modalidade, necessitando assim de orientação nutricional.

Dietary protein intake and renal function

Recent trends in weight loss diets have led to a substantial increase in protein intake by individuals. As a result, the safety of habitually consuming dietary protein in excess of recommended intakes has been questioned. In particular, there is concern that high protein intake may promote renal damage by chronically increasing glomerular pressure and hyperfiltration. There is, however, a serious question as to whether there is significant evidence to support this relationship in healthy individuals. In fact, some studies suggest that hyperfiltration, the purported mechanism for renal damage, is a normal adaptative mechanism that occurs in response to several physiological conditions. This paper reviews the available evidence that increased dietary protein intake is a health concern in terms of the potential to initiate or promote renal disease. While protein restriction may be appropriate for treatment of existing kidney disease, we find no significant evidence for a detrimental effect of high protein intakes on kidney function in healthy persons after centuries of a high protein Western diet.

Vitamin and mineral status: effects on physical performance

Public health recommendations encourage the selection of a balanced diet and increasing physical activity to foster health and well-being. Whereas the adverse effects of restricted intakes of protein, fat, and carbohydrate on physical performance are well known, there is limited information about the impact of low intakes of vitamins and minerals on the exercise capacity and performance of humans. Physically active people generally consume amounts of vitamins and minerals consistent with the recommendations for the general public. However, when intakes are less than recommendations, some noticeable functional impairments occur. Acute or short-term marginal deficiencies, identified by blood biochemical measures of vitamin B status, had no impacts on performance measures. Severe deprivation of folate and vitamin B12 result in anemia and reduce endurance work performance. Evidence of vitamin A and E deficiencies in athletic individuals is lacking apparently because body storage is appreciable. In contrast to vitamins, marginal mineral deficiencies impair performance. Iron deficiency, with or without anemia, impairs muscle function and limits work capacity. Magnesium deprivation increases oxygen requirements to complete submaximal exercise and reduces endurance performance. Use of vitamin and mineral supplements does not improve measures of performance in people consuming adequate diets. Young girls and individuals participating in activities with weight classifications or aesthetic components are prone to nutrient deficiencies because they restrict food intake and specific micronutrient-rich foods. This information will be useful to professionals who counsel physically active people and scientific groups who make dietary recommendations to improve health and optimize genetic potential.

Nutrition education intervention for college female athletes

OBJECTIVE

To evaluate the efficacy of a nutrition education intervention for college female athletes to improve nutrition knowledge, build self-efficacy with respect to making healthful dietary choices, and improve dietary intake.

DESIGN

A pretest-posttest control group design was implemented.

PARTICIPANTS

A women's soccer team (n =15) and a women's swim team (n = 15) were randomly assigned to experimental and control groups, respectively.

INTERVENTION

The intervention focused on nutrition knowledge, self-efficacy in making healthful dietary choices, and dietary practices to demonstrate treatment effect.

MAIN OUTCOME MEASURES

Dependent variables were nutrition knowledge, self-efficacy, and dietary practices. Independent variables were group assignment.

ANALYSES

The Mann-Whitney U test was used to analyze the results between groups, and the Fisher exact probability test was used to detect differences between groups in the number of positive dietary changes.

RESULTS

Treatment participants significantly improved nutrition knowledge, self-efficacy (P <.05), and the overall number of positive dietary changes (P <.03).

CONCLUSIONS

This study reduces the paucity of nutrition education intervention research among athletes and demonstrates the ability to increase not only nutrition knowledge, which is typically reported, but also self-efficacy and improvement in overall positive dietary changes during an 8-week intervention.

What are the dietary protein requirements of physically active individuals? New evidence on the effects of exercise on protein utilization during post-exercise recovery

Exercise and physical activity increase energy expenditure up to 10-fold. This brief review will focus on the effect of exercise on protein requirements. Evidence has accumulated that amino acids are oxidized as substrates during prolonged submaximal exercise. In addition, studies have determined that both endurance and resistance training exercise increase skeletal muscle protein synthesis and breakdown in the post-exercise recovery period. Studies using nitrogen balance have further confirmed that protein requirements for individuals engaged in regular exercise are increased. The current recommended intakes of protein for strength and endurance athletes are 1.6 to 1.7 g/kg and 1.2 to 1.4 g/kg per day, respectively. Presently, most athletes consume an adequate amount of protein in their diet. The timing and nutritional content of the post-exercise meal, although often overlooked, are known to have synergistic effects on protein accretion after exercise. New evidence suggests that individuals engaging in strenuous activity consume a meal rich in amino acids and carbohydrate soon after the exercise bout or training session.

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.

Magnesium, zinc, and chromium nutrition and athletic performance

Magnesium, zinc and chromium are mineral elements required in modest amounts for health and optimal performance. Accumulating evidence supports the hypothesis that magnesium and zinc play significant roles in promoting strength and cardiorespiratory function in healthy persons and athletes. Differences in study designs, however, limit conclusions about recommendations for intakes of magnesium and zinc needed for optimal performance and function. The role of chromium in supporting performance is not well established. There is a compelling need to confirm and extend findings of beneficial effects of magnesium and zinc function and performance of humans. Suggestions for an experimental model and specific topics for research to advance knowledge of mineral nutrition to promote attainment of genetic potential for optimal performance are provided.

Nutritional status, iron-deficiency-related indices, and immunity of female athletes

Nutritional status, iron-deficiency-related biochemical indices, and immunologic patterns of female Judo athletes and control subjects were evaluated. The subjects' 3-d food records showed that 41.0 kcal/kg of energy was consumed daily and the contributions of protein, fat, and carbohydrate to total energy intake were 12.5%, 29.2%, and 58.3%, respectively. The reported vitamin intakes of athletic subjects were above those of the recommended daily allowance, however, calcium and iron intakes were less than 100% of the recommended daily allowance. Intakes of energy, protein, phosphate, vitamin B1, and vitamin B2 were higher in the athletes than in the control subjects. Analysis using the Nutrient Adequacy Ratio and the Index of Nutritional Quality showed that athletic subjects had more desirable patterns than the control subjects. There was no any indication of anemia, which often occurs as a result of hemodilution in strenuously trained athletes. The subjects' immunologic patterns showed a slight immunosuppression. Iron, vitamin B1, niacin intakes were positively correlated with immunoglobulin (Ig) G levels in the athletes. The relation between nutrient intakes and the immune systems of endurance-trained athletes needs further investigation.

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.

Distúrbios nutricionais em atletas femininas e suas inter-relações

Pesquisas indicam que é elevada a prevalência de distúrbios alimentares em atletas femininas jovens envolvidas em esportes que preconizam a magreza e o baixo peso corporal, tais como ginástica olímpica e corridas de longa distância. A fim de compreender a etiologia destes problemas, esta revisão apresenta os principais distúrbios nutricionais encontrados em atletas femininas, incluindo definições, critérios para diagnóstico, fatores de risco, presença de desordens inter-relacionadas - anemia, irregularidades menstruais e desmineralização óssea e suas conseqüências sobre a saúde e rendimento atlético. É fundamental ressaltar a importância da nutrição no desempenho físico. A presença de um baixo peso corporal e um consumo energético severamente restrito é o principal fator de risco para o desenvolvimento de tais distúrbios. Como as atletas e seus treinadores não apresentam adequados conhecimentos sobre nutrição, é necessária uma orientação nutricional individualizada, de forma a evitar o desenvolvimento destas alterações.

Beyond the zone: protein needs of active individuals

There has been debate among athletes and nutritionists regarding dietary protein needs for centuries. Although contrary to traditional belief, recent scientific information collected on physically active individuals tends to indicate that regular exercise increases daily protein requirements; however, the precise details remain to be worked out. Based on laboratory measures, daily protein requirements are increased by perhaps as much as 100% vs. recommendations for sedentary individuals (1.6-1.8 vs. 0.8 g/kg). Yet even these intakes are much less than those reported by most athletes. This may mean that actual requirements are below what is needed to optimize athletic performance, and so the debate continues. Numerous interacting factors including energy intake, carbohydrate availability, exercise intensity, duration and type, dietary protein quality, training history, gender, age, timing of nutrient intake and the like make this topic extremely complex. Many questions remain to be resolved. At the present time, substantial data indicate that the current recommended protein intake should be adjusted upward for those who are physically active, especially in populations whose needs are elevated for other reasons, e.g., growing individuals, dieters, vegetarians, individuals with muscle disease-induced weakness and the elderly. For these latter groups, specific supplementation may be appropriate, but for most North Americans who consume a varied diet, including complete protein foods (meat, eggs, fish and dairy products), and sufficient energy the increased protein needs induced by a regular exercise program can be met in one's diet.

The effects of varying dietary fat on the nutrient intake in male and female runners

OBJECTIVE

The present study examined the effects of varying dietary fat levels on nutrients in female and male endurance runners.

METHODS

Three diets (low, medium and high fat) were designed for each subject using their food preferences and three-day food records. Each diet was eaten for 28 to 31 days. The diets were self-selected from seven-day sample menus. Twelve male and 13 female runners between 18 and 55 years of age who averaged 42 miles/week participated in the study. Daily food intakes, activity records and weekly palatability/hunger scales were completed.

RESULTS

Dietary fat intakes, as a percent of total energy intake (%E), averaged 17%E, 31%E, and 44%E on the low, medium and high fat diets, respectively. Energy consumption was less than their estimated energy expenditure (EEE) on all diets. On the low fat diet, the female runners were consuming approximately 60% of their EEE. As dietary fat increased, the difference between calorie intake and estimated energy expenditure became less and the subjects were less hungry on the two higher fat diets. For all subjects, as energy intakes increased, so did carbohydrate intake. Therefore, carbohydrate intake was not different on the two lower fat diets. Irrespective of gender, calcium and zinc intakes, which were below 1989 RDAs, increased with increasing fat intakes, between the low and medium fat diets. Zinc intake was also higher on the highest fat diet. Essential fatty acid intakes for females on the low fat diet were less than 2.5%E. Half of the female runners ate less than the RDA of calcium and zinc on the low fat diet and Fe on the medium fat diet.

CONCLUSION

This study suggests that endurance runners may not be consuming enough calories on a low fat diet and that increasing dietary fat increased energy consumption. On the low fat diet, essential fatty acids and some minerals (especially zinc) may be too low. A low fat diet could compromise health and performance.

Nutritional aspects of immunosuppression in athletes

The literature suggests that a heavy schedule of training and competition leads to immunosuppression in athletes, placing them at a greater risk of opportunistic infection. There are many factors which influence exercise-induced immunosuppression, and nutrition undoubtedly plays a critical role. Misinterpretation of published data and misleading media reports have lead many athletes to adopt an unbalanced dietary regimen in the belief that it holds the key to improved performance. Some sports have strict weight categories, whilst in others low body fat levels are considered to be necessary for optimal performance or seen as an aesthetic advantage. This leads some athletes to consume a diet extremely low in carbohydrate content which, whilst causing rapid weight loss, may have undesirable results which include placing the athlete at risk from several nutrient deficiencies. Complete avoidance of foods high in animal fat reduces the intake of protein and several fat-soluble vitamins. On the other hand, diets with a very high carbohydrate content are usually achieved at the expense of protein. In addition, anecdotal and media reports have often promoted the supposed performance benefits of certain vitamins and minerals, yet most athletes do not realise that micronutrient supplementation is only beneficial when correcting a deficiency, and to date there is little scientific evidence to substantiate claims that micronutrients act as an ergogenic aid. Moreover, excessive intakes of micronutrients can be toxic. Deficiencies or excesses of various dietary components can have a substantial impact on immune function and may further exacerbate the immunosuppression associated with heavy training loads. This review examines the role of nutrition in exercise-induced immunosuppression and the effect of both excessive and insufficient nutrient intake on immunocompetence. As much of the present literature concerning nutrition and immune function is based on studies with sedentary participants, the need for future research which directly investigates the relationship between exercise, training, immunity and nutrition is highlighted.

Hábitos e consumo alimentares de atletas nadadores

Estudou-se 27 atletas nadadores (14 mulheres e 13 homens) com idade entre 13 e 21 anos, com o objetivo de conhecer seus hábitos alimentares e consumo alimentar, aplicando-se questionários de registro e freqüência alimentar. O percentual de adequação foi determinado comparando-se as necessidades de cada indivíduo (calculadas teoricamente) com as quantidades consumidas. Os resultados indicaram que o consumo energético foi maior para os homens (média de 3 125Kcal contra 1 865Kcal das mulheres). O consumo dos demais nutrientes também apresentou-se superior para o sexo masculino, exceto para a vitamina C. A contribuição percentual de macronutrientes apresentou-se desequilibrada tanto para os homens quanto para as mulheres. Os homens apresentaram uma adequação baixa (70-80%) para os carboidratos e vitamina A, uma adequação excedente (> 110%) para proteínas, gordura, vitamina C e ferro, e uma adequação normal para os demais nutrientes. As mulheres apresentaram uma adequação marginal (< 70%) para os carboidratos, energia e cálcio; excedente para a vitamina C e normal para os demais nutrientes.

Diets of elite athletes: has the discipline of sports nutrition made an impact?

Although numerous descriptions exist of special diets and particular foods used by Greek athletes as early as 580 B.C., survey data on diets of Olympians of the modern era are virtually nonexistent. A survey in Helsinki in 1952 reported the diets of Olympic athletes to be high energy, high fat, and high protein. The 1952 Olympians reportedly consumed an average daily energy intake of 18,841 kJ, with 40% of energy coming from carbohydrate, 20% from protein, and 40% from fat. More recent data on elite level athletes reveal wide variation in dietary intake. For example, energy intakes of athletes from four countries ranged from 7699 to 24,845 kJ. Group percentages of energy from carbohydrate, protein, and fat ranged from 33 to 57%, 12 to 26%, and 29 to 49%, respectively. Comparing dietary intake data of athletes on an absolute basis, however, is primarily a comparison of body size. When the protein and carbohydrate intakes of elite athletes are calculated as grams per kilogram body weight, the range for protein is 1.0-4.3 g/kg body wt for protein and 3.5-6.9 g/kg body wt for carbohydrate. Interestingly, variations in carbohydrate intake diminished while protein intake varied by country. Although some data on diets of Olympians exist, the most remarkable finding when reviewing the literature is the paucity of data. The discipline of sports nutrition has arguably had a positive effect on sports performance. However, many unanswered questions remain and great strides remain to be made.

Nutrition for improved sports performance. Current issues on ergogenic aids

Several nutritional modifications have been used by athletes to improve performance. Recent attention has focused on high fat diets, branched-chain amino acids, creatine, carnitine, bicarbonate and phosphate loading, and caffeine. Of these, only caffeine, which is present in food but has no known nutritional value, appears on the list of substances banned by the International Olympic Committee (IOC). While there is a theoretical basis for each of these diet manipulations to enhance performance, there are insufficient data to state unequivocally that high fat diets, branched-chain amino acids, carnitine or phosphate loading are effective. Caffeine has been found to enhance endurance performance, while creatine and bicarbonate loading were generally found to benefit short term strenuous exercise. Acute ingestion of these diet manipulations appears safe, although some, like caffeine and bicarbonate, can cause gastrointestinal disturbances or other problems in certain individuals. Long term use of high fat diets may have negative consequences on health. The safety of long term use of these diet manipulations has not been established.

Calcium intakes of adolescent female gymnasts and speed skaters: lack of association with dieting behavior

Calcium intake and its association with dieting behavior were assessed in female adolescents competing in an aesthetic and a nonaesthetic sport (gymnastics and speed skating). Athletes were 25 skaters and 32 gymnasts competing at a provincial level or higher. Calcium intake was assessed by food frequency questionnaire; dieting behavior by the Eating Attitudes Test Dieting subscale; and body composition by skinfolds, height, and weight. Mean calcium intakes of both groups of athletes exceeded Canadian recommendations, and skaters' mean intakes exceeded U.S. recommendations; however, many individuals had low intakes. Gymnasts were leaner than skaters and had lower calcium intakes, but this difference was not associated with Dieting subscale scores, which were similar between sports and were not correlated with calcium intake. Athletes had higher mean calcium intakes than normally active adolescents studied (measured with a similar protocol) and had lower Dieting subscale scores. Thus, although calcium intakes of some athletes require attention, sport participation was associated with increased intakes. Also, for these athletes, dieting behavior did not directly interfere with calcium intake.

[Anthropometric and dietetic study of competitive swimmers from metropolitan areas of the southeastern region of Brazil]

The daily food intake and alimentary frequency of competitive swimmers of two clubs representative of the two largest cities in Brazil (S. Paulo and Rio de Janeiro) were studied. The 30 males and 37 females studied belonged to the swimming categories "junior" (15-17 yrs old) and "senior" (18-25 yrs old). Food intake obtained from self-register and 24 hour-recall showed similar results and therefore the 24 hour-recall was used for comparisons with the literature. Ages within both sexes were anthropometrically similar. The most frequently eaten foodstaffs were similar to those quoted by the metropolitan population of the respective areas. Moreover, the athletes from both cities reported similar food-supplements. The energy intake was found to average almost double the estimated value for the respective metropolitan populations, but were similar to results obtained for swimmers all over the world. Snacks between meals supplied 25-28% of the overall energy intake. The main caloric source were cereals. However, despite their contribution of almost 50% of the total energy intake, carbohydrates attained a level of only 55-60% of that recommended for competitive athletes. On the other hand, the protein intake found (2.5-3.0 g/kg/day) exceeded the recommended values by 100%. The fat intake particularly of satured fat, was also considered high. The swimmers' intake of micronutrients was well abone that quoted by the regular population of these metropolitan areas, when related to the caloric intake, but the values of Mg, Fe and vitamins A and D were somecohot lower than those recommended.(ABSTRACT TRUNCATED AT 250 WORDS)

Nutritional practices of elite athletes. Practical recommendations

The nutritional intake of elite athletes is a critical determinant of their athletic performance and ability to compete both physically and mentally. However, their demanding training and travel schedules in addition to a possible lack of nutritional knowledge may prohibit them from maintaining an optimal dietary intake. Sound scientific data about the nutritional habits of elite athletes are limited and, therefore, it is not clear as to whether elite athletes are following nutritional recommendations and maintaining nutritionally sound diets. This review takes a comprehensive look at 22 recent dietary intake studies, including 50 groups of elite athletes. The time period for food record collection ranged from 3 to 7 days except for 2 studies which collected records for 21 and 22 days. Energy intakes of > 50 kcal/kg/day for male athletes who train for > 90 min/day and 45 to 50 kcal/kg/day for female athletes training for > 90 min/day are recommended. Bodyweight should be monitored frequently as a check on calorie intake. With a sufficient calorie intake (1.2 to 2.0 kg/kg/day) protein supplementation is not necessary. Ingested carbohydrate stored as glycogen serves as the primary fuel for muscle performance. Athletes in training should consume 70% of total calories as carbohydrate. Athletes on low energy diets (< 2200 kcal/day) should have a diet of < 25% fat, and athletes with large energy needs should consume 30% fat in their diet. In general, fat intakes should be reduced and carbohydrate intakes increased. Athletes should also restrict alcohol intake during training and competition periods. Athletes with low calorie intakes should consume foods with high contents of iron, calcium, magnesium, zinc and vitamin B12. Athletes with high calorie intakes should consume foods that are naturally high in or fortified with B-group vitamins. Fluid, electrolyte and energy supplementation is desirable to support circulatory, metabolic and thermoregulatory functions. There is no special food that will help elite athletes perform better; the most important aspect of the diet of elite athletes is that it follows the basic guidelines for healthy eating.

Lack of association between indices of vitamin B1, B2, and B6 status and exercise-induced blood lactate in young adults

By means of a 5-week vitamin B-complex supplementation, associations between indices of vitamin B1, B2, and B6 status (activation coefficients [AC] for erythrocyte transketolase, glutathione reductase, and aspartate aminotransferase) and exercise-induced blood lactate concentration were studied. Subjects, 42 physically active college students (18-32 yrs), were randomized into vitamin (n = 22) and placebo (n = 20) groups. Before the supplementation there were no differences in ACs or basal enzyme activities between the groups. The ACs were relatively high, suggesting marginal vitamin status. In the vitamin group, all three ACs were lower (p < 0.0001) after supplementation: transketolase decreased from 1.16 (1.14-1.18) (mean and 95% confidence interval) to 1.08 (1.06-1.10); glutathione reductase decreased from 1.33 (1.28-1.39) to 1.14 (1.11-1.17); and aspartate aminotransferase decreased from 2.04 (1.94-2.14) to 1.73 (1.67-1.80). No changes were found after placebo. Despite improved indices of vitamin status, supplementation did not affect exercise-induced blood lactate concentration. Hence no association was found between ACs and blood lactate. It seems that marginally high ACs do not necessarily predict altered lactate metabolism.

Practices and recommendations of sports nutritionists

A three-part questionnaire was used to identify professionals in sports nutrition and survey their recommendations on various aspects of sports nutrition. The majority of respondents were women. Over half of the sample reported working in sports nutrition for 6 years or less, and 72% indicated that 40% or less of their job is dedicated to sports nutrition. A portion of the questionnaire assessed the subjects' opinions on various sports nutrition topics. Statements on water and electrolytes generated the most agreement while statements on protein generated the least agreement. There was a positive correlation (p < 0.004) between level of education and whether or not the respondents recommended glycogen loading, and a positive correlation (p < 0.008) between the subjects' use of dietary supplements and the fact that they recommended supplements to the athletes they counseled. The majority of professionals in this study worked with recreational athletes and were more concerned about encouraging a healthy diet than improving athletic performance.