Vitamin supplementation and physical exercise performance

International society of sports nutrition position stand: energy drinks and energy shots

Position Statement: The International Society of Sports Nutrition (ISSN) bases the following position stand on a critical analysis of the literature regarding the effects of energy drink (ED) or energy shot (ES) consumption on acute exercise performance, metabolism, and cognition, along with synergistic exercise-related performance outcomes and training adaptations. The following 13 points constitute the consensus of the Society and have been approved by the Research Committee of the Society: Energy drinks (ED) commonly contain caffeine, taurine, ginseng, guarana, carnitine, choline, B vitamins (vitamins B1, B2, B3, B5, B6, B9, and B12), vitamin C, vitamin A (beta carotene), vitamin D, electrolytes (sodium, potassium, magnesium, and calcium), sugars (nutritive and non-nutritive sweeteners), tyrosine, and L-theanine, with prevalence for each ingredient ranging from 1.3 to 100%. Energy drinks can enhance acute aerobic exercise performance, largely influenced by the amount of caffeine (> 200 mg or >3 mg∙kg bodyweight [BW-1]) in the beverage. Although ED and ES contain several nutrients that are purported to affect mental and/or physical performance, the primary ergogenic nutrients in most ED and ES based on scientific evidence appear to be caffeine and/or the carbohydrate provision. The ergogenic value of caffeine on mental and physical performance has been well-established, but the potential additive benefits of other nutrients contained in ED and ES remains to be determined. Consuming ED and ES 10-60 minutes before exercise can improve mental focus, alertness, anaerobic performance, and/or endurance performance with doses >3 mg∙kg BW-1. Consuming ED and ES containing at least 3 mg∙kg BW-1 caffeine is most likely to benefit maximal lower-body power production. Consuming ED and ES can improve endurance, repeat sprint performance, and sport-specific tasks in the context of team sports. Many ED and ES contain numerous ingredients that either have not been studied or evaluated in combination with other nutrients contained in the ED or ES. For this reason, these products need to be studied to demonstrate efficacy of single- and multi-nutrient formulations for physical and cognitive performance as well as for safety. Limited evidence is available to suggest that consumption of low-calorie ED and ES during training and/or weight loss trials may provide ergogenic benefit and/or promote additional weight control, potentially through enhanced training capacity. However, ingestion of higher calorie ED may promote weight gain if the energy intake from consumption of ED is not carefully considered as part of the total daily energy intake. Individuals should consider the impact of regular coingestion of high glycemic index carbohydrates from ED and ES on metabolic health, blood glucose, and insulin levels. Adolescents (aged 12 through 18) should exercise caution and seek parental guidance when considering the consumption of ED and ES, particularly in excessive amounts (e.g. > 400 mg), as limited evidence is available regarding the safety of these products among this population. Additionally, ED and ES are not recommended for children (aged 2-12), those who are pregnant, trying to become pregnant, or breastfeeding and those who are sensitive to caffeine. Diabetics and individuals with preexisting cardiovascular, metabolic, hepatorenal, and/or neurologic disease who are taking medications that may be affected by high glycemic load foods, caffeine, and/or other stimulants should exercise caution and consult with their physician prior to consuming ED. The decision to consume ED or ES should be based upon the beverage's content of carbohydrate, caffeine, and other nutrients and a thorough understanding of the potential side effects. Indiscriminate use of ED or ES, especially if multiple servings per day are consumed or when consumed with other caffeinated beverages and/or foods, may lead to adverse effects. The purpose of this review is to provide an update to the position stand of the International Society of Sports Nutrition (ISSN) integrating current literature on ED and ES in exercise, sport, and medicine. The effects of consuming these beverages on acute exercise performance, metabolism, markers of clinical health, and cognition are addressed, as well as more chronic effects when evaluating ED/ES use with exercise-related training adaptions.

Considerations for the Consumption of Vitamin and Mineral Supplements in Athlete Populations

Vitamins and minerals are of fundamental importance to numerous human functions that are essential to optimise athlete performance. Athletes incur a high turnover of key vitamins and minerals and are therefore dependent on sufficient energy intake to replenish nutrient stores. However, many athletes are poor at servicing their energy replenishment needs, especially female athletes, and although a 'food first approach' to meeting nutrient requirements is the primary goal, it may be important for some athletes to consider a vitamin and/or mineral supplement to meet their daily needs. When working to determine if an athlete requires vitamin or mineral supplements, practitioners should use a robust framework to assess the overall energy requirements, current dietary practices and the biological and clinical status of their athletes. Of note, any supplementation plan should account for the various factors that may impact the efficacy of the approach (e.g. athlete sex, the nutrient recommended dietary intake, supplement dose/timing, co-consumption of other foods and any food-drug interactions). Importantly, there are numerous vitamins and minerals of key importance to athletes, each having specific relevance to certain situations (e.g. iron and B vitamins are significant contributors to haematological adaptation, calcium and vitamin D are important to bone health and folate is important in the female athlete); therefore, the appropriate supplement for a given situation should be carefully considered and consumed with the goal to augment an athlete's diet.

Micronutrient supplement intakes among collegiate and masters athletes: A cross-sectional study

Objective

In our cross-sectional study, we evaluated micronutrient supplementation intake among Collegiate and Masters Athletes.

Methods

We conducted a cross-sectional study to assess micronutrient supplementation consumption in Collegiate and Masters Athletes, comparing sex and sport classification within each respective group. Micronutrient supplement consumption data were measured using a Food Frequency Questionnaire. A two-way analysis of variance was used to explore the differences among Collegiate and Masters Athletes' supplement intakes of the following vitamins and minerals: vitamins A, B6, B12, C, E, D, and calcium, folate, iron, magnesium niacin, riboflavin, selenium, thiamine, and zinc. When significant differences were found, a Bonferroni post hoc test was performed to identify specific group differences. The significance level was set a priori at p < 0.05.

Results

A total of 198 athletes (105 females and 93 males) were included in the study. Participants were 36.16 ± 12.33 years of age. Collegiate male athletes had significantly greater vitamin A [1,090.51 ± 154.72 vs. 473.93 ± 233.18 mg retinol activity equivalents (RAE)/day] (p < 0.036), folate [337.14 ± 44.79 vs. 148.67 ± 67.50 mcg dietary folate equivalents (DFE)/day] (p < 0.027), and magnesium (65.35 ± 8.28 vs. 31.28 ± 12.48 mg/day) (p < 0.031) intakes compared to Collegiate female athletes. Collegiate CrossFit Athletes (940.71 ± 157.54 mg/day) had a significantly greater vitamin C intake compared to Collegiate General Athletes (156.34 ± 67.79 mg/day) (p < 0.005), Collegiate Triathletes (88.57 ± 148.53 mg/day) (p < 0.027), Collegiate Resistance Training Athletes (74.28 ± 143.81 mg/day) (p < 0.020), and Collegiate Powerlifters (175.71 ± 128.63 mg/day) (p < 0.044). Masters females had significantly greater calcium intakes compared to Masters males (494.09 ± 65.73 vs.187.89 ± 77.23 mg/day, respectively) (p < 0.002). Collegiate Runners (41.35 ± 6.53 mg/day) had a significantly greater iron intake compared to Collegiate Powerlifters (4.50 ± 6.53 mg/day) (p < 0.024). Masters Swimmers (61.43 ± 12.10 mg/day) had significantly greater iron intakes compared to Masters General Athletes (13.97 ± 3.56 mg/day) (p < 0.014), Masters Runners (17.74 ± 2.32 mg/day) (p < 0.03), Masters Triathletes (11.95 ± 3.73 mg/day) (p < 0.008), Masters CrossFit Athletes (15.93 ± 5.36 mg/day) (p < 0.043), Masters Rowers (9.10 ± 3.36 mg/day) (p < 0.003), and Masters Cyclists (1.71 ± 9.88 mg/day) (p < 0.011). Masters Powerlifters (47.14 ± 9.65 mg/day) had significantly greater zinc intakes compared to Masters General Athletes (9.57 ± 2.84 mg/day) (p < 0.015), Masters Runners (10.67 ± 1.85 mg/day) (p < 0.017), Masters Triathletes (10.24 ± 2.98 mg/day) (p < 0.020), Masters Rowers (9.33 ± 2.68 mg/day) (p < 0.013), and Masters Cyclists (1.43 ± 7.88 mg/day) (p < 0.019). There were no other significant differences among the other micronutrient supplement intakes between the sexes or among the sport classification.

Conclusion

We reported significant differences among female and male Collegiate and Masters Athletes. Additionally, we reported significant differences among Collegiate and Masters Athletes sport classifications. Further research should examine both dietary and micronutrient supplement intake among Collegiate and Masters Athletes to examine the extent that athletes exceed the Recommended Dietary Allowances (RDA), and the potential effects on health and performance.

Skin Microbiome, Metabolome and Skin Phenome, from the Perspectives of Skin as an Ecosystem

Skin is a complex ecosystem colonized by millions of microorganisms, including bacteria, fungi, and viruses. Skin microbiota is believed to exert critical functions in maintaining host skin health. Profiling the structure of skin microbial community is the first step to overview the ecosystem. However, the community composition is highly individualized and extremely complex. To explore the fundamental factors driving the complexity of the ecosystem, namely the selection pressures, we review the present studies on skin microbiome from the perspectives of ecology. This review summarizes the following: (1) the composition of substances/nutrients in the cutaneous ecological environment that are derived from the host and the environment, highlighting their proposed function on skin microbiota; (2) the features of dominant skin commensals to occupy ecological niches, through self-adaptation and microbe-microbe interactions; (3) how skin microbes, by their structures or bioactive molecules, reshape host skin phenotypes, including skin immunity, maintenance of skin physiology such as pH and hydration, ultraviolet (UV) protection, odor production, and wound healing. This review aims to re-examine the host-microbe interactions from the ecological perspectives and hopefully to give new inspiration to this field.

ISSN exercise & sports nutrition review update: research & recommendations

Background

Sports nutrition is a constantly evolving field with hundreds of research papers published annually. In the year 2017 alone, 2082 articles were published under the key words ‘sport nutrition’. Consequently, staying current with the relevant literature is often difficult.

Methods

This paper is an ongoing update of the sports nutrition review article originally published as the lead paper to launch the Journal of the International Society of Sports Nutrition in 2004 and updated in 2010. It presents a well-referenced overview of the current state of the science related to optimization of training and performance enhancement through exercise training and nutrition. Notably, due to the accelerated pace and size at which the literature base in this research area grows, the topics discussed will focus on muscle hypertrophy and performance enhancement. As such, this paper provides an overview of: 1.) How ergogenic aids and dietary supplements are defined in terms of governmental regulation and oversight; 2.) How dietary supplements are legally regulated in the United States; 3.) How to evaluate the scientific merit of nutritional supplements; 4.) General nutritional strategies to optimize performance and enhance recovery; and, 5.) An overview of our current understanding of nutritional approaches to augment skeletal muscle hypertrophy and the potential ergogenic value of various dietary and supplemental approaches.

Conclusions

This updated review is to provide ISSN members and individuals interested in sports nutrition with information that can be implemented in educational, research or practical settings and serve as a foundational basis for determining the efficacy and safety of many common sport nutrition products and their ingredients.

Supplementation with a Polyphenol-Rich Extract, PerfLoad®, Improves Physical Performance during High-Intensity Exercise: A Randomized, Double Blind, Crossover Trial

Workout capacity is energy-production driven. To produce peak metabolic power outputs, the organism predominantly relies more on anaerobic metabolism, but this undoubtedly has a negative and limiting impact on muscle function and performance. The aim of the study was to evaluate if an innovative polyphenol-based food supplement, PerfLoad^®, was able to improve metabolic homeostasis and physical performance during high-intensity exercises under anaerobic conditions. The effect of a supplementation has been investigated on fifteen recreationally-active male athletes during a randomized, double-blind and crossover clinical investigation. The Wingate test, an inducer of an unbalanced metabolism associated to oxidative stress, was used to assess maximum anaerobic power during a high-intensity exercise on a cycle ergometer. Supplementation with PerfLoad^® correlated with a significant increase in total power output (5%), maximal peak power output (3.7%), and average power developed (5%), without inducing more fatigue or greater heart rate. Instead, oxidative homeostasis was stabilized in supplemented subjects. Such results demonstrated that PerfLoad^® is a natural and efficient solution capable of, similarly to training benefits, helping athletes to improve their physical performance, while balancing their metabolism and reducing exercise-induced oxidative stress.

Systematic review focusing on the excretion and protection roles of sweat in the skin

The skin excretes substances primarily through sweat glands. Several conditions have been demonstrated to be associated with diminished sweating. However, few studies have concentrated on the metabolism and excretion of sweat. This review focuses on the relationship between temperature and the thermoregulatory efficacy of sweat, and then discusses the excretion of sweat, which includes the metabolism of water, minerals, proteins, vitamins as well as toxic substances. The potential role of sweat secretion in hormone homeostasis and the effects on the defense system of the skin are also clarified.

The effects of endurance training and thiamine supplementation on anti-fatigue during exercise

The purpose of this study was to find the effect of endurance training and thiamine supplementation on anti-fatigue during the exercise. Each nine students from K Women's University went through three cross-over treatments: placebo treatment, training treatment and thiamine treatment. Training treatment was performed with bicycle ergometer exercise for four weeks (five days per week). Each exercise was performed for an hour with intensity set at 70% (50rpm) of maximal oxygen uptake. Thiamine treatment group was given 10mg of thiamine tetrahydrofurfuryl disulfide per one kilogram for four weeks. The bicycle ergometer exercise was performed at 70% of maximal oxygen uptake in exercise intensity which 60 minutes of exercise was performed at 50rpm . Lactate concentration was significantly decreased during 15 to 30 minutes of exercise for those with training treatment and 15 to 60 minutes of exercise for those with thiamine treatment compared to placebo treatment group. Ammonia concentration was significantly decreased during 15 to 60 minutes of exercise and 15 to 30 minutes of recovery for those with training and thiamine treatment compared to placebo treatment. Resting blood thiamine concentrations of placebo treatment were significantly lower than training treatment. 60 minutes after the exercise, plasma thiamine concentration was significantly increased in all treatment group. To sum up the previous, thiamine intake during exercise positively benefits carbohydrate metabolism in a way that will decrease lactate concentration, ammonia concentration, and anti- fatigue by reducing the RPE. Therefore, we can consider thiamine intake to be utilized as similar benefits as endurance training.

Elements in sera of elite taekwondo athletes: effects of vitamin E supplementation

Many researchers have emphasized the relation between nutrition and development and sustaining performance. Two methods are commonly employed to identify the interaction between physical activity and nutrition. The first consists of administering food with a variety of contents to people engaged in physical activity and observing their performance responses, and the other is concerned with determining the effects of physical activity on nutrition. Therefore, it can be said that there has been a growing interest in the explorations into the relation between exercise and vitamins, minerals, and elements. The present study reports the effects of 6 weeks administration of 300 mg/day vitamin E on the distribution of serum elements in elite taekwondo athletes. Seven male athletes, mean ages 22.1 ± 0.5 years weighing on average 66.4 ± 2.4 kg were included in the study. The athletes had been practicing taekwondo for 10-12 years. Resting blood samples were collected in duplicate before and after supplementation for determination of serum levels of cobalt, boron, cadmium, chromium, nickel, manganese, sulfur, copper, iron, zinc, phosphorus, sodium, potassium, and calcium. Supplementation resulted in significant increases of all elements relative to values before supplementation (p < 0.001), with the exception of boron and sulfur, which remained without change. The results of the present study demonstrate that vitamin E supplementation crucially influences the element and mineral metabolism in elite athletes.

B-vitamin consumption and the prevalence of diabetes and obesity among the US adults: population based ecological study

BACKGROUND

The global increased prevalence of obesity and diabetes occurred after the worldwide spread of B-vitamins fortification, in which whether long-term exposure to high level of B vitamins plays a role is unknown. Our aim was to examine the relationships between B-vitamins consumption and the obesity and diabetes prevalence.

METHODS

This population based ecological study was conducted to examine possible associations between the consumption of the B vitamins and macronutrients and the obesity and diabetes prevalence in the US population using the per capita consumption data from the US Economic Research Service and the prevalence data from the US Centers for Disease Control and Prevention.

RESULTS

The prevalences of diabetes and adult obesity were highly correlated with per capita consumption of niacin, thiamin and riboflavin with a 26-and 10-year lag, respectively (R2 = 0.952, 0.917 and 0.83 for diabetes, respectively, and R2 = 0.964, 0.975 and 0.935 for obesity, respectively). The diabetes prevalence increased with the obesity prevalence with a 16-year lag (R2 = 0.975). The relationships between the diabetes or obesity prevalence and per capita niacin consumption were similar both in different age groups and in male and female populations. The prevalence of adult obesity and diabetes was highly correlated with the grain contribution to niacin (R2 = 0.925 and 0.901, respectively), with a 10-and 26-year lag, respectively. The prevalence of obesity in US adults during 1971-2004 increased in parallel with the increase in carbohydrate consumption with a 10-year lag. The per capita energy and protein consumptions positively correlated with the obesity prevalence with a one-year lag. Moreover, there was an 11-year lag relationship between per capita energy and protein consumption and the consumption of niacin, thiamin and riboflavin (R2 = 0.932, 0.923 and 0.849 for energy, respectively, and R2 = 0.922, 0.878 and 0.787 for protein, respectively).

CONCLUSIONS

Long-term exposure to high level of the B vitamins may be involved in the increased prevalence of obesity and diabetes in the US in the past 50 years. The possible roles of B-vitamins fortification and excess niacin consumption in the increased prevalence of obesity and diabetes were discussed.

ISSN exercise & sport nutrition review: research & recommendations

Sports nutrition is a constantly evolving field with hundreds of research papers published annually. For this reason, keeping up to date with the literature is often difficult. This paper is a five year update of the sports nutrition review article published as the lead paper to launch the JISSN in 2004 and presents a well-referenced overview of the current state of the science related to how to optimize training and athletic performance through nutrition. More specifically, this paper provides an overview of: 1.) The definitional category of ergogenic aids and dietary supplements; 2.) How dietary supplements are legally regulated; 3.) How to evaluate the scientific merit of nutritional supplements; 4.) General nutritional strategies to optimize performance and enhance recovery; and, 5.) An overview of our current understanding of the ergogenic value of nutrition and dietary supplementation in regards to weight gain, weight loss, and performance enhancement. Our hope is that ISSN members and individuals interested in sports nutrition find this review useful in their daily practice and consultation with their clients.

Dietary supplements and sports performance: introduction and vitamins

Sports success is dependent primarily on genetic endowment in athletes with morphologic, psychologic, physiologic and metabolic traits specific to performance characteristics vital to their sport. Such genetically-endowed athletes must also receive optimal training to increase physical power, enhance mental strength, and provide a mechanical advantage. However, athletes often attempt to go beyond training and use substances and techniques, often referred to as ergogenics, in attempts to gain a competitive advantage. Pharmacological agents, such as anabolic steroids and amphetamines, have been used in the past, but such practices by athletes have led to the establishment of anti-doping legislation and effective testing protocols to help deter their use. Thus, many athletes have turned to various dietary strategies, including the use of various dietary supplements (sports supplements), which they presume to be effective, safe and legal.

ISSN Exercise & Sport Nutrition Review: Research & Recommendations

Sport nutrition is a constantly evolving field with literally thousands of research papers published annually. For this reason, keeping up to date with the literature is often difficult. This paper presents a well-referenced overview of the current state of the science related to how to optimize training through nutrition. More specifically, this article discusses: 1.) how to evaluate the scientific merit of nutritional supplements; 2.) general nutritional strategies to optimize performance and enhance recovery; and, 3.) our current understanding of the available science behind weight gain, weight loss, and performance enhancement supplements. Our hope is that ISSN members find this review useful in their daily practice and consultation with their clients.

Biological markers for the follow-up of athletes throughout the training season

During the training season, a state of fatigue known as overtraining may occur, resulting from an excessive load of training, both in volume and intensity. Even now, difficult to predict the risk of overtraining, although this syndrome has been the subject of numerous studies. A lot of biological markers have been propounded. Taken alone, none of them have an absolute significance. This paper aims to review these markers, considering their biological interest, the ease with which they can be measured and the cost, from the simplest (body weight daily recording) to the most up to date markers (e.g. anti-oxidant status). They are grouped into three categories: non-invasive behavioural and biological markers, biochemical markers, and hormonal and immunological markers.

Medication use in athletes selected for doping control at the Sydney Olympics (2000)

During the Olympic Games held in Sydney in September, 2000 Doping Control was undertaken as specified in the International Olympic Code. During this process information about the medications taken by athletes was collected as a routine and formed part of the paperwork associated with a urine test. In their Post Games Report the World Anti-Doping Agency (WADA) recommended that the information about medications be collated with a view to assessing their use by athletes. Mandatory doping control for winners of events as well as random selection of athletes both during competition and out of competition allowed data to be collected about medications and supplements used by athletes. At the Doping Control Stations all competitors selected for a test, after providing a urine sample for analysis, were asked the same question: "what medications have you taken in the past three days?" The answer was to include all prescription drugs, over-the-counter medications, any other substances taken by mouth, injection, inhalation, ointment or by suppository, as well as vitamins, minerals, and all other supplements. This paper reviews the data from the 2758 Declaration Forms obtained at doping control. The prevalence of use of medications, the number used by an individual, and the pattern of use by these elite sports people were examined. The trends seen in this survey point to a dangerous overuse of nonsteroidal anti-inflammatory agents and an unnecessary overuse of vitamins in this population, while pointing out the increased prevalence of asthma and the dangers of drug interactions.

OBJECTIVE

The main objective here is to review some of the medications used by athletes in the Olympic Games in Sydney 2000.

DATA SOURCES

During these Games Doping Control was undertaken as specified by the International Olympic Committee. As well as a urine test, information about medications routinely taken was collected. Mandatory doping control for winners of events as well as random selection of athletes both during competition and out of competition required data to be collected about medications and supplements used by athletes as part of the sample collection protocol. At the Doping Control Stations all competitors selected for a test, after providing a urine sample for analysis, were asked the same question: "what medications have you taken in the past three days?" The answer was to include all prescription drugs, over-the-counter medications, any other substances taken by mouth, injection, inhalation, ointment or by suppository, as well as vitamins, minerals, and all other supplements.

DATA SELECTION

In this article we review the data from the laboratory copy of the 2758 Declaration Forms obtained at doping control. The cut down version of the Declaration Form submitted to the laboratory had all information identifying the athlete removed. Thus all information used in this article is completely anonymous. The prevalence of use of medications, the number used by an individual, and the pattern of use by these elite sports people were examined at the request of the IOC.

CONCLUSIONS

In their Post-Games Report, the World Anti-Doping Agency (WADA) acting as independent observers of the anti-doping process recommended to the IOC that the information obtained in the Athlete Declaration Forms concerning medications be collated with a view to assessing their use by athletes. The trends in their use seen in this survey point to an overuse of supplements as well as a dangerous overuse of drugs such as nonsteroidal anti-inflammatory agents together with multiple drug use emphasising the dangers of drug interactions and points out the increased prevalence of asthma in this population.

Effect of physical activity on thiamine, riboflavin, and vitamin B-6 requirements

Because exercise stresses metabolic pathways that depend on thiamine, riboflavin, and vitamin B-6, the requirements for these vitamins may be increased in athletes and active individuals. Theoretically, exercise could increase the need for these micronutrients in several ways: through decreased absorption of the nutrients; by increased turnover, metabolism, or loss of the nutrients; through biochemical adaptation as a result of training that increases nutrient needs; by an increase in mitochondrial enzymes that require the nutrients; or through an increased need for the nutrients for tissue maintenance and repair. Biochemical evidence of deficiencies in some of these vitamins in active individuals has been reported, but studies examining these issues are limited and equivocal. On the basis of metabolic studies, the riboflavin status of young and older women who exercise moderately (2.5-5 h/wk) appears to be poorer in periods of exercise, dieting, and dieting plus exercise than during control periods. Exercise also increases the loss of vitamin B-6 as 4-pyridoxic acid. These losses are small and concomitant decreases in blood vitamin B-6 measures have not been documented. There are no metabolic studies that have compared thiamine status in active and sedentary persons. Exercise appears to decrease nutrient status even further in active individuals with preexisting marginal vitamin intakes or marginal body stores. Thus, active individuals who restrict their energy intake or make poor dietary choices are at greatest risk for poor thiamine, riboflavin, and vitamin B-6 status.

Biology and medicine of soccer: an update

Recent literature on the biology and medicine of soccer (primarily since 1990) has been accumulated by a combination of computer searching of relevant databases and review of the author's extensive files. From a total of 9681 papers, 540 were selected for closer scrutiny and 370 are discussed in the present review. These articles cover patterns of play and the resulting energy demands, the nutritional requirements of soccer, the anthropometric, physiological, biochemical and immunological characteristics of successful players, the influence of environmental stressors (heat, cold, hypoxia and time zone shifts), special features of female and junior competitors, selected issues in training, and the incidence and prevention of injuries. The information presented has important implications for the safety and success of soccer players; the challenge is now to ensure that this information is understood and acted upon by coaches and individual team members.

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.

Supplement use and nutritional habits in Norwegian elite athletes

The purpose of this study was to examine nutritional and supplemental habits among international alpine- and cross-country skiers and power sport athletes in Norway. Data from all the athletes of the National alpine skiing team (ALP; n = 33, 19 men and 14 women) and the National cross-country skiing team (CRO; n = 34, 17 men and 17 women) plus a mixed group of power sport athletes (POW: n = 33, all men) from the National teams of boxers, weightlifters and track and field athletes, were collected through a semi-structured interview during their annual medical examination. Twenty percent of all the athletes reported unsatisfactory nutritional habits (CRO 6%, ALP 27% and POW 27%; CRO vs. ALP/POW P < 0.05). Eight-four percent used one or more micronutrient supplement (ALP 70%, POW 88%, CRO 95%; ALP vs. CRO/POW P < 0.01). Power sport athletes had the most frequent use of supplemental creatine (45%), proteins/amino acids (30%), vitamins (88%) and minerals (82%), and CRO had the most frequent intake of iron (94%), vitamin C (88%) and fish oils (91%). Among ALP, only 7% of the female athletes supplemented iron regularly compared to 37% of male ALP (P < 0.05) Overall, male athletes supplemented mostly on a regular basis and female athletes more on an occasional basis. The results show that in spite of differences between sport groups, many elite athletes report unsatisfactory nutritional habits. Micronutrient supplementation was prevalent, but varied between both groups of sports and gender.

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.

The use of nutritional ergogenic aids in sports: is it an ethical issue?

As nutritional technology advanced, scientists have been able to synthesize and manufacture all known nutrients, and many of their metabolic by-products, essential to human physiology. Many of these substances are theorized to possess ergogenic potential when taken in quantities or forms normally not found in typical foods or diets. Research, although limited in most cases, supports the ergogenicity of some nutrients (e.g., creatine) when consumed in substantial amounts, suggesting such nutrients may function as drugs or nutraceuticals. The International Olympic Committee (IOC) doping legislation stipulates that any physiologic substance taken in abnormal quantity with the intention of artificially and unfairly increasing performance should be construed as doping, violating the ethics of sport performance. Given this stipulation, the IOC and other athletic-governing organizations should consider the legality and ethics underlying the use of ergogenic nutraceuticals in sport.

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.

Diet and athletic performance

Inadequate diet inhibits optimal performance in otherwise well-trained athletes. Controversy exists regarding specific dietary requirements, particularly in the areas of protein and vitamin/mineral supplementation. This article reviews energy substrate utilization, provides an overview of nutrient requirements during exercise, discusses ergogenic aids, and where possible, makes specific dietary recommendations for athletes.