Journal of the International Society of Sports Nutrition - Most viewed articles

Effects of eight weeks of an alleged aromatase inhibiting nutritional supplement 6-OXO (androst-4-ene-3,6,17-trione) on serum hormone profiles and clinical safety markers in resistance-trained, eugonadal males

2007-10-19

The purpose of this study was to determine the effects of 6-OXO, a purported nutritional aromatase inhibitor, in a dose dependent manner on body composition, serum hormone levels, and clinical safety markers in resistance trained males. Sixteen males were supplemented with either 300 mg or 600 mg of 6-OXO in a double-blind manner for eight weeks. Blood and urine samples were obtained at weeks 0, 1, 3, 8, and 11 (after a 3-week washout period). Blood samples were analyzed for total testosterone (TT), free testosterone (FT), dihydrotestosterone (DHT), estradiol, estriol, estrone, SHBG, leutinizing hormone (LH), follicle stimulating hormone (FSH), growth hormone (GH), cortisol, FT/estradiol (T/E). Blood and urine were also analyzed for clinical chemistry markers. Data were analyzed with two-way MANOVA. For all of the serum hormones, there were no significant differences between groups (p > 0.05). Compared to baseline, free testosterone underwent overall increases of 90% for 300 mg 6-OXO and 84% for 600 mg, respectively (p < 0.05). DHT underwent significant overall increases (p < 0.05) of 192% and 265% with 300 mg and 600 mg, respectively. T/E increased 53% and 67% for 300 mg and 600 mg 6-OXO, respectively. For estrone, 300 mg produced an overall increase of 22%, whereas 600 mg caused a 52% increase (p < 0.05). Body composition did not change with supplementation (p > 0.05) and clinical safety markers were not adversely affected with ingestion of either supplement dose (p > 0.05). While neither of the 6-OXO dosages appears to have any negative effects on clinical chemistry markers, supplementation at a daily dosage of 300 mg and 600 mg for eight weeks did not completely inhibit aromatase activity, yet significantly increased FT, DHT, and T/E.

Effects of acute and 14-day coenzyme Q10 supplementation on exercise performance in both trained and untrained individuals

2008-03-04

Background: To determine whether acute (single dose) and/or chronic (14-days) supplementation of CoQ10 will improve anaerobic and/or aerobic exercise performance by increasing plasma and muscle CoQ10 concentrations within trained and untrained individuals. Methods: Twenty-two aerobically trained and nineteen untrained male and female subjects (26.1 ± 7.6 yrs, 172 ± 8.7 cm, 73.5 ± 17 kg, and 21.2 ± 7.0%) were randomized to ingest in a double-blind manner either 100 mg of a dextrose placebo (CON) or a fast-melt CoQ10 supplement (CoQ10) twice a day for 14-days. On the first day of supplementation, subjects donated fasting blood samples and a muscle biopsy. Subjects were then given 200 mg of the placebo or the CoQ10 supplement. Sixty minutes following supplement ingestion, subjects completed an isokinetic knee extension endurance test, a 30-second wingate anaerobic capacity test, and a maximal cardiopulmonary graded exercise test interspersed with 30-minutes of recovery. Additional blood samples were taken immediately following each exercise test and a second muscle biopsy sample was taken following the final exercise test. Subjects consumed twice daily (morning and night), 100 mg of either supplement for a period of 14-days, and then returned to the lab to complete the same battery of tests. Data was analyzed using repeated measures ANOVA with an alpha of 0.05. Results: Plasma CoQ10 levels were significantly increased following 2 weeks of CoQ10 supplementation (p < 0.001); while a trend for higher muscle CoQ10 levels was observed after acute CoQ10 ingestion (p = 0.098). A trend for lower serum superoxide dismutase (SOD) was observed following acute supplementation with CoQ10 (p = 0.06), whereas serum malondialdehyde (MDA) tended to be significantly higher (p < 0.05). Following acute ingestion of CoQ10, plasma CoQ10 levels were significantly correlated to muscle CoQ10 levels; maximal oxygen consumption; and treadmill time to exhaustion. A trend for increased time to exhaustion was observed following 2 weeks of CoQ10 supplementation (p = 0.06). Conclusion: Acute supplementation with CoQ10 resulted in higher muscle CoQ10 concentration, lower serum SOD oxidative stress, and higher MDA levels during and following exercise. Chronic CoQ10 supplementation increased plasma CoQ10 concentrations and tended to increase time to exhaustion. Results indicate that acute and chronic supplementation of CoQ10 may affect acute and/or chronic responses to various types of exercise.

International Society of Sports Nutrition position stand: creatine supplementation and exercise

2007-08-30

Introduction (this article has no abstract) The use of creatine as a sport supplement has been surrounded by both controversy and fallacy since it gained widespread popularity in the early 1990's. Anecdotal and media reports have often claimed that creatine usage is a dangerous and unnecessary practice; often linking creatine use to anabolic steroid abuse. Many athletes and experts in the field have reported that creatine supplementation is not only beneficial for athletic performance and various medical conditions but is also clinically safe. Although creatine has recently been accepted as a safe and useful ergogenic aid, several myths have been purported about creatine supplementation which include: 1. All weight gained during supplementation is due to water retention. 2. Creatine supplementation causes renal distress. 3. Creatine supplementation causes cramping, dehydration, and/or altered electrolyte status. 4. Long-term effects of creatine supplementation are completely unknown. 5. Newer creatine formulations are more beneficial than creatine monohydrate and cause fewer side effects. 6. It's unethical and/or illegal to use creatine supplements. While these myths have been refuted through scientific investigation, the general public is still primarily exposed to the mass media which may or may not have accurate information. Due to this confounding information, combined with the fact that creatine has become one of the most popular nutritional supplements on the market, it is important to examine the primary literature on supplemental creatine ingestion in humans. The purpose of this review is to determine the present state of knowledge concerning creatine supplementation, so that reasonable guidelines may be established and unfounded fears diminished in regard to its use.

Effect of carbohydrate-protein supplement timing on acute exercise-induced muscle damage

2008-02-19

PurposeTo determine if timing of a supplement would have an effect on muscle damage, function and soreness. Methods: Twenty-seven untrained men (21 ± 3 yrs) were given a supplement before or after exercise. Subjects were randomly assigned to a pre exercise (n = 9), received carbohydrate/protein drink before exercise and placebo after, a post exercise (n = 9), received placebo before exercise and carbohydrate/protein drink after, or a control group (n = 9), received placebo before and after exercise. Subjects performed 50 eccentric quadriceps contractions on an isokinetic dynamometer. Tests for creatine kinase (CK), maximal voluntary contraction (MVC) and muscle soreness were recorded before exercise and at six, 24, 48, 72, and 96 h post exercise. Repeated measures ANOVA were used to analyze data. Results: There were no group by time interactions however, CK significantly increased for all groups when compared to pre exercise (101 ± 43 U/L) reaching a peak at 48 h (661 ± 1178 U/L). MVC was significantly reduced at 24 h by 31.4 ± 14.0%. Muscle soreness was also significantly increased from pre exercise peaking at 48 h. Conclusion: Eccentric exercise caused significant muscle damage, loss of strength, and soreness; however timing of ingestion of carbohydrate/protein supplement had no effect.

International Society of Sports Nutrition position stand: protein and exercise

2007-09-26

Position StatementThe following seven points related to the intake of protein for healthy, exercising individuals constitute the position stand of the Society. They have been approved by the Research Committee of the Society. 1) Vast research supports the contention that individuals engaged in regular exercise training require more dietary protein than sedentary individuals. 2) Protein intakes of 1.4 – 2.0 g/kg/day for physically active individuals is not only safe, but may improve the training adaptations to exercise training. 3) When part of a balanced, nutrient-dense diet, protein intakes at this level are not detrimental to kidney function or bone metabolism in healthy, active persons. 4) While it is possible for physically active individuals to obtain their daily protein requirements through a varied, regular diet, supplemental protein in various forms are a practical way of ensuring adequate and quality protein intake for athletes. 5) Different types and quality of protein can affect amino acid bioavailability following protein supplementation. The superiority of one protein type over another in terms of optimizing recovery and/or training adaptations remains to be convincingly demonstrated. 6) Appropriately timed protein intake is an important component of an overall exercise training program, essential for proper recovery, immune function, and the growth and maintenance of lean body mass. 7) Under certain circumstances, specific amino acid supplements, such as branched-chain amino acids (BCAA's), may improve exercise performance and recovery from exercise.

Fat intake and injury in female runners

2008-01-03

Background: Our purpose was to determine the relationship between energy intake, energy availability, dietary fat and lower extremity injury in adult female runners. We hypothesized that runners who develop overuse running-related injuries have lower energy intakes, lower energy availability and lower fat intake compared to non-injured runners. Methods: Eighty-six female subjects, running a minimum of 20 miles/week, completed a food frequency questionnaire and informed us about injury incidence over the next year. Results: Injured runners had significantly lower intakes of total fat (63 ± 20 vs. 80 ± 50 g/d) and percentage of kilocalories from fat (27 ± 5 vs. 30 ± 8 %) compared with non-injured runners. A logistic regression analysis found that fat intake was the best dietary predictor, correctly identifying 64% of future injuries. Lower energy intake and lower energy availability approached, but did not reach, a significant association with overuse injury in this study. Conclusion: Fat intake is likely associated with injury risk in female runners. By documenting these associations, better strategies can be developed to reduce running injuries in women.

ISSN Exercise & Sport Nutrition Review: Research & Recommendations

2004-05-10

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.

The effects of creatine pyruvate and creatine citrate on performance during high intensity exercise

2008-02-13

Background: A double-blind, placebo-controlled, randomized study was performed to evaluate the effect of oral creatine pyruvate (Cr-Pyr) and creatine citrate (Cr-Cit) supplementation on exercise performance in healthy young athletes. Methods: Performance during intermittent handgrip exercise of maximal intensity was evaluated before (pretest) and after (posttest) 28 days of Cr-Pyr (5 g/d, n = 16), Cr-Cit (5 g/d, n = 16) or placebo (pla, 5 g/d, n = 17) intake. Subjects performed ten 15-sec exercise intervals, each followed by 45 sec rest periods. Results: Cr-Pyr (p < 0.001) and Cr-Cit (p < 0.01) significantly increased mean power over all intervals. Cr-Cit increased force during the first and second interval (p < 0.01) compared to placebo. The effect of Cr-Cit on force decreased over time and the improvement was not significant at the sixth and ninth interval, whereas Cr-Pyr significantly increased force during all intervals (p < 0.001). Cr-Pyr (p < 0.001) and Cr-Cit (p < 0.01) resulted in an increase in contraction velocity, whereas only Cr-Pyr intake significantly (p < 0.01) increased relaxation velocity. Oxygen consumption measured during rest periods significantly increased with Cr-Pyr (p < 0.05), whereas Cr-Cit and placebo intake did not result in significant improvements. Conclusion: It is concluded that four weeks of Cr-Pyr and Cr-Cit intake significantly improves performance during intermittent handgrip exercise of maximal intensity and that Cr-Pyr might benefit endurance, due to enhanced activity of the aerobic metabolism.

Acute effects of ingesting a commercial thermogenic drink on changes in energy expenditure and markers of lipolysis

Vincent J Dalbo, Michael D Roberts, Jeffrey R Stout and Chad M Kerksick — 2008-02-20

Background: To determine the acute effects of ingesting a thermogenic drink (Celsius, Delray Beach, FL) (TD) on changes in metabolism and lipolysis. Methods: Healthy college-aged male (23.2 ± 4.0 y, 177.2 ± 6.1 cm, 81.7 ± 11.3 kg, 22.8 ± 7.3 % fat; n = 30) and female (23.4 ± 3.1 y, 165.6 ± 8.7 cm, 62.1 ± 9.9 kg, 28.3 ± 7.4 % fat; n = 30) participants were matched according to height and weight to consume 336 ml of the TD or a non-caloric, non-caffeinated placebo (PLA). After a 12 h fast, participants reported for pre-consumption measures of height, weight, heart rate, blood pressure, resting energy expenditure (REE), respiratory exchange ratio (RER), glycerol and free-fatty acid (FFA) concentrations. REE and RER were determined at 60, 120, and 180 min post-consumption. Serum glycerol and FFA concentrations were determined at 30, 60, 120 and 180 min post-consumption. Results: When compared to PLA, TD significantly increased REE at 60, 120 and 180 min (p < 0.05). FFA concentrations were significantly greater in TD compared to PLA at 30, 60, 120 and 180 min post-consumption (p < 0.05). No between-group differences were found in RER. Conclusion: Acute TD ingestion significantly increased REE, FFA and glycerol appearance. If sustained, these changes may help to promote weight loss and improve body composition; however, these findings are currently unknown as are the general safety and efficacy of prolonged consumption.

Diet and Cardiovascular Risk in University Marching Band, Dance Team and Cheer Squad Members: a cross-sectional study

2008-04-18

Background: Cardiovascular disease (CVD) is the leading cause of death in the United States. Diets high in fat, especially saturated fat, are often linked to obesity, hypertension and hypercholesterolemia, all risk factors for CVD. The purpose of this study was to determine the association between diet and CVD risk factors in members of a university marching band, dance team and cheer squad. Methods: In 2004, 232 marching band, dance team and cheer squad members completed a self-administered survey evaluating dietary intake. Body mass index (BMI), waist-to-hip ratio (WHR), blood pressure, fasting serum glucose and cholesterol were measured. Unpaired t-test and Pearson's chi square test were used to determine baseline differences by gender. Multiple linear regression analysis was used to determine the cross-sectional association between dietary intake of various food groups such as grains, meats, fruits & vegetables, dairy, water, alcohol and risk factors for CVD namely BMI, WHR, blood glucose, total cholesterol, and blood pressure (BP). Results: 45% of the participants were overweight; 30% of females and 4.3% of males had WHR ≥ 0.80 and 0.95 respectively. Almost 8% were hyperglycemic, 10% hypercholesterolemic, 15% had high systolic and 9% had high diastolic BP. Less than 50% consumed the recommended servings of grains, fruits and vegetables, dairy and water and 58% consumed alcohol. Higher grains intake was positively associated with higher BMI (Adjusted β = 1.97, p = 0.030, 95% CI: 0.19, 3.74) and; higher alcohol intake was also positively associated with higher BMI (Adjusted β = 0.15, p = 0.002, 95% CI: 0.06, 0.24). Conclusion: These results warrant the evaluation of existing college-based health programs and development of new interventions to improve dietary habits and promote a healthy lifestyle in these athletes.