This study sought to predict the use of dietary supplements marketed to enhance athletic performance among 1,737 adolescent athletes. An anonymous, paper-and-pencil, self-report survey was administered to the participants. Grade level, participation in multiple sports, and scales representing attitudes, subjective norms, and intention were all significant predictors of current dietary supplement use. The results of this study allow for the development of more appropriate prevention and intervention strategies that can target specific groups of adolescent athletes. We recommend that attitudes of adolescent athletes be addressed in interventions and that salient others be included in program planning.
R. Todd Bartee, Burke Grandjean, Michael S. Dunn, James M. Eddy and Min Qi Wang
Susan J. Massad, Nathan W. Shier, David M. Koceja and Nancy T. Ellis
Factors influencing nutritional supplement use by high school students were assessed. Comparisons were made between various groups of sports participants and non-sports participants. The Nutritional Supplement Use and Knowledge Scale was administered to 509 students. Mean supplement use score was 10.87 (SEM = 0.50, range 0-57). Mean knowledge score was 13.56 (SEM = 0.16, range 1-21). Significant relationships (p < .01) were obtained for supplement knowledge with use, and supplement use with gender. ANOVA found significant differences between supplement use by gender (p < .01), supplement use by sports category (p < .05), and knowledge scores by sports category (p < .01). Discriminant function analysis indicated knowledge, supplement use, and subscores for protein, vitamins/minerals, and carbohydrates were best discriminators of sport group membership. Greater knowledge about supplements was associated with less use; hence, education about supplements can be a deterrent to use. This study may help coaches, athletic trainers, athletic directors, teachers, physicians, and parents identify nutritional misconceptions held by adolescents.
Antoni Aguiló, Pere Tauler, Emilia Fuentespina, Gerardo Villa, Alfredo Córdova, Josep A. Tur and Antoni Pons
The aim of this work was to check the effects of antioxidant supplementation (vitamins E and C, and β-carotene) on the basal iron status of athletes prior to and following their training and competition season (3 months).
Eighteen amateur trained male athletes were randomly distributed in 2 groups: placebo (lactose) and antioxidant supplemented (vitamin E, 500 mg/d; vitamin C, 1 g/d; and β-carotene, 30 mg/d). The study was double blind. Hematological parameters, dietary intake, physical activity intensity, antioxidant status (GSH/GSSG ratio), and basal iron status (serum iron, transferrin, ferritin, and iron saturation index) were determined before and after the intervention trials.
Exercise decreased antioxidant defenses in the placebo group but not in the antioxidant-supplemented group. No changes were found in the number of erythrocytes, hematocrit, or hemoglobin concentration, or in values of serum iron parameters, after taking the antioxidant cocktail for 3 months, in spite of the exercise completed. The placebo group showed a high oxidative stress index, and decreases in serum iron (24%) and iron saturation index (28%), which can neither be attributed to aspects of the athletes’ usual diet, nor to hemoconcentration.
Antioxidant supplementation prevents the decrease of serum iron and the iron saturation index, and a link between iron metabolism and oxidative stress may also be suggested.
John P. Warber, John F. Patton, William J. Tharion, Steven H. Zeisel, Robert P. Mello, Christopher P. Kemnitz and Harris R. Lieberman
It has been reported that plasma choline levels decrease following certain types of strenuous exercise. Preliminary findings also suggest that a drop in plasma choline may limit physical performance, while choline supplementation may delay fatigue during prolonged efforts. A double-blind crossover design was used to determine the relationship between plasma choline and performance during and after 4 hr of strenuous exercise. Volunteers (N = 14) received either a placebo or treatment beverage (8.425 g choline citrate) prior to and midway through a 4-hr load carriage treadmill exercise (3% grade at 5.6 km/h × 20 km) carrying a total load of 34.1 kg. Following the treadmill test, run time-to-exhaustion and squat tests were performed, and perceived exertion, plasma choline, glycerophosphocholine, and phosphatidylcholine were measured. Plasma choline levels increased 128% after the run-to-exhaustion with the choline supplemented beverage but remained unchanged with the placebo beverage. No significant effects were seen with choline supplementation on any outcome performance measure. Consequently, soldiers conditioned to carry heavy loads over long distances do not deplete plasma choline as a result of a prolonged exhaustive exercise under a placebo beverage, nor do they benefit from choline supplementation to delay fatigue under the same conditions.
Matthias Kamber, Norbert Baume, Martial Saugy and Laurent Rivier
We report the findings of the analysis of 75 different nutritional supplements bought through the internet. Seven products (all from the class of prohormones) contained other hormone substances than indicated on the labels, and two further products contained ephedrine and caffeine without a clear indication on the labels.
Kagan J. Ducker, Brian Dawson and Karen E. Wallman
Beta-alanine supplementation has been shown to improve exercise performance in short-term, high-intensity efforts.
The aim of this study was to assess if beta-alanine supplementation could improve 800 m track running performance in male recreational club runners (n = 18).
Participants completed duplicate trials (2 presupplementation, 2 postsupplementation) of an 800 m race, separated by 28 days of either beta-alanine (n = 9; 80 mg·kg−1BM·day−1) or placebo (n = 9) supplementation.
Using ANCOVA (presupplementation times as covariate), postsupplementation race times were significantly faster following beta-alanine (p = .02), with post- versus presupplementation race times being faster after beta-alanine (–3.64 ± 2.70 s, –2.46 ± 1.80%) but not placebo (–0.59 ± 2.54 s, –0.37 ± 1.62%). These improvements were supported by a moderate effect size (d = 0.70) and a very likely (99%) benefit in the beta-alanine group after supplementation. Split times (ANCOVA) at 400 m were significantly faster (p = .02) postsupplementation in the beta-alanine group, compared with placebo. This was supported by large effect sizes (d = 1.05–1.19) and a very likely (99%) benefit at the 400 and 800 m splits when comparing pre- to postsupplementation with beta-alanine. In addition, the first and second halves of the race were faster post- compared with presupplementation following beta-alanine (1st half –1.22 ± 1.81 s, likely 78% chance of benefit; 2nd half –2.38 ± 2.31 s, d = 0.83, very likely 98% chance of benefit). No significant differences between groups or pre- and postsupplementation were observed for postrace blood lactate and pH.
Overall, 28 days of beta-alanine supplementation (80 mg·kg-1BM·day-1) improved 800 m track performance in recreational club runners.
Jeffery Sobal and Leonard F. Marquart
Vitamin/mineral supplements are often used by athletes as ergogenic aids to improve performance. This paper reviews studies of the prevalence, patterns, and explanations for vitamin/mineral supplement use among athletes. Fifty-one studies provided quantitative prevalence data on 10,274 male and female athletes at several levels of athletic participation in over 15 sports. The overall mean prevalence of athletes’ supplement use was 46%. Most studies reported that over half of the athletes used supplements (range 6% to 100%), and the larger investigations found lower prevalence levels. Elite athletes used supplements more than college or high school athletes. Women used supplements more often than men. Varying patterns existed by sport. Athletes appear to use supplements more than the general population, and some take high doses that may lead to nutritional problems. Sport nutritionists should include a vitamin/mineral supplement history as part of their dietary assessment so they can educate athletes about vitamin/mineral supplements and athletic performance.
Farnoosh Mafi, Soheil Biglari, Alireza Ghardashi Afousi and Abbas Ali Gaeini
muscle growth factors—for example, epicatechin supplement, which is a part of the chemical family of flavonoids and is abundantly present in dark chocolate and green tea. Recent studies showed that these molecules can positively affect muscle growth factors. In fact, by stimulating the concentration of
Martin P. Schwellnus and Gerhard Jordaan
This study investigated the effect of calcium supplementation in preventing bone stress injuries. Healthy male military recruits (N=1,398) served as subjects, of which 247 were randomly allocated to an experimental group (E) while 1,151 served as a control group (C). For 9 weeks both groups wore the same footwear and had the same physical training program. The baseline dietary intake of calcium in 50 randomly selected subjects of each group was assessed using a 24-hr dietary record. The E group received a daily calcium supplement while the C group did not. Injuries were monitored in all subjects by a panel of doctors who followed specific diagnostic criteria. The mean weekly injury incidence for all overuse injuries, but specifically tibial stress syndrome and stress fractures, was similar in both groups. Mean baseline daily dietary calcium intake was above 800 mg in both subgroups. This study demonstrated that large-scale calcium supplementation (500 nig/ day) beyond usual dietary intake did not influence the risk of developing bone stress injuries during a 9-wk physical training program in these young military recruits.
Hannah Bond, Lillian Morton and Andrea J. Braakhuis
Increased plasma nitrate concentrations from dietary sources of nitrate have proven to benefit exercise performance. Beetroot (BR) contains relatively high levels of nitrate (NO3 −), which increases nitric oxide stores. This study investigated whether dietary nitrate supplementation, in the form of a BR beverage, would improve rowing performance during ergometer repetitions. In a randomized crossover design, 14 well-trained junior male rowers consumed 500 ml of either BR or placebo (PL) daily for 6 d. After supplementation, rowers completed 6 maximal 500-m ergometer repetitions and times were recorded. A 7-d washout period separated the 2 trials. Blood pressure, oxygen saturation, maximum heart rate, urine (specific gravity, pH, and nitrites), and lactates were collected for analysis at baseline and pre- and postperformance. Changes in the mean with 95% confidence limits were calculated. There was a likely benefit to average repetition time in the BR condition, compared with PL (0.4%, 95% confidence limits, ± 1.0%). In particular, Repetitions 4–6 showed an almost certain benefit in rowing time on BR (1.7%, 95% CL, ± 1.0%). The underlying mechanism for the observed results remains unknown, as differences observed in rowers’ physiological measures between the 2 conditions were unclear. Conclusively, nitrate supplementation in the form of BR juice resulted in improved maximal rowing-ergometer repetitions, particularly in the later stages of exercise.