Chad M. Kerksick

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.

The Antioxidant Role of Glutathione and N-Acetyl-Cysteine Supplements and Exercise-Induced Oxidative Stress

An increase in exercise intensity is one of the many ways in which oxidative stress and free radical production has been shown to increase inside our cells. Effective regulation of the cellular balance between oxidation and antioxidation is important when considering cellular function and DNA integrity as well as the signal transduction of gene expression. Many pathological states, such as cancer, Parkinsons disease, and Alzheimers disease have been shown to be related to the redox state of cells. In an attempt to minimize the onset of oxidative stress, supplementation with various known antioxidants has been suggested. Glutathione and N-acetyl-cysteine (NAC) are antioxidants which are quite popular for their ability to minimize oxidative stress and the downstream negative effects thought to be associated with oxidative stress. Glutathione is largely known to minimize the lipid peroxidation of cellular membranes and other such targets that is known to occur with oxidative stress. N-acetyl-cysteine is a by-product of glutathione and is popular due to its cysteine residues and the role it has on glutathione maintenance and metabolism. The process of oxidative stress is a complicated, inter-twined series of events which quite possibly is related to many other cellular processes. Exercise enthusiasts and researchers have become interested in recent years to identify any means to help minimize the detrimental effects of oxidative stress that are commonly associated with intense and unaccustomed exercise. It is possible that a decrease in the amount of oxidative stress a cell is exposed to could increase health and performance.

International Society of Sports Nutrition position stand: Nutrient timing

Position Statement: The position of the Society regarding nutrient timing and the intake of carbohydrates, proteins, and fats in reference to healthy, exercising individuals is summarized by the following eight points: 1.) Maximal endogenous glycogen stores are best promoted by following a high-glycemic, high-carbohydrate (CHO) diet (600 – 1000 grams CHO or ~8 – 10 g CHO/kg/d), and ingestion of free amino acids and protein (PRO) alone or in combination with CHO before resistance exercise can maximally stimulate protein synthesis. 2.) During exercise, CHO should be consumed at a rate of 30 – 60 grams of CHO/hour in a 6 – 8% CHO solution (8 – 16 fluid ounces) every 10 – 15 minutes. Adding PRO to create a CHO:PRO ratio of 3 – 4:1 may increase endurance performance and maximally promotes glycogen re-synthesis during acute and subsequent bouts of endurance exercise. 3.) Ingesting CHO alone or in combination with PRO during resistance exercise increases muscle glycogen, offsets muscle damage, and facilitates greater training adaptations after either acute or prolonged periods of supplementation with resistance training. 4.) Post-exercise (within 30 minutes) consumption of CHO at high dosages (8 – 10 g CHO/kg/day) have been shown to stimulate muscle glycogen re-synthesis, while adding PRO (0.2 g – 0.5 g PRO/kg/day) to CHO at a ratio of 3 – 4:1 (CHO: PRO) may further enhance glycogen re-synthesis. 5.) Post-exercise ingestion (immediately to 3 h post) of amino acids, primarily essential amino acids, has been shown to stimulate robust increases in muscle protein synthesis, while the addition of CHO may stimulate even greater levels of protein synthesis. Additionally, pre-exercise consumption of a CHO + PRO supplement may result in peak levels of protein synthesis. 6.) During consistent, prolonged resistance training, post-exercise consumption of varying doses of CHO + PRO supplements in varying dosages have been shown to stimulate improvements in strength and body composition when compared to control or placebo conditions. 7.) The addition of creatine (Cr) (0.1 g Cr/kg/day) to a CHO + PRO supplement may facilitate even greater adaptations to resistance training. 8.) Nutrient timing incorporates the use of methodical planning and eating of whole foods, nutrients extracted from food, and other sources. The timing of the energy intake and the ratio of certain ingested macronutrients are likely the attributes which allow for enhanced recovery and tissue repair following high-volume exercise, augmented muscle protein synthesis, and improved mood states when compared with unplanned or traditional strategies of nutrient intake.

THE EFFECTS OF PROTEIN AND AMINO ACID SUPPLEMENTATION ON PERFORMANCE AND TRAINING ADAPTATIONS DURING TEN WEEKS OF RESISTANCE TRAINING

The purpose of this study was to examine the effects of whey protein supplementation on body composition, muscular strength, muscular endurance, and anaerobic capacity during 10 weeks of resistance training. Thirty-six resistance-trained males (31.0 ± 8.0 years, 179.1 ± 8.0 cm, 84.0 ± 12.9 kg, 17.8 ± 6.6%) followed a 4 days-per-week split body part resistance training program for 10 weeks. Three groups of supplements were randomly assigned, prior to the beginning of the exercise program, in a double-blind manner to all subjects: 48 g per day (g·d−1) carbohydrate placebo (P), 40 g·d−1 of whey protein + 8 g·d−1 of casein (WC), or 40 g·d−1 of whey protein + 3 g·d−1 branched-chain amino acids + 5 g·d−1 L-glutamine (WBG). At 0, 5, and 10 weeks, subjects were tested for fasting blood samples, body mass, body composition using dual-energy x-ray absorptiometry (DEXA), 1 repetition maximum (1RM) bench and leg press, 80% 1RM maximal repetitions to fatigue for bench press and leg press, and 30-second Wingate anaerobic capacity tests. No changes (p > 0.05) were noted in all groups for energy in-take, training volume, blood parameters, and anaerobic capacity. WC experienced the greatest increases in DEXA lean mass (P = 0.0 ± 0.9; WC = 1.9 ± 0.6; WBG =-0.1 ± 0.3 kg, p < 0.05) and DEXA fat-free mass (P = 0.1 ± 1.0; WC = 1.8 ± 0.6; WBG = −0.1 ± 0.2 kg, p < 0.05). Significant increases in 1RM bench press and leg press were observed in all groups after 10 weeks. In this study, the combination of whey and casein protein promoted the greatest increases in fat-free mass after 10 weeks of heavy resistance training. Athletes, coaches, and nutritionists can use these findings to increase fat-free mass and to improve body composition during resistance training.

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

BackgroundTo 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.MethodsTwenty-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.ResultsPlasma 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).ConclusionAcute 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.

Genome-wide DNA methylation changes with age in disease-free human skeletal muscle

A decline in skeletal muscle mass and function with aging is well recognized, but remains poorly characterized at the molecular level. Here, we report for the first time a genome‐wide study of DNA methylation dynamics in skeletal muscle of healthy male individuals during normal human aging. We predominantly observed hypermethylation throughout the genome within the aged group as compared to the young subjects. Differentially methylated CpG (dmCpG) nucleotides tend to arise intragenically and are underrepresented in promoters and are overrepresented in the middle and 3′ end of genes. The intragenic methylation changes are overrepresented in genes that guide the formation of the junction of the motor neuron and myofibers. We report a low level of correlation of gene expression from previous studies of aged muscle with our current analysis of DNA methylation status. For those genes that had both changes in methylation and gene expression with age, we observed a reverse correlation, with the exception of intragenic hypermethylated genes that were correlated with an increased gene expression. We suggest that a minimal number of dmCpG sites or select sites are required to be altered in order to correlate with gene expression changes. Finally, we identified 500 dmCpG sites that perform well in discriminating young from old samples. Our findings highlight epigenetic links between aging postmitotic skeletal muscle and DNA methylation.

Effects of a popular exercise and weight loss program on weight loss, body composition, energy expenditure and health in obese women.

ObjectiveTo determine the safety and efficacy of altering the ratio of carbohydrate and protein in low-energy diets in conjunction with a popular exercise program in obese women.DesignMatched, prospective clinical intervention study to assess efficacy of varying ratios of carbohydrate and protein intake in conjunction with a regular exercise program.ParticipantsOne-hundred sixty one sedentary, obese, pre-menopausal women (38.5 ± 8.5 yrs, 164.2 ± 6.7 cm, 94.2 ± 18.8 kg, 34.9 ± 6.4 kg·m-2, 43.8 ± 4.2%) participated in this study. Participants were weight stable and not participating in additional weight loss programs.MethodsParticipants were assigned to either a no exercise + no diet control (CON), a no diet + exercise group (ND), or one of four diet + exercise groups (presented as kcals; % carbohydrate: protein: fat): 1) a high energy, high carbohydrate, low protein diet (HED) [2,600; 55:15:30%], 2) a very low carbohydrate, high protein diet (VLCHP) [1,200 kcals; 63:7:30%], 3) a low carbohydrate, moderate protein diet (LCMP) [1,200 kcals; 50:20:30%] and 4) a high carbohydrate, low protein diet (HCLP) [1,200 kcals; 55:15:30%]. Participants in exercise groups (all but CON) performed a pneumatic resistance-based, circuit training program under supervision three times per week.MeasurementsAnthropometric, body composition, resting energy expenditure (REE), fasting blood samples and muscular fitness assessments were examined at baseline and weeks 2, 10 and 14.ResultsAll groups except CON experienced significant reductions (P < 0.05 – 0.001) in waist circumference over 14 weeks. VLCHP, LCHP and LPHC participants experienced similar but significant (P < 0.05 – 0.001) reductions in body mass when compared to other groups. Delta responses indicated that fat loss after 14 weeks was significantly greatest in VLCHP (95% CI: -5.2, -3.2 kg), LCMP (-4.0, -1.9 kg) and HCLP (-3.8, -2.1 kg) when compared to other groups. Subsequent reductions in % body fat were significantly greater in VLCHP, LCMP and HCLP participants. Initial dieting decreased (P < 0.05) relative REE similarly in all groups. All exercise groups significantly (P < 0.05) improved in muscular fitness, but these improvements were not different among groups. Favorable but non-significant mean changes occurred in lipid panels, glucose and HOMA-IR. Leptin levels decreased (P < 0.05) in all groups, except for CON, after two weeks of dieting and remained lower throughout the 14 week program. Exercise participation resulted in significant improvements in quality of life and body image.ConclusionExercise alone (ND) appears to have minimal impact on measured outcomes with positive outcomes apparent when exercise is combined with a hypoenergetic diet. Greater improvements in waist circumference and body composition occurred when carbohydrate is replaced in the diet with protein. Weight loss in all diet groups (VLCHP, LCMP and HCLP) was primarily fat and stimulated improvements in markers of cardiovascular disease risk, body composition, energy expenditure and psychosocial parameters.

Does vitamin C and E supplementation impair the favorable adaptations of regular exercise

The detrimental outcomes associated with unregulated and excessive production of free radicals remains a physiological concern that has implications to health, medicine and performance. Available evidence suggests that physiological adaptations to exercise training can enhance the bodys ability to quench free radicals and circumstantial evidence exists to suggest that key vitamins and nutrients may provide additional support to mitigate the untoward effects associated with increased free radical production. However, controversy has risen regarding the potential outcomes associated with vitamins C and E, two popular antioxidant nutrients. Recent evidence has been put forth suggesting that exogenous administration of these antioxidants may be harmful to performance making interpretations regarding the efficacy of antioxidants challenging. The available studies that employed both animal and human models provided conflicting outcomes regarding the efficacy of vitamin C and E supplementation, at least partly due to methodological differences in assessing oxidative stress and training adaptations. Based on the contradictory evidence regarding the effects of higher intakes of vitamin C and/or E on exercise performance and redox homeostasis, a permanent intake of non-physiological dosages of vitamin C and/or E cannot be recommended to healthy, exercising individuals.

Total body water estimations in healthy men and women using bioimpedance spectroscopy: a deuterium oxide comparison.

BackgroundTotal body water (TBW) estimations have been used to estimate body composition, particularly fat-free mass, to aid in nutritional interventions, and to monitor hydration status. In the past, bioimpedance spectroscopy (BIS) devices have been used to estimate TBW. Previous investigations have examined the validity of the XiTRON 4000B (XiTRON Technologies) BIS device for estimating TBW. Recently, a new BIS device (Imp™ SFB7) has become available, claiming greater precision when estimating TBW. The Imp™ SFB7 (SFB7) is based on similar BIS principles, while offering increased portability and a greater range of frequencies when compared to older devices, such as the XiTRON 4000B (4000B). The purpose of this study was to examine the validity of the SFB7 for estimating total body water in healthy college-age men and women compared to the 4000B and deuterium oxide (D2O).MethodsTwenty-eight Caucasian men and women (14 men, 14 women; 24 ± 4 yrs; 174.6 ± 8.7 cm; 72.80 ± 17.58 kg) had their TBW estimated by the SFB7, the 4000B, and D2O.ResultsBoth BIS devices produced similar standard error of estimate (SEE) and r values (SFB7, SEE = 2.12L, r = 0.98; 4000B, SEE = 2.99L, r = 0.96) when compared to D2O, though a significant constant error (CE) was detected for the 4000B (2.26L, p ≤ 0.025). The 4000B produced a larger total error (TE) and CE (TE = 3.81L, CE = 2.26L) when compared to the SFB7 (TE = 2.21L, CE = -0.09L). Additionally, the limits of agreement were larger for the 4000B (-3.88 to 8.39L) than the SFB7 (-4.50 to 4.31L). These results were consistent when sex was analyzed separately, though women produced lower SEE and TE values for both devices.ConclusionThe 4000B and SFB7 are valid BIS devices when compared to D2O to estimate TBW in college-age Caucasian men and women. Furthermore, the new SFB7 device displayed greater precision in comparison to the 4000B, which may decrease the error when estimating TBW on an individual basis.

Effects of Coleus Forskohlii Supplementation on Body Composition and Hematological Profiles in Mildly Overweight Women

PurposeThis study investigated the effects of Coleus Forskohlii (CF) on body composition, and determined the safety and efficacy of supplementation.MethodsIn a double blind and randomized manner, 23 females supplemented their diet with ForsLean™ (250 mg of 10% CF extract, (n = 7) or a placebo [P] (n = 12) two times per day for 12-wks. Body composition (DEXA), body weight, and psychometric instruments were obtained at 0, 4, 8 & 12 weeks of supplementation. Fasting blood samples and dietary records (4-d) were obtained at 0 and 12-wks. Side effects were recorded on a weekly basis. Data were analyzed by repeated measures ANOVA and are presented as mean changes from baseline for the CF and placebo groups, respectively.ResultsNo significant differences were observed in caloric or macronutrient intake. CF tended to mitigate gains in body mass (-0.7 ± 1.8, 1.0 ± 2.5 kg, p = 0.10) and scanned mass (-0.2 ± 1.3, 1.7 ± 2.9 kg, p = 0.08) with no significant differences in fat mass (-0.2 ± 0.7, 1.1 ± 2.3 kg, p = 0.16), fat free mass (-0.1 ± 1.3, 0.6 ± 1.2 kg, p = 0.21), or body fat (-0.2 ± 1.0, 0.4 ± 1.4%, p = 0.40). Subjects in the CF group tended to report less fatigue (p = 0.07), hunger (p = 0.02), and fullness (p = 0.04). No clinically significant interactions were seen in metabolic markers, blood lipids, muscle and liver enzymes, electrolytes, red cells, white cells, hormones (insulin, TSH, T3, and T4), heart rate, blood pressure, or weekly reports of side effects.ConclusionResults suggest that CF does not appear to promote weight loss but may help mitigate weight gain in overweight females with apparently no clinically significant side effects.