Efficacy of beta-hydroxy-beta-methylbutyrate (HMB) supplementation in hemodialysis patients

Patients with renal failure undergoing maintenance hemodialysis (MHD) therapy suffer from a number of co-morbidities including skeletal muscle loss, reduced physical function, a significantly increased fall risk, and reduced quality of life (QOL). Therefore, interventions to combat these co-morbidities are needed. Beta-hydroxy-beta-methylbutyrate (HMB) is a metabolite of the amino acid leucine that has been shown to improve lean mass and physical function in the elderly and clinical populations, but had not previously been studied in MHD patients. Approximately 25 percent of supplemental HMB is cleared by the kidney; therefore, we first performed an acute study to determine the clearance of supplemental HMB in hemodialysis patients. MHD patients (n=8) consumed 3g HMB prior to a standard hemodialysis session. Following supplementation with HMB, a majority of supplemental HMB was cleared within 48hrs and plasma HMB levels returned to baseline within 7 days in all participants. These results suggest that supplemental HMB is cleared in patients with impaired renal function. Based upon these results, we performed a double blind, placebo controlled, randomized trial to assess the effects of daily HMB supplementation on co-morbidities in MHD patients. MHD patients were recruited and assigned to either daily supplementation with HMB (n=16) or placebo (n=17) for 6 months. No significant effects of HMB on lean mass, strength, physical function, fall risk, or quality of life were found using an intent-to-treat analysis. However, upon analysis of plasma HMB concentrations, 5 of 16 patients (31%) who completed the study in the HMB group were found to be non-compliant at 3 or 6 months. Therefore, we performed a per-protocol analysis with compliant participants only. Although this analysis was underpowered, we observed a trend for improvements in chair stand and timed up-and-go tests with HMB supplementation. However, no effects of HMB were observed for lean mass, strength, fall risk, or quality of life. As a whole, these results do not support the efficacy of HMB to attenuate muscle loss and declines in physical function in MHD patients. However, the observed low-compliance with study pills may have affected results. Moreover, it highlights the need for future interventions targeted at reducing pill burden and improving pill compliance in this population

International Society of Sports Nutrition Position Stand: beta-hydroxy-beta-methylbutyrate (HMB)

Abstract Position Statement: The International Society of Sports Nutrition (ISSN) bases the following position stand on a critical analysis of the literature on the use of beta-hydroxy-beta-methylbutyrate (HMB) as a nutritional supplement. The ISSN has concluded the following. 1. HMB can be used to enhance recovery by attenuating exercise induced skeletal muscle damage in trained and untrained populations. 2. If consuming HMB, an athlete will benefit from consuming the supplement in close proximity to their workout. 3. HMB appears to be most effective when consumed for 2 weeks prior to an exercise bout. 4. Thirty-eight mg·kg·BM-1 daily of HMB has been demonstrated to enhance skeletal muscle hypertrophy, strength, and power in untrained and trained populations when the appropriate exercise prescription is utilized. 5. Currently, two forms of HMB have been used: Calcium HMB (HMB-Ca) and a free acid form of HMB (HMB-FA). HMB-FA may increase plasma absorption and retention of HMB to a greater extent than HMB-CA. However, research with HMB-FA is in its infancy, and there is not enough research to support whether one form is superior. 6. HMB has been demonstrated to increase LBM and functionality in elderly, sedentary populations. 7. HMB ingestion in conjunction with a structured exercise program may result in greater declines in fat mass (FM). 8. HMB’s mechanisms of action include an inhibition and increase of proteolysis and protein synthesis, respectively. 9. Chronic consumption of HMB is safe in both young and old populations

English and Black Walnut Phenolic Antioxidant Activity in Vitro and Following Human Nut Consumption

ABSTRACT Background: Walnut consumption may reduce the risk of cardiovascular disease by providing antioxidant protection to low density lipoproteins (LDL). Aim: This study compared the phenolic profile and antioxidant activity of English versus black walnuts. Methods: Nuts were extracted in methanol or acetone prior to analysis with HPLC/LC-MS-MS for phenolic identification and quantitation. The ability to prevent oxidation of LDL was examined in vitro using walnut extracts and ex vivo after walnut consumption for 28 days. Results: Flavonoids identified/quantified with HPLC/LC-MS-MS included the phenolic acids 5-caffeoylquinic acid, 3-caffeoylquinic acid (black walnut only), 4-caffeoylquinic acid, and the flavonol glycosides querceti

Cardiovascular effects of black versus English walnut consumption

English walnuts have been shown to decrease cardiovascular disease risk; however, black walnuts have not been studied for their cardioprotective effects. The purpose of this study was to determine the effects of English versus black walnut consumption on blood lipids, body weight, fatty acid composition of erythrocyte (red blood cell, RBC) membranes, and endothelial cell function. Consumption of 30 g of English walnuts per day for 30 days improved blood lipids; while the effects of black walnuts were dependent upon gender. Addition of either nut to the diet did not result in weight gain. The fatty acid composition of RBC membranes was favorably affected by walnut consumption. RBC polyunsaturated fatty acids increased after consumption of either type of nut, however, eicosapentanoic acid increased significantly more after English walnut consumption. Endothelial function was maintained after consumption of English walnuts with a high saturated fat meal; however, consumption of black walnuts with the same meal did not maintain endothelial function. Overall, these results support the recommendation that consumption of 1 oz of English walnuts per day may lower cardiovascular risk, but more research on black walnut consumption is necessary before an appropriate recommendation can be made

Nutrition Recommendations for Bodybuilders in the Off-Season: A Narrative Review

Many nutrition practices often used by bodybuilders lack scientific support and can be detrimental to health. Recommendations during the dieting phase are provided in the scientific literature, but little attention has been devoted to bodybuilders during the off-season phase. During the off-season phase, the goal is to increase muscle mass without adding unnecessary body fat. This review evaluated the scientific literature and provides nutrition and dietary supplement recommendations for natural bodybuilders during the off-season phase. A hyper-energetic diet (~10–20%) should be consumed with a target weight gain of ~0.25–0.5% of bodyweight/week for novice/intermediate bodybuilders. Advanced bodybuilders should be more conservative with the caloric surplus and weekly weight gain. Sufficient protein (1.6–2.2 g/kg/day) should be consumed with optimal amounts 0.40–0.55 g/kg per meal and distributed evenly throughout the day (3–6 meals) including within 1–2 hours pre- and post-training. Fat should be consumed in moderate amounts (0.5–1.5 g/kg/day). Remaining calories should come from carbohydrates with focus on consuming sufficient amounts (≥3–5 g/kg/day) to support energy demands from resistance exercise. Creatine monohydrate (3–5 g/day), caffeine (5–6 mg/kg), beta-alanine (3–5 g/day) and citrulline malate (8 g/day) might yield ergogenic effects that can be beneficial for bodybuilders

CONTRIBUTION OF COGNITIVE INTERFERENCE TO DECREMENTS IN WALKING PERFORMANCE IN HEMODIALYSIS PATIENTS

Patients with advanced CKD have impaired walking function that predisposes them to falls and disability. Deficits in walking function are traditionally ascribed to declines in physical function. However, walking impairment in certain clinical populations may also result from a phenomenon known as cognitive-motor interference. This is characterized by reductions in motor task performance (e.g., walking speed) when simultaneously performing a cognitive task, and is termed a dual task cost (DTC). The purpose of this study was to compare the contribution of cognitive interference to decrements in walking performance in hemodialysis patients and healthy controls. 14 hemodialysis patients (10M,4F, age=48.5+/-11.8) and 14 age-matched healthy controls (9M, 5F, age=48.5+/- 10.1) participated. Each completed a walking task in a control and dual task condition. The walking task involved walking at a comfortable pace 4 times across a 26’GAITRite TM mat. The first 2 trials were completed with no cognitive task and the last 2 trials with a simultaneous task that consisted of generating a modified word list. Walking performance was quantified with normalized gait speed, step length, base of support, and step time. DTC was determined for each variable as the % difference in performance between the single task and dual task. Major metrics of walking function under standard conditions were impaired by 20-40% in hemodialysis patients vs controls (p<0.05 for each.). In addition, CKD patients had a greater DTC for velocity, cadence, step time and double support, than the control group (p<0.05), and trends for greater DTC for step length and width (p = 0.07). These data indicate that walking impairments in hemodialysis patients are not due exclusively to declines in physical function, but that cognitive-motor interference also plays a significant role. This has significant clinical importance, as therapies designed to improve walking performance and physical function, such as nutritional and exercise interventions, may need to be augmented with cognitive training in order to have maximum benefits

Arterial Stiffness and Walk Time in Patients with End-Stage Renal Disease

Background: End-stage renal disease patients experience increased prevalence of cardiovascular disease. Heart-artery interaction may be shifted, impacting blood pressure lability, and exercise tolerance. The coupling ratio consists of the ratio of indexed arterial elastance (EaI, arterial load) to ElvI, a measure of cardiac contractility or stiffness. Our purpose was to explore the relationship between elastances and functional capacity. We hypothesized that arterial stiffness (central pulse wave velocity, PWV) and elastances would be correlated to shuttle walk time. Methods: We used applanation tonometry, ultrasonography, and a shuttle walk test to evaluate our hypothesis. Spearman's correlations were used to assess relationships between variables. Block regression was also performed. Results: Forty-two subjects on maintenance hemodialysis participated. Average age=44±5 years, body surface area=2.01 kg/m2. Mean EaI=4.45 and mean ElvI=6.89; the coupling ratio=0.82. Mean aortic pulse pressure=51 mmHg and PWV=9.6 m/s. PWV(r=-0.385) and EaI (r=-0.424) were significantly and inversely related to walking time while stroke volume index (SVI) was positively correlated to shuttle walk time (r=0.337), pConclusions: We conclude that, like other clinical populations, both arterial and heart function predict walking ability and represent potential targets for intervention; arterial stiffness and SVI are strongly related to shuttle walk time in patients with ESRD