Within-Day Amino Acid Intakes and Nitrogen Balance in Male Collegiate Swimmers during the General Preparation Phase

Low Sodium Intake, Low Protein Intake, and Excess Mortality in an Older Dutch General Population Cohort: Findings in the Prospective Lifelines-MINUTHE Study

Background: Several studies have found a U-shaped association between sodium intake and mortality. The increased mortality risk of low sodium intake has raised debates and hampers widespread acceptance of public health campaigns and dietary guidelines on reducing sodium intake. Whether the excess risk can be attributed to low sodium intake alone or concomitant inadequate intake of other relevant nutrients is unknown. Objective: We investigated whether concomitant low protein intake could explain the lower part of the U-shaped association of sodium intake with all-cause mortality. Methods: We included 1603 individuals aged between 60 and 75 years old from the gender- and socioeconomic status-balanced prospective Lifelines-MINUTHE cohort study. Using multivariable Cox regression analyses, we investigated the association of sodium intake (24 h urinary sodium excretion) with all-cause mortality, including the interaction with protein intake calculated from the Maroni formula. Results: Mean intakes of sodium and protein were 3.9 ± 1.6 g/day and 1.1 ± 0.3 g/kg/day, respectively. After a median follow-up of 8.9 years, 125 individuals (7.8%) had died. The proportion of participants with insufficient protein intake (<0.8 g/kg/day) was inversely related to sodium intake (i.e., 23.3% in Q1 versus 2.8% in Q4, p < 0.001). We found an increased risk for mortality in both the highest quartile (Q4, >4.7 g/day; hazard ratio (HR) 1.74 (95% confidence interval (CI) 1.03−2.95)) and the lowest two quartiles of sodium intake (Q1, 0.7−2.8 g/day; 2.05 (1.16−3.62); p = 0.01 and Q2, 2.8−3.6 g/day; 1.85 (1.08−3.20); p = 0.03), compared with the third quartile of sodium intake (Q3, 3.6−4.7 g/day). This U-shaped association was significantly modified by protein intake (Pinteraction = 0.006), with the increased mortality risk of low sodium intake being reversed to the lowest mortality risk with concomitant high protein intake. In contrast, the increased mortality risk of low sodium intake was magnified by concomitant low protein intake. Conclusions: We found that a higher protein intake counteracts the increased mortality risk observed in subjects with a low sodium intake. In contrast, a joint low intake of sodium and protein is associated with an increased mortality risk, allegedly due to poor nutritional status. These findings support the guidelines that advocate a lower sodium intake, while highlighting the importance of recognizing overall nutritional status among older adults.

Plasma Amino Acids and Acylcarnitines Are Associated with the Female but Not Male Adolescent Swimmer's Performance: An Integration between Mass Spectrometry and Complex Network Approaches

The main aim of this study was to compare the performance over different distances, the critical velocity (CV), and plasma acylcarnitines/amino acids of male and female adolescent swimmers. Moreover, we applied the complex network approach to identify which molecules are associated with athletes' performances. On the first day under a controlled environment, blood samples were collected after 12 h of overnight fasting. Performance trials (100, 200, 400, and 800-m) were randomly performed in the subsequent four days in a swimming pool, and CV was determined by linear distance versus time mathematical function. Metabolomic analyses were carried out on a triple quadrupole mass spectrometer performing electrospray ionization in the positive ionization mode. No difference was observed between the performance of male and female swimmers. Except for 200-m distance (p = 0.08), plasma tyrosine was positively and significantly associated with the female times during the trials (100-m, p = 0.04; 400-m, p = 0.04; 800-m, p = 0.02), and inversely associated with the CV (p = 0.02). The complex network approach showed that glycine (0.406), glutamine (0.400), arginine (0.335), free carnitine (0.355), tryptophan (0.289), and histidine (0.271) were the most influential nodes to reach tyrosine. These results revealed a thread that must be explored in further randomized/controlled designs, improving the knowledge surrounding nutrition and the performance of adolescent swimmers.

The Effects of a Nutrition Education Intervention on Sports Nutrition Knowledge during a Competitive Season in Highly Trained Adolescent Swimmers

The aim of this study was to evaluate the effects of a seven-week nutrition education intervention on the sports nutrition knowledge (SNK) of highly trained UK adolescent swimmers. Fifteen national and international adolescent swimmers (males = 5; females = 10, 15.5 ± 1.1 years, 170.2 ± 7.5 cm, 60.3 ± 5.7 kg) participated in the study during seven consecutive weeks of the competitive swimming season. The participants received 30 min of nutrition education once per week in a classroom-based setting after they had completed their regular swim training. An undergraduate sports nutrition student delivered all nutrition education sessions and SNK questionnaires were administered to the participants pre- and post-intervention. The mean total SNK score improved by 8.3% (SD = 8.4%, 95% CI = 4.1–12.6; p = 0.006; ES = 1.0) following the nutrition education sessions. On an individual basis, ten swimmers significantly improved their total SNK score, whereas four swimmers did not improve, and one swimmer performed significantly worse after the intervention. Moreover, the swimmers’ knowledge of hydration improved by 22.2% (SD = 20.6%, 95% CI = 11.8–32.6, p = 0.004, ES = 1.1) over the seven-week timeframe, which was the only nutrition topic to have a significantly increased knowledge score. The current study therefore suggests that a nutrition education intervention can positively influence the SNK of highly trained adolescent swimmers.

Protein Considerations for Athletes With a Spinal Cord Injury

Athlete participation in the Paralympic games is steadily increasing; prompting research focused on the unique needs of this population. While the Paralympic Games includes a diversity of athletes, athletes with a spinal cord injury (PARA-SCI) represent a subgroup that requires specialized recommendations. Nutritional guidelines designed to optimize performance, in the context of the neurological impairments, are required. This narrative review summarizes the current literature regarding the importance of dietary protein for optimal health and performance. Factors with the potential to affect protein needs in PARA-SCI including loss of active muscle mass, reduced energy expenditure, and secondary complications are examined in detail. Furthermore, we analyze protein intakes in PARA-SCI from the available research to provide context around current practices and trends. In conclusion, we make the case that protein recommendations for able-bodied athletes may not be directly transferable to PARA-SCI. Consequently, PARA-SCI need their own guidelines to maximize performance and ensure long-term health.

Nutritional Practice and Nitrogen Balance in Elite Japanese Swimmers during a Training Camp

The protein requirement in athletes increases as a result of exercise-induced changes in protein metabolism. In addition, the frequency, quantity, and quality (i.e., leucine content) of the protein intake modulates the protein metabolism. Thus, this study aimed to investigate whether nutritional practice (particularly, protein and amino acid intake at each eating occasion) meets the protein needs required to achieve zero nitrogen balance in elite swimmers during a training camp. Eight elite swimmers (age 21.9 ± 2.3 years, body weight 64.2 ± 7.1 kg, sex M:2 F:6) participated in a four-day study. The nitrogen balance was calculated from the dietary nitrogen intake and urinary nitrogen excretion. The amino acid intake was divided over six eating occasions. The nitrogen balance was found to be positive (6.7 ± 3.1 g N/day, p < 0.05) with protein intake of 2.96 ± 0.74 g/kg/day. The frequency and quantity of leucine and the protein intake were met within the recommended range established by the International Society of Sports Nutrition. Thus, a protein intake of 2.96 g/kg/day with a well-designated pattern (i.e., frequency throughout the day, as well as quantity and quality) of protein and amino acid intake may satisfy the increased need for protein in an elite swimmer.

Protein Intake, Fatigue and Quality of Life in Stable Outpatient Kidney Transplant Recipients

Fatigue is a frequent complaint in kidney transplant recipients (KTR), often accompanied by poor quality of life (QoL). The role of nutrition as determinant of fatigue in KTR is largely unexplored. The aims of this study are to examine the association of protein intake with fatigue and QoL in KTR and to identify other determinants of fatigue. This cross-sectional study is part of the TransplantLines Cohort and Biobank Study (NCT03272841). Protein intake was calculated from urinary urea nitrogen (UUN) in 24-h urine samples. Fatigue was assessed by the Checklist Individual Strength (CIS) questionnaire; moderate and severe fatigue were defined as a CIS score of 20–34 and ≥ 35, respectively. QoL was assessed with the RAND-36-Item Health Survey (RAND-36). Associations of protein intake with fatigue and QoL were analyzed using multinomial logistic and linear regression analyses. We included 730 stable outpatient KTR (median age 58 year [IQR 48–65], 57% male) with a mean protein intake of 82.2 ± 21.3 g/d. Moderate and severe fatigue were present in 254 (35%) and 245 (34%) of KTR. Higher protein intake was significantly associated with lower risk of moderate fatigue (OR 0.89 per 10 g/d; 95%CI 0.83–0.98, p = 0.01), severe fatigue (OR 0.85; 95%CI 0.78–0.92, p < 0.001) and was associated with higher physical component summary score of QoL (β 0.74 per 10 g/d; 95%CI 0.39–1.09, p < 0.001). Higher BMI, a history of dialysis, glomerulonephritis as primary kidney disease and a history of combined organ transplantation were also associated with severe fatigue. In conclusion, amongst the potential modifiable factors of fatigue, higher protein intake is independently associated with lower risk of moderate and severe fatigue and with better QoL in KTR. These findings underline the need to incorporate nutritional assessment in the diagnostic work-up of fatigue. Intervention studies are needed to assess the benefits and safety of higher protein intake in KTR.