A review of recent evidence of dietary protein intake and health

Sex differences in the associations of dietary protein intake with lean mass and grip strength in children and adolescents

BACKGROUND

Childhood and adolescence are critical developmental periods during which dietary protein plays a crucial role in musculoskeletal health. While the significance of protein in muscle development is well acknowledged, the complex associations between dietary protein intake and musculoskeletal parameters during these stages remain incompletely elucidated.

METHODS

This cross-sectional study utilized data from the National Health and Nutrition Examination Survey (NHANES) 2011-2014 cycles, including 3,455 children and adolescents aged 8-19 years. Dietary protein intake was assessed through two 24-hour dietary recalls. Appendicular lean mass index (ALMI) and combined grip strength were measured as indicators of musculoskeletal health. Multivariate linear regression models and smooth curve fitting techniques were employed to analyze associations.

RESULTS

Higher protein intake was positively associated with both ALMI (β = 0.003, 95% CI: 0.002, 0.004, p < 0.001) and combined grip strength (β = 0.043, 95% CI: 0.027, 0.058, p < 0.001) in fully adjusted models. Notably, sex-specific effects were observed, with stronger associations in boys, particularly in the 8-11 years age group.

CONCLUSIONS

This study reveals significant positive associations between dietary protein intake and musculoskeletal health indicators in children and adolescents, with pronounced sex-specific effects. These findings underscore the importance of adequate protein intake during critical developmental periods and may inform targeted nutritional strategies for optimizing long-term musculoskeletal health.

Discovery and mechanistic analysis of a novel source protein glutaminase PG5 and its potential application

In this study, we successfully obtained a novel source protein glutaminase PG5 with specific activity of 10.4 U/mg, good tolerance and broad substrate profile through big data retrieval. Structural analysis and site-directed mutagenesis revealed that the catalytic pocket of Mature-PG5 contained a large number of aromatic amino acids and hydrophobic amino acids, and that Ser72 greatly affects the properties of the catalytic pocket and the affinity of PG5 for the substrate. In addition, molecular dynamics analysis revealed that the opening and closing between amino acid residues Gly65 and Thr66 with Cys164 at the catalytic cleft could affect substrate binding and product release. In addition, PG5 effectively improved the solubility of fish myofibrillar proteins under low-salt conditions while enhancing their foaming and emulsification properties. This study offers valuable insights into the catalytic mechanism of PG5, which will contribute to its future directed evolution and application in the food industry.

Association between carbohydrate to protein or fat ratio and mortality: A prospective cohort study

BACKGROUND & AIMS

The effect of dietary macronutrient balance on longevity and metabolic health remains a subject of considerable interest. We aimed to investigate the association of carbohydrate-to-protein and carbohydrate-to-fat ratios with all-cause and cardiovascular mortalities.

METHODS

In this population-based study, data from the Korean Genome and Epidemiology Study were integrated with those from national data sources, including mortality records from the Korea National Statistical Office. The primary outcomes were all-cause and cardiovascular mortalities. Carbohydrate-to-protein and carbohydrate-to-fat ratios were evaluated based on dietary habits assessed through a food frequency questionnaire. Harrell's C-index was employed to determine optimal cut-off points for carbohydrate-to-protein and carbohydrate-to-fat ratios. Cox proportional hazards regression models were used to assess associations.

RESULTS

A total of 143,050 participants aged ≥40 years were included in the analyses. Compared with individuals with non-elevated carbohydrate-to-protein ratios (<5.2), those with elevated carbohydrate-to-protein ratios (>9.9) exhibited a higher all-cause mortality (hazard ratio 1.09, 95% confidence interval 1.01-1.17); however, no correlation between carbohydrate-to-protein ratio and cardiovascular mortality (hazard ratio 1.13, 95% confidence interval 0.96-1.32) was observed. Compared with those with non-elevated carbohydrate-to-fat ratios (<5.1), those with higher carbohydrate-to-fat ratios (>7.1) exhibited increased all-cause (hazard ratio 1.08, 95% confidence interval 1.00-1.16) and cardiovascular (hazard ratio 1.27, 95% confidence interval 1.06-1.52) mortalities.

CONCLUSIONS

Our findings regarding macronutrient ratios and their association with mortality suggest that reducing excessive carbohydrate intake and increasing the consumption of protein and fats may have beneficial effects on longevity and cardiovascular health. Further studies are needed to understand the underlying mechanisms of these effects.

Effects of Dietary Protein Intake Levels on Peripheral Circadian Rhythm in Mice

The regulation of the circadian clock plays an important role in influencing physiological conditions. While it is reported that the timing and quantity of energy intake impact circadian regulation, the underlying mechanisms remain unclear. This study investigated the impact of dietary protein intake on peripheral clocks. Firstly, transcriptomic analysis was conducted to investigate molecular targets of low-protein intake. Secondly, mPer2::Luc knock-in mice, fed with either a low-protein, normal, or high-protein diet for 6 weeks, were analyzed for the oscillation of PER2 expression in peripheral tissues and for the expression profiles of circadian and metabolic genes. Lastly, the candidate pathway identified by the in vivo analysis was validated using AML12 cells. As a result, using transcriptomic analysis, we found that the low-protein diet hardly altered the circadian rhythm in the central clock. In animal experiments, expression levels and period lengths of PER2 were different in peripheral tissues depending on dietary protein intake; moreover, mRNA levels of clock-controlled genes and endoplasmic reticulum (ER) stress genes were affected by dietary protein intake. Induction of ER stress in AML12 cells caused an increased amplitude of Clock and Bmal1 and an advanced peak phase of Per2. This result shows that the intake of different dietary protein ratios causes an alteration of the circadian rhythm, especially in the peripheral clock of mice. Dietary protein intake modifies the oscillation of ER stress genes, which may play key roles in the regulation of the circadian clock.

Protein Restriction in Metabolic Health: Lessons from Rodent Models

Consumption of protein-rich diets and supplements has been increasingly advocated by individuals seeking to optimize metabolic health and mitigate the effects of aging. Protein intake is postulated to support muscle mass retention and enhance longevity, underscoring its perceived benefits in age-related metabolic regulation. However, emerging evidence presents a paradox; while moderate protein consumption contributes to health maintenance, an excessive intake is associated with an elevated risk of chronic diseases, notably obesity and diabetes. Furthermore, recent studies suggest that reducing the ratio of protein intake to macronutrients improves metabolic parameters and extends lifespan. The aim of this study is to review the current evidence concerning the metabolic effects of protein-restricted diets and their potential mechanisms. Utilizing rodent models, investigations have revealed that protein-restricted diets exert a notable influence over food intake and energy consumption, ultimately leading to body weight loss, depending on the degree of dietary protein restriction. These phenotypic alterations are primarily mediated by the FGF21 signaling pathway, whose activation is likely regulated by ATF4 and the circadian clock. The evidence suggests that protein-restricted diets as an alternative approach to calorie-restricted regimes, particularly in overweight or obese adults. However, more research is needed to determine the optimal level of restriction, duration, and long-term effects of such interventions.