Protein Requirements of Elderly Chinese Adults Are Higher than Current Recommendations

Post-prandial tracer studies of protein and amino acid utilisation: what can they tell us about human amino acid and protein requirements?

Nitrogen balance (NB), the principal methodology used to derive recommendations for human protein and amino acid requirements, has been widely criticised, and calls for increased protein and amino acid requirement recommendations have been made, often on the basis of post-prandial amino acid tracer kinetic studies of muscle protein synthesis, or of amino acid oxidation. This narrative review considers our knowledge of the homeostatic regulation of the FFM throughout the diurnal cycle of feeding and fasting and what can and has been learnt from post-prandial amino acid tracer studies, about amino acid and protein requirements. Within the FFM, muscle mass in well fed weight-stable adults with healthy lifestyles appears fixed at a phenotypic level within a wide range of habitual protein intakes. However homoeostatic regulation occurs in response to variation in habitual protein intake, with adaptive changes in amino acid oxidation which influence the magnitude of diurnal losses and gains of body protein. Post-prandial indicator amino acid oxidation (IAAO) studies have been introduced as an alternative to NB and to the logistically complex 24 h [13C-1] amino acid balance studies, for assessment of protein and amino acid requirements. However, a detailed examination of IAAO studies shows both a lack of concern for homeostatic regulation of amino acid oxidation and  major flaws in their design and analytical interpretation, which seriously constrain their ability to provide reliable values. New ideas and a much more critical approach to existing work is needed if real progress is to be made in the area.

Reevaluation of the protein requirement in Chinese elderly adults without sarcopenia with the indicator amino acid oxidation technique

It is now generally believed that elderly may have slightly higher dietary protein requirements than those of the young-middle-aged adults. We have previously conducted related studies by the indicator amino acid oxidation (IAAO) technique, but more research data are needed to revise the protein requirements of the elderly. The main objective was to reevaluate the dietary protein requirements of healthy Chinese adults (65-80 years) without sarcopenia by using the IAAO technique. Nine healthy adult men and seven healthy adult women participated in the study, with protein intakes ranging from 0·1 to 1·8 g/(kg·d). Diets that delivered energy at a 1·5 resting energy expenditure were isocaloric. The amounts of phenylalanine and tyrosine needed to remain constant for each protein dosage. By applying a nonlinear mixed-effects model analysis on the F13CO2 data, which revealed a breakpoint in F13CO2 in response to graded protein intakes, the mean protein requirement was calculated. The mean estimated average requirement (EAR) for healthy elderly Chinese adults without sarcopenia was determined to be 0·94 g/(kg·d). The protein recommended nutrient intake (RNI) determined using various derivation approaches ranged from 1·13 to 1·36 g/(kg·d). The EAR for Chinese adults without sarcopenia aged 65-80 years in this study is 6·8 % higher than the current recommended EAR (0·88 g/(kg·d)). The RNI derived using various derivation approaches are all greater than the current RNI (0·98 g/(kg·d)). This trial was registered with the Chinese clinical trial registry as ChiCTR2200061382.

Evaluation of protein requirements using the indicator amino acid oxidation method: a scoping review

BACKGROUND

The indicator amino acid oxidation (IAAO) method has been accepted as an approach to evaluate habitual protein requirements under free-living conditions.

OBJECTIVES

This scoping review reports on literature that evaluated protein requirements in humans using the IAAO methods.

METHODS

Three databases (PubMed/Medline, Web of Science, and ProQuest) were systematically searched to identify studies that evaluated protein requirements using the IAAO method published in English until 5 June, 2023. We evaluated the study quality using previously developed criteria. We extracted the characteristics of the study design and the results of protein requirements. Two reviewers conducted both reviews and quality assessments independently; any differences among them were resolved by consensus or agreement of all team members.

RESULTS

We extracted 16 articles targeting children, young adults (including pregnant women, resistance training athletes, endurance-training athletes, and team sports), and older adults. In quality assessment, 14 studies were evaluated "strong," but the remaining 2 were "moderate." These studies were conducted in only 3 countries and did not include all sexes or life stages. The range of the estimated average protein requirements of each life stage was 1.30 g/kg body weight/d for children, 0.87 to 2.10 (0.87-0.93 for general young adults, 1.22-1.52 for pregnant women, 1.49-2.00 for resistance-trained athletes, 1.65-2.10 for endurance athletes, and 1.20-1.41 for team sports athletes) g/kg body weight/d for young adults, and 0.85 to 0.96 g/kg body weight/d for older adults.

CONCLUSIONS

Protein requirements in 14 studies were higher than the current reference for each sex, life stage, and physical activity that are related to protein requirements. In the future, protein requirements of various populations including sex and life stage could be assessed using the IAAO methods worldwide.

Is It Time to Reconsider the U.S. Recommendations for Dietary Protein and Amino Acid Intake?

Since the U.S. Institute of Medicine's recommendations on protein and amino acid intake in 2005, new information supports the need to re-evaluate these recommendations. New lines of evidence include: (1) re-analysis/re-interpretation of nitrogen balance data; (2) results from indicator amino acid oxidation studies; (3) studies of positive functional outcomes associated with protein intakes higher than recommended; (4) dietary guidance and protein recommendations from some professional nutrition societies; and (5) recognition that the synthesis of certain dispensable amino acids may be insufficient to meet physiological requirements more often than previously understood. The empirical estimates, theoretical calculations and clinical functional outcomes converge on a similar theme, that recommendations for intake of protein and some amino acids may be too low in several populations, including for older adults (≥65 years), pregnant and lactating women, and healthy children older than 3 years. Additional influential factors that should be considered are protein quality that meets operational sufficiency (adequate intake to support healthy functional outcomes), interactions between protein and energy intake, and functional roles of amino acids which could impact the pool of available amino acids for use in protein synthesis. Going forward, the definition of "adequacy" as it pertains to protein and amino acid intake recommendations must take into consideration these critical factors.

Effects of high protein, low-glycemic index diet on lean body mass, strength, and physical performance in late postmenopausal women: a randomized controlled trial

OBJECTIVE

To investigate whether increasing protein consumption to twice the recommended daily allowance (RDA) by The Institute of Medicine affects lean body mass (LBM), muscle strength, and physical performance in late postmenopausal women.

METHODS

Parallel-group randomized trial with 26 apparently healthy women aged ≥ 65 years. Participants were randomly assigned to low-glycemic index diets with protein consumption at current RDA (0.8 g/kg body weight) or twice the RDA (2RDA, 1.6 g/kg body weight). Protein intake was assessed by 24-hours urinary nitrogen excretion. Change in LBM was measured by dual-energy X-ray absorptiometry at 3 and 6 months. Secondary outcomes were appendicular lean mass, handgrip strength by dynamometry, and physical performance by gait speed.

RESULTS

Mean age was 70.8 ± 3.6 years, and mean BMI was 26.1 ± 3.5 kg/m2 in the overall sample. The RDA and 2RDA groups did not differ regarding baseline dietary intake. Changes from baseline in LBM (0.07 kg; 95% CI, -0.39; 0.52 kg; P = 0.100) and appendicular lean mass (0.07 kg; 95% CI, -0.34; 0.47 kg; P = 0.100) did not differ between the groups. Total body fat (-1.41 kg; 95% CI, -2.62; 0.20 kg; P = 0.019) and trunk fat mass (-0.90 kg; 95% CI, -1.55; -0.24 kg; P = 0.005) decreased similarly in both groups at the end of intervention. Adjusting for baseline BMI did not alter these findings. Handgrip strength and 4-m gait speed increased after the intervention, with no significant difference between the groups.

CONCLUSIONS

Protein intake exceeding the RDA did not increase LBM, strength, and physical performance in a sample of late postmenopausal woman consuming a low-glycemic index diet for 6 months.

Nutrient-dense protein as a primary dietary strategy in healthy ageing: please sir, may we have more?

A progressive decrement in muscle mass and muscle function, sarcopoenia, accompanies ageing. The loss of skeletal muscle mass and function is the main feature of sarcopoenia. Preventing the loss of muscle mass is relevant since sarcopoenia can have a significant impact on mobility and the quality of life of older people. Dietary protein and physical activity have an essential role in slowing muscle mass loss and helping to maintain muscle function. However, the current recommendations for daily protein ingestion for older persons appear to be too low and are in need of adjustment. In this review, we discuss the skeletal muscle response to protein ingestion, and review the data examining current dietary protein recommendations in the older subjects. Furthermore, we review the concept of protein quality and the important role that nutrient-dense protein (NDP) sources play in meeting overall nutrient requirements and improving dietary quality. Overall, the current evidence endorses an increase in the daily ingestion of protein with emphasis on the ingestion of NDP choices by older adults.

Association between Dietary Habits and Physical Function in Brazilian and Italian Older Women

The present study investigated and compared the patterns of dietary protein intake and physical function in Brazilian and Italian older women. Seventy-five Brazilian older women were recruited in a community senior center. Fifty-three age-matched Italian older women were selected from participants of the Longevity check-up (Lookup) 7+ study. In both samples, physical performance was evaluated by isometric handgrip strength (IHG) and five-time sit-to-stand (5 × STS) tests, while diet was assessed through 24-h recall. Results indicated that Brazilian women had a higher intake of plant-based protein (52.7% vs. 30.5% kcal), while Italian women consumed greater amounts of animal-derived protein (29.7% vs. 41.5% kcal). In Brazilian women, the binary logistic regression analysis indicated that body weight-adjusted protein consumption was associated with IHG adjusted by body mass index and with 5 × STS performance. In the Italian sample, the intake of isoleucine, leucine, and valine was significantly associated with 5 × STS performance. Our findings indicate that Brazilian and Italian community-dwelling older women show different patterns of protein intake, with higher consumption of plant-based protein in the Brazilian sample and higher ingestion of animal-derived protein in the Italian subgroup. These dietary patterns may differentially impact the relationship between physical function and protein intake observed in Brazilian and Italian older women.