With aging comes the loss of lean mass accompanied by a gradual decline in self-care capabilities in some older adults, resulting in the need for assisted living or specialized geriatric care. Frailty is a medical condition usually seen in adults above 65 years of age where there is a functional decline in performing daily living activities. Some characteristic features of frailty are weakness, exhaustion, and weight loss.
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Previous studies have highlighted the link between nutritional status and increased risk of frailty syndrome. Some of the factors that have an influence on developing frailty syndrome are Vitamin D status, calorie intake, as well as protein and calcium intake.
Dietary protein and protein supplements
Optimal intake of protein is required to maintain skeletal muscle mass. Several clinical trials have demonstrated the link between lack of optimal intake of dietary protein to physical frailty consequently affecting immunity and bone health.
A recent prospective, longitudinal study in North East England on adults aged 85 years and above by Mendonca et al. examined the effect of protein intake and the progression of frailty. The enrolled subjects were followed for approximately 5 years. The study also included multi-state models to adjust for energy intake, age, sex, education, and presence of baseline chronic diseases.
A lower incidence of frailty was observed in subjects between 85 and 90 years of age whose protein intake was above 0.8 g/kg adjusted body weight/day (95%CI [0.43-0.84]) as well as in those subjects whose protein intake was above 1g/kg adjusted body weight/day (95% CI [0.44-0.90]). In addition, Mendonca et al. noticed that energy intake partly influenced the lowering of incidences of frailty.
Another randomized clinical trial (RCT) that studied the long-term effects of protein supplementation on pre-frail and frail elderly demonstrated improved executive functioning than the placebo group. However, the study did not notice any improvement in other cognitive functions when compared to the placebo group.
While a 12-week RCT study by Park et al. on undernourished pre-frail and frail elderly subjects demonstrated protein supplementation to improve gait speed and muscle mass, a meta-analyses study by Oktaviana et al. did not find any significant improvement in the frailty indices. Oktaviana et al. assessed the effect of four types of protein supplements on 503 subjects with frailty syndrome.
The outcomes measured were lean body mass, leg press strength and extension, handgrip, gait velocity, and short physical performance battery score. The study observed that protein supplements alone did not significantly improve these frailty indices in pre-frail or frail older adults.
Physical activity, exercise and protein supplementation
A number of research studies have focused on the effect of adequate physical activity or exercise combined with protein supplementation on improving frailty. A hospital-stay RCT by Niccoli et al. focused on the effect of whey protein supplementation on geriatric patients along with high-intensity resistance training.
The group that was supplemented with whey protein showed improved knee extensor force and grip strength compared to the control group. This indicates that protein supplements paired with exercise may improve overall rehabilitation and nutritional status.
Similarly, a randomized, double-blind, placebo-controlled trial by Dirks et al. studied the effect of protein supplements on 34 frail adults aged 77 ± 1 years. Subjects in the protein group and placebo group underwent 24 weeks of progressive resistance training.
Muscle biopsies were performed at baseline, at 12th week, and at 24th week of the study period. There was an increase in type I and type II muscle fibers noted in the protein group compared to the placebo group.
Factors that influence dietary intake of protein
The recommended dietary intake of protein is approximately 0.8 mg/kg. However, many of the older adults do not get the recommended dietary intake due to reasons such as reduced appetite due to underlying physiological or psychological conditions.
While protein supplementation is beneficial in such cases, it can also have adverse outcomes depending on the subjects’ health status. In some subjects, long-term protein supplementation can have deleterious effects on the vascular, renal, and digestive system.
In addition, scientists have observed different protein sources have varied health effects and can affect optimal protein synthesis in frail elderly adults who require higher supplements of protein.
Researchers have noted that a diet high in plant protein could reduce the effect of frailty in older adults. Epidemiological studies have suggested that a diet high in plant proteins can prevent cardiovascular diseases compared to a high animal protein diet.
A multi-center cross-sectional study in Japan on old Japanese women aged 65 years and older monitored the effect of total protein intake from animal-based foods and plant-based foods on frailty. This study not only examined the effect of protein intake on frailty but also the role of amino acids on frailty.
Many studies have suggested the ability of amino acids in preventing oxidative stress thereby regulating protein synthesis and suppressing loss of muscle mass. Kobayashi S et al. noted that while protein sources and related amino acids may not be crucial in delaying frailty, the presence of plant-based amino acids supported the beneficial effects of total protein on the frailty criteria.
Many researchers tried to study the effect of optimal protein supplementation on mood, cognition, and comorbidities commonly seen in frail elderly individuals. However, the results obtained from most studies have been inconclusive indicating the need for further robust clinical trials in this area to bring out effective therapies to frailty.
Liao CD et al. (2018). Effects of Protein Supplementation Combined with Exercise Intervention on Frailty Indices, Body Composition, and Physical Function in Frail Older Adults. Nutrients. Doi: 10.3390/nu10121916
Morante JJH et al. (2019). Dietary Factors Associated with Frailty in Old Adults: A Review of Nutritional Interventions to Prevent Frailty Development. Nutrients. doi: 10.3390/nu11010102
Oktaviana J et al. (2020). The effect of protein supplements on functional frailty in older persons: A systematic review and meta-analysis. Archives of Gerontology and Geriatrics. Doi: https://doi.org/10.1016/j.archger.2019.103938
Mendonca N et al. (2020). Protein intake and transitions between frailty states and to death in very old adults: the Newcastle 85+ study. Age and Aging. Doi: https://doi.org/10.1093/ageing/afz142
Niccoli S et al. (2017). Whey Protein Supplementation Improves Rehabilitation Outcomes in Hospitalized Geriatric Patients: A Double Blinded, Randomized Controlled Trial. Journal of Nurition in Gerontology and Geriatrics. Doi: 10.1080/21551197.2017.1391732.
Dirks ML et al. (2017). Protein Supplementation Augments Muscle Fiber Hypertrophy but Does Not Modulate Satellite Cell Content During Prolonged Resistance-Type Exercise Training in Frail Elderly. Journal of the American Medical Doctors Association. doi: 10.1016/j.jamda.2017.02.006.
Schoufour JD et al. (2019). Dietary Protein, Exercise, and Frailty Domains. Nutrients. doi:10.3390/nu11102399.
Hanna MT et al. (2009). Effect of Dietary Protein on Bone Loss in Elderly Men and Women: The Framingham Osteoporosis Study. Journal of Bone and Mineral Research. https://doi.org/10.1359/jbmr.2000.15.12.2504
Kobayashi S et al. (2013). High protein intake is associated with low prevalence of frailty among old Japanese women: a multicenter cross-sectional study. Nutrition Journal. https://doi.org/10.1186/1475-2891-12-164