Protein: what the science says

Evidence-Based Recommendation for Optimal Dietary Protein Intake in Older People: A position paper from the PROT-AGE Study Group. Bauer et al. Journal of the American Medical Directors Association. 14 (2013) 542-559

The PROT-AGE Study Group is an International group of experts, set up to review dietary protein needs with aging. This group reviewed extensive medical literature and current recommendations for protein. It was noted that old methods of nitrogen balance studies underestimated protein requirements.

They agreed that inadequate protein leads to muscles loss and an increase in sarcopenia, osteoporosis and results in an impaired immune response. Also that losses in physical function capacity predict a loss of independence, falls, fractures and ultimately mortality. The paper cites studies that support Whey (a “fast” protein) as the best protein source and that Leucine supplementation triggers muscle protein synthesis.

The group recommended that older adults (specifically over 65’s in this paper) need at least 1.2g protein/kg/day in order to maintain and regain lean body mass and function. This should be more than 1.2g/kg/day for active older adults.

They also stated that because of a declining anabolic response in older people (put simply, a reduced ability to use protein), more protein and specifically leucine, is required in each meal. Specifically 25-30g protein and 2.5 to 2.8g leucine per meal.

The study group also concluded that Creatine supplementation may be justified for older people. In combination with increased protein intake, exercise is recommended at individual levels that are safe and tolerated.

Protein Intake and Exercise for Optimal Muscle Function with Aging. Recommendations from the ESPEN expert group. Clinical Nutrition Journal. 33 (2014) 929-936

ESPEN is the European Society for Clinical Nutrition and Metabolism. They met in 2013 with the goal of providing recommendations for healthcare professionals to help older adults sustain muscle strength and function into older age.

They noted that the aging process is associated with gradual and progressive loss of muscle mass along with lowered strength and physical endurance (“Sarcopenia”). Also that older adults may develop resistance to the positive effects of dietary protein on muscle protein synthesis (repairing and rebuilding muscle) – this is known as “Anabolic resistance”.
It was stated that limited protein intake predicts frailty and low bone density, and that this can be prevented or reversed by greater protein intake and exercise.

The group recommended that the optimal protein intake is 1-1.5/g/kg/day. They also recommended that daily physical exercise should be undertaken by all older people for as long as possible.

Strength and Muscle Mass Loss with Aging Process. Muscles, Ligaments and Tendons Journal. Keller K & Engelhardt M. (2013); 3 (4): 346-350

The aim of this German study was to investigate the changes in muscle mass and strength during the aging process. 26 participants were divided into 2 groups; either under or over 40 years old. The 2 groups were matched for anthropometrics. The strength and circumference of the knee joint were measured as well as the range of motion.

Study Conclusion: The aging process leads to distinct muscle mass and strength loss. Specifically muscle strength declines from people aged less than 40 years to those aged more than 40 years between 16.6% and 40.9%.

Growing older with Health and Vitality. A nexus of physical activity, exercise and nutrition. Biogerontology. Witard et al. (2016) 17:529-546

This was a review of clinical data with the purpose of presenting the latest, evidence based recommendations for physical activity, exercise and diet for older adults that would help preserve muscle mass and strength.

It advised that greater emphasis should be placed on optimal rather than minimum protein intakes for older adults, and that the concepts of health span and aging well are being championed as priority public health messages by bodies such as WHO.

Data suggest that older adults who consume a diet with protein intake higher than the RDA better preserve muscle size and functional ability. It stated that Leucine acts as both a trigger for initiating muscle protein synthesis, and as a substrate for the synthesis of new muscle protein.

For maximal stimulation of rebuilding muscle in older adults, it is clear that optimal meal protein intake exceeds that of younger adults, and that increasing leucine will help the body to use the protein that’s ingested.

This review recommended 1.2-1.5g/kg/day to help preserve muscle mass and strength, and that these levels are safe for older adults.

National Health and Nutrition Examination Survey (NHANES) 2007-2016 data

This is a program of studies designed to assess the health and nutritional status of adults and children in the United States.

For this survey there were over 8,070 participants who were over the age of 60 years. It looked at the association between daily protein intake and functional disability.

It concluded that individuals consuming more than 1g protein/kg/day had a 22% decreased odds for functional disability as assessed by 19 different tasks.

Dietary Protein Intake Is Protective Against Loss of Grip Strength Among Older Adults in the Framingham Offspring Cohort. The Journals of Gerontology. Series A, Biological sciences and Medical sciences. McLean et al. (2015) 71, 356–361

This study was a longitudinal analysis over 6 years with 1,746 men and women participants, with an average age of 59 years at the start of the study.

It concluded that higher dietary intakes of total and animal protein (but not plant) were protective against loss of grip strength in community-dwelling adults aged 60 years and older.

Increasing intake of protein may help maintain muscle strength and support prevention of mobility impairment in older adults. (Trends in participants younger than 60 years were not statistically significant).

Protein Ingestion to Stimulate Myofibrillar Protein Synthesis Requires Greater Relative Protein Intakes in Healthy Older Versus Younger Men. The Journals of Gerontology. Series A, Biological sciences and Medical sciences. Moore et al (2015) Jan; 70 (1): 57-62

This was a retrospective analysis of data from laboratories that measured muscle protein synthesis in healthy older (average 71 years) and younger (average 22 years) men. The data were taken from 6 studies which used high quality, rapidly digested, animal-based proteins (5 studies used whey, and 1 used egg).

The study noted that healthy older men are less sensitive to low protein intakes and require a greater protein intake, in a single meal, than young men to maximally stimulate rates of muscle protein synthesis.

It is recommended that this should be considered for nutritional strategies to maintain muscle mass. In fact, in this study, 67% more dietary protein was required in older adults compared to younger to reach maximum protein synthesis.

Inadequacy of Protein Intake in Older UK Adults. Morris et al. Geriatrics (2020) Mar; 5 (1): 6

The aim of this study was to analyse the protein intake of older adults in a UK region (South Yorkshire), and compare it to current guidelines. It included 256 participants between the ages of 65-89 years.

The study stated that age related anabolic resistance to muscle protein synthesis is believed to increase dietary protein requirements.

It explained that the suggested amount for phased intake is 25-30g protein, 3 times a day, in older adults with an emphasis on the consumption of leucine rich proteins for the activation of muscle protein synthesis.

Only one participant met the guidelines of 25g protein per meal recommendation across 3 meals.

The results showed that less than 15% of participants met the ESPEN recommendation of 1.2g protein/kg/day.

It concluded that the study population fell short of both UK and European guidelines for protein intake.

Low Protein Intake is Associated with Frailty in Older Adults. Nutrients. Jose Coelho-junior et al. (2018) 10(9) 1334

The aim of this study was to conduct a review and meta-analysis to look at the relationship between protein intake and frailty status of older adults. A total of 10 observational studies (cross sectional and longitudinal) that met the eligibility criteria were included. 50,284 older adults (age 60+) from 3 different continents between 2006 to 2018 were included.

Frailty is a multifactorial condition associated with poor prognosis. It includes features such as; slowness, weakness, exhaustion and sedentary behaviour, which are strongly associated with sarcopenia. Low protein has been proposed among the factors involved in this.

The findings suggest that sufficient protein intake may reverse or at least prevent functional decline in frail older adults.

The importance of protein distribution was noted: meals with at least 30g protein were associated with greater lower limb muscle strength and lean mass.

This study supports the need for increased protein intake in older adults to avoid frailty.

Supplemental Protein in Support of Muscle Mass and Health: Advantage Whey. Journal of Food Science. Devries et al. (2015) Mar;80 Suppl

This review examined the existing data supporting the role for protein consumption in the regulation of muscle mass and body composition across the adult lifespan.

It noted that the role of maintaining muscle mass as we age is an emerging concept which has implications in; chronic disease prevention, functional capacity, and quality of life.

The progressive loss of muscle mass and strength, i.e. Sarcopenia, that accompanies aging has been shown to make it more difficult to perform activities of daily living and increases the risk of falls, thus impacting quality of life.

It also stated that protein quality is important to the gain and maintenance of muscle mass. The quality of a protein depends on; protein digestibility, amino acid content and availability to support metabolic function.

The review concluded that whey protein is one of the highest-quality proteins given its amino acid content (high essential, branched-chain, and leucine amino acid content) and rapid digestibility.

And that the consumption of whey protein has a robust ability to stimulate muscle protein synthesis. In fact, whey protein has been found to stimulate muscle protein synthesis to a greater degree than other proteins such as casein and soy.

A Whey Protein-based multi-ingredient nutritional supplement stimulates gains in lean body mass and strength in healthy older men: A randomized controlled trial. Bell et al. (2017) 12 (7)

The objective of this study was to evaluate the efficacy of a protein-based nutritional supplement to increase strength and lean mass either with or without exercise in healthy older men. 49 participants were allocated to either the nutritional supplement group or a control (placebo) group, and the study ran for 20 weeks.

The study group noted that age-related declines in muscle mass and function, termed Sarcopenia, contribute to various negative health outcomes: metabolic disorders like type 2 diabetes mellitus and progression to frailty. Also that muscle strength is a strong and independent predictor of all-cause mortality in older adults.

In conclusion, they demonstrated that daily consumption of a whey protein-based supplement containing creatine was effective in stimulating strength and lean body mass gains in the absence of exercise in a group of healthy older men.

Strategies to Prevent Sarcopenia in the Aging Process. Role of Protein Intake and Exercise. Nutrients. Rogeri et al. (2022) 14, 52

The objective of this comprehensive review of clinical data, was to analyse optimal nutritional strategies focused on the maintenance of muscle mass in older adults to achieve healthy aging.

It noted that one of the main problems observed in older adults is related to a loss of muscle mass, defined as Sarcopenia, which increases risk related to falls, reduces physical capacity, and enhances problems associated with disabilities. It has been established that an insufficient dietary protein intake is associated with loss of muscle mass in older adults due to lower muscle protein synthesis (rebuilding and repairing of muscle).

The review reported that Creatine is one of the most studied supplements consistently showing positive improvements in strength, physical function and lean body mass in older adults.

In summary the study made practical recommendations for optimal protein intake and muscle contraction in the aging population, including:

• Daily protein intake of 1.6-1.8g/kg/day
• 3 main meals containing 0.6g protein/kg body weight
• At least 5g leucine to be included per meal
• When protein supplementation is needed prioritise high quality, fast digestive protein i.e. whey

Protein Supplementation at Breakfast and Lunch for 24 Weeks beyond Habitual Intakes Increases Whole-Body Lean Tissue Mass in Healthy Older Adults. Journal of Nutrition. Norton et al (2016) Jan;146(1):65-9

The aim of this study was to determine the effect of protein supplementation at breakfast and lunch for 24 weeks (above habitual intakes) on lean tissue mass in healthy adults aged 50–70 years.

A total of 60 men and women were randomly assigned to take either a whey protein supplement or a control drink.

The study group reported that older people often have a skewed distribution of their daily protein intake, with low amounts consumed at breakfast and lunch, with the majority of their daily protein intake consumed at dinner. This is sub-optimal for the support of skeletal muscle health and function. Therefore it would be a good practice to supplement these lower protein meals with a protein supplement.

They concluded that protein supplementation (whey protein) at breakfast and lunch for 24 weeks in healthy older adults resulted in a positive difference in lean tissue mass, compared with the control group. This suggests that an optimized and balanced distribution of meal protein intakes could be beneficial in the preservation of lean tissue mass in the elderly.