Protein and Healthy Aging

Aging well is a challenge. Regardless of cultural background, socioeconomic status or whether male or female, aging does not discriminate. However, there are recommendations for vibrant longevity. One science-based approach for healthy aging is consuming protein in amounts that exceed the Recommended Dietary Allowance (0.8 g/kg/day) but rest well within the Acceptable Macronutrient Distribution Range (10-35% of energy intake). When combined with an active lifestyle, this level of protein intake may thwart muscle loss, improve bone health, and enhance nutritional status in individuals as they grow older.

KEY POINTS

• The Recommended Dietary Allowance (RDA) sets the minimal amount of dietary protein for most adults, and is based on nitrogen balance, not functional outcomes. This is particularly relevant to dietary directives for healthy aging.

• Protein intake ranging from 1.1 to 1.3 g/kg/day distributed over three meals a day – approximately 25 to 30 grams per meal – will maximize muscle protein synthesis and contribute to better bone health when consumed with adequate calcium.

• For optimal protein synthesis, all amino acids – including the nine indispensable amino acids which must come from the diet – need to be present simultaneously. Most plant-based proteins are incomplete therefore need to be paired with a complete animal-based protein or a plant-based protein containing the missing amino acids.

• With reduced appetites, regular consumption of high quality protein foods like meat, fish, eggs and poultry can assist in optimizing nutritional status in older men and women.

• From a practical perspective, a diet based on whole foods, complemented with an active lifestyle suitable to the individual, provides a feasible and reasonable approach to aging well.

Following are the tangible benefits of increasing protein throughout the adult years:

1. MAINTAINING MUSCLE AND STRENGTH

Sarcopenia occurs as men and women progress into later life, starting as early as 40 years of age. Changes in body composition that occur with age are the reduction in lean body mass with a simultaneous increase in fat mass.¹ The loss of lean body mass is paralleled by reductions in muscle strength.2 This specific outcome is cause for most concern because loss of muscle strength is a prequel to loss of muscle function which predisposes older men and women to falls and fractures that can significantly affect quality of life. Physical inactivity follows and the loss of muscle mass is perpetuated.

Researchers have found routine consumption of high quality protein foods such as beef, pork, fish, eggs, and poultry, distributed evenly throughout the day – approximately 25 to 30 grams per meal – optimizes muscle protein synthesis in old, as well as young, persons.³

For optimal protein synthesis, all amino acids – including the nine indispensable amino acids which must come from the diet – need to be present simultaneously.⁴ Evidence suggests high quality animal-based proteins stimulate muscle protein synthesis more effectively than plant-based proteins.⁵

2. BONE HEALTH

The relationship between dietary protein consumption and bone health has changed as evidence showing a favourable effect of protein on bone has mounted.⁶ The common misconception that increased protein intake causes calcium losses from the body that can ultimately weaken bone has been disproven. Like muscle protein, the skeleton and its constituent proteins are dynamic – constantly being broken down and synthesized.

Studies have demonstrated that higher protein intakes combined with recommended calcium consumption enhanced calcium absorption.6 Contrary to popular belief, lower protein diets (< 0.8 g/kg/day) actually compromise bone’s ability to repair and recover from fractures, whereas diets moderate in protein (1-1.5 g/kg/day) are associated with normal calcium metabolism, greater bone mass, and fewer fractures when calcium intakes are adequate.6 This relationship is significant in the context of the musculoskeletal system and reinforces the integration of muscle and bone for healthy aging.

An appreciation for the parallel that exists between osteoporosis and sarcopenia is important when considering lifestyle interventions such as protein intake and routine physical activity for healthy aging.

3. NUTRITIONAL STATUS

In the context of longevity, living well, and staying healthy, the role of high quality protein foods as nutrient rich sources of essential micronutrients cannot be overstated.⁷ Iron, calcium, zinc, B vitamins, and antioxidants such as vitamin E are found in animal products like meat, dairy, poultry, and seafood. With reduced appetites common with increasing age, choosing high quality protein foods takes on greater importance. That is, meal patterns should consider protein quality – foods containing the indispensable amino acids – and protein density – the amount of protein relative to the calories – and the micronutrients of the food choices.

Protein, more is better? Find out the answer…

References:

1. St-Onge MP. Relationship between body composition changes and changes in physical function and metabolic risk factors in aging. Curr Opin Clin Nutr Metab Care. 2005; 8:523–8.

2. Kalyani R et al. Age-related and disease-related muscle loss: the effect of diabetes, obesity, and other diseases. Lancet Diabetes Endocrinol. 201

4 Oct; 2(10): 819–829. 3. Phillips SM et al. Protein “requirements” beyond the RDA: implications for optimizing health. Appl Physiol Nutr Metab, 2016, 41(5): 565-72.

4. Wolfe R et al. Protein quality as determined by the Digestible Indispensable Amino Acid Score: evaluation of factors underlying the calculation. Nutr Rev. 2016 Sep; 74(9): 584-99.

5. Gorissen SHM and Witard OC. Characterizing the muscle anabolic potential of dairy, meat and plant-based protein sources in older adults. Proc Nutr Soc, 2018; 77(1):20-31.

6. Gaffney-Stomberg E et al. Increasing dietary protein requirements in elderly people for optimal muscle and bone health. Journal of the American Geriatrics Society, 2009; 57(6): 1073-1079.

7. Asp ML et al. Dietary protein and beef consumption predict for markers of muscle mass and nutrition status in older adults. J Nutr Health Aging. 2012; 16(9):784-90.