The world’s total population of older adults has experienced a steady increase on an annual basis. A continued decline in birth rates combined with increased life expectancy has resulted in an increase in the total number and proportion of adults aged 60 and over.
According to the World Health Organization (WHO), the world population of adults in this age group has doubled since 1980 and is projected to reach two billion by 2050. Approximately 400 million adults will be aged 80 or older.
The world’s ageing population can be seen in nearly every country and older populations are beginning to outnumber younger populations. The MIT Age Lab reports nearly 77 million American baby boomers are well into their sixties, while China’s total population over the age of 60 already exceeds that of the entire population of Russia.
Wheelchairs and walkers outnumber baby strollers in parts of Europe. The number of adults in Japan over the age of 65 is expected to comprise nearly one-third of the country’s total population by 2050. Ageing populations can be a strain for individual economies, as they require more health and other services, and produce less wealth than younger populations.
As the total population of older adults continues to increase and life expectancy is extended, it is imperative that the specific wellness and nutrition needs of older adults are addressed.
Health Span Over Life Span
University of the Fraser Valley
Life span is how long we live, and health span is how long we live with the best possible health. Improvements in sanitation, use of antibiotics, and improved medical care have all significantly contributed to increasing life span, but the quality of health tends to decline with increasing age.
Understanding how to address the health challenges of our ageing population is essential for maintaining optimal health and improving overall quality of life. Common health challenges of older adults include:
- Loss of bone mass (osteopenia, a precursor of osteoporosis)
- Loss of muscle mass (sarcopenia)
- Frailty (a state of high vulnerability for adverse health outcomes, including falls, hospitalisation, disability, and death)
- Metabolic syndrome (having a combination of three or more metabolism-related disorders at the same time, increasing risk of heart disease, stroke, and diabetes. Disorders include: obesity, high blood sugar, high blood pressure, high cholesterol)
- Heart disease
The above are all age-related diseases with direct links to nutrition that have raised new questions about optimal dietary ratios of carbohydrates, fats and protein for long-term health. Recent nutritional research strongly indicates that most adults would benefit from replacing some dietary carbohydrates with protein.
Potential benefits include help in maintaining body composition and mobility, improved blood lipid and lipoprotein profiles, and increased satiety. With optimal nutrition, health span can be extended.
Dietary Protein & Musculoskeletal Health
Conventional dietary guidelines for protein recommend 0.8 g/kg body weight as adequate for adult health. However, a growing body of research suggests high dietary protein intakes of 1.5 g/kg body weight are more beneficial for maintaining muscle function, mobility, and for preventing and treating sarcopenia.
Dietary protein intake is not only vital for muscle health, but it is also a very important component of maintaining optimal bone health. This is because osteopenia and sarcopenia are closely related phenomena of ageing: they go hand in hand over an individual’s life span.
Factors that affect muscle synthesis, including protein intake, also affect bone mass. Stimulating muscle synthesis is one approach to balancing muscle loss that occurs with ageing. There are three factors that play an important role in muscle protein synthesis: hormones, exercise, and diet.
Amino Acid Leucine & Whey Protein Isolate
Nutritionally, not all proteins are created equal. Proteins are made from building blocks called amino acids and different proteins have different amino acid profiles. There are 20 different amino acids consumed from food, nine of which are considered essential (must be obtained through dietary means) because they are not synthesised by the human body, though they are necessary for human health.
One of these essential amino acids (EAA), leucine, is a branched-chain amino acid which plays an important role in muscle protein synthesis (MPS). Leucine is exceptional because it is the critical metabolic trigger required to initiate MPS.
The richest sources of dietary leucine are animal proteins. In general, animal proteins (dairy, eggs and meat) contain more leucine and have a more complete balance of EAAs than plant proteins, such as wheat, oats, and soy.
Championship Catering, Bloomington, US
Whey proteins are known to be a good source of leucine. Whey protein isolate (WPI) is exceptionally high in leucine, containing approximately 11-13 percent leucine, which makes it an ideal protein source for use in supplements for individuals seeking to preserve or grow lean muscle mass.
Different isolation methods result in protein with different leucine concentration. WPI made from ion-exchange process contains higher leucine than membrane filtration process.
The leucine content of individual proteins ultimately determines the optimal amount of total protein per meal. Research has shown that 2.5-3 g of leucine per meal is needed to maximise muscle protein synthesis (MPS).
This leucine threshold is of critical importance because a meal containing less than 2 g of leucine fails to initiate MPS. A meal containing leucine content of 2.5 g corresponds to approximately 20-40 g of total protein, depending on the particular source of protein.
Therefore, on average, 30 g of protein is recommended per meal to provide enough leucine to initiate protein synthesis; only 20 grams of total protein is necessary if the protein source is whey protein isolate.
A study from a group led by Dr Douglas Paddon-Jones, professor at the University of Texas Medical Branch, demonstrated the importance of daily distribution of protein at individual meals. They showed that it is necessary to distinguish optimal protein content per meal, rather than per day, because MPS is a cycling process lasting only up to three hours after consuming a meal containing adequate protein.
Eating protein only at a single meal limits overall daily stimulation of MPS, while eating protein in frequent small meals may fail to trigger the leucine response and produce an anabolic resistance.
It is important to recognise that the total quantity of protein necessary for MPS can be reduced when high quality protein, such as whey protein isolate, is consumed. This reduction in the necessary total quantity has critical implications for senior adults, who commonly experience loss of appetite and cannot consume a large amount of food.
This focus on quality over quantity also results in lower cost, improved palatability, and avoidance of unnecessary weight-gain due to over-consumption of calories from larger amounts of lower-quality protein.
Amino acid leucine concentration
Sarcopenia is the loss of skeletal muscle mass and function as a natural part of the ageing process. This loss of muscle mass typically coincides with increased fat mass.
Sarcopenia is a complex process, with a combination of factors responsible for its onset. Contributing factors include changes in anabolic hormones, sedentary lifestyle, insulin resistance, inadequate dietary protein or caloric intake, chronic disease and inflammation.
Ian Ransley, San Francisco, US
Since adults lose approximately eight percent of lean muscle mass per decade after the age of 25-30 years old, there is a wide opportunity for pre-emptive intervention and preservation of muscle health well before advanced ageing occurs. Ideally, adults should begin focusing on consumption of high quality proteins rich in leucine long before signs of sarcopenia are noticed.
Protein turnover is the balance between protein synthesis and protein degradation. The primary purpose of protein synthesis is to repair and replace proteins in the body that have been degraded. Proteins are synthesised and degraded in the body every day and this continuous cycling of proteins is a normal part of healthy ageing.
According to Dr Donald Layman, professor at the University of Illinois, both growing adolescents and middle-aged adults have similar needs for daily repair and replacement of body protein. Adults break down and need to re-synthesise approximately 250 g of proteins every day.
When the rate of protein synthesis does not keep up with protein degradation, sarcopenia arises. Additionally, ageing reduces the efficiency of amino acid use. Older adults need at least 30 percent more EAA to get the same protein turnover, increasing daily protein needs.
Micah Sittig, Shanghai, China
Osteoporosis is characterised by a decrease in bone mass and density, causing bones to become fragile and more likely to fracture. Osteoporosis-related fractures most commonly occur in the hip, wrist or spine.
Bone health is a multifactorial musculoskeletal issue. Although we often think of calcium as the main micronutrient needed to prevent osteoporosis, dietary protein interacts synergistically with calcium to affect bone health and is equally as important.
Intake of both calcium and protein must be adequate to fully realise the benefit of each nutrient on bones. Approximately one-half of bone volume and one-third of its mass is comprised of protein. Bone is a living tissue, undergoing continuous turnover and remodelling. Osteoporosis occurs when the rate of bone removal exceeds that of new bone creation, similar to sarcopenia and muscle protein synthesis.
Many factors are known to influence bone mass. The impact of dietary protein on bone health has been shown to depend upon a variety of factors, including total protein intake, protein source, calcium intake and weight loss.
There has been a long-held belief that excessive dietary protein could cause bone loss, due to an observed association with increased urinary calcium. More recent studies have shown, however, that increased dietary protein is associated with increased intestinal absorption of calcium, as well as enhancing bone matrix turnover.
Research also suggests that different protein sources may vary in their impact on bone metabolism. Animal protein sources have been associated with increased bone mineralisation and fewer fractures when compared with plant-based proteins.
Dietary Protein & Weight Loss
In addition to musculoskeletal degeneration, ageing adults are often challenged with increased weight gain. Many ageing adults, particularly women, are concerned with both obesity and osteoporosis. Treating obesity often increases risk for osteoporosis because many people lose bone mass when they lose weight.
A study from Dr Layman’s group, however, showed that protein-rich weight-loss diets help preserve muscle mass and improve body composition while lowering blood sugar. This illustrates that a diet rich in protein, emphasising a high quality protein like whey protein isolate, can effectively result in weight loss without bone loss.
As the number of ageing adults in our world population continues to rise, it is more important than ever to address their specific health and nutrition needs. Many of the common health problems experienced by ageing adults can be dramatically influenced by dietary intake.
Understanding the increased need for high quality proteins in ageing populations is crucial for optimising their health span. Incorporation of high-leucine containing proteins, like whey protein isolate, into each meal, in adequate quantities and at the right frequency, can positively and significantly impact musculoskeletal health and weight.