We are what we eat, or fail to eat. Assistant Professor Faidon Magkos, Department of Physiology and Professor Brian Kennedy (Director, Centre for Healthy Ageing, National University Health System) explain why nutrition plays such a key role in healthy ageing.

 

Life expectancy has increased sharply over the past 150 years, from <50 years in 1850 to >80 years at the present time in many developed countries. This is a result of better medical care and living standards and has dramatically increased the number of elders. As the body grows older, there is a gradual deterioration of physiological function at the cellular level, which eventually manifests at the organ and whole organism level.

 

Ageing in humans is associated with a reduction in physical stature, a decrease in total body lean mass (mostly because of decreased muscle mass), an increase in fat mass (i.e. obesity), and accumulation of fat in the intra-abdominal area (i.e. central or android obesity). Furthermore, even after adjusting for these changes in body size and composition, ageing is accompanied by a decrease in daily total energy expenditure; this results from a reduction in resting metabolic rate (because of a decrease in organ size and organ-specific metabolic rate), and a reduction in exercise-induced thermogenesis (because of reduced participation in vigorous physical activities.

All these age-associated changes in physiological and metabolic function increase the risk for developing many chronic diseases. In fact, as people live longer and the age distribution of the population shifts toward a greater number of older adults, there is an \increase in the prevalence of all age-related diseases, predominantly cancer, cardiovascular and cardiometabolic diseases (e.g. heart disease, diabetes), and neurodegenerative diseases (e.g. Parkinson’s and Alzheimer’s).

 

Diet can have a big impact on health, regardless of age, and adopting healthy dietary habits can help prevent, delay the onset, or even possibly treat many chronic diseases. Good nutrition can therefore promote healthy ageing by not only increasing years of life (i.e. “lifespan”) but also, and perhaps more importantly, by extending healthy active years (i.e. “healthspan”). The role of nutrition as one ages becomes ever so more important because ageing can compromise one’s ability to meet nutritional requirements at a time when specific nutrient needs may be high (i.e. “nutritional frailty”).

 

Many older adults experience changes in taste and smell, loss of appetite, dental and chewing problems, and limitations in mobility that restricts access to high quality food and as a result, adopt a nutrient-dense diet. Age-related changes in gastrointestinal absorption and nutrient utilisation and the use of medications can further increase specific nutrient needs.

In fact, several nutrients are inadequately consumed in relation to health risk among older adults: these include protein, omega-3 fatty acids, dietary fiber, carotenoids, calcium, magnesium, potassium, and vitamins B6, B12, D, and E. This is the result of inadequate consumption of fruit, vegetables, legumes, whole grains, nuts or seeds, fish, lean meat, poultry, and low-fat dairy products, and excessive consumption of refined grain products, processed and fatty meats, fried foods, solid fats, and added sugars.

 

Sarcopenia is a hallmark of ageing and is defined as the progressive loss of skeletal muscle mass, quality, and strength. The term comes from the Greek words σάρκα (sarka), meaning flesh, and πενία (penia), meaning poverty. Sarcopenia in older adults is typically characterised by reduced muscle area and muscle fibre number and size (particularly for fast twitch type II fibres), and results from an imbalance between muscle protein synthesis and breakdown. What is less clear is how ageing affects protein requirements and whether a protein-rich diet or dietary protein supplementation could be beneficial. Evidence from large cohort studies suggests that the loss of lean (muscle) mass with age is partly mediated by inadequate consumption of dietary protein. Other nutritional factors such as vitamin D status have also been linked to age-related declines in muscle mass and functional capacity. The muscle protein synthesis response to major nutrient and hormonal stimuli, such as insulin, glucose and amino acids, diminishes with advancing age, which favors a negative protein balance even in the face of adequate nutrient supply.

 

Neurodegeneration often occurs in older adults. A wealth of epidemiologic evidence suggests that a Mediterranean diet pattern (rich in fruit, fish, vegetables, and olive oil) may lower the risk of both mild cognitive decline and Alzheimer’s disease. On the other hand, randomised controlled trials that evaluated the effects of dietary supplementation with various nutrients (vitamins B6, B12, C, E; folate; omega-3 polyunsaturated fats) failed to provide consistent evidence of a beneficial effect. This underscores the importance of promoting food-based approaches rather than nutrient-specific ones to maintain cognitive function in the elderly.

A healthy eating pattern for older adults should focus on:

 

1) Plant-based foods, such as vegetables, fruits, whole grains and beans, which are rich in fibre, vitamins, minerals, and phytochemicals that can help prevent cancer and heart disease, maintain a healthy weight and promote good digestion


2) Lean meat foods, such as fish, poultry and low-fat dairy products, which are rich in protein, calcium, vitamin D and other nutrients that can help maintain muscle mass and function, and bone integrity


3) Whole-grain bread and pasta products, and other unrefined carbohydrates such as brown rice, wild rice, oatmeal, quinoa, barley, and spelt, which are rich in fibre that can improve gastrointestinal function (slow digestion, prevent constipation, protect epithelial lining), lower blood sugar and cholesterol levels (cardiometabolic risk factors), and thereby help decrease risk of diabetes, heart disease, and cancer


4) Healthy fats, such as olive and canola oils, and omega-3 fats in fish like tuna and salmon, which are rich in monounsaturated fatty acids, low in saturated fatty acids, and contain little or no cholesterol and can therefore help protect against all age-related diseases

 

On the other hand, older adults should limit consumption of red meat (beef, lamb and pork) and processed meat products (ham, bacon, sausage and bologna), saturated fat (found predominantly in meat, full-fat milk, cheese, eggs, butter and lard), salt (found in processed foods such as soups, sauces, processed meats, frozen dinners, chips and crackers, but also table salt added on food).

 

Sensible dietary choices with respect to quality and quantity, but also the maintenance of a physically active lifestyle, and avoidance of tobacco in any form, are all important components of a healthy lifestyle that can help achieve and maintain good health with advancing age. Eating a healthy diet may not always be easy, but it is worth it when it comes to enhancing healthspan and lifespan.