Nutrition and ageing

Healthy behaviours throughout life, in particular eating a balanced diet and engaging in regular physical activity, contribute to reducing the risk of non-communicable diseases and improving the physical and mental capacity in older age. It is estimated that between 2015 and 2050, the proportion of the world's population over 60 years will nearly double from 12 to 22 per cent. Older persons are particularly at risk of malnutrition. Lean body mass (muscle) and the basal metabolic rate decline with age. Micronutrient deficiencies are common, in part because of a reduced food intake and a lack of variety in the foods elderly people eat. Increasing obesity and reduction in bone density leading to osteoporosis are other problems. Osteoporosis and associated fractures are a major cause of illness, disability and death in older people, especially in postmenopausal women. The World Health Organization (WHO) estimates that the annual number of hip fractures worldwide will rise from 1.7 million in 1990 to around 6.3 million by 2050.

If not addressed, they can have adverse impact on individuals, including pain, deformity, physical and mental health problems, and death.

The IAEA supports the application of stable isotopes and other nuclear techniques to measure changes in body composition (normally loss of muscle mass and increase in body fat) and physical activity, bone health and micronutrient bioavailability:

• The WHO has established dual-energy X ray absorptiometry (DXA) as the best technique for assessing bone mineral density in postmenopausal women and based the classification of osteoporosis on its results.
• Body composition changes with age. Loss of muscle mass is known as sarcopenia and is influenced by the diet and the level of physical activity. It also reflects the quality of the diet and the level of physical activity. Energy requirements decrease with age, but this decrease is often not matched with an appropriate decline in energy intake, ultimately leading to increased body fatness and abdominal obesity. Therefore, monitoring body composition is important, because changes in body composition are associated with physiological changes in the body that can lead to disease.
• Measures of total energy expenditure can be used to objectively assess quality of life in older persons, as physical activity is generally associated with better quality of life and better mental health. Physical activity is also important to slow down loss of muscle and reduce the effects of osteoporosis. The doubly labelled water technique can be used to validate measurements of physical activity and to assess the impact of interventions aiming at increasing physical activity in elderly people.
• Assessing the quality of the diet: absorption and retention of provitamin A, iron and zinc from fortified foods, or biofortified foods (accumulation of higher levels of minerals and vitamins during plant growth), or mixed diets; and protein bioavailability from plant foods.

Activities in this field support the Sustainable Development Goal 3.4, which aims to reduce by 2030 pre-mature mortality from non-communicable diseases by one-third through prevention and treatment, as well as the promotion of mental health and wellbeing.

How dual energy X ray absorptiometry works

• DXA is a technique that uses two X ray beams of differing energies to measure the density of bone and soft tissues. It was mainly designed to measure bone mineral density in adults to diagnose osteoporosis. However, DXA can also measure body composition with a high degree of accuracy.
• DXA uses a three-compartment model of body composition and assumes the body is made of bone mineral, fat and fat free soft tissue.
• DXA can report measures for the whole body or for sub-regions: arms, legs, pelvis, trunk and head.
• Sarcopenia, or loss of muscle in the elderly, can be diagnosed on the basis of loss of fat-free soft tissue in the arms and legs.
• DXA systems generate ionising radiation. People being scanned and the equipment operators receive a small radiation dose during the procedure. The radiation dose is similar to the natural background radiation received in one day.