Improved social, medical, economic, and environmental hygiene conditions have led to a population explosion over the course of little more than a century. The resultant demographic shift represents a fundamental transition towards a new paradigm, with over-65-year-olds now the fastest growing age group globally and over 2 billion estimated to be aged over 60 years old by 2050. Yet despite life expectancy near doubling since the start of the Victorian era, these gains have not necessarily translated to an increase in years lived without disability and disease. Rather, the greatest proportion of healthcare expenditure is now concentrated in old age, with age a determinant for a number of diseases including cardiovascular disease, cancer, dementia and respiratory tract infections. Improving health in old age (termed, ‘healthy ageing’) is therefore important both for individual quality-of-life (QoL), and in order to avoid the predicted social and financial strain on healthcare systems globally. These changing demographics are adding urgency to the need to understand the role of nutritional interventions in aiding healthy ageing.
Understanding the ageing process and its impact on nutrition
Ageing is best understood as a process, whereby a gradual accumulation over the life-course of cellular and molecular damage can result in increased risk of age-related disorders. Ageing is therefore a gradual, inconsistent process that is only loosely associated with biological age. As such, healthy ageing is more than simply absence of disease, with the World Health Organisation (WHO) urging a societal approach to the promotion of healthy ageing, and a shift away from disease-based curative models towards more integrated healthcare provision.
Nutrition can play a key role in determining healthy ageing, with the relationship a bi-directional and complex one. Physiological and socio-cultural changes associated with ageing can impact on nutritional status, with nutritional deficiencies common among the elderly and particularly prevalent in institutional and care home settings. Sensory impairment (e.g. loss of vision and taste), poor oral health, loss of mobility, and psychosocial changes such as poor finances and increased isolation can severely impact dietary intake, while decreased gastric acid secretion can impact on nutrient absorption. Sarcopenia, the loss of muscle mass and function with ageing, is a significant contributor to disability, impacting on QoL and independence. After the age of around 30 years, an average of 3-5% muscle mass is lost every decade, with the rate of decline increasing after age 60 resulting in around 1 in 20 in this age group suffering the effects of sarcopenia.
Other age-associated changes that can impact on nutritional status include changes in immunocompetence as the immune system matures. The elderly population typically lose lymphoid tissue (particularly in the thymus), have a decreased response to vaccination due to impairment of long-term immune memory, reduced production of T-cells, and experience changes to skin and mucous membranes which would usually act as the body’s first line of defence against external pathogens. Together, these changes can impact on both the innate and acquired immune systems, with low grade chronic inflammation (termed ‘inflammaging’) often observed in the elderly. When these changes combine with environmental and lifestyle factors, the elderly are left more susceptible to infections ‘than any other age-group except young children' [1]. Infection has a significant impact on nutrition status, increasing the risk of malnutrition via a number of different mechanisms including appetite loss and malabsorption problems.
Figure 1: The vicious cycle of undernutrition and infectious disease
Nutrition for the promotion of healthy ageing
Yet the relationship between ageing and nutrition also works in reverse, with both macro and micronutrients playing key roles in maintaining healthy physiological status. Given the plasticity of the ageing process, nutrition and lifestyle interventions have the potential to promote healthy ageing and reduce non-communicable disease risk. Micronutrient deficiencies are associated with both physical and cognitive decline, with vitamins D, C and B9 for example playing important roles in promoting bone density and reducing inflammation, while Vitamin B12 deficiencies place elderly populations at risk of both neurological and bone density problems. Essential dietary minerals such as calcium, zinc, iron and selenium also contribute to bone density and a functioning immune system, with protein malnutrition playing a role in the development of sarcopenia. Evidence suggests that around 35% of over 50-year-olds in Europe, Canada and the USA have a deficiency of > 1 micronutrient, and with 1 million over-65-year-olds malnourished in the UK alone, adequate nutrition of elderly populations is of both clinical and public health significance.
The role of nutrition interventions
Trials to date have produced rather inconsistent results for interventions targeting single nutrients, although there is some evidence to suggest that beneficial effects can be seen in those most deficient at baseline. The strongest evidence for nutrition that supports healthy ageing is for a Mediterranean-style dietary pattern, incorporating polyunsaturated fatty acids, anti-oxidant rich foods, and with a focus on more nutrient-dense foods. This helps to negate the issue of energy requirements for the elderly often being low, despite micronutrient requirements remaining unchanged.
In line with the WHO’s framework for ageing, a recent round-table meeting aiming to reach a consensus position on healthy ageing, highlighted the need for a life course approach that takes into account the multifactorial nature of ageing. Nutrition at all stages of life plays an important role in health and well-being, with food and activity habits often established in youth. A wide-ranging approach that promotes good nutrition throughout the life-course is therefore recommended, although proactive action promoting diet, nutrition, and physical activity would appear to support the maintenance of body composition, cognitive health, immune function and vascular health into old age.
What next?
The coming months are likely to see the topic of healthy ageing increasingly in the spotlight, with The Scientific Advisory Committee on Nutrition (SACN) currently working on a position statement on nutrition and older adults. More information about this work can be found on SACN’s webpage, and a call for evidence is now available online, with a deadline of 5 February 2019.
As such, the Society is delighted to announce that we will be organising a session entitled "Nutrition Challenges of an Ageing Population" for the Parliamentary and Science Committee at the House of Commons on Monday 25 March 2019. Chaired by Stephen Metcalfe MP, this is the first time the Nutrition Society have hosted a parliamentary meeting. A review of the debate and any relevant outcomes will be shared on the website after the event, and we look to engage the membership in parliamentary activities in the future.
[1] Maggini, S. et al (2018). Immune function and micronutrient requirements change over the life course. Nutrients. 10(10), 1-27.