Nutrition for older adults: appetite, muscle and cognitive health

As we get older, many of us notice subtle changes that gradually become harder to ignore. Food no longer has quite the same appeal, energy levels dip, muscles seem to ache more easily, and memory occasionally lets us down. It is easy to dismiss these changes as simply part of getting older, but they should not automatically be accepted as an inevitable consequence of ageing.

Although ageing brings genuine physiological and metabolic changes, many of the problems commonly accepted as “just old age” may be influenced by nutrition. Changes in appetite, digestion, medication use, nutrient absorption and body composition can all affect health, while social factors such as bereavement and loneliness may make eating well increasingly difficult.

In this article, I explore why nutritional deficiencies become more common with age, how inadequate nutrition affects muscle, bone and independence, and why maintaining nutritional status is equally important for protecting cognitive and metabolic health.

Why nutrition becomes more challenging with age

Eating well often becomes more challenging with age for reasons that develop gradually. A declining sense of smell can make aromas harder to detect and, because so much of flavour depends on smell, food may become less appealing than it once was (Schiffman, 1997; Doty & Kamath, 2014).

Digestion begins long before food reaches the stomach. The sight, smell, and anticipation of a meal stimulate saliva, along with gastric, pancreatic, and biliary secretions, preparing the digestive system for the work ahead. Dental problems may make chewing uncomfortable, while reduced saliva can affect both swallowing and the first stages of digestion. Some medications can also alter taste, affect bowel function or worsen symptoms such as reflux, constipation and bloating, making eating less enjoyable and further reducing food intake.

The social side of eating can be just as important. After the loss of a partner, or when someone begins eating alone, meals may no longer hold the same enjoyment. Shopping and cooking can also become more difficult as mobility or health declines, leading many people to rely on foods that are quick and easy to prepare. Unfortunately, these are often lower in protein and other essential nutrients than freshly prepared meals, so over time the gap between what the body needs and what the diet provides begins to widen.

Even when the diet appears adequate, changes within the digestive system may reduce the amount of nutrition that is ultimately absorbed. Stomach acid helps denature dietary proteins and activates pepsin, the enzyme responsible for protein digestion. It also supports the absorption of nutrients such as iron, calcium and magnesium and releases vitamin B12 from food so that it can bind to intrinsic factor, a protein produced by the parietal cells of the stomach, before being absorbed in the terminal ileum.

This finely coordinated process can be disrupted by atrophic or autoimmune gastritis, loss of functioning parietal cells, disorders affecting the small intestine or surgery involving the stomach or terminal ileum. As these conditions become more common in later life, so too does the risk of vitamin B12 deficiency (Stover, 2010).

Medications can present additional nutritional challenges. Proton pump inhibitors, widely prescribed for reflux, suppress stomach acid further. Long-term use has been associated with altered absorption and poorer status of several nutrients, particularly vitamin B12, iron, calcium and magnesium, with older or malnourished people potentially at greater risk (Freedberg et al., 2017; Heidelbaugh, 2013).

Metformin, one of the most widely prescribed treatments for type 2 diabetes, has also been shown to increase the risk of vitamin B12 deficiency (de Jager et al., 2010). Diuretics can increase losses of minerals such as magnesium and potassium, antibiotics disrupt the gut microbiome, and regular laxative use affects fluid and electrolyte balance. Antidepressants, painkillers and many other commonly prescribed medicines can also alter appetite and taste or contribute to nausea, constipation and diarrhoea, making regular medication review an important part of maintaining nutritional health in later life.

The hidden consequences of eating less

A sustained reduction in food intake makes it increasingly difficult to consume enough energy, protein and essential nutrients. Unintentional weight loss is a common consequence, but in older adults this rarely reflects a loss of body fat alone. Muscle and bone are often lost as well, particularly when poor nutrition is accompanied by declining physical activity and age-related hormonal changes.

Muscle is continually being broken down and rebuilt, so preserving it depends on both adequate protein and regular movement. Where mobility is limited and exercise is infrequent, the stimulus needed to maintain muscle is greatly reduced. This often coincides with inadequate protein intake and less efficient digestion, accelerating the progressive loss of muscle mass and function known as sarcopenia.

As sarcopenia progresses, declining strength and balance can make everyday tasks such as shopping, cooking and even eating more difficult. This can make it harder to maintain a nutritious diet, creating a self-perpetuating cycle in which poor nutrition accelerates muscle loss and further decline increases the risk of frailty, loss of independence, falls and fractures (Merchant et al., 2021; Cruz-Jentoft et al., 2019).

Bone health is closely linked to many of the same factors. A diet that provides too little protein, calcium and other essential nutrients limits the body’s ability to maintain the skeleton, while chronic illness and ongoing inflammation may further impair bone metabolism and vitamin D status. Reduced mobility often means less exposure to sunlight, increasing the likelihood of vitamin D deficiency. As vitamin D is required for calcium absorption, persistently low levels can weaken bone and increase the risk of osteomalacia, osteoporosis and fracture.

Nutrition, memory and the ageing brain

Although the brain accounts for only around 2% of body weight, it uses approximately 20% of the body’s energy at rest. It relies on a constant supply of energy together with the nutrients needed to maintain brain cells, support nerve signalling and produce neurotransmitters.

Protein provides amino acids such as tryptophan and tyrosine, which are used to produce serotonin and dopamine, while choline is required to make acetylcholine, a neurotransmitter involved in memory and learning. The omega-3 fat DHA, found predominantly in oily fish, is also a major structural component of brain cell membranes and plays an important role in maintaining normal brain function (Denis et al., 2013; Welty et al., 2023).

Vitamin B12 and folate are essential for nerve function, DNA synthesis and red blood cell production. Deficiency can contribute to fatigue, poor concentration and memory problems and, when severe or prolonged, may lead to permanent neurological damage. Magnesium and zinc also support energy production and nerve signalling, yet their status may be affected by poor dietary intake, impaired absorption or medications that interfere with absorption or increase losses, including some commonly prescribed diuretics.

The importance of muscle extends well beyond strength and mobility. During exercise, contracting skeletal muscle releases signalling molecules known as myokines, which communicate directly with the brain and help regulate inflammation. These molecules are being investigated for their effects on neuronal function, neuroplasticity and healthy cognitive ageing, providing another reason why preserving muscle throughout life is so important (Rai & Demontis, 2022).

Maintaining muscle is equally important for metabolic health. Skeletal muscle is the body’s largest site for glucose disposal, helping remove glucose from the bloodstream in response to insulin. As muscle mass declines, particularly alongside physical inactivity, inadequate protein intake and chronic illness, insulin resistance becomes more common. Cells become less responsive to insulin, making it harder to take up and use glucose efficiently. This has important consequences not only for metabolic health but also for the brain, where impaired insulin signalling has been associated with altered brain energy metabolism, cognitive decline and Alzheimer’s disease (Arnold et al., 2018).

Chronic low-grade inflammation provides another important link between metabolism and cognitive health. Inflammatory signalling often increases with age, particularly in the presence of insulin resistance and chronic disease, and is increasingly recognised as a contributor to neurodegenerative disorders.

Communication between the gut and the brain adds another layer of complexity. Neural, hormonal, immune and metabolic pathways collectively form the gut-brain axis, allowing changes in the gut microbiome to influence inflammation, immune function and brain health. Although research in this field is advancing rapidly, the precise contribution of the microbiome to cognitive decline in humans is still being clarified (Cryan et al., 2019).

Changes in appetite, weight, energy or memory are often attributed to ageing, yet they may signal a problem that deserves closer attention. Poor nutritional intake, medication effects and declining digestive function can all play a part, while bereavement or living alone may gradually change the way someone shops, cooks and eats.

Persistent loss of appetite or unintentional weight loss should therefore be investigated rather than accepted as inevitable. This may involve reviewing medication with the GP, arranging a dental assessment where needed and looking more closely at digestion, mood, cognition and the overall quality of the diet. A suitably qualified nutrition professional for elderly adults can also help identify nutritional gaps and develop practical ways to improve intake alongside medical care.

Recognising these changes early may help preserve muscle, bone, cognitive health and independence. Ageing brings real physiological changes, but many of the problems commonly put down to getting older can still be identified and addressed, with meaningful benefits for both health and quality of life.

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