Last Updated: September 1, 2026
When an older person becomes tired, low in mood or more forgetful, it is often put down to age. Sometimes that is the right answer. Often, though, something more practical is going on. The body may not be getting, or may no longer be absorbing, the nutrients the brain needs to work properly.
The brain is one of the hungriest organs in the body. It accounts for only around 2% of body weight but uses roughly 20% of our energy at rest. It also relies on a steady supply of protein, fats, vitamins and minerals to produce the chemical messengers involved in mood, motivation and memory. When that supply falls short, mood and thinking are usually among the first things to suffer.
Lauren Wallis is a registered nutritional therapist with a background in nutritional biochemistry and medical molecular biology (BSc Nutritional Biochemistry, MSc Medical Molecular Biology, DipCLN). She is a registered practitioner with the Federation of Nutritional Therapy Practitioners and an Institute for Functional Medicine certified health coach. Her clinical work covers digestive health, metabolic function, cognitive wellbeing and healthy ageing, including nutrition and lifestyle factors in neurodegenerative conditions such as Parkinson’s disease.
Digestion changes as we get older
Ageing gradually changes the way the digestive system works, and long-term illness, medication and reduced mobility often add to this.
Appetite commonly falls. Taste and smell change, so food becomes less appealing. Sore teeth or a dry mouth can make chewing harder, and getting to the shops or standing to cook a meal can become an effort in itself. Loneliness plays a part too as few people enjoy cooking for one.
At the same time, digestion itself becomes less efficient. Stomach acid production commonly declines with age and it does more than most people realise. It breaks down food, acts as a first line of defence against harmful microbes and is needed to release vitamin B12 from protein. It also helps the body absorb iron, calcium and magnesium. Digestive enzymes may reduce as well, and food moves through the gut more slowly, which can lead to bloating, discomfort and constipation.
The upshot is that an older person may appear to be eating reasonably well and still not be getting what they need (Cavalcoli et al., 2017; Heidelbaugh, 2013).
The gut and the brain are in constant conversation
The link between gut health and mental wellbeing is real and well supported by research. The gut and brain communicate continuously through the nervous system, the immune system, hormones and the gut microbiome meaning changes in one influence the other, which is known as the gut-brain axis (Carabotti et al., 2015; Martin et al., 2018).
The microbiome, the community of bacteria and other microbes living mainly in the large intestine, is a large part of this. These microbes break down parts of our food and produce compounds that help regulate mood, stress, sleep and thinking (Clarke et al., 2014).
Lauren does not think this connection gets enough attention in routine care. Poor mental health in later life is rarely explained by one thing; life events, physical health and medication all matter. But nutrition is the piece that most often goes unexamined, and it is one of the more modifiable.
The nutrients that matter most
There is no single brain food or superfood. Brain health depends on a steady supply of energy and a wide range of nutrients working together. That said, a few come up repeatedly.
Protein is broken down into amino acids, which are the raw material for serotonin, dopamine and noradrenaline, the messengers involved in mood, attention and motivation. Protein also protects muscle, which matters more than people expect (Burd et al., 2013).
Omega-3 fats, particularly those found in oily fish, are concentrated in the membranes of brain cells and help them communicate with one another. A low intake over many years may contribute to poorer brain function (Denis et al., 2013; Welty et al., 2023).
Vitamin B12 and folate are essential for the nervous system, red blood cell production and DNA. Low levels can cause fatigue, low mood and memory problems, and in more severe cases nerve damage. Both are commonly low in older adults, partly because B12 absorption depends on stomach acid (Miller, 2018; Bell, 2022).
Magnesium and zinc are involved in energy production, nerve signalling and immune function. Both can be affected by poor intake, reduced absorption and certain medications.
Vitamin D is worth its own mention. Low levels are very common in the UK, particularly among people who spend most of their time indoors, and are consistently associated with low mood and poorer cognitive function (Sultan et al., 2020; Akpınar and Karadağ, 2022). Where a genuine deficiency exists it should be corrected in line with clinical guidance. Lauren would avoid treating vitamin D as a standalone answer to low mood, as nutrition works as a system, and one nutrient rarely explains the whole picture (Public Health England and NICE, 2020).
Muscle deserves a mention alongside food. When muscle contracts during exercise it releases signalling molecules that communicate with the brain, helping support energy use, reduce inflammation and protect memory and learning. Keeping muscle through resistance exercises and preserving muscle mass is amongst some of the better investments anyone can make in healthy ageing (Arosio et al., 2023).
Medication is part of the picture
Taking several medications long term is extremely common in later life and can affect nutritional status (Akamine et al., 2007; Mohn et al., 2018).
Acid-suppressing medicines such as omeprazole can reduce absorption of vitamin B12, magnesium, iron and calcium. Metformin is associated with B12 deficiency. Diuretics increase losses of magnesium, potassium and thiamine. Statins reduce the body’s production of coenzyme Q10, and methotrexate can deplete folate (Heidelbaugh, 2013; Jung et al., 2022; Banach et al., 2015).
The symptoms these deficiencies produce, including fatigue, low mood, poor concentration, memory problems, pins and needles, are symptoms that are most likely to be attributed to ageing or to the illness being treated. No one should stop or change a prescribed medicine on their own, but a regular medication review, with nutrition being a part of the conversation, is worth asking for.
When appetite drops, take it seriously
Loss of interest in food should never be dismissed as simply part of getting older. More often than not it is the body signalling that something is wrong: an underlying illness, depression, medication side effects, poor oral health, swallowing difficulties or digestive problems. Sometimes the cause is social rather than medical, such as bereavement, isolation or simply struggling to shop and cook (de Souto Barreto et al., 2022; Wysokiński et al., 2015; Landi et al., 2016).
The consequences can build quietly. Eating less means less protein and fewer nutrients at a stage of life when requirements remain high. Weight loss often follows, along with loss of muscle, which reduces strength, balance and independence. Bone health suffers, falls become more likely, immunity weakens and mood and memory decline further. It becomes a downward spiral that is much easier to interrupt early than to reverse later (Merchant et al., 2021; Fielding et al., 2023).
Making every mouthful count
When appetite is poor, smaller and more frequent meals are usually easier to manage than three large ones, and every mouthful needs to earn its place.
Lauren encourages families to build meals around good-quality protein, such as eggs, fish, meat and dairy where tolerated, rather than relying on convenience foods that fill someone up without giving them much. It is quite possible to eat regularly and still fall short (Aragon and Schoenfeld, 2023).
Homemade soups, stews, casseroles and slow-cooked meats work particularly well because they are soft, easy to eat and genuinely nourishing. Oily fish such as sardines and mackerel provide protein and omega-3 fats. Eggs are excellent. Some of the traditional foods that have fallen out of fashion are among the most nutrient-dense of all, liver is one of the richest sources of vitamin B12, folate and easily absorbed iron, and many older people grew up eating it (Fuerniss et al., 2024).
A couple of eggs with smoked salmon, a bowl of homemade stew, or liver once a week will do considerably more than a shelf of ready meals.
Steady energy through the day
Diets high in sugar, refined carbohydrates and ultra-processed foods cause repeated rises and falls in blood sugar. That can leave someone feeling shaky, irritable or anxious, and over years it contributes to the chronic low-grade inflammation that becomes more common with age (Barrientos et al., 2015; Kearns, 2024). Reduced ability to use glucose efficiently in the brain is increasingly recognised as part of the wider picture of cognitive decline (Yoon et al., 2023).
Hydration matters too, and it depends on minerals such as sodium and potassium as well as water. Even mild dehydration can affect concentration and mood, and this is especially relevant for anyone taking diuretics. Drinks throughout the day need not be plain water, they can be milk, soups and broths (Khow and Lau, 2014; Białecka-Dębek et al., 2019; Li et al., 2023).
Stress increases the body’s demand for energy and certain nutrients, so someone already eating too little has fewer reserves to draw on when they most need them (Lopresti, 2020; Madison and Kiecolt-Glaser, 2024).
Sleep, daylight and routine
Sleep is when the brain clears waste products, consolidates memory and carries out repair. Poor sleep over months and years affects attention, mood and memory, so protecting it is one of the most useful things anyone can do for long-term brain health (Xie et al., 2013; Rasch and Born, 2013).
Nutrition plays a part on both sides. A heavy meal close to bedtime can cause discomfort, and going to bed hungry disturbs sleep too. Blood sugar swings can wake people feeling restless or unusually alert. Alcohol may bring on drowsiness but fragments sleep later in the night. And the nutrients involved in producing sleep-related messengers, protein for tryptophan, magnesium, iron and the B vitamins, need to be there in the first place (Ebrahim et al., 2013; Gardiner et al., 2025; Sutanto et al., 2022; Winkelman et al., 2025).
Routine is as important as diet. Keeping mealtimes, activity and bedtime reasonably consistent helps, and one of the simplest things of all is getting outside into natural daylight soon after waking. Morning light helps set the body clock, supports melatonin production at night and improves sleep quality (Figueiro, 2017; Blume et al., 2019; Savage et al., 2024).
A note on Parkinson’s disease
Families supporting someone with Parkinson’s face many of the same challenges, reduced appetite, weight loss, swallowing difficulties, with the added complication that tremor makes shopping, cooking and eating harder.
One point worth knowing is that protein-rich meals can reduce the absorption of levodopa, the main medication used in Parkinson’s, because amino acids and levodopa compete for the same transport route. It is often suggested that larger protein-containing meals are eaten separately from doses. Any change to meal timing should be discussed with the Parkinson’s specialist team first (Cereda et al., 2010; Rusch et al., 2023).
Where families can start
Keep it simple, familiar and consistent.
Begin by reducing the foods most likely to disrupt blood sugar including, sugary snacks, biscuits, refined breakfast cereals and other ultra-processed foods, and build regular meals around protein and healthy fats instead. Eggs, fish, meat, softly cooked vegetables, soups, stews, omelettes and casseroles all deliver good nutrition without meals becoming complicated. Batch cooking a few dishes makes it much easier to keep something nourishing in the house.
It helps to write down the foods the person already enjoys and tolerates well, then rotate a small number of familiar meals through the week with a straightforward shopping list. Fewer decisions, less reliance on ready meals.
Finally, pay attention to anything making eating harder. Sore teeth, swallowing difficulty, constipation, medication side effects or simply not being able to get to the shops are all fixable, and fixing them is usually the first step towards better nutrition and better mood.
When to seek further support
General healthy eating advice has its limits once frailty, cognitive changes, persistent digestive symptoms, several medical conditions or multiple medications are involved.
It is worth seeking a proper nutritional assessment if someone is losing weight without trying, becoming weaker, eating noticeably less, or showing changes in mood, memory or day-to-day function (Kok et al., 2022; Volkert et al., 2022; NICE, 2006). A good assessment looks at the whole picture, diet, digestion, medications, blood results, sleep, activity and the practical ability to shop and cook, rather than treating each symptom separately.
It is also reasonable to ask a GP about blood tests that build a fuller picture, including a full blood count, vitamin B12 and folate, iron studies, vitamin D, thyroid function, blood sugar markers and a marker of inflammation. No single result gives the whole answer, but interpreted together and alongside someone’s symptoms and medications, patterns often emerge that would be missed in isolation.
What needs to change
Nutritional psychiatry is now a recognised and rapidly growing field, yet nutrition is still treated as separate from mental health care in everyday practice (Marx et al., 2017; Adan et al., 2019).
When an older person’s mood or memory changes, attention moves quickly to diagnosis and prescribing, while the nutritional picture goes unexamined. Sometimes another prescription is added to manage the side effects of the last one, without anyone asking why the symptom appeared (Sternberg and Rochon, 2021).
NICE already recommends screening for malnutrition risk in hospitals, care homes and community settings. What is needed is for that screening to lead to meaningful assessment and follow-up rather than becoming a box-ticking exercise (NICE, 2012).
Before we accept that low mood, poor sleep or fading memory are simply what happens with age, it is worth asking a more basic question: does this person have the nutritional foundations they need for their brain and body to work properly? Very often, they do not — and that is something we can do something about.
Lauren Wallis is a registered nutritionist. This article is for general information and is not a substitute for individual medical advice. Always speak to a GP or pharmacist before making changes to prescribed medication.
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