"Exercise helps to drive tryptophan into the brain, which can turbocharge serotonin levels. Multiple research studies have demonstrated that exercise can boost mood and cognitive flexibility." Dr Daniel Amen, psychiatrist and founder of Amen Clinics, and author of You, Happier

Have you ever noticed how differently you can respond to the same situation depending on the day?

Sometimes, a problem feels manageable. You can think clearly, consider your options and move forward.

Other times, the smallest setback can leave you feeling frustrated, anxious or stuck. You might find yourself replaying a conversation, dwelling on something that went wrong or struggling to shift your attention to something more positive.

Of course, life circumstances play a part. But what's happening inside your brain also influences how you feel and respond.

One of the chemical messengers involved is serotonin.

Often described as the feel-good chemical, serotonin has a much broader role than simply making us happy. It helps regulate mood, sleep, appetite and the way different brain networks communicate.

And while we can't control every aspect of our brain chemistry, there are practical things we can do to support the systems that help us feel and function at our best.

Let's explore five of them.

What is serotonin, and why does it matter in midlife?

Serotonin is a neurotransmitter — a chemical messenger that helps nerve cells communicate with one another.

In the brain, serotonin contributes to several important functions, including:

• Mood regulation: Helping the brain process emotions and respond to life's challenges.

• Sleep: Playing a role in the systems that regulate our sleep-wake cycle.

• Appetite: Contributing to feelings of hunger and fullness.

• Thinking and behaviour: Influencing brain networks involved in decision-making, emotional responses and cognitive flexibility.

Cognitive flexibility is particularly interesting. It's our ability to change perspective, adapt when circumstances change and move our attention away from thoughts that are no longer helpful.

When we're stressed or exhausted, that flexibility can become harder to access. We may find ourselves dwelling on problems rather than looking for solutions.

Serotonin is one part of the complex brain circuitry involved in these processes, although repetitive thinking doesn't necessarily mean our serotonin is low.

Interestingly, around 90% of the body's serotonin is produced in the gut. However, this serotonin doesn't cross directly into the brain. The brain makes its own supply, using nutrients obtained from our diet.

As we move through midlife, changes in sleep, stress, hormones and everyday routines can all affect our emotional wellbeing. Also, research has found that certain serotonin receptors and transporters become less available with age, which may affect how effectively serotonin signals are transmitted between brain cells. However, these changes vary between individuals and don't necessarily mean that serotonin production itself declines.

The encouraging news is that we can take steps to support our brain's health and resilience.

How do antidepressants affect serotonin?

You may have heard of medications called SSRIs, or selective serotonin reuptake inhibitors. These include commonly prescribed antidepressants such as sertraline and fluoxetine.

When one nerve cell releases serotonin, the chemical travels across a tiny gap, called a synapse, to communicate with another nerve cell. Some of that serotonin is then taken back up into the original cell.

SSRIs work by blocking this reuptake process, allowing serotonin to remain available in the synapse for longer.

However, the full picture is more complicated than simply increasing serotonin.

Depression isn't just a matter of having too little serotonin, and researchers now recognise that the benefits of antidepressants involve longer-term changes in brain signalling and adaptation. This helps explain why improvements in symptoms can take several weeks.

SSRIs can be an effective treatment for depression and certain anxiety disorders. For some people, medication is an important part of getting well.

But whether or not we take medication, our daily habits also influence our mood, stress response and overall brain health.

Here are five ways to put that knowledge into practice.

1. Nourish your brain with tryptophan-rich foods

Our brains need raw materials to produce neurotransmitters, including serotonin. One of those raw materials is an essential amino acid called L-tryptophan. It's described as essential because our bodies can't manufacture it. We have to obtain it through food.

Tryptophan is used to produce serotonin through a series of chemical reactions, with nutrients such as vitamin B6 helping the process along.

Fortunately, tryptophan is found in a wide range of everyday foods, including:

• Eggs, chicken and turkey

• Fish

• Chickpeas and lentils

• Pumpkin and sunflower seeds

• Nuts, including almonds and cashews

But there's an interesting complication.

Tryptophan has to cross the blood-brain barrier to be used in serotonin production. To get there, it shares a transport system with several other amino acids. This means the amount of tryptophan reaching the brain depends partly on how much competition it faces.

Where do carbohydrates come in?

Eating carbohydrates stimulates the release of insulin, which can influence the balance of amino acids circulating in the blood. Under certain conditions, this may make it easier for tryptophan to enter the brain.

For everyday meals, the best approach is to combine tryptophan-rich foods with fibre-rich, minimally processed carbohydrates, such as oats, brown rice or wholemeal bread.

For example:

• Porridge topped with pumpkin seeds and natural yoghurt

• Eggs on wholemeal toast

• Chickpeas served with brown rice and vegetables

• Grilled salmon with quinoa and leafy greens

These meals provide a useful combination of protein, complex carbohydrates, fibre and other nutrients important for brain health.

Try this: Look at your breakfast tomorrow. Could you include a good source of protein and a fibre-rich carbohydrate to help provide steady energy throughout the morning?

2. Get moving to support your mood

Physical activity is one of the most consistently supported lifestyle strategies for improving mental wellbeing. And you don't have to become a marathon runner to benefit.

Research shows that regular exercise can reduce symptoms of depression and anxiety, improve sleep and help us manage stress more effectively.

Movement affects several biological systems involved in mood, including neurotransmitter signalling, stress hormones and brain plasticity — the brain's ability to adapt and form new connections.

Serotonin may be part of this response, although the benefits extend well beyond any one chemical.

Exercise also improves blood flow, supports metabolic health and can provide a welcome change of focus when we've spent too long sitting or worrying.

Find movement you enjoy

The best activity is one you're likely to keep doing. That might mean:

• A brisk 20–30-minute walk

• Cycling or swimming

• Dancing to your favourite music

• Playing tennis or another sport

• Strength training a couple of times a week

• Gardening or tackling an active job around the house

If you've been inactive for a while, start with what feels manageable and build gradually.

You might begin with ten minutes of walking after lunch and increase the time as your fitness improves.

And if you can get outside during daylight hours, even better. Natural light helps regulate your body clock, which supports healthier sleep patterns.

Try this: Choose one opportunity to move today, particularly if you've been sitting for a long time. Notice how you feel afterwards, both physically and mentally.

3. Notice something daily you feel proud of

Think about your typical day. How often do you focus on everything you haven't finished, the things that went wrong or what you still need to improve?

And how often do you stop to acknowledge what you've done well?

For many of us, especially when juggling work, family responsibilities and other commitments, the unfinished tasks receive far more attention than our achievements. Yet recognising progress matters.

Psychological research suggests that noticing our accomplishments can strengthen our sense of competence and self-efficacy — our belief that we can take action and make a difference.

This can support motivation and positive emotions.

Be your own cheerleader

At the end of each day, ask yourself: What's one thing I did today that I'm pleased about?

It doesn't need to be a major achievement. Perhaps you:

• Went for a walk when you would rather have stayed on the sofa.

• Prepared a nourishing meal.

• Handled a difficult conversation constructively.

• Learned something new.

• Took a break instead of pushing yourself to exhaustion.

• Made time for someone who matters to you.

The aim isn't to pretend every day has been wonderful. It's to train your attention to notice evidence of progress alongside the challenges.

Over time, this can help you develop a more balanced view of yourself and what you're capable of achieving.

And that matters in midlife, when it's easy to become preoccupied with what may be changing or becoming more difficult.

Try this: Before you go to bed tonight, write down one thing you're proud of. Repeat the exercise for a week and see what you notice.

4. Support healthy brain cells with omega-3 fatty acids

For serotonin to do its job, it needs to be released by one nerve cell and received by another. And this is where omega-3 fatty acids may play an important role.

Two particularly valuable omega-3s are EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid). Both support brain health, but they work in different ways.

EPA: Supporting serotonin release

EPA helps regulate inflammatory processes in the body. This matters because inflammation can affect the way neurotransmitters, including serotonin, function in the brain.

Researchers have proposed that EPA may support serotonin release by reducing the production of certain inflammatory compounds called prostaglandins, which can interfere with serotonin signalling.

In other words, EPA may help create conditions that allow serotonin to communicate more effectively between nerve cells.

This is a promising biological explanation, although scientists are still investigating how much of this effect occurs in the human brain.

DHA: Helping brain cells communicate

DHA has a different role. It's a major structural component of brain-cell membranes — the outer layers that surround our nerve cells. These membranes need to maintain the right physical properties for cells to communicate effectively.

DHA contributes to membrane flexibility, which may influence how certain receptors function, including those that respond to serotonin.

What does this mean for our mood?

Clinical studies have investigated whether omega-3 supplements can help people experiencing depression.

Some have found improvements in depressive symptoms, particularly when omega-3s are used alongside conventional treatment. However, results vary, and the evidence generally favours supplements containing a higher proportion of EPA rather than DHA.

This doesn't make DHA any less important for brain health. It simply means that DHA's established structural role and EPA's clinical evidence for mood are two different considerations.

How can you get more omega-3s?

One of the best dietary sources of EPA and DHA is oily fish, including:

• Salmon

• Sardines

• Mackerel

• Trout

• Herring

UK dietary guidance recommends eating at least two portions of fish each week, including one portion of oily fish, while observing any relevant limits on oily fish consumption.

If you don't eat fish, algae-based supplements can provide DHA, and some also contain EPA.

If you're considering an omega-3 supplement, check how much EPA and DHA it contains rather than relying on the total fish-oil amount. A healthcare professional can advise whether supplementation is appropriate, particularly if you take medication.

Try this: Include a portion of oily fish in your meals this week, or check whether you're regularly getting enough omega-3s from your diet.

5. Take a break when your thoughts get stuck

Perhaps you've had a disagreement and keep replaying what was said. Or you're facing a problem at work and find yourself going over the same possibilities without getting any closer to a solution. You might even lie awake at night thinking about something that happened hours earlier.

This kind of repetitive thinking is often called rumination. It's different from productive problem-solving.

When we're solving a problem, we're exploring possibilities and making progress. When we're ruminating, we often circle around the same thoughts without reaching a useful conclusion.

Serotonin is involved in brain networks associated with emotional processing and behavioural flexibility. However, getting stuck in a thought loop doesn't automatically mean you have a serotonin deficiency. Stress, anxiety, fatigue and established thinking habits can all contribute.

The good news is that we can practise interrupting these patterns.

Change your activity to change your focus

When you notice that your thoughts are going around in circles, try three simple steps.

1. First, recognise what's happening: Ask yourself: Am I making progress with this thought, or am I just repeating it?

2. Second, change what you're doing. Stand up, move to another room or step outside. Physical movement and a change of surroundings can help redirect your attention.

3. Third, give your brain something different to focus on. For the next ten minutes, try an activity that engages your attention without adding more pressure.

You could:

• Go for a short walk.

• Do some gardening.

• Listen to music.

• Work on a puzzle.

• Call a friend.

• Tackle a straightforward practical task.

This isn't about avoiding problems that genuinely need attention. It's about recognising when more thinking isn't helping and giving yourself the opportunity to return with a clearer perspective.

Sometimes, the most productive thing we can do is stop trying to force a solution.

Try this: The next time you catch yourself replaying the same thought, deliberately switch activities for ten minutes. Afterwards, ask whether you're better placed to decide what to do next.

Small habits can make a meaningful difference

Serotonin plays an important role in the way our brains function, although our mood is influenced by many interacting factors, including sleep, stress, physical activity, nutrition, relationships, hormones and our overall health.

That's why there isn't one food, supplement or daily habit that can guarantee higher serotonin levels or a happier mood.

But that doesn't mean we're powerless. In fact, research gives us good reasons to be optimistic about the influence of everyday lifestyle choices on our mental and physical wellbeing.

We can nourish our brains with the nutrients they need.

We can use movement to improve our mood and resilience.

We can recognise our achievements rather than focusing exclusively on what remains undone.

We can support healthy brain-cell function through good nutrition.

And we can learn to interrupt unhelpful thinking patterns instead of allowing them to dominate our day.

Our brains have a remarkable capacity to adapt, learn and respond to the way we live, even as we get older. That's one of the most exciting things about healthy ageing. The choices we make today can help shape how we feel, function and enjoy life in the years ahead.

And that's worth investing in.