As you age, your brain starts to change. The frontal lobe and hippocampus, two areas involved in cognitive function and encoding new memories, start to shrink when you hit the ripe age of 60. The bundles of nerves that carry signals between your brain cells also shrink.

When you’re older, your brain produces fewer chemical messengers like the feel-good hormones, dopamine and serotonin. This can hasten depression and cognitive decline. Additionally, this puts you at greater risk of developing brain diseases like Alzheimer’s.

Thankfully, regular exercise can help address these issues because it increases the number of mitochondria, or the power houses in brain cells.

Ian Mudway, a senior lecturer at the School of Public Health at Imperial College London, advised that you should avoid “areas of high pollution” to enjoy the health benefits of exercise.

He referenced a study published in the journal Neurology that showed how going for a jog is good for the brain, but not if you are in a polluted area.

The study examined data from 8,600 people, including their exposure to pollution, which was estimated according to where they lived, how much exercise they did and markers of brain health. The results showed that people who exercised in areas of high air pollution didn’t get the same benefits.

According to one theory, tiny particles of pollution are inhaled and then accumulate in the brain. The second theory suggests that pollution leads to systemic inflammation throughout the body, which has adverse effects on brain health over time.

In both cases, experts believe that particles cause oxidative stress, which then causes damage to neurons or brain cells.

Eat red and yellow peppers

Tony Dickenson, a professor of neuroscience, physiology and pharmacology at University College London, explained that you need to keep your glial cells healthy for various brain functions.

Glial cells are found throughout the nervous system. These cells support the neurons, or nerve cells, bring nutrients and remove waste.

But if your glial cells become inflamed, they can release toxic chemicals that have adverse effects on the normal function of neurons. Chronic inflammation has been linked to problems like depression and dementia, said Dickenson.

Fortunately, there are dietary approaches to reduce inflammation.

Studies have shown that plant flavonoids — the compounds that produce the colourful pigments found in red and yellow peppers, purple eggplants and green leafy vegetables — have anti-inflammatory effects on cells and antiviral and anti-tumour actions.

This means you can boost your brain health by following a balanced diet and eating nutritious vegetables like red and yellow peppers.

Keep your thyroid healthy

Many people have an underactive thyroid, which means the gland doesn’t produce enough of the hormone thyroxine. This can cause symptoms that are troublesome, but non-specific. It can also result in cognitive decline.

According to data, at least one in 20 people in the U.K. has a thyroid problem.

Stephen Shalet, an emeritus professor of endocrinology at the Christie Hospital in Manchester, advised that an underactive thyroid can cause poor memory and cognitive decline since thyroid hormones are crucial for brain function.

Thyroid hormone deficiency, even of a short duration, may cause irreversible brain damage, “the consequences of which depend not only on the severity, but also on the specific timing of onset and duration of the deficiency,” warned Shalet.

You can’t prevent an underactive thyroid, but you can treat it by taking tablets to replace the hormones that your thyroid isn’t producing.

Shalet added that if you’re a woman aged 40 to 50 and are experiencing symptoms of lethargy or unexplained weight gain, it’s best to have your thyroid tested.

Eating these nutritious foods can also help if you have hypothyroidism:

• Eggs
• Fish
• Fruits
• Gluten-free grains and seeds
• Meat like beef, chicken and lamb
• Vegetables, but consume cruciferous vegetables in moderate amounts

Beware of open fires and wood stoves

Barbara Maher, a professor of environmental science at Lancaster University, advised that when it comes to brain health, exposure to a specific pollutant called magnetite nanoparticles “is particularly damaging.”

Magnetite nanoparticles are iron-rich particles that form by combustion or frictional heating from vehicle engines or brakes. Other ultra-fine pollutants from traffic fumes are also a hazard because they are small enough to enter your brain.

Maher warned that magnetite is dangerous because it is the catalyst for the formation of compounds that cause cell damage or cell death.

In a study published in 2016, Maher discovered that there were a lot of magnetite nanoparticles in the brain tissue of Mexico City and Manchester residents. These people are often exposed to wood stoves, traffic fumes and industrial pollution.

The study findings suggest that magnetite nanoparticles in the atmosphere can enter the brain and “might pose a risk to our health, including conditions such as Alzheimer’s disease.”

Get enough restful sleep

Sleep is when the brain does a deep clean. If the waste isn’t flushed out, it can turn into clumps of toxic proteins linked with dementia. Russell Foster, a neuroscientist at the University of Oxford, recommends getting at least seven to nine hours of sleep.

Get enough sleep, eat nutritious vegetables and exercise away from busy roads to “age-proof” your brain.