As you get older, your immune system naturally becomes less effective. This means it can take longer to fight infections, respond to vaccines and recover after illness. Doctors call these age-related changes immunosenescence.

At the same time, many older adults develop a constant mild level of inflammation in the body. Scientists sometimes call this inflammageing – a combination of inflammation and ageing. Over time, it can put extra strain on the immune system and has been linked to conditions such as heart disease, type 2 diabetes and some cancers (Nikolich-Žugich, 2018; Franceschi et al., 2018).

Although ageing is something we can’t prevent, the way our immune system ages varies from person to person. Your lifestyle choices, diet and overall health all play an important role. The good news is that there is plenty you can do to help keep your immune system healthy as you age.

Build a strong foundation

The best way to support your immune system is through your everyday habits.

Prioritise good-quality sleep

While you're asleep, your immune system is hard at work. It produces important signalling molecules, repairs damage and prepares to fight future infections. People who don’t get enough sleep are more likely to catch common illnesses such as colds and may not respond as well to vaccines, meaning they miss out on their full protective effect.

Stay physically active

Regular exercise helps immune cells travel around your body more efficiently, making it easier for them to do their job – to detect and fight infections. It also helps reduce chronic inflammation. Walking, swimming, cycling and strength training can all support healthier ageing. You don’t need to become an athlete – staying regularly active is what matters most.

Eat a balanced diet

A balanced diet provides your immune system with the nutrients it needs to work well. Protein helps your body build and repair tissues, while fruit and vegetables provide vitamins, minerals and natural plant compounds that help protect your cells from damage.

Eating enough fibre is important too. Fibre feeds the beneficial ‘friendly’ bacteria that live in your gut, known as the gut microbiome. Much of your immune system is found in and around your gut, so keeping your gut microbiome healthy also helps support your immune system. Maintaining a healthy body weight is also beneficial, as carrying excess body fat can increase long-
term inflammation.

Get enough Vitamin D

Vitamin D deserves special mention. Many people in the UK have low vitamin D levels, especially during autumn and winter because we get less sunlight, which means our bodies can’t make it in the amounts we need. Vitamin D helps the immune system recognise harmful germs and respond. In the UK, many health organisations recommend taking a vitamin D supplement during the autumn and winter months.

Manage stress

Stress doesn’t just affect your mood – it can affect your immune system too. Long-term stress increases levels of the hormone cortisol, which can reduce the activity of some of the immune cells that help fight off infections. Simple activities such as relaxation techniques, regular exercise, spending time with friends and family, and making time for hobbies you enjoy can all help keep stress under control.

Avoid smoking and excess alcohol

Smoking damages the immune system and makes it harder for the body to fight infections. Drinking too much alcohol can also weaken the immune system over time. Keeping long-term health conditions such as diabetes, obesity and heart disease well managed can also help your immune system stay as healthy as possible.

Together, these lifestyle habits have the strongest scientific evidence for helping your immune system stay healthy.

Can supplements help?

Supplements should be viewed as an addition to a healthy lifestyle, not a replacement for it.

Many supplements claim to "boost" your immune system, but the reality is a little more complicated. A healthy immune system isn't one that's permanently switched on. Instead, it responds quickly when it needs to, then settles down again once the threat has passed.

If you are low on important nutrients, correcting that can help support a normal immune function. Nutrients that are particularly important include vitamin D, vitamin C, zinc and selenium. Some studies also suggest that omega-3 fatty acids may help regulate inflammation, while probiotics (beneficial bacteria or supplements that support them) may improve gut health for some people.

AHCC®: A promising immune-support supplement

One supplement that has attracted growing scientific interest is Active Hexose Correlated Compound (AHCC®).

AHCC® is a natural extract made from the root-like part of shiitake mushrooms, called mycelia. Rather than simply making the immune system more active, research suggests AHCC® helps immune cells work more effectively while maintaining a healthy balance. (Matsui et al., 2002).

Scientists describe this as an immunomodulatory effect, which simply means helping the immune system respond appropriately rather than making it work harder all the time.

Support for immune cells

Research suggests that AHCC® supports several important types of immune cells (Yin et al., 2010). One of the best-studied is the natural killer (NK) cell. NK cells are one of your body’s first lines of defence against viruses and abnormal cells. Several clinical studies have found that people taking AHCC® had more active NK cells, which may help strengthen the body's natural defences.

AHCC® may also support other immune cells, including:

• macrophages, which help remove germs and damaged cells
• dendritic cells, which alert the immune system to potential threats and
• T cells, which help target and destroy infected cells.

Research suggests AHCC® also helps immune cells communicate by increasing the production of important chemical messengers involved in fighting viral infections (Yin et al., 2010) (Roman et al., 2013).

Support for gut health

AHCC® may also support gut health. Early research suggests it encourages the growth of beneficial, "friendly", bacteria in the digestive system and may help reduce inflammation. Since much of the immune system is found in the gut, this could provide additional immune support.

One area attracting particular interest is AHCC®'s potential to help the body clear persistent human papillomavirus (HPV) infections. Early clinical studies have reported encouraging results (Smith et al., 2019), although we still need larger independent trials before scientists can come to firm conclusions.

Overall, the research suggests AHCC® may help immune cells work more effectively and support a balanced immune response. However, we need more high-quality studies to better understand its long-term benefits, particularly in older adults.

The bottom line: you can keep your immune system healthier for longer

While you can’t stop your immune system ageing, you can help it stay healthier for longer. Regular exercise, a balanced diet, good-quality sleep, managing stress and keeping long-term health conditions under control remain the best ways to support your immune system as you age.

If you're low in important nutrients such as vitamin D, vitamin C, zinc or selenium, supplements may help restore normal immune function.

For people looking for additional support, AHCC® is one of the better-researched immune supplements available. While it isn't a cure and can't prevent ageing, research suggests it may help several important immune cells work more effectively and support a healthy, balanced immune response.