One of the most recognised consequences of ageing is a decline in immune function, which increases your risk of contracting diseases you would have otherwise been resistant to.
With age, the immune system loses its memory for pathogens it has encountered before, white blood cells become sluggish, and the body is increasingly slower to respond to infections. The immune response itself becomes less powerful, too. This translates to more frequent infections that are harder to get over and wounds that take longer to heal.
There is some good news, however: there are easy ways to boost your immune system at any age to prevent illness and speed up your recovery.
How does age affect your immune system?
Below are a few ways in which natural ageing alters the function of your immune system:
- T cell function decreases. T cells are white blood cells that directly attack pathogens and help to coordinate other limbs of the immune system, but they become less efficient as we age.
- Immune organs shrink. The thymus makes T cells and hormones that help the immune system to function well. Unfortunately, this organ begins to shrink in young adulthood and is only 15% of its maximum size by middle age. As time goes on, the thymus becomes even smaller and less effective.
- Macrophages become sluggish. These are white blood cells that ingest and destroy pathogens and damaged cells, as well as repair damaged tissues. They’re an essential part of the body’s first line of defence against disease and a cornerstone of many immune functions. As time goes on, macrophages become slower and less effective.
- White blood cells decline. All cell division begins to slow down as we age, and it takes longer to replenish white blood cells. With a lower number of troops, our immune defences are weakened. One study even suggests that the number of white blood cells you have at age 75 is a predictor of how much longer you may live!
- Fewer antibodies are made. The body uses antibodies to identify and then attack infective pathogens. As we age, the immune system fails to create enough antibodies, creating a higher risk of contagious infections like pneumonia and influenza in older people.
- Inflammation in the gastrointestinal tract increases. Recent research has confirmed that the gut influences the whole body’s immune system, and any inflammation in the intestines can compromise its function.
How can we improve our immune system as we age?
Regularly eating a diet rich in fresh fruits, vegetables, whole grains and healthy fats provides the nutrients that the immune system needs to thrive and has been shown to boost immune health at all ages.
Vitamin C is an essential nutrient that the immune system uses for a vast range of processes from protecting the skin against pathogens, to fuelling white blood cells to kill microbes. Although vitamin C is abundant in fresh fruits and vegetables, a surprising number of people have low vitamin C.
Studies suggest that taking vitamin C supplements can increase the rate of healing, boost the number and function of white blood cells, improve the actions of T cells, and increase the production of antibodies.
Vaccines are designed to teach the immune system about a virus so that it can produce enough antibodies to fight off the actual pathogen. While vaccinations are vital in protecting older people against infections, they may not be as effective as they are on younger people.
Vaccines are still an essential element of healthy ageing, and they are more effective if you also use other strategies to support your immune system – like taking probiotics.
Looking after your gut microbiome
Targeting the gut microbiome — the communities of bacteria and other microorganisms that inhabit the gastrointestinal tract — could be a way to treat a range of age-related conditions.
People’s gut immune response becomes less effective with age. Studies have linked this decline to age-related changes in the gut microbiome. Inflammation, increased frailty, and a predisposition to intestinal illnesses also accompany these changes. 
Your gut microbiome can be helped through having a healthy balanced diet as well as ensuring you are getting the right intake of fibre. Fibre plays a vital role in digestion, enabling your good gut bacteria (bifidobacteria) to grow. Research shows that only 9% of adults in the UK achieve the recommended daily intake of 30g of fibre per day. Consuming foods that contain prebiotics such as leeks, onions and Jerusalem artichokes can help feed the bacteria in your gut that play a role in good gut health.
Believe it or not, frequently washing your hands is the most effective way to prevent catching a cold or the flu – particularly when your immune system is struggling. However, half-hearted hand rinsing is not the same as proper, hygienic hand-washing. To get rid of germs from your hands, lather soap on your hands and wrists for 2 minutes, rinse for 2 minutes, and dry with a clean towel or air dryer. 
What happens to your immune system as you age may seem inevitable and even uncontrollable, but there are many ways you can boost your resistance to disease and speed up your recovery.
 Salam, N., et al. (2013) T cell ageing: Effects of age on development, survival & function. Indian J Med Res., 138:5, 595:608. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3928693/
 Linehan, E. & Fitzgerald, D. C. (2015) Ageing and the immune system: focus on macrophages. Eur J Microbiol Immunol (Bp)., 5:1, 14 – 24. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4397845/
 Simell, B., et al. (2008) Effects of Ageing and Gender on Naturally Acquired Antibodies to Pneumococcal Capsular Polysaccharides and Virulence-Associated Proteins. Clin Vaccine Immunol., 15:9, 1391 – 1397. https://cvi.asm.org/content/15/9/1391
 Landete, J. M., et al. (2017) Probiotic Bacteria for Healthier Aging: Immunomodulation and Metabolism of Phytoestrogens. Biomed Res Int., 2017. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5646295/
 Carr, A. C. & Maggini, S. (2017) Vitamin C and Immune Function. Nutrients., 9:11, 1211. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5707683/
 Could perking up gut bacteria promote healthy aging? https://www.medicalnewstoday.com/articles/325382.php
 Merk, H., et al. (2014) Associations of hand-washing frequency with incidence of acute respiratory tract infection and influenza-like illness in adults: a population-based study in Sweden. BMC Infect Dis., 14, 509. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4177698/