With age, the human immune system becomes less effective at tackling infections and less responsive to vaccinations. At the same time, the aging immune system is associated with chronic inflammation, which increases the risk of almost all conditions linked to old age.
The good news is that exercising and adopting the right diet may help a person maintain healthy immunity into older age.
Chimpanzees and gorillas, our closest primate relatives, live for only 10–15 years in the wild once they have reached maturity. After the human evolutionary lineage split from theirs, our ancestors’ life expectancy doubled over the next 5 million years.
Scientists believe that it remained relatively stable into the 18th century. In the 250 years between then and now, however, life expectancy more than doubled again due to improvements in sanitation and healthcare.
We live in a time of high average life expectancies. However, our long evolutionary history has adapted us for different lifestyles (and even life expectancies), and these have changed drastically.
As a result, immunity not only weakens in older age; it also becomes imbalanced. This affects the two branches of the immune system — “innate” immunity and “adaptive” immunity — in a double whammy of “immunosenescence.”
“Innate” immunity, which is our first line of defense against infections, fails to resolve after the initial threat has passed, causing chronic, systemic inflammation.
“Adaptive” immunity, which is responsible for remembering and attacking particular pathogens, steadily loses its ability to defend against viruses, bacteria, and fungi.
Chronic, low-grade inflammation is associated with almost all conditions linked to older age, including type 2 diabetes, cardiovascular disease, cancer, and dementia. It also plays a leading role in certain autoimmune conditions that are more common in older adults, such as rheumatoid arthritis.
Meanwhile, the loss of adaptive immunity that comes with older age not only makes people more susceptible to infections; it can also reactivate dormant pathogens that were previously suppressed.
In addition, the weaker adaptive immunity of older adults means that their bodies respond less strongly to vaccinations, such as the annual flu shot.
Getting regular physical activity
Exercise has a profound effect on the immune system, according to a recent overview of research in the journal Nature Reviews Immunology.
Inevitably, people become less physically active as they age, but there is evidence to suggest that getting as much exercise as possible can slow or even reverse some of the effects of immunosenescence.
Skeletal muscle produces a range of proteins called myokines that reduce inflammation and preserve immune function. Therefore, it makes sense that maintaining muscle mass through exercise protects against infection and conditions such as type 2 diabetes and cardiovascular disease, which are closely linked to chronic inflammation.
Adopting the Mediterranean diet
For now, there is no direct evidence to suggest that making dietary changes can slow the rate of immunosenescence in older adults. However, there is plenty of indirect evidence.
In particular, research suggests that diet helps determine older adults’ risk of developing sarcopenia. This condition causes a loss of muscle mass, strength, and functionality.
There appears to be a two-way relationship between skeletal muscle and the immune system. Muscles produce anti-inflammatory myokines, but recent evidence suggests that chronic inflammation also accelerates the muscle loss in sarcopenia.
Taking dietary supplements that reduce the risk of sarcopenia — such as vitamin D and polyunsaturated fatty acids — may help, due to their anti-inflammatory properties.
A growing body of evidence also suggests that people who eat a Mediterranean diet are less likely to become “frail” in older age, such as by losing muscle strength, walking slowly, and tiring easily.
Maintaining a moderate weight
Although muscle plays a role in reducing inflammation in older adults, fat, or “adipose,” tissue may have the opposite effect.
Normal aging often leads to weight gain, due to an accumulation of adipose tissue beneath the skin and around the organs. According to a roundup of research on the aging immune system, adipose tissue may make a significant contribution to inflaming.
Up to 30% of the pro-inflammatory cytokine IL-6 in the bloodstream may originate from adipose tissue. Therefore, having obesity or overweight in older age may significantly contribute to chronic inflammation.
Medical reference: Medical News Today