Does exercise help your immune system as you get older?
Exercise helps older adults: it lowers mild inflammation in the blood and noticeably reduces the risk of physical frailty. How it works on the deeper ageing of the immune system remains an open question.
Two inflammation markers in the blood, one called CRP and another known by a different name, fall slightly in older adults who exercise regularly. That picture comes from many studies combined. For a third marker, the results still contradict each other: some studies see a drop, others find no effect or even a small rise. There is therefore no clear-cut conclusion for that third marker.
The evidence is stronger when it comes to reducing frailty in people over 50. Twelve of the thirty-seven studies, covering more than 25,000 participants together, show that aerobic training and strength training can reduce the risk of frailty by a third. Fitness also improves in a measurable way: peak oxygen uptake rises by an average of around 3.6 mL per kilogram per minute, which is noticeable in everyday activities.
Functional exercises, meaning movements that practise everyday actions such as getting up from a chair or climbing stairs, improve muscle strength, stamina and physical functioning in women over 60. Whether they also slow the ageing of the immune system itself remains unclear: there are indications, but the results are too inconsistent for a firm conclusion.
Researchers know little about deeper immune ageing, the wear and tear of the immune system at the cellular level. This is a recognised gap in knowledge. One small study in young adults showed that even a single exercise session increases the production of NAD+ in immune cells. NAD+ plays a role in how cells generate energy and declines with age. Whether this effect also occurs in older adults and whether it matters in practice has not yet been studied.
This answer draws on many studies combined and controlled studies involving tens of thousands of participants in total. However, the researchers themselves are critical of their own material: for the inflammation markers, the quality of the evidence was rated critically low in as many as eleven of the twenty-one reviewed summaries, nine were rated low quality, and only one was rated moderate. The confidence rating for each individual inflammation marker, using the standard scale for judging how much to trust a finding, was "very low". For frailty and physical functioning the quality is better, partly because the underlying studies were larger and more rigorously designed. The evidence on immune ageing at the cellular level is sparse and is described by the authors themselves as limited and to be interpreted with caution.
Does spending more time outdoors help your immune system as you get older?
Spending more time outdoors may support your immune system as you get older, mainly through improved vitamin D production, but whether this actually leads to less illness has not yet been conclusively demonstrated. How polluted the outdoor air is also matters: in areas with serious air pollution, being outside can in fact be detrimental.
Does your immune system weaken as you get older?
Your immune system demonstrably weakens with age, but eating healthily and exercising can reduce the smouldering inflammation that accompanies it. It is still too early to rely on drugs targeting senescent cells.
Can you slow down the ageing of your immune system?
The immune system demonstrably ages, and there are promising avenues for slowing that process, but no single approach has been proven safe and effective in humans. Eating less processed food is the only step you can concretely take right now; everything else requires more research in humans before any conclusions can be drawn.
Does your immune system age at a different rate than your heart?
Yes, your immune system and heart age at measurably different rates, and an ageing immune system is more strongly linked to a longer life than the heart is. These are associations, not causal evidence, but that is still a reason to take both seriously.
What does ageing of your immune system mean for your health?
Your immune system ages in measurable ways: it responds less effectively to new threats and maintains a smouldering inflammation that is associated with cardiovascular disease, dementia and cancer. An active lifestyle is the best-supported way to slow that process.
Does eating enough protein help my immune system as I get older?
Eating enough protein helps your immune system in later life. Aim sustainably for at least 1.0 to 1.2 grams per kilogram of body weight per day, spread across your meals, and preferably obtain this from regular food.