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.
The immune system ages along two tracks simultaneously. The immune response becomes slower and less effective, while at the same time a smouldering low-grade inflammation builds up. T-cells, the coordinators of the immune defence, lose their ability to renew themselves, become stuck in a kind of exhausted standby state, or die without being replaced. This makes older people more vulnerable to infections and cancer, and explains why vaccines are less effective in the elderly. This is well documented in humans.
A Western diet high in saturated fats and fast-acting sugars accelerates that smouldering inflammation. This works through excess weight, a disrupted gut microbiome, and adipose tissue that itself produces inflammatory compounds. A concrete takeaway: eating less processed food is the best-supported lifestyle choice you can make right now.
The most talked-about intervention is the TRIIM trial, in which nine healthy men received a combination of growth hormone, metformin and DHEA for one year. Their biological age, measured via DNA methylation patterns, decreased by an average of 1.5 years. The effect persisted for six months after stopping. However: there was no control group, the group was very small, and growth hormone carries real risks, including an increased risk of insulin resistance. These are preliminary signals, not a proven treatment.
Another approach is the targeted removal of aged cells, so-called senolytics. The compound ABT263 did this effectively in mice, but also inhibits platelet survival, which creates a bleeding risk. A step further are modified immune cells (CAR-T cells) specifically targeted at senescent cells. In mice, this improved liver fibrosis and extended survival; in non-human primates, no side effects were observed. But this research is still at an early stage in humans. Clinical trials are ongoing.
This answer draws on multiple reviews of immune ageing in humans and on animal research into new interventions. The ageing of the immune system itself is strongly documented in humans. The interventions are a different matter: the TRIIM trial included nine participants with no control group, and the senolytic and CAR-T studies were conducted almost exclusively in mice and, in one case, also in non-human primates. None of the experimental approaches has been tested in large groups of humans. Some of the researchers involved in the TRIIM trial have a financial interest in the results, which makes that study particularly important to interpret with caution.
Does your immune system really weaken as you get older, and can you do anything about it?
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.
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 associated with a longer lifespan than the heart is. These are associations, not causal evidence, but that is reason enough to take both seriously.
Does exercise help your immune system as you age?
Regular, moderate exercise helps your immune system by reducing smouldering inflammation. Suddenly training very hard without a gradual build-up can actually temporarily lower your immune defences.
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 really weaken as you get older?
Your immune system does indeed weaken as you get older, but how quickly that happens varies considerably from person to person. Lifestyle factors play a role in this, although little has yet been proven specifically for humans.
Which factors weaken your immune system?
Several factors demonstrably weaken your immune system: deficiencies in vitamin A, zinc and iron are the best supported, but medical treatments, chronic stress and strenuous exercise also play a role. When using high-dose steroids medically or in the case of an HIV infection, it is advisable to involve your doctor in infection prevention.