A healthy immune system needs both an accelerator and a brake. It must respond forcefully when infection or injury occurs—but once the danger passes, it must also know how to stop.
With age, that braking system may become less reliable. The immune system can grow less effective at responding to genuine threats while remaining chronically activated at a low level. This paradox helps explain why aging is associated with both greater vulnerability to infection and a rising burden of inflammation-related disease.
Ou Han-wen, a functional medicine expert, describes healthy immunity not as maximum strength but as the ability to respond appropriately and then return to balance. Preserving that capacity, he said on “Health 1+1” on NTD, a sister outlet of The Epoch Times, may be an overlooked foundation of healthy aging.
When the Immune Alarm Stays On
Inflammation is not inherently harmful. It is one of the body’s essential defenses, helping control infection and repair damaged tissue. Problems arise when an inflammatory response does not fully resolve, and the immune alarm remains faintly switched on.
Researchers sometimes call this persistent, age-related background inflammation “inflammaging.” It has been associated with cardiovascular disease, type 2 diabetes, arthritis, dementia, and other chronic conditions, although it is one contributor among many—not the sole cause of aging or disease.
That lingering inflammation is closely connected to metabolism. Poor blood sugar control, excess visceral fat, and loss of muscle can promote inflammatory signaling. In turn, inflammation can further interfere with glucose regulation, lipid metabolism, sleep, and muscle maintenance, creating a cycle in which metabolic dysfunction and immune activation reinforce one another.
Chronic stress may tighten the loop. Cortisol normally helps mobilize energy during an immediate challenge and prevents immune responses from becoming excessive. But when physical or psychological stress persists, the body’s stress-response system can become disrupted, making it harder to regulate blood sugar, sleep, and inflammation.
Ou said some patients in his practice have experienced improvements in blood sugar or blood pressure after factors such as poor sleep, digestive problems, or metabolic dysfunction were addressed. Such observations do not establish inflammation as the sole cause of those conditions. Rather, they illustrate why reducing one source of strain may produce benefits across several interconnected systems.
Because immune regulation depends partly on distinguishing genuine threats from harmless exposures, one of its most important training grounds is the gut.
The Gut as a Training Ground for Immunity
The intestinal tract contains one of the body’s largest and most active immune compartments. Every day, immune cells there encounter food components, beneficial microbes, and potential pathogens. They must tolerate what is harmless while remaining ready to attack what is dangerous.
Ou advised paying attention to persistent constipation, diarrhea, bloating, nausea, and other digestive changes. These symptoms are common and do not necessarily indicate immune dysfunction, but persistent or unexplained symptoms may signal that digestion, diet, medication use, or an underlying condition needs attention.
For everyday support, Ou recommended eating slowly, avoiding overeating, reducing heavily processed and high-sugar foods, and obtaining fiber from a variety of plant foods.
Fiber is especially relevant to the immune “off switch.” Gut bacteria ferment certain fibers into short-chain fatty acids, which nourish cells lining the colon and help regulate the intestinal barrier and immune responses. Vegetables, fruits, legumes, whole grains, nuts, and seeds provide different fibers, making dietary variety more useful than relying on a single “superfood.”
Probiotics, by contrast, should not be treated as universal immune boosters. Their effects vary by strain and health condition, and more is not necessarily better.
The gut is only one part of the regulatory system. If the goal is immune flexibility rather than maximum activation, daily habits should be judged by a broader question: Do they help the body return to baseline?
Helping the Body Return to Baseline
Sleep may be one of the clearest examples. Sleep and immunity communicate in both directions: Immune activity influences sleep, while sleep helps regulate innate and adaptive immune responses. Prolonged sleep deficiency can favor persistent low-grade inflammation, making regular, sufficient sleep more than a matter of feeling rested.
Ou suggested beginning with a small, sustainable change, such as going to bed 30 minutes earlier and keeping sleep and wake times consistent. The value of the habit lies not in a particular bedtime, but in giving the body a dependable period for recovery.
Movement provides another regulatory signal. Regular activity improves insulin sensitivity, helps preserve muscle, and reduces visceral fat—all of which can lower sources of inflammatory stress. Individual bouts of exercise also produce signals that help coordinate inflammatory and anti-inflammatory activity. The goal does not have to be intense training; walking, resistance exercise, swimming, cycling, or other sustainable movement can be adapted to a person’s health and ability.
Stress-management practices serve a similar purpose. Breathing exercises, meditation, prayer, time outdoors, social connection, and physical activity do not eliminate life’s pressures, but they may help prevent the body from remaining in a prolonged state of physiological alert. Persistent anxiety, depression, or insomnia, however, may require professional care rather than self-help alone.
Finally, Ou cautioned against taking multiple supplements simply because they are advertised for immunity or longevity. A supplement can fill a documented need, but it cannot substitute for sleep, movement, nourishing food, or appropriate medical care. Some products can also duplicate ingredients or interact with medications, so the goal should be purposeful supplementation—not maximal supplementation.
Together, these habits may help the body respond when needed and return to balance once the threat has passed. Healthy aging requires more than strong defenses; it also depends on the restraint to stand down and the resilience to recover.