Robert had always been the healthy one. At 71, he still played golf twice a week, took no regular medications, and had a lifelong habit of shrugging off whatever cold or flu was going around the office. So when he walked into my practice, he wasn’t alarmed—just puzzled. In the two years since his wife had died, something in him seemingly had stopped working.
A scrape on his shin that should have closed in a week now took a month to heal. Colds he would once have brushed off now knocked him flat. Then came shingles, the same virus that had flared once in his 50s and, he’d assumed, gone dormant for good, spreading across his ribs as if no time had passed at all.
His internist ran the standard tests: a complete blood count, a metabolic panel. Everything came back normal. “This is just what aging looks like,” he was told. But normal-for-age was exactly where the real problem was hiding because three separate arms of Robert’s immune defense were failing at once in sync with the two hardest years of his life. That was not a coincidence.
To make sense of what was happening to Robert, I looked at him across four dimensions I use to evaluate every aging system. I call this approach the ACES Model: anatomy, chemistry, energy, and soul. The structure of the body houses its defenses. Chemistry inflames or calms defenses. Energy fuels them. The unmetabolized weight in one’s life—grief, isolation, and loss can drain defenses in ways no standard blood panel is built to detect. Of all the body’s systems, the immune system may be the one in which the fourth dimension matters most.
The Aging Army
The immune system is the body’s standing army. It is a vast network that distinguishes self from invaders, remembers old enemies, repairs damaged tissues, and clears out cells that have become dangerous.
It has organs most people never think of as such: bone marrow, which produces white blood cells that do the fighting; the thymus, a small gland behind the breastbone that trains immune cells, such as T cells, that coordinate the whole defense; the spleen and the lymph nodes, which filter blood and catch invaders as they pass; and the lining of the gut, home to much of the immune system and the largest barrier between the body and the outside world.
With age, that army does not simply shrink; it changes character. It responds more slowly to new threats, more quickly to inflammation, and is less reliable in what it remembers. Scientists call this slow transformation “immunosenescence.” The thymus offers the clearest example: It begins shrinking right after puberty and, by later life, has largely turned into fat. The primary reason older adults respond poorly to new infections and vaccines is that the body simply produces fewer cells trained to recognize new threats it hasn’t met before.
Meanwhile, the gut lining grows leakier, and bone marrow shifts its output toward the cells that drive blunt, generalized inflammation rather than precise, targeted defense.
Robert’s anatomy was unremarkable for his age, meaning that his defenses had not failed overnight. They had been gradually thinning for years, the way most aging immune systems do, so nothing looked abnormal on paper.
Although immunosenescence can not be stopped, much that can effectively slow the aging of our immune system is within reach. A diet rich in fiber and fermented foods feeds the gut bacteria that help train immune cells—fiber nourishes the microbes already there, while fermented foods add live microbes that diversify the microbiome and help calibrate immune responses. Regular, moderate exercise measurably sharpens immune surveillance. Diet and exercise were areas Robert could begin with.
The Slow Fire of Inflammation
The chemical story of the aging immune system has a name: inflammaging. As we grow older, the body tends to settle into a state of chronic, low-grade inflammation—not the sharp, useful kind that flares in response to an injury and then fades, but a constant, smoldering fire that never burns out.
Several things feed that fire: visceral fat, which behaves like its own inflammatory organ; poor sleep, which raises inflammatory markers; a diet heavy in sugar and processed food; and chronic psychological stress, which pours fuel directly onto the flames.
Slow-burning inflammation is corrosive. It is now understood to sit beneath many of the major diseases of aging—heart disease, Type 2 diabetes, Alzheimer’s, several cancers, and frailty—by damaging blood vessels and tissues and wearing down the immune system’s ability to respond when a real threat appears.
Robert’s inflammatory markers were elevated, though only modestly. His frequent infections and slow healing were the visible smoke rising from the fire.
Immunosenescence does not show on a standard panel. It requires tests few clinics run, such as the naïve-memory regulatory T-cell ratio, the lifelong burden of certain common viruses, the level of inflammatory signals in the blood, and how weakly the body responds to a vaccine.
If you recognize this pattern in yourself, ask your doctor for the markers a routine panel leaves out—high-sensitivity C-reactive protein at a minimum—and treat a persistently elevated result as a signal to act. Reducing visceral fat lowers inflammation directly, and a diet built around vegetables, fatty fish, and olive oil helps cool the fire that sugar and ultra-processed food keep feeding.
Through the Energetic Lens
So far, we have looked at Robert’s immune system in terms of anatomy and chemistry. The traditional Chinese medicine (TCM) I trained in adds a third-dimensional perspective, one that Western physiology is only beginning to corroborate. Here the word “energy” points to the body’s functional vitality—its capacity to power its own work, including its defenses. When that capacity runs low, the machinery still exists, but there’s too little force behind it, which is what an aging immune system looks like.
TCM calls this protective vitality “wei qi,” or defensive qi. It is the body’s protective layer—the vitality that circulates on the surface and guards against external threats. When it is weak, invaders pass through, and the person falls sick easily and often. Replace “invaders” with “pathogens” and “wei qi” with “immune defense,” and the two systems describe much the same reality.
Someone with weak digestion, or reserves drained early by overwork, illness, or grief, cannot produce the strong wei qi. They become susceptible to illness—not so different from what immunosenescence describes in modern terms—just seen from the side of vitality rather than cells.
TCM also ties wei qi to the lungs and the rhythm of sleep. Wei qi is said to circulate at the body’s surface by the day and retreat inward at night to restore itself. Broken sleep interrupts that cycle, which may be another way of describing the well-established modern finding that poor sleep undermines immune function.
Robert, who had barely slept well since his wife died, was a textbook case: digestion dulled by grief, deep reserves drawn down, and defensive energy unable to replenish itself night after night.
The way to rebuild vitality, in TCM terms, is straightforward: strengthen digestion with warm, easily digested foods; protect sleep in which defensive energy is rebuilt; and work with a trained practitioner for acupuncture and immune-supporting herbs. These are not substitutes for the anatomical and chemical work, but the energetic complement to it.
Can the Spirit Fight Back?
Few of the body’s systems respond to the state of the spirit as directly as the immune system. TCM principle plainly states: a person worn down by grief becomes easy prey for illness. In other words, prolonged grief weakens the defenses.
When I finally asked him about his grief, the fuller picture emerged. He had stopped cooking, because cooking had been something he and his wife did together. He had pulled back from his friends. He slept in a chair rather than the bed they had shared. He was, in the truest sense, undefended—his sorrow scattering his protective energy, as TCM would put it, and his isolation suppressing his immune cells, as modern research would describe it.
The same pathways that allow grief to weaken immunity also let connection and purpose strengthen it. What I coached Robert toward was less a prescription than a re-entry into life.
We restored his sleep first, because little else works without it. We rebuilt his meals—which meant cooking again—and treated each meal as both nourishment and a small daily refusal of despair. We found concrete reasons to be among people: a standing weekly dinner with his golf partners, a return to the club, a regular volunteer shift.
Finally, we named the grief directly, rather than letting it run beneath everything. Over the following year his infections grew less frequent, and part of his spirit was restored.
Reading the Immune System as One Story
Robert’s internist was correct in that his immune system was aging. However, the definitiveness of that conclusion missed what made it fixable. His anatomy showed an army thinned by time. His chemistry showed the slow fire of inflammation burning hotter than it should.
His energy revealed a defensive vitality drained by grief and broken sleep—and his soul uncovered the force beneath it all: a profound loss, actively suppressing his defenses through pathways science can now reinvigorate.
Had we treated only Robert’s infections, with one antibiotic after another, we would have been fighting the smoke while the fire burned on. The ACES model insists on reading all four dimensions as a whole because, in the immune system, they feed each other: Grief raises inflammation, inflammation ages immune cells, broken sleep starves defensive energy, and each turn of the wheel drives the next. Working across all four together is what finally broke the cycle for Robert.
The immune system ages. That much is true for all of us. But it is not deaf to the life we are living, and it is not beyond repair. The spirit can indeed fight back; and when it does, the body’s oldest army comes to life.
Lidan Du-Skabrin, who holds a doctorate in nutrition, contributed to this article.
