It sounds like the plot of a horror film, but you have a little bit of zombie inside you — in some of your cells, to be specific. And while they’re not eating your flesh, so-called zombie cells are still wreaking havoc on your body and causing changes that can shorten your healthspan and lifespan.
Zombie cells—aka senescent cells—are cells that don’t functioning properly, but they’re not dead, either. Instead, they hang out in your body and secrete compounds that affect the cells around them, with deleterious effects: Recent research in Nature Structural & Molecular Biology links them to age-related diseases like cancer, dementia, and heart disease (1).
While this may be the first time you’ve heard of zombie cells, they’ve been on longevity scientists’ radar for years.
Zombie cells were discovered by a group of scientists who were trying to figure out why some cells become cancerous and others don’t, explains family medicine doctor Jim Staheli, D.O. The researchers found that when they suppressed a certain gene in mice, their tumors disappeared (2).
The downside? “The mice had aged dramatically,” says Staheli. “They had thinning hair, cataracts, had lost weight, developed heart disease, and many of them died at a much earlier age than what they should have.” During an autopsy of the mice, researchers found a large number of zombie cells.
So what exactly are zombie cells, how do they impact aging, and how can you protect yourself from their undead wrath? Let’s dive in.
What Are Zombie Cells?
Cells die all the time. As they prepare to meet their maker, they divide to create two new identical cells through a process called mitosis.
But zombie cells don’t follow these rules. Instead, they go rogue and stop dividing, according to the National Institutes of Health.
“In a senescent cell, something occurs to halt that process,” Staheli says. “The result of it is you get this cell that’s just kind of sitting out there.”
What Do Zombie Cells Do?
Zombie cells do have some benefits. They’re thought to promote wound healing, help in the repair of broken bones, and even suppress some tumor growth (3).
But the benefits are far outweighed by the negative impacts.
As zombie cells linger in your body, they signal other cells to increase inflammation. That inflammation can lead to a host of diseases including neurodegenerative diseases such as Alzheimer’s or Parkinson’s, as well as cardiovascular disease, cancer, and arthritis. Researchers have found senescent cells accumulate in fat tissue in both humans and rodents and may be linked to the development of diabetes (3).
“It doesn’t take much,” Staheli says. “Science shows that one senescent cell out of 7,000 to 15,000 healthy cells can initiate this degenerative aging process.”
How Are Zombie Cells Related to Aging?
When you’re younger, your immune system is pretty good at clearing out zombie cells. But as you age, it becomes less efficient and effective at removing them.
But your body is also more likely to create new zombie cells as you age. One reason: telomere shortening, Staheli says. Telomeres are protective caps at the ends of chromosomes. As cells divide more and more as you age, your telomeres get a little shorter. After about 40 to 60 rounds, they shorten to the point where the cell can’t divide anymore, and the cell dies. This phenomenon is known as the Hayflick limit.
Environmental damage can speed up this process. Exposure to harmful free radicals from environmental pollution or UV rays can cause oxidative stress, and recent research has found oxidative stress can damage telomeres (1).
Oncogenic stress may be responsible, as well, Staheli says, when normal cell activity is disrupted by the start of what’s known as the cancer cascade: an acceleration of the replication process that promotes the growth of tumors.
There’s more, he adds: mitochondrial dysfunction, the accumulation of excess metals in the body, and elevated blood sugars—all of which are more likely with age—can also contribute to cell damage and stop cells from reproducing.
Could Zombie Cells Hold the Key to Healthy Aging?
It looks that way. Scientists studying senescent cells in mice found when they eliminated about 30% of the senescent cells, they extended the mice’s lifespan by between 17 and 42%. They also delayed tumor growth and reduced inflammation.
“Unlike cancer, in which a single remaining cell can spark a new tumor, there’s no need to kill every senescent cell in a tissue,” Staheli says. “Mouse studies suggest dispatching most of them is enough to make a difference.”
Can We Kill Zombie Cells?
We can’t pop a pill and blast zombie cells into oblivion yet— but the time is coming.
Currently, lots of drugs are in clinical trials to study their efficacy and safety. One class of drugs called senolytics remove zombie cells and shows particular promise for treating age-related conditions and degeneration. Early clinicals trials in humans found senolytics effectively reduced the number of senescent cells, reduced inflammation, and alleviated frailty (4).
“So far, each senolytic kills a particular flavor of senescent cell,” Staheli says. “Targeting the different diseases of aging, therefore, will require multiple types of senolytics.”
Ok, So What Do I Do in the Meantime?
For now, the best strategy is preventing the formation of zombie cells to begin with. The good news is a lot of the lifestyle and dietary recommendations you’ve already heard are some of the best ways to protect our cells. Here’s what Staheli recommends:
- Get plenty of sleep. (Seven to eight hours a night is the goal.)
- To mitigate inflammation and promote cell health, maintain a healthy diet, with an emphasis on plant-based, antioxidant-rich foods: fruits, vegetables, legumes, and whole grains.
- Avoid inflammatory foods, such as dairy, processed foods, and sugar-filled sweets.
- Exercise about 150 minutes per week, including three days of resistance training and three days of yoga or other flexibility training.
- Practice stress-reduction techniques like breath work, since both acute and chronic stress are linked to increased inflammation.