To understand how your habits can boost your immune functioning, know that there are two basic types of immunity in the body: innate and acquired. The innate immune system is your body’s first line of defense. “When an infectious agent, such as a bacteria or virus, attempts to invade your body, it immediately confronts the innate immune system, which has several components, each of which acts to restrict access to the body,” Dr. Schachter says.
The first component involves physical barriers, like the skin and respiratory tract. While the skin is almost impenetrable, the respiratory tract is covered by mucus secretions, which trap infectious agents. But if the air you’re breathing is dry, the lack of moisture can dry out those secretions and help viruses and bacteria gain a foothold.
The second line of defense consists of chemical factors like enzymes that help the body destroy invaders. Alongside those enzymes are specialized white blood cells called phagocytes—what Dr. Schachter calls “the workhorse of the defense system”—which devour unwanted bacteria and viruses.
If these first-line defenses of the innate immune system fail, however, the acquired immune system activates, and it calls up several white blood cells to accomplish its mission.
This is where lifestyle habits become critical. “Lifestyle choices play an important role in the function of these essential white blood cells, including macrophages, T and B lymphocytes, and natural killer (NK) cells,” he explains.
So how can you improve your immunity to protect and encourage these natural defenses? Here are the seven lifelong habits to adopt for a killer immune system.
1- Long Sleep
Sleep is critical for your brain, your heart, and, yes, your immune system, so it’s imperative to get the sleep you need, which is generally seven to eight hours a night for the average adult.
Without adequate sleep, your NK cells decline, and you get a rise in what’s called inflammatory cytokines that contribute to numerous health issues like rheumatoid arthritis and Crohn’s disease, Dr. Schacther says.
Along with following good sleep hygiene habits, like keeping the room cool and dark and being consistent with your sleep and wake times, look to modify two factors that can negatively impact sleep: caffeine consumption and GERD, or reflux.
First, limit caffeine consumption by switching to decaffeinated versions of tea and coffee (which still have some caffeine), and sipping no more than one cup of decaf coffee or two cups of decaf tea no later than 2 p.m. If you do have reflux, limit alcohol, spicy foods, sodas, and large meals, especially at night.
2- Eat Plant Diet
You really are what you eat—and if you nosh on a high number of plant-based foods, you’ll be fueling your body with the nutrients your immune system needs, including vitamin B12, calcium, iron, zinc, and iodine.
You can find an abundance of all these nutrients in whole-food, plant-focused eating plans like the Mediterranean and DASH diets, even a vegan diet, as long as it’s well planned, Dr. Schachter says.
But you don’t need to overhaul your diet completely (and go straight vegan), as long as you make sure you’re getting enough of the right nutrients for a strong immune system. If you’re struggling to eat the vitamins and minerals you need, talk to your doctor and consider taking a daily multivitamin with vitamins C, D, and E, recommends Robert G. Lahita, MD, PhD, director of the Institute for Autoimmune and Rheumatic Disease at St. Joseph’s Health in Wayne, N.J., and author of Immunity Strong.
3- Exercise Regularly
You know you need to exercise regularly, and if there were ever motivation to move, let this be it: “Killer T cells (immune cells) in your body increase when you exercise,” Dr. Lahita says. That’s right, a solid sweat session directly benefits your immune system. Regular moderate exercise may even help increase vaccine efficacy, as studies on flu vaccination have shown.
But here’s a catch: Excessive exercise isn’t the answer. “Adults who exercise more than 90 minutes a day three to four times a week have depressed immune profiles,” Dr. Schachter says.
4- Take Daily Stress Break
It’s impossible to be alive and not experience stress, but we all need to find ways to manage it. Give yourself daily time-outs from stress. “While studies show that life events such as relationship problems, divorce, career problems, and job loss can depress levels of NK and T cells, thus lowering immunity, even routine daily stressors such as deadlines, traffic jams, and long Starbucks lines can cause changes in immunity,” Dr. Schachter says.
You can’t avoid stress, but you can at least improve your coping mechanisms, which is why he recommends taking a time-out at least once a day to give your immune system a break and regain equilibrium. Spend 30 minutes every day doing something you enjoy, whether that’s reading, meditating, doing yoga, taking a walk, or meeting friends to talk.
5- Don’t Drink Too Much Alcohol
Know your limits: Excessive alcohol consumption is a downer for your immune system, Dr. Lakita confirms. But you don’t have to cut it out altogether, as a glass of wine three to five times a week has been linked to improved resistance to infectious disease, according to Dr. Schachter.
What’s more, studies show that people who abstain from alcohol have a lower immune profile than people who drink in moderation, he adds.
6- Maintain a Healthy Weight for Your Body Type
Weight isn’t just a trigger for chronic health conditions—it can also lower your immune functioning. “Studies have shown that people who meet the definition of obese (body mass index higher than 25) have lowered levels of lymphocytes and NK cells (which can then lower immune functioning),” Dr. Schachter explains. Fortunately, though, research has shown that when individuals who have obesity lose a healthy amount of weight, their immune function actually improves.
7- Quit Smoking
There are a million reasons not to smoke, and keeping your immune system strong is absolutely one of them. “When you smoke, mucus builds up in the airways and offers bacteria a wonderful breeding ground to multiply,” Dr. Schachter says, adding that not only are respiratory infections more frequent in smokers, but they also tend to be more severe and last longer.