Put simply, your immune system defends your body against illness and disease. This complex system comprises the skin cells, blood, bone marrow, tissues, and organs that — when working the way they should — protect your body against potentially harmful pathogens (like bacteria and viruses), and limit damage from noninfectious agents (like sunburn or cancer), according to the National Institutes of Health (NIH).

Think of the immune system as an orchestra. For the best performance, you want every instrument and every musician in the orchestra to perform at their best. You don’t necessarily want one musician to perform at double speed or one instrument to suddenly produce sound at twice the volume it usually does. You want every part to perform exactly according to the score.

The same goes for your immune system. To best protect your body from harm, every component of your immune system needs to perform exactly according to plan. The best way you can ensure this happens is to practice the good-for-you behaviors your immune system runs on every day. Here are seven key ones.

1. Incorporate Physical Activity Each Day

Regular exercise lowers your risk of developing chronic diseases (like obesity, type 2 diabetes, and heart disease), as well as viral and bacterial infections, according to a review published in the April 2018 Frontiers in Immunology.

Physical activity increases the release of endorphins (a group of hormones that reduce pain and create feelings of pleasure), making it a great way to manage stress. “Since stress negatively impacts our immune system, this is another way exercise can improve immune response,” says Yufang Lin, MD, an integrative medicine doctor at Cleveland Clinic in Ohio.

And while there is some evidence that very long or intense exercise sessions may suppress the immune system, making you more susceptible to illness and infection in the hours immediately after your workout, other evidence contradicts this, according to the aforementioned Frontiers in Immunology review. And there is a wealth of epidemiological evidence — that is, studies that followed human behavior and outcomes — suggesting that people who are more active overall tend to have lower incidences of both acute illnesses (like infections) and chronic ones (like cancer and type 2 diabetes). Studies that have looked at how exercise affects the body on a cellular level suggest that bouts of physical activity may make your immune system more vigilant by distributing immune cells throughout your body to look for damaged or infected cells, according to that 2018 report.

At a minimum, try to meet the physical activity guidelines outlined by the Centers for Disease Control and Prevention (CDC). Adults should be getting at least 150 minutes (two and a half hours) of moderate-intensity aerobic exercise — like walking, jogging, or cycling — or 75 minutes (one hour and 15 minutes), of high-intensity aerobic exercise (like running) every week.

And while taking 10,000 steps (about five miles) per day is a common goal, research suggests you may see health benefits with even fewer steps. For instance, one observational study published in the March 2020 issue of the Journal of the American Medical Association found that a greater number of daily steps was associated with a lower risk of premature death from any cause. Of the nearly 5,000 adults ages 40 and older included in the study, those who walked about 8,000 steps per day were half as likely to die prematurely as adults who scored 4,000 steps a day. Those who took 12,000 steps daily saw slightly more benefits, though researchers concluded increasing step count, regardless of step intensity, was beneficial for lengthening your life span.

Strength training at least twice a week is also a boon to your health, fortifying your bones, keeping disease at bay, and improving food processing in the body, per the National Institutes of Health. Authors of a review published in July 2020 in Clinical and Experimental Medicine recommend exercise, including muscle building, to strengthen the immune system and potentially protect against viral infections such as COVID-19.

For even more immune system benefits, take your exercise outside, recommends Ben Kaplan, MD, an internal medicine physician at Orlando Health Medical Group Internal Medicine in Florida. Dr. Lin says that time in nature has been shown to support mood, lower blood pressure, reduce inflammation, and support immune system health. According to a Frontiers in Psychology article published in August 2015, natural environments contain compounds with known health benefits. For example, many plants emit antimicrobial molecules, such as those formed in the metabolism of fungi and bacteria, that may help lower blood pressure and support immune function. The absence of air pollution may also reduce your risk of heart inflammation, such as myocarditis, and respiratory conditions, the authors wrote. What’s more, the sights and sounds of nature have been shown to activate the parasympathetic, often referred to as the “rest and digest” side, of the autonomic nervous system, which plays a key role in immune health.

Sunshine also boosts vitamin D in the body, another huge factor in immune health, according to a past review.

2. Reach for Nutritious Foods and Stay Hydrated

The nutrients you get from food — in particular, plant-based foods like fruits, vegetables, herbs, and spices — are essential to keeping your immune system functioning properly, says Lin. “Many plant-based foods also have antiviral and antimicrobial properties, which help us fight off infection,” adds Lin.

For example, spices like clove, oregano, thyme, cinnamon, and cumin curb the growth of food-spoiling bacteria like Bacillus subtilis and Pseudomonas fluorescens, harmful fungi like Aspergillus flavus, and antibiotic-resistant microorganisms like Staphylococcus aureus, according to a review published in June 2017 in the International Journal of Molecular Sciences.

Furthermore, the zinc, folate, iron, selenium, copper, and vitamins A, C, E, B6, and B12 you get from the food you eat are the nutrients your immune system needs to do its job, according to the Academy of Nutrition and Dietetics. Each one plays a unique role in supporting immune function.

Research suggests, for example, that vitamin C deficiency may increase the likelihood of infection, according to a review published November 2017 in Nutrients. Our bodies do not produce this essential water-soluble vitamin on their own, so we need to get it through foods (such as citrus fruits, kiwis, and several cruciferous vegetables). You can get 95 milligrams (mg) of vitamin C, an excellent amount of the nutrient, from ½ cup of raw red pepper, according to the NIH.

Protein is also critical for immune health. The amino acids in this macronutrient help build and maintain immune cells, and skimping on it may lower your body’s ability to fight infections. The Harvard T.H. Chan School of Public Health recommends getting your protein from plant sources like legumes, nuts, and seeds whenever possible. Meats like poultry (chicken, turkey, and duck) and seafood are also good choices, but consume red meat, like unprocessed beef, pork, and lamb, only on a limited basis, the website recommends. Avoid processed meats like bacon, hot dogs, sausages, and cold cuts.

In one study published in the Journal of Infectious Diseases, mice who ate a diet consisting of only 2 percent protein were more severely impacted by the flu than mice who ate a "normal protein" diet with 18 percent protein. But once researchers started feeding the first group a "normal protein" diet, the mice were able to get rid of the virus. More studies in humans are needed.

When it comes to a diet that supports good immune health, focus on incorporating more plants and plant-based foods. Add fruits and veggies to soups and stews, smoothies, and salads, or eat them as snacks, Lin says. Carrots, broccoli, spinach, red bell peppers, apricots, citrus fruits (oranges, grapefruit, tangerines), and strawberries are all great sources of vitamins A and C, while seeds and nuts provide protein, vitamin E, and zinc, according to the Academy of Nutrition and Dietetics. Some of these eats are so-called superfoods.

Additional sources of protein and zinc include seafood, lean meat, and poultry, according to the Academy of Nutrition and Dietetics.

Last, hydrate with healthy fluids such as water, and limit dehydrating, immune-suppressive beverages like sugary drinks and alcohol (more on the latter later). “Dehydration can negatively affect your health and hinder your physical performance, focus, mood, and heart and kidney function. These complications can increase your susceptibility to illness,” says Vivek Cherian, MD, an internal medicine physician affiliated with the University of Maryland Medical System in Baltimore. Meanwhile, sugar-laden beverages suppress your immune system — particularly the white blood cells that attack harmful bacteria — for several hours, says Dr. Cherian.

This notion is based on a research study from 1973 in which adults donated blood after ingesting 100 grams (g) of simple carbohydrates (from glucose, fructose, honey, or orange juice). Researchers then added Staphylococcus epidermis, a bacteria that can cause skin infections, to the blood and observed how white blood cells responded. They found that ingestion of simple sugars significantly decreased the ability of the white blood cells to engulf and kill the bacteria. These effects lasted at least five hours. Unfortunately, this study has yet to be repeated with more modern techniques, according to the authors of a past review.

3. Get Plenty of Restorative Sleep

Your body heals and regenerates while you sleep, making adequate sleep critical for a healthy immune response, Lin says.

More specifically, sleep is a time when your body regulates key immune cells and molecules like cytokines (a type of protein that can either fight or promote inflammation), T cells (a type of white blood cell that regulates immune response), and interleukin 12 (a pro-inflammatory cytokine), according to a review published in Pflugers Archiv European Journal of Physiology. “Getting adequate rest may strengthen your body’s natural immunity,” Cherian says.

When you don’t get enough sleep, your immune system may not do these things as well, making it less able to defend your body against harmful invaders and making you more likely to get sick. One study published in the July–August 2017 issue of published in the July–August 2017 issue of Behavioral Sleep Medicine found that compared with healthy young adults who did not have sleep problems, otherwise healthy young adults with insomnia were more susceptible to the flu even after getting vaccinated.

Sleep deprivation also elevates cortisol levels, which of course is also not good for immune function, Lin says. “Our immune system wears down as a result, and we tend to have [fewer] reserves to fight off or recover from illness.”

The National Sleep Foundation recommends all adults get between seven and nine hours of sleep per night to optimize health. To ensure you get quality sleep, prioritize good sleep hygiene: Turn off the electronics at least two to three hours before bed, and avoid violent or stressful books or conversations, Lin says.

4. Strive for Mental Balance

According to a review published in the October 2015 issue of Current Opinion in Psychology, long-term stress leads to chronically elevated levels of as the steroid hormone cortisol. The body relies on hormones like cortisol during short-term bouts of stress (when your body goes into “fight-or-flight” response); cortisol has a beneficial effect of actually preventing the immune system from responding before the stressful event is over (so your body can react to the immediate stressor). But when cortisol levels are constantly high, it essentially blocks the immune system from kicking into gear and doing its job to protect the body against potential threats from germs like viruses and bacteria.

There are many effective stress-reduction techniques; the key is to find what works for you. “I like to give my patients options,” says Dr. Kaplan.

He recommends meditation (apps like Headspace and Calm can help), journaling, and any activity that you enjoy (such as fishing, playing golf, or drawing).

Similarly, opportunities to laugh may lower overall stress, making you less susceptible to illness in the long run, Cherian notes. A past article reveals that laughing may improve natural killer (NK) cell activity, albeit temporarily. NK cells belong to the same family as T and B cells; they play the important role of killing cells infected with virus, as well as detecting and controlling early signs of cancer, according to the British Society for Immunology. Low NK cell activity is linked to decreased disease resistance.

Try to do at least one stress-reducing activity every day.

Also, don’t underestimate the power of nurturing your relationships. An article in the Journal of Health and Social Behavior describes how social ties may lead to a greater sense of social support, in turn reducing levels of stress hormones.

5. Stay Up-to-Date on Vaccinations

To support your immune system, get regular vaccinations, which bolster your body’s natural defenses against harmful viruses and bacteria.

Without a vaccination, it can take your immune system 10 to 14 days to organize and launch a full-scale attack against those invaders. “And unfortunately, depending on how much you’re exposed to and whether you’re a healthy young person or a more senior person whose immune response is waning, the end of those 14 days can result in you getting infected or staying healthy,” says LJ Tan, PhD, the chief strategy officer for the Immunization Action Coalition (IAC) in Saint Paul, Minnesota, and a former director of infectious disease, immunology, and molecular medicine at the American Medical Association. If you get sick, your immune system will then handle bringing things back under control so you can recover.

Vaccines shorten that two-week waiting period by letting your immune system engage with a piece of that virus or bacteria. “We introduce it to your immune system in a very controlled manner, such that it cannot cause infection,” Dr. Tan says.

“Once your immune system has gone through this initial stimulation, it generates memory immune cells that have seen the enemy and are ready to go when they see the enemy again,” he continues. The official term for this phenomenon is the “anamnestic response.” An article published in June 2021 in the journal Nature found that participants who had not previously been infected with COVID-19 showed a surprisingly high number of memory cells designed to target the virus 12 weeks after their second COVID-19 mRNA vaccination. Thanks to the presence of memory cells, it takes your immune system only a couple of days to generate the antibodies needed to prevent that virus from reproducing and making you sick, Tan says. In other words, COVID-19 vaccinations are safe and effective, and produce immune-protective responses in those who get vaccinated.

In general, memory immune cells eventually die off, and protective antibodies decline over time. With some infectious diseases, you have to reintroduce your body to pathogens with regular vaccination, such as with a booster, to keep your immune system responsive. How often you require a booster will vary depending on the pathogen — for example, the U.S. Food and Drug Administration (FDA) recommends a flu shot every year — so be sure to touch base with your physician. At this time, COVID-19 vaccine boosters are recommended for specific groups of the population, per the FDA.

While vaccines are safe and effective for most people, Tan advises some individuals to consult their healthcare teams prior to inoculation. That includes people who are immunocompromised because of treatments like chemotherapy and anyone with a history of allergic reactions to vaccines.

6. Make Conscious Hygiene Part of Your Routine

Personal hygiene may not directly improve immune system health, but basic habits like washing your hands, using hand sanitizer, wearing a mask, and self-isolating when you do get sick can prevent the spread of germs. “We have this incredible immune system that helps us stay healthy, but if we can avoid challenging that immune system, we’re going to stay healthier in general,” Tan says. “This way, you can also hopefully reduce your exposure to pathogens that we don’t have vaccines for.”

Wash or sanitize your hands after using the bathroom, before and after shaking hands with others, after coughing or sneezing, and after making contact with high-touch surfaces like countertops and door handles. “I carry a bottle of hand sanitizer with me everywhere, simply because I’m an infection control expert and I know what the benefits are,” Tan says. According to a review published July 2020 in the Journal of Advanced Oral Research, hand sanitizers that contain at least 60 percent alcohol can be just as effective for killing germs as washing your hands with soap and water. In fact, classrooms that use hand sanitizers may reduce the frequency of absenteeism by 20 percent. Yet soap and water are a better option if your hands are greasy or visibly dirty.

While mask restrictions have loosened in many areas, Tan encourages everyone to wear face masks in public spaces — especially during cold and flu season. “If you’re inside a crowded indoor place where you’re in close contact with someone else, you should be wearing a mask. And if everyone else in that room were wearing a mask, we would really reduce the opportunity for germs to spread, and everyone will be healthier as a result,” he says. According to a study of face mask materials published June 2020 in Physics of Fluids, a stitched face mask made of quilting cotton (70 threads per inch) was the most effective at preventing the spread of droplets, or respiratory particles that could contain a virus.

Cover your nose and mouth when you cough or sneeze so you don’t spread your droplets to people around you. Stay home if you do get sick to prevent spreading your germs to others.

7. Avoid Toxins Like Alcohol and Cigarettes

To optimize your immune system, limit or avoid alcohol, and stop smoking if this is a current habit.

High alcohol consumption is associated with a range of negative health effects, including lowered immune function. When you drink to excess, your body is too busy trying to detoxify your system to bother with normal immune system function, Kaplan explains.

According to a review published in February 2017 in Progress in Neuro-Psychopharmacology & Biological Psychiatry, chronic heavy alcohol use can lower levels of B cells and T cells in your body, thereby weakening your ability to fight infection and slowing your recovery time. As a result, people who drink heavily face a greater likelihood of pneumonia, acute respiratory distress syndrome, alcoholic liver disease, and certain cancers, according to a review from 2015 in Alcohol Research.

If you don’t already drink, don’t start. If you drink occasionally, limit your alcohol consumption to one drink (equivalent to a 4 ounce glass of wine) per day if you’re a woman, and two drinks per day if you’re a man, as the CDC recommends.

Like alcohol, cigarette smoking can affect immune health. “Anything that’s a toxin can compromise your immune system,” Kaplan says.

In particular, the chemicals released by cigarette smoke — carbon monoxide, nicotine, nitrogen oxides, and cadmium — can interfere with growth and function of immune cells, like cytokines, T cells, and B cells, according to a review in Oncotarget from November 2016.

Smoking also worsens viral and bacterial infections (especially those of the lungs, like pneumonia, flu, and tuberculosis), postsurgical infections, and rheumatoid arthritis (an autoimmune disease in which the immune system attacks the joints), according to the CDC.

“Don’t smoke,” Lin says. And avoid secondhand smoke whenever possible.

If you currently smoke, there are many resources available to help you kick your habit, including counseling, nicotine replacement products, prescription non-nicotine medications, and behavioral therapy, says the CDC.

8. Keep Symptoms of Chronic Conditions Well Managed

Chronic conditions like asthma, heart disease, and diabetes can affect the immune system and increase your risk of infections.

For example, when people with type 2 diabetes don’t manage their blood sugar properly, a chronic, low-grade inflammatory response can ensue that weakens the body’s defense system, according to a review published in October 2019 in Current Diabetes Reviews.

Similarly, people with asthma are more susceptible to catching — and even dying from — the flu, and often experience worse flu and asthma symptoms as a result of the infection, per a study published in the July 2017 issue of the Journal of Allergy and Clinical Immunology.

Living with a chronic condition can be like trying to drive a car that has only three tires, Kaplan says. “If you get sick with a virus, it’s going to take more effort for your body to recover,” he explains.

If you manage your chronic conditions better, you'll free up more reserves to help your body fight off infection, Lin says. So be sure to stay on top of any medications, doctor visits, and healthy habits that keep your symptoms at bay. Your immune system will thank you.

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