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Preventative Health & Wellness

Reviewed 9/27/22

Boosting Your Immune System

Scientists recognize that a healthy immune system fights infection. As we age, our immune response is reduced, which makes our bodies more susceptible to cancer and infections. Respiratory infections such as COVID-19 virus, the flu, and pneumonia are a leading cause of death in people over 65 years of age. In addition, people who are malnourished are more susceptible to infectious diseases, and those who don’t get enough healthy food with micronutrients, have poor absorption, or a lack of variety in their diet may also be more vulnerable to infections due to weaker immune systems.

These evidence-based methods help boost the immune system:

  • Get balanced nutrition (with recommended allowances of vitamins and supplements)
  • Keep your gut (digestive tract) healthy
  • Exercise regularly
  • Maintain a healthy weight
  • Get enough sleep
  • Minimize stress
  • Drink alcohol only in moderation
  • Don't abuse drugs or smoke
  • Keep hands clean to avoid germs and infection


How Does Nutrition Help Boost the Immune System?

Studies show that getting proper nutrition and eating foods rich in nutrients and antioxidants protect against chronic oxidative stress-related diseases and reduce inflammation in the body. Maintaining gut (digestive tract) health is also important for overall health and supporting your immune system. Bacteria in your gut not only helps you digest foods but it also works throughout your body to keep you healthy. An array of gut bacteria and other microbes - called flora or microbiota - aid in regulating body weight, reducing inflammation, and fighting diseases and illnesses such as type 2 diabetes, rheumatoid arthritis, allergies, asthma, and other respiratory conditions. Studies have shown that taking certain oral vitamins and supplements can also help boost your immune system and reduce respiratory infections.

For example, although more research is needed, studies have linked vitamin D deficiencies with autoimmune diseases such as type 1 diabetes and multiple sclerosis (MS), and respiratory infections such as the flu and tuberculosis. People at risk for vitamin D deficiency are older, do not get sun, have dark skin, have problems absorbing fat, and are taking certain medications.

A study released in April 2022 found that a concentration of vitamin D in the body was associated with a lower risk of COVID-19 infection. In the same study, a high intake of vitamin D from supplements was associated with a lower risk of hospitalization from COVID-19.

See the next question for more information about vitamin D and other vitamins and supplements.


What Vitamins & Supplements Are Important for a Healthy Immune System?

Vitamin C: Vitamin C supports immune cell function and helps to replace old cells with new ones. Studies have shown that it reduces duration and severity of respiratory infections. The current recommended Daily Value (DV) for vitamin C is 90mg for adults.

Vitamin D: Vitamin D enhances white blood cells and decreases inflammation. Studies have shown that it may improve immune response, and expedite healing and stall inflammation in the respiratory system. The current recommended Daily Value (DV) is 600 IU (15mcg) for adults, and 800 IU (20mcg) for adults over 70.

Zinc: Zinc helps the immune system's ability to function properly and may protect against respiratory infections. Studies have shown that it influences antiviral immunity. The current recommended Daily Value (DV) is 11mg for adults.

Quercetin: Quercetin is a natural bioflavonoid polyphenol. Research shows that it has anti-inflammatory and anti-oxidant properties. Used with zinc, polyphenols such as Quercetin, have the potential to transport zinc (as an ionophore) into cell membranes, making zinc more effective. The current recommended allowance is 500mg daily for adults.

Elderberry: Elderberry has been shown to enhance immune system response and may help shorten the duration and severity of respiratory symptoms caused by viral infections. Elderberry should be used only under the direction of a healthcare professional as it could potentially have health risks.

Note: Some vitamins and supplements may interact with medications. Consult with your doctor about whether you should include certain vitamins and supplements in your diet.


What Foods Contain Vitamins & Supplements for a Healthy Immune System?

The following foods contain higher levels of the following vitamins and supplements:

Vitamin C: Bell peppers (red, green), chili peppers, kiwifruit, broccoli, strawberries, Brussels sprouts, citrus fruit (lemons, oranges, grapefruit, orange juice), papaya, pineapple, mango, cantaloupe, cauliflower, tomatoes, sweet potatoes, snow peas, raspberries, blackberries, kale, spinach, and blueberries.

Vitamin D: Few foods are naturally rich in vitamin D. The best sources are fatty fish such as salmon, sardines, herring, canned tuna, and cod liver oil. Wild mushrooms contain vitamin D2, which may not be as effective as vitamin D3. Many foods are fortified with vitamin D including dairy products (yogurt), orange juice, and cereals.

Zinc: Red meat, shellfish (oysters, crab, shrimp, lobster), legumes (baked beans, chickpeas, lentils), seeds (hemp, squash, pumpkin, sesame), Swiss cheese, cashew nuts, eggs, and whole grains. Some foods such as cereals are fortified with zinc.

Quercetin: Red wine, green or black tea, onions, parsley, capers, green or yellow peppers, asparagus, kale, broccoli, red leaf lettuce, cherries, red apples, red grapes, cranberries, and raspberries.

Note: These are not complete lists. Some foods may interact with medications. If you take medications, consult with your doctor about whether you should include certain foods in your diet.

How Can I Keep My Gut Healthy to Support My Immune System?

A number of internal and external factors can affect your digestive track or gut health. Your genetics, internalizing stress, and the food you put into your body all play a role. Eating a diet rich in fiber, "prebiotics," and "probiotics" promote a well-balanced digestive system and help the body absorb nutrients.

What to Eat: Eat a wide variety of vegetables in a rainbow of colors such as broccoli, zucchini, cabbage, cauliflower, carrots, brown or red potatoes, peas, collard greens, kale, radish, bok choy, arugula, and Brussels sprouts. Fruits are also beneficial for gut health including bananas, blueberries, kiwis, apples, raspberries and pears. Garlic, onions, artichokes, leeks, asparagus, whole grains, and oats are high in fructan which act as "prebiotics" to promote the production of good bacteria. Coffee, and black or green tea also increase the bacteria in the inner lining of the intestines. Fermented foods are natural "probiotics" which help improve absorption of minerals and increase good bacteria. These include yogurt, some raw cheeses (cheddar, feta, gruyere, Parmesan, Gouda), chickpeas, pickles, sauerkraut, salsa, kefir, miso, sourdough bread and other naturally fermented breads without the use of packaged yeast. Research also suggests that herbs and spices such as ginger, turmeric, cumin, fennel, coriander, cinnamon, cayenne pepper, rosemary, and oregano provide digestive or overall gut health benefits.

What to Reduce or Avoid: Emulsifiers and artificial ingredients can break the protective mucus layer where good microbiota are, causing inflammation and other problems. Some foods to avoid or cut back on include processed meats (sausage, pepperoni, hot dogs, bacon, ham), refined grains (white bread, bagels, white rice, noodles), processed cheeses (sliced singles), pre-flavored packaged foods (microwave popcorn, flavored nuts), frozen dinners, and other ready-to-eat foods. Watch for labels on foods that contain high-fructose corn syrup (soda drinks, candy bars, ice cream, condiments), as well as artificial sweeteners such as sucralose, aspartame, and saccharin. Also look out for trans fats (fried foods, margarine), processed seed oils (corn, canola, cottonseed, soy, sunflower, safflower, grapeseed), synthetic dyes, and preservatives (potassium bromate, BHA/BHT, sodium nitrite/nitrate, monosodium glutamate (MSG), sodium benzoate).

Note: These are not complete lists. Consult with your doctor about foods in your diet. If you have stress or anxiety see more information below in the What Are Ways to Prevent and Treat Stress section.


How Does Exercise Help Boost the Immune System?

Physical activity improves health-aerobic activity and muscle strength. It can reduce stress and depression, sharpen focus, and improve sleep. Over time, it can help with living a longer, healthier life by lowering risk of diseases such as heart disease, type 2 diabetes and some cancers. It may also help control blood pressure, keep a healthy weight, decrease pain, and improve function in people with osteoarthritis.

In addition, studies show that physical activity has anti-inflammatory benefits, stimulating the immune system and producing an anti-inflammatory cellular response. It is believed that exercise causes antibodies and white blood cells to circulate more rapidly to detect and fight disease earlier. It may also help flush bacteria out of the lungs and airways, which may reduce respiratory infections, and the brief rise in body temperature during and right after exercise may prevent bacteria from growing.

Recent findings from a CDC review found that physical activity is associated with a decrease in COVID-19 hospitalizations and deaths, while inactivity increases that risk.


What Type of Exercise and How Much Is Needed?

The Centers for Disease Control (CDC) provides the following exercise guidelines for various age groups, conditions, and disabilities. Your doctor may also suggest certain types of exercise or safety tips based on the specific needs of you and your children.

Children (3-5 years): Physical activity every day throughout the day. Active play with a variety of activities.

Children & Adolescents (6-17 years): 60 minutes or more of moderate-to-vigorous physical activity daily, with a variety. On at least 3 days a week, the 60 minutes should include vigorous activity such as running or soccer; activity that strengthens muscles such as climbing or push ups; and activity that strengthens the bones such as gymnastics or jumping rope.

Adults (18-64 years): At least 150 minutes a week of moderate-intensity activity that gets the heart beating faster and keeps lungs healthy such as brisk walking, bicycling, swimming, playing ball, light gardening, or dancing. The activity doesn't need to be all at once and can be spread out throughout the week. At least 2 days each week activities should strengthen the major muscles (legs, hips, back, chest, abdomen, shoulders, arms). Muscle strengthening may include lifting weights, working with resistance bands, exercises using body weight resistance (push-ups, sit-ups), heavy gardening (digging, shoveling), or some forms of yoga.

Older Adults (65 years and older): At least 150 minutes a week of moderate-intensity activity that gets the heart beating faster and keeps lungs healthy including aerobic, muscle-strengthening, and balance training. The activity doesn't need to be all at once and can be spread out throughout the week. Aerobic activity may include brisk walking, hiking, bicycling, swimming, water aerobics, light gardening, dancing, or yard work such as raking or mowing. At least 2 days each week activities should strengthen the major muscles (legs, hips, back, chest, abdomen, shoulders, arms). Muscle strengthening may include lifting weights, working with resistance bands, exercises using body weight resistance (push-ups, sit-ups), heavy gardening (digging, shoveling), or some forms of yoga.

Adults with Chronic Conditions and Disabilities: At least 150 minutes a week of moderate-intensity activity that gets the heart beating faster and keeps lungs healthy such as walking, bicycling, swimming, water aerobics, or wheelchair rolling. The activity doesn't need to be all at once and can be spread out throughout the week. At least 2 days each week activities should strengthen the major muscles (legs, hips, back, chest, abdomen, shoulders, arms). Muscle strengthening may include using handheld weights, weight machines, some yoga postures, and working with exercise bands.

Healthy Pregnant or Postpartum Women: Unless there is a medical reason to avoid physical activity during or after pregnancy, women can begin or continue moderate-intensity aerobic physical activity, such as brisk walking. According to scientific evidence, the risks are very low. However, if you are pregnant, you should be under the care of a doctor who can monitor your pregnancy. Consult your doctor about whether or how to adjust your physical activity during and after your pregnancy.


Why Does a Healthy Weight Help the Immune System?

According to the CDC, a Body Mass Index (BMI) of 18.5 - 25 is considered a healthy weight range, 25 - 30 is overweight, 30 or higher is obese, and 40 or higher is severely obese. Click here to determine your BMI. Any category of obesity is linked to impaired immune function, and increases the risk of severe illness from COVID-19 and other diseases. A recent study shows that excess fat, especially abdominal fat, can trigger production of pro-inflammatory immune cells, which circulate in the blood and promote inflammation in the body. Health conditions associated with obesity and excess weight include type 2 diabetes, coronary heart disease, stroke, gallbladder disease, osteoarthritis, sleep apnea and breathing problems, various cancers, and body pain.


What Are the Best Ways to Maintain or Lose Weight?

Nutrition and exercise are the best ways to control and keep a healthy weight to support the immune system.

It's important to eat foods that are packed with nutrients, including vitamins and supplements for boosting the immune system (see Vitamins sections above). The number of calories needed for maintaining or losing weight varies from person to person, and is related to physical activity, which helps burn calories. If the goal is to prevent weight gain, supply your body with the appropriate number of calories to maintain your weight. If the goal is to lose weight, fad diets are not recommended. Instead, make a commitment for dietary changes and healthy eating habits. Set realistic benchmarks, keep a food diary, and monitor progress. Eating habits, such as chewing slowly and only eating when hungry, can help improve outcomes.

In addition, physical activity provides immediate and long term benefits. The amount of physical activity needed depends partly on whether the goal is to maintain a healthy weight or lose weight (see minimum Exercise requirements in the section above).

Note: Consult your doctor before starting any weight loss program.


Why Is Sleep Important for a Healthy Immune System?

Sleep deprivation has many adverse effects, including damaging the immune system. Without enough sleep, studies show that the body has lower levels of white blood cells and infection-fighting antibodies, making it more susceptible to infections and respiratory diseases. In addition, during sleep, cytokines are released by the immune system to help fight infection and inflammation but without enough sleep, cytokine production is also reduced.


How Much Sleep Is Needed to Stay Healthy?

The amount of sleep needed varies by age. The CDC recommends that adults get at least 7 hours of sleep each night, while people over the age of 60, children, and babies need more sleep. Click here for a bedtime calculator. If you are having difficulty sleeping, there are a number of strategies you can try at home including keeping a consistent and relaxing bedtime routine, getting regular exercise, making your bedroom peaceful and quiet, and limiting or avoiding caffeine, alcohol and tobacco.

Turning off cell phones and other devices 30 minutes before you go to bed is also helpful for your overall health. Our bodies have melatonin, a hormone that regulates and synchronizes our sleep-wake cycle. Darkness activates melatonin production while light from cell phones and other devices stops it. In addition, having a device nearby can stimulate the urge to check messages, respond, read, and post, which can keep you from the rest you need.

Sometimes insomnia is related to anxiety. Relaxation techniques such as meditation, breathing exercises and sleep apps may be helpful in reducing stress and normalizing sleep patterns. More research is needed but some studies have indicated that natural dietary supplements such as melatonin and valerian may also help adults relieve insomnia as an alternative for over-the-counter and prescription sleep medication.

Consult your doctor if you are concerned about a lack of sleep and before trying new remedies. Some remedies may interact with medications, and sleep medications can cause adverse effects or become habit forming.


How Does Stress Affect the Immune System?

We all have stress, whether at home or at work. Sometimes stress is triggered by financial hardship, a demanding boss, a fight with a loved one, or a long commute. Physical symptoms of stress vary but commonly include sleep challenges (fatigue or insomnia), muscle aches, headaches, gastrointestinal issues, and eating problems (weight gain or weight loss). Emotional and behavioral symptoms may include anxiety, anger, depression, sadness, lack of creativity, disinterest, and frustration.

When we have stress, our bodies release powerful neurochemicals and the hormone cortisol. If the stress continues over an extended period time, our bodies will think it is normal and continue to producing high levels of cortisol. Research has shown that chronic stress affects wound healing, antibody responses to vaccines, susceptibility to infectious illnesses, the ability of the immune system to suppress latent viruses, and various inflammatory processes.


What Are Ways to Prevent or Treat Stress?

Everyone handles stress in different ways. Taking care of your body can lower the effects of stress. Getting the right nutrients, exercising regularly, sleeping well, and avoiding excessive alcohol, tobacco and substance abuse are healthy ways to cope with stress.

When you are having difficulty coping, there are a number of self-help techniques that you can try such as inhaling and exhaling slowly, or counting to ten slowly and repeating if necessary. You can also try taking breaks from news stories that may be causing you stress, or spending less time in front of the TV, computer or mobile device. Another option is to do activities or hobbies that help you relax and get your mind off of stressful thoughts. Some people find baking, knitting, writing in a journal, listening to music, creating artwork, bird watching, gardening, playing with a pet, connecting with friends, or volunteering in the community can be helpful for reducing stress. Find something that works for you.

If you are struggling to cope there are many ways to get help and treatment. Contact your doctor if stress gets in the way of your daily activities for several days in a row. Free and confidential resources are also available.

Mental Health Resources:

  • Contact your doctor
  • Call Los Angeles County Department of Mental Health (LACDMH) toll-free at 800.854.7771
    • Press option 1 for the Access Center to get screenings, assessments, referrals to a provider, crisis counseling, and other resources - available 24/7
    • Press option 2 for an emotional support warm line with trained listeners - available 9 am - 9 pm daily
    • Press option 3 for Veterans to connect with Veteran Programs - available 9 am - 9 pm daily
  • Click here for additional information and a list of local and national resources
  • If you are in crisis, call 911 for immediate help


Why Is Alcohol, Drug Abuse and Smoking Harmful to the Immune System?

Research shows that excessive alcohol consumption disrupts immune pathways by impairing the body's ability to defend against infection, contributes to organ damage, impedes recovery from tissue injury, and slows wound healing. As alcohol passes through the gut (digestive track), it damages cells and alters the numbers of good microbiota, which can adversely affect the immune system. Alcohol intake has been linked to systemic inflammation, acute respiratory stress syndrome, viral infection, pulmonary disease, sepsis, alcohol liver disease, and certain cancers.

On the other hand, studies suggest that moderate consumption, may be beneficial to the immune system, with red wine leading the pack with possible "prebiotic" benefits for gut health and protection against heart disease. The CDC defines moderate alcohol consumption as 1 drink or less in a day for women and 2 drinks or less in a day for men. It has issued guidelines for who should not drink any alcohol, which includes women who are pregnant, anyone under the legal drinking age, anyone recovering from an alcohol use disorder, and anyone with certain medical conditions or are taking medications that can interact with alcohol.

Evidence shows that chronic drug abuse has serious health consequences. It can harm or weaken the body, including the immune system, and may make it more vulnerable to infection. Certain types of substances, such as opioids and methamphetamines, may present greater risks for developing diseases and severe illnesses.

According to the CDC's tobacco fact sheet, smoking also harms the immune system and can impair its ability to fight disease. It increases risks for immune and autoimmune disorders such as rheumatoid arthritis and harms nearly every organ of the body. Diseases and conditions that can be worsened by smoking include viral infections, bacterial infections (pneumonia, influenza, tuberculosis), periodontal or gum disease, bacterial meningitis, infections after surgery, Crohn's disease, and cancer.


What Are Ways to Treat Alcohol and Drug Addictions or Kick a Smoking Habit?

The first step to treating an alcohol or drug addiction is to contact your doctor to talk about a treatment plan. Your doctor can refer you to a therapist, counselor, or treatment center that can help you. Another option is to contact the Los Angeles County Department of Public Health (LACDPH) for a free screening, resources, and referrals to services.

While you are recovering from an addiction, it is important to have friends, family, or group therapy to support your treatment goals. Shift your focus to taking care of your mind and body through exercise, balanced nutrition, and finding activities and stress prevention techniques that don't involve alcohol or drugs.

Substance Abuse Resources:

  • Contact your doctor
  • Call LACDPH Substance Abuse Service toll-free at 844.804.7500 or click here for additional information
  • If you are in crisis, call 911 for immediate help

To quit smoking, a number of treatments are available that can help you stop using nicotine. These include counseling, medications, or nicotine replacement therapies such as patches, gums, or prescription inhalers. Talk to your doctor about a treatment plan that is best for you. Other options are also available including free texting programs, mobile apps, and a quit-smoking hotline with trained coaches.

Stop Smoking Resources:

  • Contact your doctor
  • Call a free confidential Quit Smoking Coach in 5 languages toll-free at 800.784.8669 or click here for additional information
  • Click here to sign up for a free text program that give 24/7 encouragement, advice and tips
  • Click here to get a free app for your smartphone with tailored tips, inspiration, and progress monitoring


The information on this page is provided for general, informational purposes and not personalized medical advice. Please contact your health care provider for medical advice specific to your situation. If you are having a medical emergency please call 911.

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