How to improve the immune system
Written by SaVanna Shoemaker, MS, RDN, LD on April 1, 2020 — Medically reviewed by Kathy W. Warwick, R.D., CDE
An important note
No supplement, diet, or lifestyle modification — aside from physical distancing, also known as social distancing, and practicing proper hygiene — can protect you from developing COVID-19.
The strategies outlined below may boost your immune health, but they don’t protect specifically against COVID-19.
If you want to boost your immune health, you may wonder how to help your body fight off illnesses.
While bolstering your immunity is easier said than done, several dietary and lifestyle changes may strengthen your body’s natural defenses and help you fight harmful pathogens, or disease-causing organisms.
Here are 9 tips to strengthen your immunity naturally.
1. Get enough sleep
Sleep and immunity are closely tied.
In fact, inadequate or poor quality sleep is linked to a higher susceptibility to sickness.
In a study in 164 healthy adults, those who slept fewer than 6 hours each night were more likely to catch a cold than those who slept 6 hours or more each night (1).
Getting adequate rest may strengthen your natural immunity. Also, you may sleep more when sick to allow your immune system to better fight the illness (2).
Adults should aim to get 7 or more hours of sleep each night, while teens need 8–10 hours and younger children and infants up to 14 hours (3).
If you’re having trouble sleeping, try limiting screen time for an hour before bed, as the blue light emitted from your phone, TV, and computer may disrupt your circadian rhythm, or your body’s natural wake-sleep cycle (4).
Other sleep hygiene tips include sleeping in a completely dark room or using a sleep mask, going to bed at the same time every night, and exercising regularly (3).
Inadequate sleep may increase your risk of getting sick. Most adults should get at least 7 hours of sleep per night.
2. Eat more whole plant foods
Whole plant foods like fruits, vegetables, nuts, seeds, and legumes are rich in nutrients and antioxidants that may give you an upper hand against harmful pathogens.
The antioxidants in these foods help decrease inflammation by combatting unstable compounds called free radicals, which can cause inflammation when they build up in your body in high levels (5).
Chronic inflammation is linked to numerous health conditions, including heart disease, Alzheimer’s, and certain cancers.
Meanwhile, the fiber in plant foods feeds your gut microbiome, or the community of healthy bacteria in your gut. A robust gut microbiome can improve your immunity and help keep harmful pathogens from entering your body via your digestive tract (6).
Furthermore, fruits and vegetables are rich in nutrients like vitamin C, which may reduce the duration of the common cold (7).
Several whole plant foods contain antioxidants, fiber, and vitamin C, all of which may lower your susceptibility to illness.
3. Eat more healthy fats
Healthy fats, like those found in olive oil and salmon, may boost your body’s immune response to pathogens by decreasing inflammation.
Although low-level inflammation is a normal response to stress or injury, chronic inflammation can suppress your immune system (8).
Olive oil, which is highly anti-inflammatory, is linked to a decreased risk of chronic diseases like heart disease and type 2 diabetes. Plus, its anti-inflammatory properties may help your body fight off harmful disease-causing bacteria and viruses (9, 10).
Omega-3 fatty acids, such as those in salmon and chia seeds, fight inflammation as well (11).
Healthy fats like olive oil and omega-3s are highly anti-inflammatory. Since chronic inflammation can suppress your immune system, these fats may naturally combat illnesses.
4. Eat more fermented foods or take a probiotic supplement
Fermented foods are rich in beneficial bacteria called probiotics, which populate your digestive tract (12).
These foods include yogurt, sauerkraut, kimchi, kefir, and natto.
Research suggests that a flourishing network of gut bacteria can help your immune cells differentiate between normal, healthy cells and harmful invader organisms (13).
In a 3-month study in 126 children, those who drank just 2.4 ounces (70 mL) of fermented milk daily had about 20% fewer childhood infectious diseases, compared with a control group (14).
If you don’t regularly eat fermented foods, probiotic supplements are another option.
In a 28-day study in 152 people infected with rhinovirus, those who supplemented with probiotic Bifidobacterium animalis had a stronger immune response and lower levels of the virus in their nasal mucus than a control group (15).
Gut health and immunity are deeply interconnected. Fermented foods and probiotics may bolster your immune system by helping it identify and target harmful pathogens.
5. Limit added sugars
Emerging research suggests that added sugars and refined carbs may contribute disproportionately to overweight and obesity (16, 17).
Obesity may likewise increase your risk of getting sick.
According to an observational study in around 1,000 people, people with obesity who were administered the flu vaccine were twice as likely to still get the flu than individuals without obesity who received the vaccine (18).
Curbing your sugar intake can decrease inflammation and aid weight loss, thus reducing your risk of chronic health conditions like type 2 diabetes and heart disease (19, 20).
Given that obesity, type 2 diabetes, and heart disease can all weaken your immune system, limiting added sugars is an important part of an immune-boosting diet (18, 21, 22).
You should strive to limit your sugar intake to less than 5% of your daily calories. This equals about 2 tablespoons (25 grams) of sugar for someone on a 2,000-calorie diet.
Added sugars contribute significantly to obesity, type 2 diabetes, and heart disease, all of which can suppress your immune system. Lowering your sugar intake may decrease inflammation and your risk of these conditions.
6. Engage in moderate exercise
Although prolonged intense exercise can suppress your immune system, moderate exercise can give it a boost.
Studies indicate that even a single session of moderate exercise can boost the effectiveness of vaccines in people with compromised immune systems (23).
What’s more, regular, moderate exercise may reduce inflammation and help your immune cells regenerate regularly (23).
Examples of moderate exercise include brisk walking, steady bicycling, jogging, swimming, and light hiking. Most people should aim for at least 150 minutes of moderate exercise per week (24).
Moderate exercise can reduce inflammation and promote the healthy turnover of immune cells. Jogging, biking, walking, swimming, and hiking are great options.
7. Stay hydrated
Hydration doesn’t necessarily protect you from germs and viruses, but preventing dehydration is important to your overall health.
Dehydration can cause headaches and hinder your physical performance, focus, mood, digestion, and heart and kidney function. These complications can increase your susceptibility to illness (25).
To prevent dehydration, you should drink enough fluid daily to make your urine pale yellow. Water is recommended because it’s free of calories, additives, and sugar (25).
While tea and juice are also hydrating, it’s best to limit your intake of fruit juice and sweetened tea because of their high sugar contents (26, 27).
As a general guideline, you should drink when you’re thirsty and stop when you’re no longer thirsty. You may need more fluids if you exercise intensely, work outside, or live in a hot climate (28).
It’s important to note that older adults begin to lose the urge to drink, as their bodies do not signal thirst adequately. Older adults need to drink regularly even if they do not feel thirsty.
Given that dehydration can make you more susceptible to illness, be sure you’re drinking plenty of water each day.
8. Manage your stress levels
Relieving stress and anxiety is key to immune health.
Long-term stress promotes inflammation, as well as imbalances in immune cell function (7, 9).
In particular, prolonged psychological stress can suppress the immune response in children (29).
Activities that may help you manage your stress include meditation, exercise, journaling, yoga, and other mindfulness practices. You may also benefit from seeing a licensed counselor or therapist, whether virtually or in person.
Lowering your stress levels through meditation, yoga, exercise, and other practices can help keep your immune system functioning properly.
9. Supplement wisely
It’s easy to turn to supplements if you hear claims about their ability to treat or prevent COVID-19.
However, these assertions are unfounded and untrue.
According to the National Institutes of Health (NIH), there’s no evidence to support the use of any supplement to prevent or treat COVID-19 (30).
However, some studies indicate that the following supplements may strengthen your body’s general immune response:
Vitamin C. According to a review in over 11,000 people, taking 1,000–2,000 mg of vitamin C per day reduced the duration of colds by 8% in adults and 14% in children. Yet, supplementing did not prevent the cold to begin with (7).
Vitamin D. Vitamin D deficiency may increase your chances of getting sick, so supplementing may counteract this effect. Nonetheless, taking vitamin D when you already have adequate levels doesn’t seem to provide extra benefits (31).
Zinc. In a review in 575 people with the common cold, supplementing with more than 75 mg of zinc per day reduced the duration of the cold by 33% (32).
Elderberry. One small review found that elderberry could reduce the symptoms of viral upper respiratory infections, but more research is needed (33).
Echinacea. A study in over 700 people found that those who took echinacea recovered from colds slightly more quickly than those who received a placebo or no treatment, but the difference was insignificant (34).
Garlic. A high quality, 12-week study in 146 people found that supplementing with garlic reduced the incidence of the common cold by about 30%. However, more research is needed (35).
While these supplements demonstrated potential in the studies mentioned above, that doesn’t mean they’re effective against COVID-19.
Furthermore, supplements are prone to mislabeling because they aren’t regulated by the Food and Drug Administration (FDA).
Thus, you should only purchase supplements that have been independently tested by third-party organizations like United States Pharmacopeia (USP), NSF International, and ConsumerLab.
Though some supplements may fight viral infections, none have been proven to be effective against COVID-19. If you decide to supplement, make sure to purchase products that have been tested by a third party.
The bottom line
You can make several lifestyle and dietary changes today to strengthen your immune system.
These include reducing your sugar intake, staying hydrated, working out regularly, getting adequate sleep, and managing your stress levels.
Although none of these suggestions can prevent COVID-19, they may reinforce your body’s defenses against harmful pathogens.