Immune Boosting in Action: Key Tips to Keep Your Immune System Strong

/ Pacific Nutrition Partners/
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While social distancing, wearing masks, limiting contact with others, and handwashing have been the more publicized first line defenses to protect yourself and your loved ones against COVID-19, I’m sure you’ve wondered to yourself if there is something more we can be doing to boost our immune defenses. 

The simple answer is, yes.

  1. Eat Whole Foods: Eat a balanced diet rich in whole fruits and vegetables, whole grains, and lean proteins to ensure that you are maximizing your nutrient intake and getting a well rounded variety of the necessary nutrients for immunity into your diet daily. 

  2. Stay Hydrated: Drinking enough water daily is important for immunity because it helps rid our body of toxins and supports proper cell function and activity. 

  3. Take a Multivitamin: If a balanced diet is not achievable then a multivitamin may be a more practical way to protect your nutrient intake to ensure that you are not at increased risk for deficiency of any key immunity boosting nutrients. 

  4. Exercise Regularly: Exercising helps to increase efficiency of circulation and helps rid the body of toxins. Regular exercise positively impacts the immune system and helps promote the efficiency of our defenses. 

  5. Get Adequate Sleep: Studies suggest a bidirectional link between sleep and immunity. Adequate and quality sleep is associated with reduced risk and improved outcomes for infection (18).

  6. Manage Stress: Chronic stress has been associated with a decreased immune response and greater susceptibility to infection and disease. Stress management techniques have been known to support immune boosting responses in the body. 

  7. Drink Alcohol In Moderation: Alcohol inhibits the absorption or encourages rapid depletion of some nutrients so it is advisable to consume alcohol in moderation to help protect against deficiency of key immune boosting nutrients. 

  8. Don’t Smoke: Smoking increases the toxic load in our bodies and increases the oxidative stress levels, which inhibits the actions of the immune system. Quitting smoking is best to reduce risk for a compromised immune system. 

THE WHOLE FOODS APPROACH

The food we eat plays a big role in either strengthening or weakening our immune defenses (1). The immune system is a complex network within our bodies that works hard to keep us safe from invaders called pathogens that may cause infection or disease (2). 

There are many foods that we can eat and behaviors that we can adopt to help keep our immune system strong, which is particularly important in the face of the COVID-19 pandemic (1). 

Some key nutrients for immunity are vitamin C, vitamin D, zinc, iron, and protein. There are a number of immune boosting foods that are easy to incorporate into your daily diet to help keep your defenses alert and on guard. 

A whole foods approach is the best way to get your nutrients in for maximum benefit and minimized risk. Getting immune boosting nutrients via the diet is ideal, though supplementation is a helpful alternative when certain foods items are not available for you to consume dietarily. While there are key nutrients that may offer enhanced immune support like vitamin C, vitamin D, and zinc, a well rounded and balanced diet will provide a number of important vitamins and minerals that will work together to provide maximum health benefits and enhance overall immune support. 

KEY NUTRIENTS FOR IMMUNITY

Vitamin C: This nutrient is important for building and repairing tissues and fighting off viruses and bacteria. Pathogens are often accompanied by inflammation and oxidative stress, which is a disturbance in the balance between free radicals and the antioxidative response (3). A build up of oxidative stress in the body can cause harmful cell damage and even cell death that may increase our risk of cancers or other chronic diseases. Oxidative stress is also noted to be one of the key contributors to the aging process ( (3). Vitamin C is a powerful antioxidant that works against the damage caused by  free radicals. Vitamin C is necessary for the growth and repair of all tissues in the body. It is also crucial to help make skin, tendons, ligaments, and blood vessels (4). Vitamin C is essential to the synthesis of collagen, which helps to maintain the elasticity in your skin to keep it healthy and firm (20). It is important for wound healing and forming scar tissue and it helps repair and maintain the cartilage, bones, and teeth (4). 

Vitamin C can be found naturally in many fruits and vegetables like oranges (or other citrus fruits), tomatoes, strawberries, red bell peppers, kiwi, broccoli, and potatoes (5). Vitamin C in its natural form is very temperature-sensitive and can be easily destroyed during the cooking process (21). Studies have shown that cooking vitamin C-rich foods at high heats or for long durations of time contribute to significant vitamin C losses in food (21). To ensure the maximum benefit, fresh fruits and vegetables are the most ideal source of vitamin C. 

Currently, there is insubstantial research to support a direct correlation between vitamin C supplementation and positive outcomes with COVID-19, however, some studies suggest that  supplementation may be beneficial due to the high level of oxidative stress caused by the disease and the ability for vitamin C to combat these conditions in the body (6).

The  recommended dietary allowance (RDA) to prevent deficiency is 90mg and 75mg for adult males and females 19+, respectively (5). Vitamin C deficiency is rare but some at risk groups include smokers and individuals with limited food variety. Studies suggest that increased levels of vitamin C  in the body are  most beneficial in reducing risk for the development of chronic disease and illness. Vitamin C can have adverse effects when consumed in excess, as a result of supplementation, so it is not recommended to supplement more than 2000mg daily. (5)

Vitamin D: Vitamin D has long been known for the role it plays in bone health, however, recent research has shown that it also plays a big part in helping us keep our immune system strong. Vitamin D deficiency is actually associated with increased autoimmunity (when the body elicits an immune response against its own healthy tissues) and increased susceptibility to infection (7). Vitamin D is known to decrease the inflammatory response and increase the antimicrobial response, which is beneficial for fighting off infections and disease (7). Specific to COVID-19, it has been found that vitamin D deficiency is a common factor amongst patients diagnosed with the disease that may be associated with increased risk for infections (8). In a sample population of 216 COVID-19 positive patients, 82% of patients were vitamin D deficient and also had a greater prevalence of hypertension and cardiovascular disease as well as a longer length of hospital stay compared to those with adequate levels of vitamin D (8). These findings support a significant correlation between vitamin D deficiency and an increased risk for morbidities associated with COVID-19. 

There are few foods that naturally contain vitamin D, but some foods offer small amounts like fatty fish (salmon, trout, mackerel), cheese, egg yolk, and UV treated mushrooms. Fortified dairy products are how most Americans achieve the recommended vitamin D intake, however, one of the best sources of vitamin D is actually the sun. Our skin absorbs the sunlight and uses special enzymes to help convert it into usable vitamin D, however, a number of factors like length of exposure, skin color, climate, and season impact the level of absorption (9). Because so many factors can impact your vitamin D intake from the sun it may be hard for you to estimate how much you are getting on your own, however, there is a free app called D-Minder that helps calculate your estimated intake by taking all of these external factors into consideration. 

The RDA for vitamin D is 15mcg (or 600 IU) for adults aged 19-70 and the need increases at age 70+. Individuals at risk for deficiency are breastfed infants, people with darker skin, older adults, people with impaired ability to absorb fat, obese individuals, individuals who have undergone gastric bypass surgery and people with limited sun exposure (9). 

Excessive amounts of vitamin D can be toxic so it is important not to exceed the upper limit, which is 100mcg (4000IU)/day (9). Toxicity is usually associated with excessive supplementation and not by food intake or by the absorption of vitamin D from the sun (9). While studies suggest an association between increased levels of vitamin D and reduced risk for infection and disease, more research is necessary in order to deem these findings definitively conclusive (10). 

Zinc: The importance of zinc in the human body has only recently started to be explored in depth. Zinc plays an important role in immunity and also in growth and cognition. Zinc deficiency has been linked to severe immune dysfunction, increased susceptibility to infection and disease, in addition to growth retardation. Zinc is also an antioxidant and helps to elicit an anti-inflammatory response. Adequate zinc helps to support the work of the pathogen fighting cells of the immune system. It aids in their appropriate growth, development, and effectiveness against invaders. It also helps in the prevention of “free-radical induced injury during the inflammatory process” (11). Some research has shown that in the event of the common cold zinc has improved outcomes by inhibiting the replication of the virus and shortening the duration of sickness (12).

Food sources of zinc include shellfish like oysters, lobster, and crab, red meat, chicken, whole grains, some seeds, beans and legumes, fortified cereals, and some dairy (13). 

The RDA for zinc in adult males and females 19+ is 11mg and 8mg, respectively. While advanced zinc deficiency is rare, it is also challenging to accurately measure zinc levels using lab tests. Generally, when zinc deficiency is present it is due to inadequate intake/absorption or increased losses from the body (13). 

While research on the benefits of zinc in the face of COVID-19 is still ongoing, researchers hypothesize that the anti-inflammatory effects and the immune supporting influence of zinc in the body could be beneficial. Preliminary research supports that zinc supplementation is associated with decreased risk for mortality in hospitalized COVID-19 positive patients (14). Long term zinc supplementation can result in other nutrient deficiencies and is not recommended, however, when nutritional needs are met through foods the risk for excessive intake is diminished substantially. Intake should not exceed supplementation in excess of 40mg/day (13). 

Some additional nutrients that aid in enhancing immune responses are iron, protein, and probiotics. Iron helps with the proliferation and maturation of immune cells (15). Foods high in iron include meat, poultry, fish, beans, nuts, seeds, legumes, grains, and some leafy greens (15). Protein helps to build and repair body tissues that may be damaged from inflammation. Protein also helps to fight pathogens by supporting the growth of pathogen-fighting immune cells and antibodies (16). Protein-rich foods include meat, poultry, fish, eggs, dairy, beans, legumes, nuts, seeds, and soy products (16). Probiotics are important because they help keep the gut healthy which is where 70% of our immune system is located (17). Probiotic-rich foods include fermented foods like yogurt, sauerkraut, kimchi, kefir or soy products like miso or tempeh (17).  

SUMMING IT UP

The most recent Dietary Guidelines for Americans notes that a food first approach should be the first line defense against protecting against nutritional deficiencies and meeting nutritional needs (19). A whole foods approach is always going to be the best way to maximize your nutrient intake for optimal wellness. While nutrients like vitamin C, vitamin D, and zinc play a role in enhancing immune defenses, it is important to reiterate that a well-balanced, whole foods diet will provide a diverse range of important  vitamins and minerals that are all key contributors to achieve overall wellness and health. In the face of the COVID-19 pandemic it is crucial for us to continue to maintain healthy habits inclusive of social distancing, hand washing, limiting interactions with others and, most importantly, a diet rich in nutritious foods. 

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By: Alicia Rodrigo-Miller

Alicia is a student of Nutrition and Dietetics at the University of Southern California pursuing a Master’s of Science in Nutrition, Healthspan and Longevity. Alicia has a professional background in wholesale fashion, but made the decision to pursue her true passion, dietetics, in 2016. As an RD to be, Alicia is passionate about working with women, children, and those in underrepresented and underserved communities. She seeks to play a hand in making nutrition information and education more accessible to the disenfranchised with a specific focus on chronic disease and prevention. Alicia is a Los Angeles native but currently lives in Oahu, Hawaii. She is a military wife and has a beautiful 2 yr old daughter, Reign. She has two dogs and her favorite food is tacos. Feel free to follow her on social media @itsthecardamom to get great nutrition tips or to follow her journey as an RD to be.

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