This time of the coronavirus presents many unknowns. One action you can take to protect yourself is to eat as healthily as possible.
If you do catch COVID-19, your immune system will be responsible for fighting it. Nutrition is one way to support optimal immune function (1).
The first nutritional step to a robust immune system is to eat a variety of nutrient-rich foods that moderate blood sugar and support gastrointestinal function.
One of the underlying diseases that predisposes people to complications when they contract the coronavirus is diabetes, so eating in a way that aids insulin sensitivity is important.
Supporting GI health is also key because scientists estimate that as much as 70 percent of our immune cells reside in the gut. Additionally, the gut is the site of much of your lymphatic system, which plays a central role in defending your body against viruses, bacteria, and foreign pathogens.
Both of these goals can be achieved by planning meals around high-quality protein, healthy fats, and whole, complex carbs, including colorful veggies and fruits, beans, and grains. Eating plenty of naturally occurring fiber and including fermented foods or probiotics is also important. On the avoid list, you have all the usual suspects:
- Processed and refined foods
- Foods that trigger an inflammatory response or that make you feel unwell
Once you get your overall nutrition dialed in, it’s time to consider specific immune support nutrients. It would be great if we could get all of our nutrition from a well-rounded diet, but the reality is that this approach can leave you with nutritional deficits that compromise immunity. For example, aging causes changes to the GI tract that make it harder to absorb some vitamins and minerals from food. This may be one reason why older individuals have reduced immune function and are more at risk of severe symptoms when they get sick.
Another issue is that certain disorders, such as a high stress load, diabetes, cardiovascular disease, cancer, and autoimmune conditions increase your nutritional needs beyond what is available from the healthiest diet.
Micronutrients essential to fight infection include the fat-soluble vitamins A, D, E, and K, vitamin C, and the mineral zinc. In this article, we will cover how each of these nutrients supports the immune system.
Vitamin C is an essential immune nutrient that aids both innate and adaptive immunity by the following actions (2,3,4).
- Increases pathogen-killing cells (known as natural killer cells and phagocytes)
- Enhances B and T immune cells
- Donates electrons to act as an antioxidant scavenger
- Necessary for clearance of spent immune cells, thereby lowering tissue damage
- Contributes to hormone regulation, which impacts the body’s immune-related stress response
- Supports epithelial barrier function against pathogens
The thing about vitamin C is that current evidence doesn’t show that it will keep you from getting sick. It can’t block a virus from entering your body. Rather, vitamin C supports immune function so that your body is more capable of fighting a virus off. This is why vitamin C has failed to reduce the incidence of colds in otherwise healthy people (5).
What vitamin C can do is reduce the duration of cold symptoms, minimizing nasal congestion and running nose (6). Regarding other acute illnesses, such as pneumonia and complications that are being seen with the coronavirus, vitamin C may reduce the severity of symptoms and boost immune markers:
In a randomized, placebo trial of elderly patients admitted to the hospital with acute respiratory infections, supplementing with 200 mg of vitamin C significantly improved immune cells and decreased respiratory symptoms (7).
In the case of acute lung infections, intravenous vitamin C was shown to lead to rapid clearance of chest X-rays (8).
In pneumonia patients, a low dose of vitamin C of 800 mg a day reduced the hospital stay by 20 percent compared with no vitamin C supplement. A higher dose group that took 1,600 mg of vitamin C a day reduced hospital duration by 36 percent (9).
Supplementation is most important in individuals with low vitamin C intake. For example, individuals with inadequate vitamin C levels who took 1,000 mg of vitamin C for 8 weeks had decreased incidence of the cold compared to a placebo group (10).
Vitamin C deficiency is frequently encountered in ill patients due to increased metabolic consumption and high rates of oxidative stress. Unlike many animals, humans don’t have the ability to synthesize vitamin C, so they have to get it from diet. In normal situations, assuming diets replete with vegetables and fruit, you can probably meet vitamin C needs, but if you are suffering from health conditions or compromised GI function, you are at risk of insufficiency. Stress also depletes vitamin C and we can all agree that the coronavirus era is one of the more stressful times in our generation. Research into athletes shows that vitamin C supplementation can help clear cortisol after intense training (11).
It should be noted that as yet no studies have been published testing vitamin C on COVID-19 but there is currently a trial of intravenous vitamin C for severe COVID-19-induced pneumonia in China that should be published at the end of the year (12).
How To Take:
Vitamin C is a safe supplement and there is no risk of toxicity. In a deficiency state or when trying to combat an illness, doses ranging from 1 to 10 grams a day may be indicated. Doses should be divided, taking half in the morning and half in the evening.
Zinc plays an essential function in both the innate and adaptive immune systems by the following actions (13,14):
- Supports the production of antioxidants, such as superoxide dismutase, that scavenge free radicals
- Maintains the integrity of physical barriers to viruses, including skin and mucous membranes
- Enhances activity of T and B immune cells
- Improves pathogen-killing immune cells like monocytes and natural killer cells
- Reduces viral replication, lowering your overall viral load
A deficiency of zinc is considered a disaster for the immune system (15). Ensuring that you have proper zinc levels can go a long way to supporting immunity and preventing severe health problems. This is because lack of zinc leads to fewer mature immune cells that are necessary for fighting off viruses and other pathogens.
For people who have adequate zinc, supplementation is less likely to be effective for preventing colds or illness. However, once you are sick, zinc supplementation can be beneficial: A meta-analysis found that high-dose zinc lozenges that supplied more than 75 mg of zinc a day led to a 20 percent reduction in cold duration (16), whereas lower doses of less than 75 mg a day had no effect. A second analysis showed that zinc lozenges in doses of 80 to 92 mg a day reduced the duration of upper respiratory illness, decreasing nasal congestion by 37 percent, scratchy throat by 33 percent, hoarseness by 43 percent, and cough by 46 percent. The duration of muscle aches decreased by 54 percent (17).
Similar to vitamin C, low zinc is common in people with poor health, the elderly, and those with gastrointestinal problems, including IBS and celiac disease. Additionally, vegetarians and people who don’t eat plenty of zinc-containing foods are prone to zinc deficiency. The best sources of dietary zinc are meat, shellfish, and dairy. Seeds, nuts, and vegetables do contain zinc but they also contain phytates that result in poor zinc bioavailability.
How To Take: You need to be careful not to overdose on zinc because too much can be toxic. When you have an upper respiratory illness, it is fine to use higher dose zinc lozenges that supply between 75 and 90 mg a day, but it is not recommended that you go over 100 mg.
When trying to raise levels from a deficiency, supplementing zinc with 25 to 45 mg a day should be sufficient. As a daily preventative, a lower dose of 5 to 10 mg is considered safe. The zinc RDA for adult men is 11 mg a day and for women it is 8 mg a day. Zinc is not stored in the body, so you need to get it from your diet or supplement on a regular basis.
The Fat Soluble Vitamins A, D, E, and K
Few people think of the vitamins A, D, E, and K when it comes to virus protection but these fat-soluble vitamins play an essential role in immune function and many people’s levels are not optimal. They are unique because unlike most vitamins, which are water soluble, fat-soluble vitamins are best absorbed when eaten with fat. They are present in healthy high-fat foods, such as whole-fat dairy, meat, and fish. They are also available in certain plant foods, though this form is not easily used by the body.
Each fat-soluble vitamin plays a special role in immunity:
Vitamin A acts as an antioxidant and helps maintain your body’s physical barriers against pathogens, supporting integrity of the skin, mucous membranes, blood vessels, and the cellular lining of the digestive and respiratory tract. Vitamin A also enhances activity of B and T immune cells (18,19). Studies show the importance of vitamin A in several diseases that affect the lungs, including HIV and tuberculosis.
Vitamin D raises levels of immune cells to attack invading pathogens. It also helps regulate the immune response so that inflammatory markers that are part of the immune response don’t get out of control and damage cells and tissue (20). One randomized trial of 140 immunodeficient patients found that daily supplementation of 4000 IUs of vitamin D over one year significantly reduced infectious symptoms and lowered the number of specific pathogens in the nasal fluid (21).
Vitamin E is an antioxidant that improves activity of various immune cells, including natural killer cells and B and T cells. Poor immune function is a symptom of vitamin E deficiency and studies show vitamin E confers improved resistance to infection in people with poor health. For example, nursing home patients who took 200 IUs a day of vitamin E for a year had fewer cases of upper respiratory infection (22).
Vitamin K has anti-inflammatory action that suppresses immune-damaging cells, including nuclear factor KB. It is especially important in reducing the onset of age-related diseases (23) and lowers the risk of heart disease (24). Vitamin K deficiency can occur in people who don’t eat animal foods, who don’t absorb fat efficiently, or who suffer poor gut function, such as IBS, celiac, and cystic fibrosis. Use of antibiotics can also lead to a deficiency.
The fat-soluble vitamins are especially important in the coronavirus era because this is a disease that targets people with pre-existing health conditions or who have poor immune systems (25). Deficiencies in fat soluble vitamins are also common in people with low sex hormones (low testosterone or estrogen), chronic inflammation, high cortisol and stress, and diabetics (25,26).
The role of the fat-soluble vitamins in respiratory health is evident in people with cystic fibrosis, the most common genetic disease that causes respiratory failure. Deficits of vitamins D and K. are especially common and contribute to worsening of the disease (26).
How To Take:
If you are healthy, regularly eat a variety of high-quality animal products, and get sun exposure (for vitamin D), you may not need to supplement. For everyone else, a blended A, D, E, and K supplement can support absorption of these vitamins to aid the immune system. Individuals who are deficient and need to bring their levels up require higher intake than those who are supplementing as a maintenance dose.
Vitamin A should be from A palmitate, which is more efficiently used by the body than beta-carotene.
Vitamin D should be in the cholecalciferol D3 form (not the D2 ergocalciferol form) that is used to improve your body’s vitamin D stores.
Vitamin E should be from mixed tocopherols (not tocotrienols) because this form makes up around 90 percent of the vitamin E in the blood.
Vitamin K should be from the menaquinone K2 form (not the K1 phylloquinone form) because this is the active form that is useful to the body.
Final Words: If you’ve been putting off taking your nutrition seriously, now is the time. As much as possible, focus on eating a wide variety of nutrient rich foods and consider supplementing any deficits to protect you and your family during the coronavirus era. Shop for these immune support aids in our online store.