Nutrients for Viral Infections

Whole Systems Healthcare

In this time of COVID-19 many people are wondering if there are ways they can protect themselves in addition to important public health recommendations such as social distancing and frequent hand washing. Though there is no treatment guaranteed to prevent or cure COVID-19, Naturopathic Medicine has many tools for strengthening overall vitality and preparing the body to successfully counter viral infections. One important area is nutrition. We all need adequate nutrients to help our immune systems function well and to successfully move through an infection if we do get sick. 

Summary of Recommendations

  • Preformed vitamin A, not beta-carotene
    • Children: 500-1,000 IUs daily
    • Adults: 2,000-3,000 IUs daily
  • Vitamin D3, not D2
    • Children: 1,000-2,000 IUs daily
    • Adults: 3,000-5,000 IUs daily
  • Vitamin K2, 100-200 micrograms daily
  • Vitamin C
    • Adults: 1-2 grams daily
    • Children: 500-1,000 mg daily
  • Zinc
    • Adults: 10-15 mg daily
    • Children: 5 mg daily
  • Selenium
    • Adults: 200 mcg (micrograms) daily
    • Children: 50-100 mcg daily

Vitamin A

Vitamin A has been known to be important for preventing infection almost since its discovery, and was initially known as the anti-infective vitamin. Today we know that it has a number of effects on different cells of the immune system and is critical for a robust and well-modulated innate immune response. Vitamin A deficiency is a clear factor in decreased resistance to infectious disease, and this may be true even for subclinical (not obvious) deficiencies. 

Many food sources and supplements list vitamin A content when referring to carotenoids like beta-carotene, and for healthy people getting enough beta-carotene can satisfy vitamin A requirements. However, this isn’t the form that’s needed by the body, and the conversion of beta-carotene (the plant form) to retinol or retinoic acid (the animal forms) is not particularly efficient, even in healthy humans. It’s important for optimal immune function to get preformed vitamin A, either from an animal source, or from a supplement. 

Good food sources of preformed vitamin A include liver, butter, egg yolk, whole milk, and cod liver oil. If eating liver as a source of vitamin A, 1 ounce 2-3 times per week is sufficient. For supplements, adults should take 2,000-3,000 IUs daily, and should not take over 10,000 IUs on a regular basis to avoid any chances of overdose and toxicity. For children, the dose should be lowered accordingly, and young children should avoid taking more than 2,000 IUs daily to avoid any chance of toxicity.

Vitamin D

Vitamin D is an important vitamin for a number of different body functions, including proper immune function. Though vitamin D has been studied for its influence on autoimmune conditions, it is also known to support the innate immune system. The innate immune system is nonspecific and protects us from infection by destroying microbes before they can penetrate and infect our cells. This vitamin helps support our innate immune system by increasing cell production of antimicrobial peptides. Vitamin D has been found specifically to reduce respiratory infections in patients with asthma, as well as to increase positive outcomes in patients with sepsis. 

As I wrote in a previous article on vitamin D, it is probably better to synthesize this vitamin directly from appropriate sun exposure, or to obtain it directly from a food source (such as cod liver oil), instead of as a supplement. However, in order to increase levels in the body, and especially at this time of year when sun exposure is not sufficient for vitamin D production, supplementing with vitamin D is a very low risk way to increase innate immunity. The best approach is to get your levels tested so the dose can be individualized, but for most people, taking 3,000-5,000 IUs of vitamin D daily is sufficient to increase blood levels.

Vitamin K2

This vitamin synergizes with both vitamins A and D and is important in allowing the body to utilize both of the above effectively. Though it doesn’t appear to have any direct anti-infective properties at this time there is some evidence that it does have an influence over the immune system. There is currently no known toxic dose but the requirement for vitamin K2 is relatively small. 100-200 micrograms daily is sufficient. 

Vitamin C

Vitamin C is well known in the public sphere for its importance in immune function. This is substantiated by studies looking at its influence on different types of white blood cells, stimulating both the production and function of these cells. Vitamin C also helps to protect white blood cells from damage when they release antimicrobial compounds, as these non-specific compounds can injure the cells themselves as well. 

Any metabolic activity, including a heightened immune response to infection, will deplete vitamin C, as it is used up to protect the cells of the immune system from the inflammation generated to fight the infection. There is evidence that taking vitamin C prevents pneumonia, and there is some evidence that vitamin C is helpful in cases of septic shock. 

Making sure the body has adequate reserves of vitamin C during infection is easy and very low risk. For adults, supplement with 1-2 grams (1,000-2,000 mg) per day. For children, take 500-1,000 mg per day. At the first sign of illness, double this dose. If these dosages cause any diarrhea, reduce the total dose, or spread the amount out over the day in 2 or 3 doses to avoid overloading the digestive system. 


Zinc is essential to proper immune function, and zinc deficiency increases susceptibility to a number of different types of infections. This important mineral is needed for normal development and function of white blood cells that are part of the innate immune system, as well as playing a role in multiple other aspects of our immunity. 

The Recommended Daily Allowance for adults is about 10mg per day, less for children. As a daily supplement 10-15 mg is an appropriate amount for an adult; for children, 5 mg per day. 


Selenium has definite effects on the immune system and plays a role in protecting the body from the effects of oxidative stress. There is some evidence that selenium deficiency can not only increase oxidative stress in the body, but that deficiency can cause an otherwise mild virus to become much more pathogenic. There have been multiple studies examining selenium nutritional status and showing positive impacts of adequate selenium levels in cases of viral infection.

For adults, supplement with 200 mcg (micrograms) daily to ensure adequate selenium stores in the body. For children, 50-100 mcg daily. 

Other Vitamins and Minerals

Because humans evolved to obtain all of our important nutrients from food, we necessarily developed complex systems that make use of multiple different types of nutrients. Other important vitamins and minerals include (but are not limited to) the full complement of B vitamins, vitamin E, iron, and copper. If you are eating a healthy diet consisting primarily of whole foods, it is unlikely you will require additional supplementation. However, if you have a chronic health condition, are pregnant or nursing, or have any condition that affects your ability to digest and absorb nutrients, speak with your doctor and see what additional supplementation might be important for you.