The Best Vitamins for the Immune System Boost: A Review

The immune system is a complex network of interconnected biological and physiological processes that protect your organism from various pathogens. What are the best vitamins for the immune system? What supplements can help you boost your immunity to infection? Here is our detailed review.

1. Vitamin C

Vitamin C (ascorbic acid) is the best-known and most popular of all vitamins. Not only does it stimulate immunity, it is also a powerful antioxidant that protects cells from free radicals. What’s more, ascorbic acid is highly beneficial for the skin (smoking leads to the depletion of ascorbic acid supply in the body; hence the yellow skin the smokers are known for) and can stimulate iron absorption, which is important for the treatment and prevention of iron-deficiency anemia. 

A 2017 review makes the conclusion that ascorbic acid supplementation can improve the body’s resistance to respiratory and systemic infections. It also recommends taking from 100 to 200 mg of this compound per day to achieve adequate ascorbic acid plasma levels for prophylactic prevention of infection. To treat established infections doses of ascorbic acid up to 1 gram per day can be used.

What Form to Choose

There are three main forms of ascorbic acid that can be found in dietary supplements:

• Ascorbic acid that is not modified in any way. The principal disadvantage of this form is that it is quickly excreted from the body so that its plasma levels start to noticeably drop down in about three hours after the intake. It can also cause indigestion if taken in a large dose;
• Ascorbates or compounds of ascorbic acid with such metals as sodium and calcium. While they do not lead to indigestion, ascorbates are excreted from the blood just as quickly as ascorbic acid itself;
• Liposomal vitamin C or ascorbic acid that is placed inside a liposome — a minuscule sphere made of two layers of lipid molecules. In contrast to both other forms, the liposomal version stays in the blood till it is almost fully absorbed by the cells. 

You can buy liposomal vitamin C — arguably the best immune system supplement — on iHerb. Here is one of the most popular dietary products that contains this form of ascorbic acid and comes from a reputable brand:

Liposomal vitamin C by Dr. Mercola

• 500 mg per capsule
• 180 capsules
• One capsule per day is enough for most adults

If your budget is limited, you can use an affordable sodium ascorbate supplement that doesn’t cost much and can be used for a very long time: 

Sodium Ascorbate Powder, 227 g (8 oz) by NOW Foods

• Easy to use powder form
• If you follow the manufacturer’s advice and use ½ level teaspoon, you will get an equivalent of as much as 1,670 mg of ascorbic acid. This quantity, however, is about 18 times as high as your real daily need
• Take a twentieth of a teaspoon of crystals or even less three to four times a day to achieve stably high ascorbic acid plasma levels
• Pharmaceutical grade

2. Vitamin D

Vitamin D (cholecalciferol) is a fat-soluble compound that is required for the proper absorption of calcium and magnesium. What’s more, cholecalciferol can boost immunity and thus has antibacterial and anti-inflammatory effects. Daily doses of cholecalciferol that range from 400 to 1,000 IU can decrease (albeit, only slightly) the incidence of acute RTIs (respiratory tract infections). This protective effect is especially high in people who have vitamin D deficiency. 

Cholecalciferol was also found to be of help to people who suffer from COPD (chronic obstructive pulmonary disease). Its antiviral properties are currently being studied in connection with the COVID-19 epidemic with a lot of scientists agreeing that this kind of treatment shows promise.

You can find the best vitamins to boost the immune system on iHerb. Here is one of the most popular products that is safe for everyday use:

Vitamin D₃ by NOW Foods

• 1,000 IU per softgel
• 360 softgels will be enough for a year of use
• Oil-filled softgels guarantee maximal bioavailability
• Trusted brand

3. Vitamin A

Vitamin A (retinol) is another fat-soluble compound that is important for immunity and resistance to infections. It was found that people who have retinol deficiency are more prone to infectious diseases. What’s more, normal serum levels of retinol prevent immune system overreaction which can lead to allergic reactions, chronic inflammation, and autoimmune diseases.

Large quantities of vitamin A can be found in beef and chicken liver. Plant sources such as yellow, orange, and red vegetables do not contain vitamin A itself but rather its precursors called carotenoids. Unfortunately, the percentage of carotenoids that is normally absorbed by the body from food sources is small, so vitamin A deficiency is not an uncommon condition. 

As retinol is fat-soluble, it is best taken in the form of oil-filled softgels. Here is one of the most popular retinol supplements on iHerb:

Vitamin A, 100 softgels, 10,000 IU per softgel

• Reliable yet affordable brand
• Dissolved in organic olive oil 
• High doses of retinol can be toxic. Never exceed the dose of 1 softgel daily.

4. Vitamin E

Just like vitamins A and D, vitamin E (tocopherol) is a fat-soluble compound that has marked anti-oxidant properties. Recent studies also demonstrate that tocopherol can also be used to boost immunity: it decreases susceptibility to respiratory infections and such allergic diseases as asthma.

A 2018 review makes a conclusion that tocopherol enhances immune responses in animal and human models and can be used as a protection from infectious diseases.

Here is one of the highest-rated tocopherol supplements on iHerb:

Vitamin E by Solgar

• 100 IU per softgel
• 100 softgels
• Well-known brand
• Naturally sourced
• Dissolved in safflower oil for maximal absorption

5. Zinc and Selenium

While technically zinc and selenium are minerals, not vitamins, they are often recommended to be used together with the best vitamins for immune health for maximal effect. 

Zinc is essential for both development of immune cells and communication between them. The deficiency of this element is known to depress immunity; this condition is very common in older adults (over 30% of them suffer from it).  

Selenium is used by the body for protection against oxidative stress. A 2015 review concludes that it can be useful for strengthening the immune system. This element was found to enhance antiviral defense against various influenza strains.

Here is one of the highest-rated zinc supplements on iHerb:

Zinc by NOW Foods

• Each tablet contains 50 mg of zinc 
• 250 tablets will be enough for eight months of use

And here is one of the most-popular selenium supplements in this online store:

Selenium, 100 tablets, 100 mcg per tablet by Solgar

• 100 tablets containing 100 mcg of selenium each 
• Dependable brand
• L-selenomethionine is a highly bioavailable form of selenium

Now you know the best vitamins for immune system support. Taking them, do not neglect physical exercise and a healthy diet. Take care and see you next time!