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Vitamin C

Buffered L-ascorbate (1,000–5,000 mg), divided throughout the day, can be used to boost your immune system. As a powerful natural anti-oxidant and anti-viral, vitamin C can help protect you when you’re under stressful conditions. Goats and other animals that make their own vitamin C can make up to 13 times their normal amount when under stress.

Vitamin D

Vitamin D (400–4,000 IU) is especially important when you can’t go outside into the sunshine. Vitamin D can strengthen your immune system and help reduce the rates of respiratory infections—however, 400 IU is likely the maximal dose for children. It is important to note that, across the nation and among Military Service Members, blood vitamin D levels are typically below the recommended levels. Upper limits of intake are controversial, but 4,000 IU is reasonable.


Zinc (20–30 mg) is essential for optimum immune function. A number of studies have shown that zinc supplementation might protect against respiratory tract infections, so it can only help at this time. The upper limit for zinc is 40 mg.


Magnesium (200 mg)—as magnesium citrate, glycinate, or ascorbate—is critical because it participates in many immune-response pathways. Also, magnesium helps maintain an optium pH balance, which helps protect cells from viral invasion. Average magnesium intakes across the country are less than recommended, so supplemental magnesium can only help. The upper limit for supplemental magnesium is 350 mg.


Taking a multivitamin can be useful when you aren’t eating a well-balanced diet. Multivitamins often contain vitamin C, vitamin D, zinc, and magnesium, so it’s important to check how much of each nutrient is in a product. If you combine a multivitamin with a single-nutrient supplement, make sure the combined amount of each ingredient doesn’t exceed daily upper limits. (Look for %DV on the label.) We also suggest you look for a product that has been third-party certified by NSF or USP.

Logo: Contents certified NSF   Dietary Supplement USP Verified

Remember: More isn’t necessarily better—and might be worse! And avoid taking other supplements you don’t normally use.


Updated 03 April 2020


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