A healthy, balanced diet is important to overall immune health. A variety of foods such as fruits, vegetables, whole grains, beans and legumes, nuts and seeds, low-fat dairy products, skinless poultry, and fish provide necessary vitamins and minerals for a healthy lifestyle. When you can’t fill your plate with whole foods, when your diet is inadequate, or if your healthcare provider has found certain nutrient deficiencies, specific vitamin and mineral supplements can be useful. However, since the start of COVID-19, thousands of products are now promoted to support or boost your immunity. These products are accompanied by claims, including “daily immune support,” “immune defense,” and “immune boost.” Here, OPSS breaks down the latest research on the most common vitamins and minerals in dietary supplements marketed with claims for immune health.

Some single- ingredient vitamin and mineral supplements
might be useful for overall immune health, especially when you can’t
get enough of certain nutrients from your diet.

The most common vitamins and minerals listed on the labels of products marketed for immune health are vitamins A, B, C, D, E, and K, and the minerals calcium, magnesium, selenium, and zinc. Many products list such ingredients in combination, such as in multi-vitamin products, and sometimes with other types of ingredients, including botanicals. There is no clear evidence that various multi-ingredient products provide the claimed benefits for healthy individuals. The discussion below relates only to single-ingredient vitamin and mineral supplements marketed to support immune health.

Can any vitamin or mineral supplements support or boost immune health?

Vitamin C is an essential vitamin that serves an important role in how the immune system functions. The recommended daily amount is 90 mg [milligrams] for men and 75 mg for women. That’s equivalent to about a medium-size orange a day—an amount easy to get from various fruits and vegetables.

Research as far back as the early 1970s suggested that 2 grams a day or more of vitamin C could help fight the common cold. Today the established tolerable upper limit (the amount not to exceed) is 2 grams a day for adults. Too much might lead to stomachaches and diarrhea. The latest research shows that taking a vitamin C supplement won’t necessarily reduce the risk of developing a cold. However, a vitamin C supplement might help during times of extreme physical activity, especially during winter. Studies involving competitive swimmers, and marathon runners, for example, report less-severe symptoms or fewer days sick with an upper-respiratory illness, such as the common cold, when taking up to 1 gram per day of vitamin C.

Vitamin D is essential to maintain bone and overall health. It also helps build immunity. It is found in foods such as fish, eggs, and fortified milk. Vitamin D is also produced naturally in the body when the skin is exposed to sunlight . However, it’s challenging to get enough sunlight during the winter months or for a shift worker. It’s also challenging for those who usually wear clothes that cover their skin, don’t like the outdoors, or have dark skin. The daily amount needed depends on age, but the amount recommended for adults is 600 IU (or 15 µg [micrograms] per day), which is the amount in about five cups of milk fortified with vitamin D.

Unfortunately, vitamin D insufficiency is common in the U.S., so it’s important to get checked by a physician from time to time. Some studies have shown that those with lower levels of vitamin D are more likely to report having a common cold or an upper respiratory tract infection than those with “normal” levels. However, more research is needed to determine whether taking a vitamin D supplement might protect against getting such illnesses. On the other hand, too much vitamin D is harmful and can be toxic, which could lead to nausea, vomiting, or even kidney stones. Even more serious health issues such as kidney failure and, in rare cases, death could occur. So before taking a vitamin D supplement, check with a healthcare provider to determine if you need one and how much is needed.

During the COVID-19 pandemic, vitamin D was touted as one of the top “immune boosting” strategies. However, no reliable scientific evidence supports any claim that vitamin D can improve immunity to COVID-19.

Zinc is an essential mineral that, like vitamin D, helps support your immune system. It’s found in foods such as meat, shellfish, and legumes such as chickpeas, lentils, and beans. Many breakfast cereals are also fortified with zinc. The daily amount adults need is 11 mg for men and 8 mg for women. That’s equivalent to about one pound of ground turkey or three ounces of lean beef. Zinc is also available as a dietary supplement. Product labels list various forms, such as elemental zinc, zinc picolinate, zinc citrate, zinc acetate, zinc glycerate, and zinc monomethionine. Zinc is also available in other forms sold as over-the-counter cold remedies, including nasal sprays, but many of these are drugs or homeopathic products, rather than dietary supplements.

Some studies have shown that supplemental zinc might reduce the occurrence, frequency, or length of respiratory illnesses such as the common cold or influenza if taken when exposed to physical or mental stressors during the winter season. Most adults tolerate zinc well in amounts below the tolerable upper limit of 40 mg per day. The most common adverse effects are stomachache, diarrhea, vomiting, and a metallic taste.

Other vitamins and minerals

No evidence is available to suggest that single-ingredient dietary supplements with vitamins A, B complex, E, or K, or the minerals calcium, magnesium, or selenium can support or boost your immune system. For individual fact sheets on these and other nutrients, visit the Office of Dietary Supplements, National Institutes of Health.

Bottom line

No dietary supplement should ever be a substitute for a nutritious, whole-food diet, and no dietary supplement can truly “boost your immunity.” Always speak with a healthcare professional before taking any dietary supplement. And remember: No dietary supplement can be legally marketed to diagnose, treat, cure, or prevent any disease or health condition, including flu, colds, and COVID-19.

The information in this article is only related to the use of vitamins and minerals as single dietary supplement ingredients by healthy individuals looking to support immune health and does not represent the evidence for these supplements in combination with other ingredients. Unfortunately, little or no evidence is available regarding the various combinations of ingredients found in such products.

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