Supplements for Immunity: Benefits and Limitations


the immune system is a vast network of cells, organs and proteins. It works to protect the body against harmful microorganisms and toxins.

When the immune system is functioning optimally, it does an excellent job of defending the body. But having a weakened immune system can increase the risk of delayed healinginfectious diseases like colds and other infections.

Various vitamins and minerals, often called “micronutrients”, are necessary for the proper functioning of the immune system.

The main micronutrients that play a role in the immune response include:

Ideally, we would all get optimal amounts of these micronutrients through a well-balanced diet, but that can be difficult to achieve.

Many people around the world suffer from nutritional deficiencies. In the United States, nearly 95% of the population does not meet their daily vitamin D requirements, 84% not getting enough vitamin E, 46% not getting enough vitamin C, 45% not getting enough vitamin A, and 15% not getting enough zinc.

Studies show that even a marginal deficiency in one or more of these vitamins and minerals can lead to impaired immune function.

Many factors, such as stress and infections, can further deplete nutrient stores throughout the body.

Meanwhile, aging increases the body’s demand for micronutrients. People more than 50 tend to need more of certain nutrients, including vitamin D, calcium, vitamin B6 and vitamin B12.

To support a healthy immune system and meet nutritional needs, a person can make sure their diet is healthy and take a multivitamin that contains 100% of the recommended daily allowance (RDA) of each nutrient.

However, many standard multivitamins may not contain enough vitamin C. Researchers believe that 200 milligrams (mg) a day is needed for immune health.

If a person already has a deficiency, they likely need more of this nutrient than a multivitamin provides.

Although some studies suggest that supplementation with several immune-supporting micronutrients is beneficial, more research is needed.

Currently, the the strongest evidence suggests that these three micronutrients provide immune support: vitamin C, vitamin D and zinc.

Below, we take a look at what the research says about taking supplements of these nutrients.

Vitamin C

Vitamin C, or ascorbic acid, is a water-soluble vitamin known for its ability to support a strong immune system. In addition to supporting various cellular functions of the immune system, vitamin C helps the body grow and repair tissues, heal wounds, and absorb iron.

Vitamin C is also an antioxidant, which means it fights free radicals, which may help prevent certain cancers and heart disease.

Studies show that vitamin C deficiency can lead to impaired immune system and increased risk of infection.

The human body cannot make vitamin C, so it must come from foods or dietary supplements.

The RDA for vitamin C is 90mg for adult men and 75 milligrams for adult women. However, many scientists believe this is not enough and recommend 200mg per day for maximum health benefits.

Although most studies show that taking vitamin C does not prevent the common cold in the general population, it can help reduce the symptoms and severity of a cold. For example, a 2018 meta-analysis found that taking extra doses of vitamin C can help reduce the duration of a cold by up to half a day, as well as symptoms such as chest pain, fever and chills.

Vitamin C supplementation may be even more beneficial for people who engage in intense physical activity. In five trials involving a total of 598 participants, who were exposed to short periods of extreme physical stress, vitamin C reduced the risk of the common cold by nearly 50%.

Vitamin D

Vitamin D plays a vital role in maintaining a strong immune system so the body can fight off bacterial and viral illnesses, such as the common cold. Some clinical trials suggest that supplementation with 400 international units (IU)or 10 micrograms (mcg) of vitamin D a day can help prevent colds.

Other studies show that vitamin D treatment can reduce respiratory tract infections, especially in people with vitamin D deficiency.

Some researchers also believe there is a link between vitamin D deficiency and an increased risk of hospitalization for COVID-19, although there is controversy over this claim. In some cases, it has been used to minimize the impact of socio-economic factors on risk groups.

Many experts believe that the current vitamin D RDA of 600 IU (15 micrograms) for people up to age 70 and 800 IU (20 micrograms) for people over 70 are not enough to support healthy immune function.

However, the evidence remains inconclusive and finding the dosage that best supports immune function requires further research.


Zinc deficiency can weaken the immune system by impairing the formation, activation and maturation of lymphocytes, white blood cells which are an active part of the immune system.

Many studies suggest that low levels of zinc may increase the risk of viral infections. Some also show that zinc lozenges can shorten the duration from the common cold.

However, identifying the best dosages to support immune health and treat the common cold will require further research.

Many have touted probiotics, or “good bacteria,” as another natural way to boost immunity.

We know they play a key role in helping to maintain a healthy balance of bacteria in the gut, and new research supports the idea that they have beneficial effects on immunity.

For example, a 2020 study — conducted, it should be noted, by a company that produces probiotics — found that using probiotics can reduce the incidence and duration of upper respiratory tract infections.

The authors call for more research to establish a relationship between probiotics and the immune system.

Many people take a supplement or a combination of supplements to prevent or treat COVID-19.

But there is Not enough data to support the use of any vitamin, herb or other supplement to treat or prevent this disease.

Only vaccines, combined with strict hygiene measures, have been proven to help prevent COVID-19. For severe cases of COVID-19, doctors may use specific medications.

To research suggests that vitamin and mineral supplementation may be an inexpensive way to support optimal immune function.

Even vitamin C and D supplementation above current RDAs can benefit the immune system, as long as dosages remain below recommended safe limits.

Many supplements can interact with medications and other supplements. And combining different supplements can also lead to very high amounts of certain nutrients in the body, which can have potentially serious side effects.

For example, excess vitamin C is excreted in the urine and usually does not cause any serious side effects. But very high amounts can cause diarrhea, abdominal pain and nausea.

Too much vitamin D — more than 4000 IU or 100 mcg – may be harmful and cause nausea, vomiting, kidney stones, confusion, loss of appetite and muscle weakness.

Very high levels can even lead to kidney failure, abnormal heartbeat, and death. Vitamin D also interacts with medications, such as orlistat, diet pills (Alli, Xenical), steroids, and cholesterol-lowering statins.

If a person has too much zinc, he may cause negative effects such as nausea, vomiting, diarrhea and headache. Over time, excess zinc can lead to low copper levels, decreased immunity, and lower levels of useful cholesterol. Zinc can also interact with other medications.

Probiotics are safe for Most people. However, they can make illnesses worse or cause bacterial infections in people with very weak immune systems or who are seriously ill.

Living a healthy lifestyle can help the body’s natural defenses and benefit overall health. This may involve:

  • no smoking
  • to exercise
  • avoiding excessive alcohol consumption, for those who drink
  • wash your hands frequently
  • manage stress well
  • keep up to date with recommended vaccines
  • have a balanced diet with lots of fruits and vegetables
  • have a moderate weight
  • get at least 7 hours sleep per 24 hour period

There is no evidence that mega-doses of vitamins and nutrients can boost the immune system. The best way to ensure that the immune system is working well is to eat a balanced diet, get enough sleep, exercise and take the vaccines offered.

Anyone suffering from nutritional deficiencies and unable to eat a healthy, balanced diet may find it beneficial to take a daily multivitamin. But while some research shows that getting more than the RDAs of vitamins C and D might help support immune health, confirming this needs more research.

If a person thinks they have a nutrient deficiency, they should consider talking to a doctor about getting a blood test. This will help identify deficiencies and determine the right approach to supplementation.

Before taking any supplement, a person should have a conversation with a primary care physician who knows their medical history.


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