How does your immune system work?

Your immune system is made up of cells, tissues, and organs that help fight viruses, bacteria, and other germs that cause infections and other diseases. For example, your skin helps prevent germs from getting inside your body. Cells that line your digestive tract also help protect against harmful germs that cause diseases. White blood cells try to destroy substances they recognize as foreign to your body. Some white blood cells also recognize germs they have been exposed to before and develop antibodies to defend against them in the future.

What do we know about specific dietary supplement ingredients and immune function?

Your immune system needs certain vitamins and minerals to work properly. These include vitamin C, vitamin D, and zinc. Herbal supplements, probiotics, and other dietary supplement ingredients might also affect your immune system.

Eating a variety of nutritious foods can give you enough vitamins, minerals, and other nutrients for a healthy immune system. However, you might wonder whether taking certain dietary supplements can improve your body’s immune system and its ability to fight infections.

Vitamins and Minerals

Getting enough vitamins and minerals through the foods and beverages you consume is important for a healthy immune system. It’s especially important to get enough of vitamins A, B6, B12, C, D, E, and K as well as folate, copper, iodine, iron, magnesium, selenium, and zinc.

If your diet doesn’t include adequate amounts of certain vitamins and minerals, your immune system will not be able to function as well as it could, you might be more likely to get infections, and you might not recover as well. If your health care provider determines that you are not getting enough of a specific nutrient, vitamin and mineral supplements can help increase intakes to recommended amounts. In most cases, however, if you don’t have a deficiency, increasing your intake of vitamins and minerals through dietary supplements doesn’t help prevent infections or help you recover from them any faster.

In studying the variety of essential vitamins available today, Vitamin A is among these essential vitamins that improve our vision, immune system, skin, and overall health.

Vitamin A

Vitamin A is an essential nutrient found in many foods. It exists in two different forms:

• Preformed vitamin A is found in fish, organ meats (such as liver), dairy products, and eggs.
• Provitamin A carotenoids are turned into vitamin A by your body. They are found in fruits, vegetables, and other plant-based products. The most common provitamin A carotenoid in foods and dietary supplements is beta-carotene.

Vitamin A is important for healthy immune function as well as vision, reproduction, growth, and development.

Vitamin A deficiency is rare in the United States, but it is common in many low- and middle-income countries.

The recommended daily amount (known as Recommended Dietary Allowance or RDA) ranges from 300 to 1,200 microgram (mcg) retinol activity equivalents (RAE) for infants, children, and teens, depending on age, and from 700 to 1,300 mcg RAE for adults.

Does it work?

Diarrhea in children

Children with a vitamin A deficiency are more likely to get diarrhea caused by germs. These children also have a higher chance of dying of diarrhea, especially in sub-Saharan Africa and south Asia.

Research suggests that vitamin A supplements lower the risk and severity of diarrhea in children in low- and middle-income countries. However, vitamin A supplementation might not help very young infants in these countries.

HIV infection

HIV infection can decrease your appetite and weaken your body’s ability to use nutrients from food. HIV can also increase the risk of related health problems, such as diarrhea and respiratory diseases.

It’s not clear if vitamin A supplements lower the risk of spreading HIV or keep the disease from getting worse. Some studies in young children with HIV have found that vitamin A supplements help lower the risk of death. However, it’s not clear whether vitamin A supplements affect the risk of diarrhea or respiratory infections in young children with HIV. Other studies in adults with HIV have found that vitamin A supplements do not improve immune function.

Research in pregnant people with HIV has found that vitamin A supplements do not help reduce the chance of passing HIV from mother to infant. However, one study found that pregnant people with HIV who took vitamin A were more likely to carry their babies to full-term.

Measles in children

In low- and middle-income countries where vitamin A deficiency is common, children with measles are more likely to have severe symptoms and may die from the disease. In these children, vitamin A supplements might help prevent measles, but it’s unclear whether they lower the risk of dying from measles.

Pneumonia and other respiratory infections in children

Children who don’t get enough vitamin A might have a higher risk of respiratory infections. However, it’s not clear whether taking vitamin A supplements affects the risk or severity of pneumonia and other respiratory infections. Some studies in young children with pneumonia have found that vitamin A supplements shorten the length of time children need to be hospitalized and decrease the number of days they have symptoms (such as fever and cough). However, other studies in children have found that vitamin A supplements don’t lower the risk of getting or dying from pneumonia or other respiratory infections. In addition, some research suggests that taking higher than recommended doses of vitamin A supplements might increase the risk of respiratory infections in children who already get enough nutrients from the foods they eat.

Is it safe?

Preformed vitamin A is safe at daily intakes up to 600 to 2,800 mcg for infants, children, and teens, depending on age, and up to 3,000 mcg for adults. There are no upper limits for beta-carotene and other forms of provitamin A.

Getting too much preformed vitamin A can cause severe headache, blurred vision, nausea, dizziness, muscle aches, and problems with coordination. In severe cases, getting too much preformed vitamin A can even lead to coma and death.

If you are pregnant, taking too much preformed vitamin A can cause birth defects, including abnormal eyes, skull, lungs, and heart. If you are or might be pregnant or breastfeeding, you should not take high-dose supplements of preformed vitamin A.

High intakes of beta-carotene (provitamin A) do not cause the same problems as preformed vitamin A. Consuming high amounts of beta-carotene can turn the skin yellow-orange, but this condition is harmless and goes away when you eat less of it. However, several studies have shown that smokers, former smokers, and people exposed to asbestos who take high-dose beta-carotene supplements have a higher risk of lung cancer and death.

Vitamin A supplements might interact with some medications such as orlistat (used for weight loss), acitretin (used to treat psoriasis), and bexarotene (used to treat the skin effects of T-cell lymphoma).

More information about vitamin A is available in the ODS consumer fact sheet on vitamin A.

Source: NIH