During the flu season or times of illness, people often seek special foods or vitamin supplements that are believed to boost immunity. A balanced diet consisting of a range of vitamins and minerals, combined with healthy lifestyle factors like adequate sleep and exercise and low stress, most effectively primes the body to fight infection and disease. Eating enough nutrients as part of a varied diet is required for the health and function of all cells, including immune cells. Each stage of the body’s immune response relies on the presence of many micronutrients. Examples of nutrients that have been identified as critical for the growth and function of immune cells include vitamin C, vitamin D, zinc, selenium, iron, and protein (including the amino acid glutamine).1
A deficiency of single nutrients can alter the body’s immune response. Animal studies have found that deficiencies in zinc, selenium, iron, copper, folic acid, and vitamins A, B6, C, D, and E can alter immune responses. These nutrients help the immune system in several ways: working as an antioxidant to protect healthy cells, supporting growth and activity of immune cells, and producing antibodies. Epidemiological studies find that those who are poorly nourished are at greater risk of bacterial, viral, and other infections.1
Vitamin A: Vitamin A supports healthy eyesight and immune system functions. Children with vitamin A deficiency face an increased risk of blindness and death from infections such as measles and diarrhea.2
Vitamin C: Vitamin C is needed for the growth and repair of tissues in all parts of your body. It is used to form an important protein used to make skin, tendons, ligaments, and blood vessels. It also helps heal wounds and form scar tissue. Vitamin C deficiency has been estimated to occur in 14% of males and 10% of females in the United States.2
Vitamin D: Vitamin D builds strong bones by helping the body absorb calcium. It also helps the immune system resist bacteria and viruses. Vitamin D is required for muscle and nerve functions. Bodies make vitamin D from sunlight.2
Zinc: Zinc promotes immune functions and helps people resist infectious diseases including diarrhea, pneumonia and malaria. Zinc is also needed for healthy pregnancies. Globally, 17.3% of the population is at risk for zinc deficiency due to dietary inadequacy; up to 30% of people are at risk in some regions of the world.2
Folate: Folate (vitamin B9) is essential in the earliest days of fetal growth for healthy development of the brain and spine. Folic acid is another form of vitamin B9. Women of reproductive age need 400 micrograms of folic acid every day.2
Iron: Iron is critical for motor and cognitive development. Iron deficiency is a leading cause of anemia which is defined as low hemoglobin concentration. Anemia affects 40% of children younger than 5 years of age and 30% of pregnant women globally.2
1. Harvard School of Public Health. https://www.hsph.harvard.edu/nutritionsource/nutrition-and-immunity/.
2. Centers for Disease Control and Prevention. https://www.cdc.gov/nutrition/micronutrient-malnutrition/micronutrients/index.html.