A healthy immune system depends on a combination of adequate nutrition, sleep, physical activity and other healthy habits rather than a single food or drink.
A varied diet that includes fruits, vegetables, whole grains, legumes, nuts and other nutrient-rich foods provides vitamins and minerals needed for normal immune function. The World Health Organization recommends eating at least 400 grams of fruits and vegetables a day for adults and children older than 10.
Vitamin C is among the nutrients involved in immune function. The body cannot produce vitamin C, so it must come from food or supplements. Citrus fruits such as oranges and grapefruit are sources of the vitamin, as are peppers, broccoli, tomatoes, strawberries and other fruits and vegetables.
Getting enough vitamin C is important, particularly because a deficiency can impair immune function. But taking extra vitamin C does not automatically make the immune system stronger in someone who is already getting enough. Research suggests regular vitamin C supplementation may modestly reduce the duration or severity of common-cold symptoms in some people, while taking it after a cold begins may provide little benefit.
Foods to include in a healthy diet
Citrus fruits and other sources of vitamin C
Oranges, grapefruit, lemons and other citrus fruits can contribute to daily vitamin C intake. Other useful sources include red and green peppers, broccoli, tomatoes, strawberries, kiwifruit and potatoes.
Eating whole fruit also provides dietary fibre and other nutrients. Fruit juice can contain vitamin C, but whole fruit is generally a better way to increase fibre intake.
Colourful vegetables
Vegetables such as tomatoes, peppers and broccoli contain vitamins, minerals, fibre and other compounds with antioxidant properties.
WHO recommends a varied intake of vegetables and fruit because they provide essential nutrients and other beneficial compounds. A diet containing a wide range of plant foods is more useful for overall health than focusing on one so-called immune-boosting food.
Chicken soup
Chicken soup has long been used as a comfort food during colds and other respiratory illnesses. There is some laboratory research suggesting that chicken soup can affect the movement of neutrophils, a type of white blood cell involved in inflammation, but that finding does not establish that eating chicken soup strengthens the immune system or treats an infection in people.
Soup can nevertheless be an easy way to consume fluids and food when someone has a reduced appetite.
Garlic and other foods
Garlic contains compounds that have been studied for their potential health effects. However, evidence that garlic prevents or treats infections is limited. The U.S. National Center for Complementary and Integrative Health says there is not enough clinical evidence to establish that garlic prevents or treats the common cold.
Ginger, onions and garlic can be part of a varied diet, but they should not be presented as treatments for flu, colds or other infections.
Water and hydration
Adequate fluid intake is important for normal body function. Water helps maintain the body’s fluid balance and supports processes throughout the body.
There is no evidence that drinking large amounts of water “flushes out toxins” or directly increases the production of antibodies. People who are ill should maintain adequate hydration, particularly when fever, vomiting or diarrhea can increase fluid loss.
Habits that can affect immune health
Food is only one part of maintaining healthy immune function. Sleep, physical activity, stress and exposure to tobacco smoke also matter.
Get enough sleep
Sleep is important for overall health and normal immune function. The amount needed varies by age. The CDC recommends eight to 10 hours a night for teenagers ages 13 to 17 and at least seven hours for adults ages 18 to 60.
Persistent sleep problems should be discussed with a health professional rather than treated simply as a sign of a weak immune system.
Manage chronic stress
Long-term psychological stress has been associated with changes in immune function. A large review of research involving more than 300 studies found that chronic stress was associated with suppression of several measures of cellular and hormonal immune responses.
Managing stress through healthy routines, adequate sleep, physical activity and support from trusted people can contribute to overall well-being. Persistent or severe anxiety or stress may require professional help.
Avoid smoking
Cigarette smoke damages the lungs and weakens immune defenses involved in fighting respiratory infections. The CDC says avoiding smoking can support immune health and help the body respond better to illness and vaccines.
Secondhand smoke can also cause health problems, particularly in children, including respiratory infections and asthma attacks.
Limit alcohol exposure
Heavy alcohol use can interfere with several parts of the immune response and make it harder for the body to defend itself against infections. According to the National Institute on Alcohol Abuse and Alcoholism, both a single episode of heavy drinking and chronic heavy alcohol use can impair immune defenses.
Overall, there is no single food that can “boost” the immune system in the way that some health articles suggest. A balanced diet that supplies adequate nutrients, combined with sufficient sleep, regular physical activity and avoidance of smoking, supports the body’s normal defenses.
