The immune system is a complex network of cells, organs, and tissues that work together to protect us against disease. When the immune system is weakened, we are more vulnerable to catching any 'bugs' that are going around; this includes common colds, flu, and other viruses.
Nutrition plays a vital role in keeping the immune system healthy. Current research shows that more than 20 different nutrients are necessary to keep the system functioning at its best. Vitamin A, vitamin C, vitamin D, vitamin E, zinc, selenium, and probiotics are among the most well-known and well-researched.
No single food can 'boost' the immune system, however, there are foods that, as part of a varied and balanced diet, can provide some of the key nutrients it requires. Foods that support your immune system function and overall health include brazil nuts, oatmeal, yogurt, berries, sweet potatoes, bell peppers, mushrooms, and more...
Brazil nuts are by far the best dietary source of selenium, containing around 100 times more than other nuts and providing more than the recommended daily allowance in a single nut! (1) Selenium is essential for immune system function and has many roles in immunity, including enabling a type of white blood cell, called neutrophils, to defend us against invading pathogens. (2) Studies have found that higher blood selenium levels are associated with an enhanced immune response. (3)
Oats contain a special type of soluble fiber called beta-glucans, which may stimulate the immune system to help protect us against bacterial and viral infections. Preliminary research (in test tubes and animals) has shown that beta-glucans activates certain types of white blood cells. (4) Oats are a healthy addition to any diet; they also provide immune system essentials selenium and zinc, along with several other minerals, B vitamins, and fiber.
Live, natural yogurt contains beneficial bacteria called probiotics, which help keep the gut healthy. The balance of bacteria in our gut influences many aspects of health including our immunity. (5,6,7) 70% of our immune system is in fact, thought to be located in the gut, and increasing the numbers of beneficial bacteria here, strengthens our body?s defenses. Choose natural, unsweetened (preferably organic) yogurt to avoid added sugar, sweeteners, and other additives.
Berries are an excellent source of immune essential vitamin C, along with many protective antioxidants. Vitamin C is integral to the immune system by enhancing the activity of various immune cells (8) and functions as an antioxidant itself. When the immune system fights invading organisms, free radicals are produced and these must be neutralized by antioxidants to prevent them from causing harm. (9) A constant supply of vitamin C and other antioxidants is thus beneficial for a healthy immune system.
Sweet potatoes are a top dietary source of immune system 'hero' beta-carotene. This nutrient has double immune-enhancing actions, both as beta-carotene itself and vitamin A, into which it is converted in the body. Vitamin A deficiency is well known to lead to an impaired ability to fight off infections. Beta-carotene supports and protects the immune system further via antioxidant effects and by increasing immune cell numbers and activity. (10)
Bell peppers (capsicum) are a top source of two immune essentials: vitamin C and beta-carotene. Just half an average red pepper contains 150% of your daily value for vitamin C. Studies have shown that vitamin C (as high dose supplements) can slightly reduce the severity of the common cold and help you recover more quickly. (11) Other top sources of vitamin C are strawberries, guavas, kiwi, kale, broccoli, citrus fruits, tomatoes, and papaya plus all other fruits and vegetables.
Mushrooms are a great source of several key nutrients that support immune function including beta-glucans, selenium, and zinc. Mushrooms also contain a small amount of vitamin D, but can provide much higher amounts if they are exposed to sunlight or UV light before consumption. (12) This is achieved if they are grown outside, treated with UV by growers, or simply by putting them out in the sun for a few hours yourself! Mushrooms exposed to UV are the only vegetarian source that naturally provide substantial amounts of bioavailable vitamin D. (13)
Broccoli contains many beneficial phytochemicals (natural substances found in plants) with antioxidant and anti-inflammatory effects. (14) Sulforaphane, one of these phytochemicals, has recently been generating scientific interest regarding its positive effects on immune function and ability to defend against viruses. (15) Regular consumption of broccoli may also favorably influence the composition of the gut bacteria. (16) Broccoli is also an excellent source of vitamin C, vitamin E, and beta-carotene.
Fermented foods like sauerkraut and kimchi are another top source of natural probiotics to support healthy digestive and immune systems. The beneficial bacteria in fermented foods help keep the lining of the digestive tract strong and healthy, which in turn reduces the chances of harmful substances entering the body. These ?friendly? bacteria support various aspects of immune function including antibody function. Other great fermented foods to try are kombucha (fermented tea), tempeh (fermented soya beans) and miso. (17)
Garlic provides mild antiviral, antibacterial, and antiseptic properties and is described as 'nature?s own antibiotic'. Taking garlic supplements over winter was shown in one study to reduce the chances of catching a cold by 63% and to speed up recovery in those who were infected. (18) In another study, aged garlic extract was shown to stimulate the proliferation of two kinds of immune cells (natural killer cells and T-cells), resulting in reduced severity of colds and flu. (19) Crushing garlic and eating it raw or lightly cooked will retain its potency.
Oily fish is the best naturally occurring dietary source of omega-3 fats and vitamin D, along with being a good source of selenium, B vitamins, antioxidants and protein. Omega-3 fats regulate inflammation in the body, an important process in our "innate" (inbuilt) immunity. In addition, omega-3 fats have a structural role in cell membranes, helping cells, including those involved in immunity, communicate and function more effectively. In addition, omega-3 fats have been shown to have direct effects on various cells of the immune system. (20)
12Nuts and Seeds
Seeds are a top source of both zinc and vitamin E, two key nutrients for immune system function. Zinc has been described as the 'gatekeeper of immune function', due to its role in regulating immune responses. (21) Zinc aids wound healing is required for white blood cell production and stimulates antiviral immune mechanisms. (22) The body cannot store zinc, so a regular supply in the diet is essential. Vitamin E is an antioxidant found in particularly high concentrations in immune cells and has been shown to support immune function and reduce the risk of infections, especially in older people. (23)