Our nutrition has a significant impact on the strength of our immune system. Disruptions in nutrition or inadequate nutrition can result in increased susceptibility to infections as a result of nutrient deficiency or chronic inflammation. Clinical research supports the connection between immune strength and nutrition, with studies monitoring nutrition and modulation of immune function in both healthy individuals and those with compromised immune systems.1
Ensuring that you’re eating foods rich in the particular compounds that strengthen the immune system against illnesses is one science-backed method for reducing your chances of getting sick and reducing illness severity when you do get sick. Yes, you can and should take measures to avoid coming into contact with germs (e.g., sanitizing surfaces, washing hands regularly), but germs are everywhere, and modern living often entails existing in close quarters with many people. And despite preventative measures, you’ll still come into contact with germs. Taking care of your body, however, inside and out, will increase its ability to protect you from illness. This could take the form of a multivitamin, but we suggest first improving your eating habits. Luckily, there are plenty of ways to achieve optimal immune health through a variety of foods. Important compounds for fighting illnesses like the flu or the common cold are antioxidants such as vitamin C, as well as vitamin D and the mineral zinc.
Antioxidant is an umbrella term for a substance that removes potentially damaging oxidizing agents in a living organism. Specific antioxidants include carotenoids like beta-carotene, lutein, and lycopene, vitamins C, A, E, the mineral selenium, and polyphenolic flavonoids. Antioxidants fight oxidative stress—an imbalance between the production of free radicals and the ability of the body to counteract or detoxify their harmful effects through neutralization by antioxidants. Oxidative stress damages our cells and genes and can cause a plethora of health issues. There are many studies that have uncovered the highly beneficial effects of antioxidants on the immune system. For example, epidemiological studies have strong associations between diets rich in antioxidant nutrients and a reduced incidence of cancer; a boost to the body’s immune system by antioxidants might, at least in part, account for this. In addition, antioxidants have shown to modify cell-mediated immune responses in individuals of all ages.2
A study conducted in November of 2009 at the height of the H1N1 pandemic concluded that antioxidants from plant-based sources prevent the influenza (flu) virus from damaging our lung cells. The flu virus damages our lungs through its M2 protein, which attacks epithelial cells and disrupts their ability to remove liquid from the This sets the stage for pneumonia and other flu- associated complications. Antioxidants, however, inhibit this M2 protein from causing this damage.3
Antioxidants can be found in plant foods such as blackberries, pecans, walnuts, cranberries, strawberries, artichoke hearts, blueberries, dark chocolate, raspberries, and cherries.4
Research has shown that the antioxidant, vitamin C, can alleviate prevent some infections caused by bacteria, viruses, or protozoa. Vitamin C levels in white blood cells are tens of times higher than in plasma, which suggests functional roles of the vitamin in these immune system cells. Vitamin C has been shown to affect the functions of phagocytes, production of interferon, replication of viruses, and maturation of T-lymphocytes in laboratory studies. In addition, studies have shown that vitamin C can help prevent and treat pneumonia. It is generally recommended that we consume 90mg of vitamin C per day, with the upper limit being 2,000mg a day.5 Boost your vitamin C intake by consuming foods such as broccoli, bell peppers, strawberries, Brussels sprouts, kiwi, mango, papaya, and pineapple.5 All of these foods contain about 80 to 90mg of vitamin C per cup, with the exception of yellow peppers, which pack a crazy 340mg per serving. If you’re eating a diet rich in these fruits and veggies, you’ll likely surpass your vitamin C recommendation before dinner.6
The positive role that vitamin D plays in immune function has only been discovered within the last decade.
Until then, vitamin D was mainly associated with bone health. However, researchers have recently found the vitamin D receptor and the vitamin D activating enzyme in cells of the intestine, pancreas, prostate, and the immune system. Research on the role of vitamin D within the immune system has uncovered specific processes within immune cells that metabolize vitamin D. These processes, researchers explain, seem essential for normal immune function, suggesting that vitamin D deficiency would lead to dysregulation of immune responses. Another immune system benefit of vitamin D is its possible ability to prevent autoimmune diseases, such as Type 1 diabetes and multiple sclerosis. While early studies suggest vitamin D’s potential to prevent these diseases, researchers are eager to do more intensive, comprehensive research on this topic.
Vitamin D can be found naturally in only a few foods, including fatty fish (salmon, mackerel, sardines, and cod liver oil) and mushrooms (especially if they are sundried). In the United States, many types of milk, both dairy and non- dairy, are fortified with vitamin D, though this is not naturally occurring. Researchers explain that vitamin D is mainly synthesized in the skin after exposure to UVB rays. If you decide to take a vitamin D supplement, it is recommended to stay below 4000IU per day.7
In the last few decades, the mineral zinc has been shown to play a role in immune modulation. It is believed that zinc is involved in the creation and survival of cells involved in both innate immunity (immunity with which we’re born) and adaptive immunity (immune responses developed over time to invading pathogens, such as viruses). Zinc deficiency causes a decrease in both kinds of immunity, and chronic deficiency can lead to inflammatory diseases, such as rheumatoid arthritis.
One of the most notable immune benefits of zinc is its evident ability to shorten the lifespan of the common cold. In a review of clinical trials involving zinc supplementation and the common cold, authors concluded that 75mg of zinc administered within 24 hours of the onset of cold symptoms resulted in a significant reduction in the duration of the cold. Researchers note that zinc lozenges are the safest and most effective way to administer this cold combating micronutrient.9
Healthy individuals should aim to consume about 16mg of zinc per day. Foods high in zinc include oysters; toasted wheat germ; pumpkin, sesame, and hemp seeds; whole grains; and leafy green vegetables.10
Cooper E, Ma M. Understanding nutrition and immunity in disease management. J Tradit Complement Med. 2017 Oct; 7(4): 386–391. Hughes, DA. Effects of dietary antioxidants on the immune function of middle-aged adults. Proc Nutr Soc. 1999 Feb;58(1):79-84.
Science Daily (site). Scientists discover influenza’s achilles heel: antioxidants. October 30, 2009. https://www.sciencedaily.com/ releases/2009/10/091029125538. htm. Accessed February 10, 2018. Polk J. Health (site). 10 antioxidant foods you should be eating.
January 17, 2018. http://www. health.com/food/top-foods-with- antioxidants#raspberries-antioxidants. Accessed February 12, 2018.
Hemila H. Vitamin C and infections. Nutrients. 2017 Apr; 9(4): 339.
Ekelkamp S. Prevention (site). 9 food with more vitamin C than an orange. https://www.prevention.com/food/9- foods-with-more-vitamin-c-than-an- orange. Accessed February 12, 2018. Prieti, B. Treiber, G, Pieber, T. Vitamin D and immune function. Nutrients. 2013 Jul; 5(7): 2502–2521. Bonaventura P, Benedetti G,
Albarède F, Miossec P. Zinc and its role in immunity and inflammation. Autoimmun Rev. 2015 Apr;14(4):277– 85.
Singh M, Das RR. Zinc for the common cold. Cochrane Database Syst Rev. 2013 Jun 18;(6):CD001364. MyFoodData (site). The 10 best foods high in zinc. February 13,
2018. https://www.myfooddata.com/ articles/zinc.php. Accessed February 13, 2018. NHR