The weather is beginning to cool down, and soon cold and flu season will be upon us. Cold and flu are a larger burden than we may think. Between treatments, illness-compromised productivity, and lost workdays, it is estimated that the common cold alone costs the U.S. $40 billion each year.1
We all know the basics for reducing exposure – wash your hands, avoid touching your face, and avoid being exposed to people who are already ill. However, exposure to these viruses is not the only factor here – excellent nutrition can reduce our vulnerability to infection and reduce the length and severity of illness if we do become infected.
Many micronutrients are required to support proper function of the immune system, and phytochemicals from colorful produce have additional anti-microbial and immune-boosting effects. A well-nourished body houses a high-functioning immune system.
Mushrooms have a unique ability to activate the body’s natural immune defenses. Reishi and shiitake mushrooms enhance activity of natural killer (NK) cells, which attack cancerous and virus-infected cells.2, 3 Shiitake mushrooms protect against influenza infection in animal studies.4-6 Fortunately though, it is not only exotic mushrooms that benefit the immune system. Eating white button mushrooms daily was found to enhance immune defenses in mucosal linings such as those in the mouth and respiratory tract.7 Dendritic cells are another type of immune cell that protects the respiratory tract, and their activity is also enhanced by white button mushroom phytochemicals.8
The cruciferous family of vegetables includes kale, collards, mustard greens, arugula, watercress, broccoli, broccoli rabe, cabbage, cauliflower, kohlrabi, and more. The bitter, spicy, or pungent flavors of these vegetables are provided by glucosinolates, which are converted into potent anti-cancer compounds called isothiocyanates (ITCs) upon chopping or chewing. In addition to their anti-cancer effects, ITCs also support the immune system and have antimicrobial properties. Cruciferous vegetable phytochemicals may enhance interferon activity, which is an important component of the body’s antiviral response.9, 10
Berries are powerful anti-cancer foods that also offer protection against viruses. Antioxidants called flavonoids, which are abundant in berries, have antiviral activity.11 In fact, if you do get the flu, taking anthocyanin-rich elderberry juice may even shorten the duration of your symptoms.12-14 Berries and grapes are also rich in resveratrol, another antioxidant phytochemical with strong antiviral effects – resveratrol has been shown to block the replication of influenza and other respiratory viruses.15-17 Plus, strawberries are high in vitamin C, which protects immune cells from oxidative damage.18 The benefits of berries go far beyond cold & flu protection. Flavonoid antioxidants like those in berries are not just antioxidants – flavonoids also act on signaling within the cell leading to many beneficial effects: flavonoids activate the body’s natural detoxification enzymes, block the growth of cancer cells, decrease inflammation, and support proper blood pressure regulation.19 Berries (and pomegranates) are also extremely rich in another antioxidant called ellagic acid, a compound known to block cancer cell and tumor growth.20-22
Onions & garlic
There is no convincing evidence for using garlic supplements for symptoms of the common cold.23 However, eating garlic and onions daily has clear benefits when it comes to cancer prevention, and may also help to build immune defenses, including macrophage, T cell, and NK cell activity.24, 25 Plus, several garlic phytochemicals have virus-killing activity against common respiratory viruses.26
By eating nutrient-dense plant foods (vegetables, fruits, beans, seeds and nuts) every day, you will provide your body with a spectrum of immunity-boosting phytochemicals, and you’ll get an additional perk too – these same foods protect against heart disease, cancer, diabetes, and other devastating chronic illnesses.
1. Fendrick AM, Monto AS, Nightengale B, et al. The economic burden of non-influenza-related viral respiratory tract infection in the United States. Arch Intern Med 2003;163:487-494.
2. Wachtel-Galor S, Yuen J, Buswell JA, et al: Ganoderma lucidum (Lingzhi or Reishi): A Medicinal Mushroom. In Herbal Medicine: Biomolecular and Clinical Aspects. 2nd edition. Edited by Benzie IFF, Wachtel-Galor S. Boca Raton (FL); 2011
3. Yamaguchi Y, Miyahara E, Hihara J. Efficacy and safety of orally administered Lentinula edodes mycelia extract for patients undergoing cancer chemotherapy: a pilot study. Am J Chin Med 2011;39:451-459.
4. Ciric L, Tymon A, Zaura E, et al. In vitro assessment of shiitake mushroom (Lentinula edodes) extract for its antigingivitis activity. J Biomed Biotechnol 2011;2011:507908.
5. Rincao VP, Yamamoto KA, Ricardo NM, et al. Polysaccharide and extracts from Lentinula edodes: structural features and antiviral activity. Virol J 2012;9:37.
6. Suzuki F, Suzuki C, Shimomura E, et al. Antiviral and interferon-inducing activities of a new peptidomannan, KS-2, extracted from culture mycelia of Lentinus edodes. J Antibiot (Tokyo) 1979;32:1336-1345.
7. Jeong SC, Koyyalamudi SR, Pang G. Dietary intake of Agaricus bisporus white button mushroom accelerates salivary immunoglobulin A secretion in healthy volunteers. Nutrition 2012;28:527-531.
8. Ren Z, Guo Z, Meydani SN, et al. White button mushroom enhances maturation of bone marrow-derived dendritic cells and their antigen presenting function in mice. J Nutr 2008;138:544-550.
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10. Xue L, Pestka JJ, Li M, et al. 3,3′-Diindolylmethane stimulates murine immune function in vitro and in vivo. The Journal of nutritional biochemistry 2008;19:336-344.
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14. Zakay-Rones Z, Thom E, Wollan T, et al. Randomized study of the efficacy and safety of oral elderberry extract in the treatment of influenza A and B virus infections. J Int Med Res 2004;32:132-140.
15. Campagna M, Rivas C. Antiviral activity of resveratrol. Biochem Soc Trans 2010;38:50-53.
16. Xie XH, Zang N, Li SM, et al. Resveratrol Inhibits Respiratory Syncytial Virus-Induced IL-6 Production, Decreases Viral Replication, and Downregulates TRIF Expression in Airway Epithelial Cells. Inflammation 2012;35:1392-1401.
17. Palamara AT, Nencioni L, Aquilano K, et al. Inhibition of influenza A virus replication by resveratrol. J Infect Dis 2005;191:1719-1729.
18. Oregon State University. Linus Pauling Institute: Micronutrient Information Center. Vitamin C. [https://lpi.oregonstate.edu/infocenter/vitamins/vitaminC/index.html]
19. Higdon J: Flavonoids. In An Evidence-Based Approach to Dietary Phytochemicals. New York: Thieme; 2006: 114-126
20. Adams LS, Zhang Y, Seeram NP, et al. Pomegranate ellagitannin-derived compounds exhibit antiproliferative and antiaromatase activity in breast cancer cells in vitro. Cancer Prev Res (Phila) 2010;3:108-113.
21. Wang N, Wang ZY, Mo SL, et al. Ellagic acid, a phenolic compound, exerts anti-angiogenesis effects via VEGFR-2 signaling pathway in breast cancer. Breast Cancer Res Treat 2012;134:943-955.
22. Anitha P, Priyadarsini RV, Kavitha K, et al. Ellagic acid coordinately attenuates Wnt/beta-catenin and NF-kappaB signaling pathways to induce intrinsic apoptosis in an animal model of oral oncogenesis. Eur J Nutr 2011.
23. Lissiman E, Bhasale AL, Cohen M. Garlic for the common cold. Cochrane Database Syst Rev 2012;3:CD006206.
24. Lau BH, Yamasaki T, Gridley DS. Garlic compounds modulate macrophage and T-lymphocyte functions. Mol Biother 1991;3:103-107.
25. Hassan ZM, Yaraee R, Zare N, et al. Immunomodulatory affect of R10 fraction of garlic extract on natural killer activity. Int Immunopharmacol 2003;3:1483-1489.
26. Weber ND, Andersen DO, North JA, et al. In vitro virucidal effects of Allium sativum (garlic) extract and compounds. Planta Med 1992;58:417-423.