Prime Your Immune System for the Flu Season with Cranberry!

For a long time now, the humble cranberry has been relegated to an oft-ignored condiment at Thanksgiving, but it appears the time has come for this little fruit to shine. A growing body of research is revealing that the cranberry has some unique and powerful properties when it comes to immunity.

Recent studies have found that compounds in cranberries interfere with the flu virus’ ability to replicate and establish an infection, in addition to reducing the symptoms of the flu. “Cranberries are incredibly rich in proanthocyanidins, which exert a regulatory effect on human immune cells, priming them to fight off an infection,” Jonathan Clinthorne, PhD, whose doctoral work focused on nutritional immunology, explains. Clinthorne says that these proanthocyanidins seem to be especially beneficial to our immune barriers—the GI tract, the urinary tract, and the mouth. “These are the places where infection can take hold, so if we strengthen these areas, we can prevent viruses and bacterial infections from taking hold in the first place.”

The results of one human study support this idea: the proliferation of a specific type of T-cell—an immune cell found in the immune barriers and a first line of defense against infection—was nearly five times higher after 10 weeks of daily consumption of a cranberry beverage.[1] [2]

Researchers have also discovered that cranberry juice can inhibit the norovirus (the dreaded stomach flu) from adhering to human cells, the essential first step in initiating an infection.[3] [4] Cranberry has been shown to have similar anti-adhering effects on certain types of bacteria, including E. coli and Staphylococcus aureus (staph).[5] [6]

The most effective way to use cranberry is as a preventative; i.e., start taking it before you get sick. “Proanthocyanidins only stay in the body for about 6-12 hours, so it should be taken twice daily to maintain consistent levels,” Clinthorne says.


[1] Weiss E, Houri-Haddad Y, et al. “Cranberry juice constituents affect influenza adhesion and infectivity.” Antiviral Res. 2005 Apr;66(1): 9-12

[2] Nantz MP, Rowe CA, et al. “Consumption of cranberry polyphenols enhances human T cell proliferation and reduces the number of symptoms associated with colds and influenza: a randomized, placebo-controlled intervention study.” Nutr J. 2013 Dec 13;12:161.

[3] Su X, Howell AB, D’Souza DH. “The effect of cranberry juice and cranberry proanthocyanidins on the infectivity of human enteric viral surrogates.” Food Microbiol. 2010 Jun;27(4):535-40.

[4] Dan L, Leen B, et al. “Effects of a Variety of Food Extracts and Juices on the Specific Binding Ability of Norovirus GII.4 P Particles.” J Food Prot. 2012 Jul; 75(7): 1350-1354.

[5] Prachi Gupta, Biqin Song, Catherine Neto, Terri A. Camesano. “Atomic force microscopy-guided fractionation reveals the influence of cranberry phytochemicals on adhesion of Escherichia coli.” Food Funct., 2016; 7 (6): 2655

[6] Worcester Polytechnic Institute. “Cranberry juice shows promise blocking Staph infections.” ScienceDaily. 3 September 2010.

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