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Green Tea and Broccoli Inhibits Flu in Nasal Cells


Researchers at Chapel Hill North Carolina University's Center for Environmental Medicine have identified how two nutritional supplements, epigallocatechin-3-gallate (EGCG), an extract from green tea, and sulforaphane, a compound from raw broccoli, increase the expression of Nrf2 (nuclear factor erythroid 2-related factor 2) in the human body, accounting for a “significant decrease in influenza virus entry and replication in human nasal cells.”(1)

Nrf2 helps remove damaged proteins from the body. This cell regulator is considered a “guardian of healthspan, and gatekeeper of species longevity,” according to researchers at the Department of Cellular and Structural Biology, University of Texas. Nrf2 has been found to interact with tumor suppressor protein 53 (p53), and nuclear factor-kappa beta (NF-κB) who’s combined effects can protect against many age related diseases, including cancer and neurodegenration. (1a)

An additional Nrf2 effect was identified by the Chapel Hill researchers. In the absence of infection, the activity of Nrf2 via nutritional sulforaphane supplements SFN and EGCG increased baseline response of antiviral agents, RIG-I, IFN-beta, and MxA, suggesting a protective effect against flu infections. Study researchers of this comment how the nutritional influence of phase II antioxidant enzyme pathways of EGCG, and sulforaphane may prove to be an effective therapy for virus inflammation and immune clearance. This research was published in the Free Radical Biological Medicine, April 2011.(1)

Broccoli spear slice

Brassica (Broccoli) → hydrolysis by myrosinase (Myrosine) → glucosinolate (Glucoraphanin) → isothiocyanate (Sulforaphane)

Broccoli is a rich source of glucoraphanin, the glucosinolate precursor of sulforaphane. Evidence suggests sulforaphane can reduce and prevent influenza infection, inflammation and cancer.

Other cruciferous vegetables besides, broccoli, are considered for their immune building effects including, brussels sprouts, garden cress, mustard greens, turnip, cabbage (savoy), kale, watercress, kohlrabi, red cabbage, horseradish, cauliflower and bok choy.

Bioavailable Nutrients - Raw or Cooked?

Thorough chopping, or chewing, of raw broccoli helps to improve metabolism and bioavailability of Glucoraphanin by releasing the catalyst myrosine. Myrosine provides an increased breakdown of glucosinolates, that translate into biologically active compounds called isothiocyanates.(2a)

Selected Isothiocyanates, such as sulforaphane, not only have been shown to inhibit viral replication(2b), but have also have been researched for their ablitily to inhibit bladder cancer(2c).

The myrosinase catalyst in cabbage is completely destroyed by heat, however the myrosinase activity of human intestinal bacteria allows for some formation, and absorption of isothiocyanates. (3).

Intestinal bacteria appear to use hydrolysis, converting glucoraphanin into a bioactive form of sulforaphane. Researchers using “US Pharmacopeia methods,” found that “glucoraphanin is not destroyed by digestive enzymes during passage through the digestive tract.” They noted how sulforphane are able to cross the enterocyte cells that line the intestinal wall. (3a)

The body’s absorption, and excretion, of isothiocyanates is significantly higher from raw vegetables than from cooked. (2, 4, 5) Glucosinolates are water soluble, migrating from plant cells into hot water when boiled. Boiling vegetables for 9 to 15 minutes results in a 18 to 59% decrease in glucosinolates.(52) Using less while cooking vegetables like steaming or microwaving, may reduce the loss of glucosinolate. However, some cooking practices, including boiling (2), steaming (4, 58), and microwaving at high power (750-900 watts) (5, 58, 59), cause the inactivation of myrosinase, the enzyme that catalyzes glucosinolate.

Several studies have found that consuming five or more servings per week of cruciferous vegetables provides a significant reduction in cancer risk. (6-8)

Glucosinolate Content
Food (raw)Serving
Glucosinolates (mg)
Brussels sprouts ½ cup (44g)
Garden cress½ cup (25g)
Mustard greens½ cup, chopped (28g)
Turnip½ cup, cubes (65g)
Cabbage, savoy½ cup, chopped (45g)
Kale1 cup, chopped (67g)
Watercress 1 cup, chopped (34g)
Kohlrabi½ cup, chopped (67g)
Cabbage, red½ cup, chopped (45g)
Broccoli½ cup, chopped (44g)
Horseradish1 tablespoon (15g)
Cauliflower ½ cup, chopped (50g)
Bok choi (pak choi)½ cup, chopped (35g)

Food Sources of Isothiocyanates
IsothiocyanateGlucosinolate (precursor)Food Sources
Allyl Isothiocyanate (AITC) Sinigrin Broccoli, Brussels sprouts, cabbage, horseradish, mustard, radish
Benzyl Isothiocyanate (BITC) Glucotropaeolin Cabbage, garden cress, Indian cress
Phenethyl-Isothiocyanate (PEITC) Gluconasturtiin Watercress
Sulforaphane (SFN) Glucoraphanin Broccoli, Brussels sprouts, cabbage


1. Kesic MJ, Simmons SO, Bauer R, Jaspers I.
Nrf2 expression modifies influenza A entry and replication in nasal epithelial cells.
Free Radical Biological Medicine, 2011 April. PMID:21549835

1a. Lewis KN, Mele J, Hayes JD, Buffenstein R.
Nrf2, a guardian of healthspan and gatekeeper of species longevity.
Integr Comp Biology. 2010 Nov;50(5):829-43 PMID:21031035

2a. Shapiro TA, Fahey JW, Wade KL, Stephenson KK, Talalay P.
Chemoprotective glucosinolates and isothiocyanates of broccoli sprouts: metabolism and excretion in humans.
Cancer Epidemiol Biomarkers Prevention. 2001;10(5):501-508. PMID:11352861

2b. Inhibition of virus multiplication by selected isothiocyanates.
Rada B, Hanusovská T, Drobnica L, Nĕmec P.
Acta Virol. 1971 Jul;15(4):329-32. PMID:4398087

2c. Inhibition of bladder cancer by broccoli isothiocyanates sulforaphane and erucin: Characterization, metabolism, and interconversion.
Abbaoui B, Riedl KM, Ralston RA, Thomas-Ahner JM, Schwartz SJ, Clinton SK, Mortazavi A.
Mol Nutrition Food Research. 2012 Oct 5. PMID: 23038615

3. Shapiro TA, Fahey JW, Wade KL, Stephenson KK, Talalay P.
Human metabolism and excretion of cancer chemoprotective glucosinolates and isothiocyanates of cruciferous vegetables.
Cancer Epidemiol Biomarkers Prevention. 1998;7(12):1091-1100. PMID:9865427

3a. Lai RH, Miller MJ, Jeffery E.
Glucoraphanin hydrolysis by microbiota in the rat cecum results in sulforaphane absorption.
Division of Nutritional Sciences, University of Illinois, Food Funct. 2010 Nov;1(2):161-6.

4. Conaway CC, Getahun SM, Liebes LL, et al.
Disposition of glucosinolates and sulforaphane in humans after ingestion of steamed and fresh broccoli.
Nutrition Cancer. 2000;38(2):168-178. PMID:11525594

5. Rouzaud G, Young SA, Duncan AJ.
Hydrolysis of glucosinolates to isothiocyanates after ingestion of raw or microwaved cabbage by human volunteers.
Cancer Epidemiol Biomarkers Prevention. 2004;13(1):125-131. PMID:14744743

6. Feskanich D, Ziegler RG, Michaud DS, et al.
Prospective study of fruit and vegetable consumption and risk of lung cancer among men and women.
Journal of the National Cancer Institute. 2000;92(22):1812-1823. PMID:11078758

7. Giovannucci E, Rimm EB, Liu Y, Stampfer MJ, Willett WC.
A prospective study of cruciferous vegetables and prostate cancer.
Cancer Epidemiol Biomarkers Prevention. 2003;12(12):1403-1409. PMID:14693729

8. Michaud DS, Spiegelman D, Clinton SK, Rimm EB, Willett WC, Giovannucci EL. Fruit and vegetable intake and incidence of bladder cancer in a male prospective cohort.
Journal of the National Cancer Institute. 1999;91(7):605-613. PMID:14693729


are assistants of board reviewed doctors that are medical editors, authors, and reviewers, providing oversight for Heartspring.net. This article is currently undergoing doctor reveiw.


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Updated: Dec 21 2013