Bottom Line: Broccoli sprouts contain compounds that have anticancer effects. Further studies are warranted.
Broccoli sprouts are young broccoli plants. They contain compounds with strong chemopreventive effects. Small studies in humans suggest that broccoli sprouts can help to eliminate environmental toxins, protect against bacterial infections and against oxidative damage. More research is needed to confirm these effects.
- Cancer Prevention
Studies done in the lab and in animals have shown that broccoli sprouts contains sulforaphane, which has strong anticancer properties. In a study conducted in humans, broccoli sprouts were found to play a role in eliminating cancer-causing chemicals. Large scale studies are needed to confirm such effects.
- Bacterial Infections
Small studies in humans suggest that broccoli sprouts may help reduce inflammation of the stomach caused by the bacterium Helicobacter pylori.
Laboratory studies show that broccoli sprouts have anticancer effects, but human studies have yet to be conducted.
Brassica oleracea L. var. italica Plenck
Broccoli sprouts are young broccoli plants that are rich in glucoraphanin, a precursor of sulforaphane. Sulforaphane has been shown in vitro studies to have anticancer effects against prostate (1), breast (2) (3), and urinary cancers (4). It may also protect the skin from ultraviolet radiation (5).
Consumption of broccoli sprouts was found to help reduce Helicobacter pylori induced gastritis (6) (7), protect against oxidative stress-induced upper airway disease (8) and against oxidative DNA damage (9). Glucoraphanin extracted from broccoli sprouts may play a role in the excretion of environmental toxicants (10). A small Phase I study in healthy volunteers found broccoli sprout extract to be safe and well tolerated (11). Further research is warranted.
No adverse effects have been reported with consumption of broccoli sprouts.
- Isothiocyanates: Sulforophane
- Carotenoids (12)
Mechanism of Action
Glucoraphanin is converted in the gut to sulforaphane, an isothiocyanate, by the action of myrosinase enzymes from the plants. Sulforaphane blocks the initiation stage in carcinogenesis by inhibiting enzymes that convert procarcinogens to carcinogens and by inducing phase 2 enzymes that detoxify carcinogens and facilitate their excretion from the body. Induction of phase 2 enzymes is done via anti-oxidant response element (ARE)-driven gene expression whose targets include NAD(P)H:quinone reductase (NQO1), heme oxygenase 1 (HO1) and gamma-glutamylcysteine synthetase (ã-GCS), a rate-limiting enzyme in glutathione (GSH) synthesis. These genes are regulated by nuclear factor E2-factor related factor (Nrf2) (13). Sulforaphane also suppresses cancer development through various molecular targets. It induces G2/M cell cycle arrest suppressing proliferation via cyclin-dependent kinases (CDKs) and triggers dose-dependent apoptosis via death-receptor caspase cascades or the mitochondrial caspase cascades. Also, sulforaphane inhibits histone deacetylase (HDAC) by its metabolites in vitro (13).
Upon oral administration, broccoli sprout extract is absorbed rapidly reaching peak plasma concentration after 1 hour (4). The half-life of the sprouts is 1.77±0.13 hours. The primary metabolite is sulforaphane-N-acetylcysteine (SFN-NAC) and is excreted in urine (13). It is completely cleared from the body within 72 hours (13). The bioavailability of sulforaphane varies greatly between individuals (10).
Literature Summary and Critique
In vitro studies indicate anticancer effects of broccoli sprouts, but human studies have yet to be conducted.
1. Abdulah R, Faried A, Kobayashi K, et al. Selenium enrichment of broccoli sprout extract increases chemosensitivity and apoptosis of LNCaP prostate cancer cells. BMC Cancer. 2009;9:414.
2. Li Y, Zhang T, Korkaya H, et al. Sulforaphane, a dietary component of broccoli/broccoli sprouts, inhibits breast cancer stem cells. Clin Cancer Res. 2010;16(9):2580-2590.
3. Fahey JW, Haristoy X, Dolan PM, et al. Sulforaphane inhibits extracellular, intracellular, and antibiotic-resistant strains of Helicobacter pylori and prevents benzo[a]pyrene-induced stomach tumors. Proc Natl Acad Sci U S A. May 28 2002;99(11):7610-7615.
4. Munday R, Mhawech-Fauceglia P, Munday CM, et al. Inhibition of urinary bladder carcinogenesis by broccoli sprouts. Cancer Res. Mar 1 2008;68(5):1593-1600.
5. Talalay P, Fahey JW, Healy ZR, et al. Sulforaphane mobilizes cellular defenses that protect skin against damage by UV radiation. Proc Natl Acad Sci U S A. Oct 30 2007;104(44):17500-17505.
6. Moon JK, Kim JR, Ahn YJ, Shibamoto T. Analysis and anti-Helicobacter activity of sulforaphane and related compounds present in broccoli ( Brassica oleracea L.) sprouts. J Agric Food Chem. Jun 9 2010;58(11):6672-6677.
7. Yanaka A, Fahey JW, Fukumoto A, et al. Dietary sulforaphane-rich broccoli sprouts reduce colonization and attenuate gastritis in Helicobacter pylori-infected mice and humans.Cancer Prev Res (Phila Pa).Apr 2009;2(4):353-360.
8. Riedl MA, Saxon A, Diaz-Sanchez D. Oral sulforaphane increases Phase II antioxidant enzymes in the human upper airway. Clin Immunol. 2009;130(3):244-251.
9. Hoelzl C, Glatt H, Meinl W, et al. Consumption of Brussels sprouts protects peripheral human lymphocytes against 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) and oxidative DNA-damage: results of a controlled human intervention trial. Mol Nutr Food Res. 2008;52(3):330-341.
10. Kensler TW, Chen JG, Egner PA, et al. Effects of glucosinolate-rich broccoli sprouts on urinary levels of aflatoxin-DNA adducts and phenanthrene tetraols in a randomized clinical trial in He Zuo township, Qidong, People’s Republic of China. Cancer Epidemiol Biomarkers Prev. 2005;14(11 Pt 1):2605-2613.
11. Shapiro TA, Fahey JW, Dinkova-Kostova AT, et al. Safety, tolerance, and metabolism of broccoli sprout glucosinolates and isothiocyanates: a clinical phase I study. Nutr Cancer. 2006;55(1):53-62.
12. Park EJ, Pezzuto JM. Botanicals in cancer chemoprevention. Cancer Metastasis Rev. 2002;21(3-4):231-255.
13. Clarke JD, Dashwood RH, Ho E. Multi-targeted prevention of cancer by sulforaphane. Cancer Lett.2008;269(2):291-304.
This article was originally published on the Memorial Sloan-Kettering Cancer Center’s website.