The Durk Pearson & Sandy Shaw®
Life Extension NewsTM
Volume 11 No. 7 • December 2008

Absorption of Sulforaphane in Humans Higher After
Consuming Raw As Opposed to Cooked Broccoli

One of the important health-promoting constituents of broccoli, cauliflower, and other cruciferous vegetables is the isothiocyanate, sulforaphane. Animal studies have shown sulforaphane to be a potent anti-carcinogen that is proposed to work by inhibiting carcinogen-activating phase 1 biotransformation enzymes, inducing phase II detoxification enzymes, anti-inflammation, and induction of apoptosis (programmed cell death).1

A new study1 reports that, in eight men who ate 200 grams of crushed broccoli, either raw or cooked, with a warm meal in a randomized free-living open cross-over trial, sulforaphane was found in significantly greater amounts in the blood and urine of those who ate the raw as compared to the cooked broccoli. The bioavailability of sulforaphane was reported to be 37% after raw broccoli consumption as compared to 3.4% after cooked broccoli consumption. The absorption of sulforaphane was also delayed after eating cooked broccoli, with peak plasma levels for sulforaphane reached at 6 hours for cooked versus 1.6 hours for raw broccoli.

Phase II Detoxification Pathway to Better Health

The induction of phase II enzymes has been reported in many animal studies to promote important health-protective effects (for example, anti-inflammation,1a suppression of neuron loss in a fruit fly model of Parkinson’s disease,2 hypolipidemic effects of green tea,3 silibinin in cancer chemoprevention,4 protection against chemical carcinogenesis by curcumin,5 and healthier aging.6 Phase II enzyme inducers include, in addition to those found in cruciferous vegetables, black tea,7 green tea,3 green onion,8 BHT,1a and anthocyanins (the blue and purple colored substances found in, for example, berries).9

1. Vermeulen et al. Bioavailability and kinetics of sulforaphane in humans after consumption of cooked versus raw broccoli. J Agric Food Chem 56:10505-10509 (2008)
1a. Juurlink. Therapeutic potential of dietary phase 2 enzyme inducers in ameliorating diseases that have an underlying inflammatory component. Can J Physiol Pharmacol 79:266-282 (2001)
2. Trinh et al. Induction of the phase II detoxification pathway suppresses neuron loss in Drosophila models of Parkinson’s disease. J Neurosci 28(2):465-472 (2008).
3. Lin et al. Hypolipidemic effect of green tea leaves through induction of antioxidant and phase II enzymes including superoxide dismutase, catalase, and glutathione S-transferase in rats. J Agric Food Chem 46:1893-9 (1998).
4. Zhao and Agarwal. Tissue distribution of silibinin, the major active constituent of silymarin, in mice and its association with enhancement of phase II enzymes: implications in cancer chemoprevention. Carcinogenesis 20(11):2101-8 (1999).
5. Iqhal et al. Dietary supplementation of curcumin enhances antioxidant and phase II metabolizing enzymes in ddY male mice: possible role in protection against chemical carcinogenesis and toxicity. Pharmacol Toxicol 92:33-8 (2003).
6. Noyan-Ashraf et al. Phase 2 protein inducers in the diet promote healthier aging. J Gerontol A Biol Sci Med Sci 63A(11):1168-76 (2008).
7. Patel and Maru. Polymeric black tea polyphenols induce phase II enzymes via Nrf2 in mouse liver and lungs. Free Radic Biol Med 44:1897-1911 (2008).
8. Xiao and Parkin. Isolation and identification of phase II enzyme-inducing agents from nonpolar extracts of green onion (Allium spp.). J Agric Food Chem 54:8417-24 (2006).
9. Shih et al. Anthocyanins induce the activation of phase II enzymes through the antioxidant response element pathway against oxidative stress-induced apoptosis. J Agric Food Chem 55:9427-35 (2007).

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