More Reasons Not to Skip Your Broccoli

A University of Illinois study shows that healthy gut flora and daily doses of broccoli — even when it's been cooked to within an inch of its life — help fight cancer.
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Though the upcoming holidays signal mass poultry-cide in the name of family togetherness, recent findings in the journal Food & Function might very well change the way we gobble, with more green and less gravy.

A University of Illinois study of rats has shown for the first time that sulforaphane, a cancer-fighting chemical compound in broccoli, can be harnessed by bacteria in our lower gut.

Sulforaphane is a chemical compound released by vegetables like broccoli as a defense mechanism after damage has been done to the plant (like damage from chewing). It's responsible for the vegetable's sometimes sharp and bitter taste, and hence its legion of haters, but with that unpleasantness come great benefit. Sulforaphane has been shown to inhibit cancer cell growth after a regimen of less than one serving of broccoli a day.

Sulforaphane is produced from the metabolism of another broccoli compound, glucosinolate, by the enzyme myrosinase. Glucosinolates also carry cancer-fighting chemicals that boost DNA repair in cells (indole-3-carbinol, if you must know) and that block the initiation of tumors (diindolylmethane).

These chemical powerhouses have already been linked to the reduction of breast, ovarian, prostate, colon and skin cancers. Topping off broccoli's bravado are its walloping anti-viral, anti-bacterial, anti-inflammatory and anti-diabetic properties.

Researchers once believed the key to maximizing broccoli's anti-cancer power was in its preparation. Many people overcook broccoli and destroy the enzyme (myrosinase) that unlocks sulforaphane, leaving the body to naturally eliminate the compound without harnessing its benefits. Boiling also reduces levels of the compound, at losses of 20-30 percent after five minutes, 40-50 percent after 10 minutes, and 77 percent after 30 minutes.

In 2005, University of Illinois professor of human nutrition Elizabeth Jeffrey reported that sulforaphane was maximized when broccoli had been heated for 10 minutes at 140 degrees Fahrenheit or, roughly, steamed for three to four minutes.

In this latest study, also authored by Jeffrey, researchers found that food preparation was only one front for boosting broccoli's benefits — another stems from actually eating it.

Jeffery and colleagues Michael Miller and Ren-Hau Lai injected the lower gut of lab rats with glucosinolates — the intestinal environment of overcooked, myrosinase-free broccoli. The rat's lower gut, called the cecum, houses bacteria that aid in digestion and metabolism, and is similar to the human colon.

Researchers found traces of sulforaphane present in a vein that runs from the cecum to the liver. "The presence of sulforaphane in measurable amounts shows that it's being converted in the lower intestine and is available for absorption in the body," Jeffery said. "Now we know the microbiota in our digestive tract can salvage some of this important cancer-preventive agent."

The team's findings change how we understand cancer prevention and therapy, merging cancer treatment with the popular world of probiotics.

Miller suggested two ways bacteria in the colon could be manipulated to maximize broccoli properties: "One way might be to feed the desirable bacteria with prebiotics like fiber to encourage their proliferation. Another way would be to use a probiotic approach — combining, say, broccoli with a yogurt sauce that contains the hydrolyzing bacteria, and in that way boosting your cancer protection."

"One of the things we don't think about very much is the enormous amount of benefit we experience when a healthy community of bacteria colonizes the lower intestine," Jeffrey said. "We humans have a symbiotic relationship with countless hungry microbes that metabolize vitamins and other bioactive components of food. Now we can see another exciting example of their activity with the role they play in delivering sulforaphane from broccoli."

Jeffrey's study runs on the cover of Food & Function's November 2010 issue.

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