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Antioxidants in broccoli provide long-term protection


A new study shows that a cancer-preventing compound found in broccoli, first isolated a decade ago at John Hopkins University, may prove to protect against a much broader spectrum of diseases than previously thought.

Research cited in a recent issue of the Proceedings of the National Academy of Sciences has demonstrated that the compound, sulforaphane, helps cells defend themselves for days against highly reactive and toxic molecules called oxidants.

"Our work with sulforaphane has focused on cancer, but now it assumes wider significance for human disease because the compound also helps prevent oxidative damage," said Professor Paul Talalay. "The finding that a compound from the diet can provide powerful, chemically versatile and prolonged protection against oxidative stress may particularly impact human retinal disease," he added.

Unlike standard antioxidants that use the molecular equivalent of hand-to-hand combat, sulforaphane works indirectly. Oxidants damage DNA and kill cells, eventually leading to cancer, retinal degeneration, atherosclerosis and other conditions unless they are neutralised.

However the anti-cancer properties in sulforaphane and its indirect antioxidant effects are both due to its ability to make cells create a diverse group of enzymes, called "phase 2" enzymes, that protect against cancer by blocking select chemicals from becoming carcinogens. Not previously considered oxidant fighters, the research shows that the enzymes have the ability to detoxify oxidants, which increases their value in disease prevention.

Studying a variety of cell types and oxidants, the scientists discovered that sulforaphane triggers a cellular response that protects cells against oxidants for two or three days.

"There are many dangers to cells, and it makes sense that cells have protection against these dangers, which include oxidants," commented Talalay. "Elevating these intrinsic protection mechanisms by administering a wide variety of chemicals, many of which are in the diet already, can be an effective way to prevent disease."

While it is widely recognized that diet influences the risk of diseases including cancer, diabetes, cardiovascular disease and stroke, antioxidants have been one of the most promising dietary strategies for preventing disease.

Blindness resulting from damage to the retina has long been linked to attacks by oxidants. Recent evidence suggests that dietary antioxidants can help prevent or reduce damage to retinal cells.

Three different cell types were tested in the experiments including cancer cells and cells from the retina. When the cells were treated briefly with sulforaphane before exposure to an oxidant, all cell types defended themselves against damage. The extent of protection was tied to the amount of sulforaphane as well as the type of oxidant and its amount.

"This adds to already good evidence that eating large quantities of vegetables - and cruciferous ones play a special role - is one thing that really works to fight disease," Talalay said.

First isolated from broccoli, sulforaphane is especially concentrated in three-day-old broccoli sprouts and belongs to a class of molecules called isothiocyanates. Talalay, his colleagues and Johns Hopkins hold patents related to the sulforaphane and broccoli sprout research.