Combining broccoli with spicy foods including mustard, horseradish, or wasabi could enhance its cancer-fighting power, new research has found.
A study by the University of Illinois found teaming the vegetable with spicy food containing the enzyme myrosinase also ensures it is absorbed in the upper part of the digestive system for maximum health benefit.
"To get this effect, spice up your broccoli with broccoli sprouts, mustard, horseradish, or wasabi," said Elizabeth Jeffery, University of Illinois professor of nutrition.
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"The spicier, the better; that means it's being effective."
In the study, when fresh broccoli sprouts were eaten with broccoli powder scientists could measure bioactive compounds - compounds found naturally in food that have a health benefit beyond basic nutrition -in the blood 30 minutes later.
When these peaked at three hours they were much higher when the foods were eaten together than when either was eaten alone.
Doctoral candidate Jenna Cramer, lead author of the study - which is available online ahead of its publication in the British Journal of Nutrition - said urine samples corroborated the blood results.
"It's no secret that many people cook the benefits right out of broccoli instead of steaming it lightly for two to four minutes to protect its healthful properties," she said.
"However, this study shows that even if broccoli is overcooked, you can still boost its benefits by pairing it with another food that contains myrosinase."
Co-author Dr Maragarita Teran-Garcia, assistant professor of food science and human nutrition at the university, said myrosinase is needed to form sulforaphane, the vegetable's cancer-preventive component.
The researchers said in the experiment with fresh broccoli sprouts and broccoli powder, the powder did not contain myrosinase, but did contain the precursor to the anti-cancer agent sulforaphane.
Eaten together, the sprouts lent their myrosinase to the powder - so both foods produced sulforaphane and gave greater anti-cancer benefit.
Other foods to boost broccoli's benefits if they are put together include radishes, cabbage, arugula, watercress, and Brussels sprouts.
"Here's another benefit of protecting and enhancing the myrosinase in your foods," Jeffery said.
"If myrosinase is present, sulforaphane is released in the ilium, the first part of your digestive system. Absorption happens well and quickly there, which is why we saw bioactivity in 30 minutes."
An earlier study by Jeffery showed that microbiota are capable of releasing sulforaphane in the lower gut, but absorption happens more slowly in the colon than in the upper intestine, she said.
And the scientists say as little as three to five servings of broccoli a week give a cancer-protective benefit.
Cramer added: "But it pays to spice it up for added benefits and find ways to make it appealing so you don't mind eating it if you're not a broccoli fan.
"I add fresh broccoli sprouts to sandwiches and add them as one of my pizza toppings after the pie is out of the oven."
