Research reveals how cooks can maximize
fruits’ and vegetables’ cancer-fighting compounds
BETHESDA, MD — Steaming your broccoli for three to four minutes until it turns a bright green will enhance its cancer-fighting compounds, according to new research presented today at the American Institute for Cancer Research (AICR) Annual Research Conference.
The research finding was presented today at a session focused on the role of food processing and preparation in the enhancement of cancer protection.
“Past food processing has tended to focus on improving taste, visuals and microbiological safety,” said Elizabeth Jeffery, PhD, a researcher at University of Illinois at Urbana-Champaign. “Now our task is to go further. Processing can ensure that the bioactives – the cancer protective compounds – arrive in your digestive system in a form the body can use.”
Broccoli and other cruciferous vegetables are a top source of sulforaphane, a phytochemical (naturally occurring plant compound) that has shown strong cancer-preventive actions in lab studies. The enzyme myrosinase in broccoli is needed for sufulforaphane to form. Destroy the myrosinase, and sufulforaphane cannot form.
A study by Jeffery that compared boiling, microwaving, and steaming found that steaming broccoli for up to five minutes was the best way to retain its myrosinase. Boiling and microwaving broccoli for one minute or less destroyed the majority of the enzyme.
Another study by Jeffery suggests that if you do eat well-cooked broccoli, you can still get sulforaphane to form by adding raw foods containing myrosinase to your meal. In this study, participants ate a broccoli supplement with no active myrosinase. When some participants ate a second food with myrosinase, their blood and urine levels of sulforaphane were significantly higher than those who did not eat the food.
“Mustard, radish, arugula, wasabi and other uncooked cruciferous vegetables such as cole slaw all contain myrosinase, and we’ve seen this can restore the formation of sulforaphane,” Jeffery said.
The studies on food processing add to the existing research on food preparation techniques that maximize plant foods’ cancer protective compounds. Previous research has shown:
- Crushing or chopping garlic then waiting 10 to 15 minutes before exposing it to heat allows its inactive compounds to convert into the active, protective phytochemical known as allicin
- Cooking tomatoes and other foods that contain lycopene allows our body to more easily absorb the phytochemical
- Boiling vegetables for a long time means you will lose water-soluble vitamins, such as vitamin C, folate and niacin that leach into the water
“As we’re learning, food processing isn’t just what happens to food before it reach the grocery shelves,” said AICR Associate Director of Nutrition Programs Alice Bender, MS, RD. “This research highlights that what you do in your kitchen can make those fruits and vegetables on your plate even more cancer protective.”
Other research on food preparation/processing presented at today’s session highlighted:
- How mixing, blending and heat can increase our body’s use of carotenoids, a cancer-protective compound found in orange-colored fruits and vegetables, presented by Marc E. G. Hendrickx, PhD, Center for Food and Microbial Technology, KU Leuven, Belgium.
- How to process and prepare meat to minimize the formation of carcinogens, presented by Amanda J. Cross, PhD, Imperial College London, London, UK.
- How yogurt, buttermilk and other fermented foods may be linked to lower cancer risk, presented by Johanna W. Lampe, PhD, RD, Fred Hutchinson Cancer Research Center
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To the Editors: