Can high heat cooking damage the phytonutrients in bell peppers?
Higher heat cooking can damage some of the delicate phytonutrients in bell peppers. In one recent study from Turkey, the effects of grilling on sweet green bell peppers were studied with respect to one particular phytonutrient--the flavonoid called luteolin. Prior to grilling, the bell peppers were found to contain about 46 milligrams/kilogram of this important antioxidant and anti-inflammatory flavonoid. After grilling for 7-8 minutes at a temperature of 150°C (302°F), about 40% of the luteolin was found to be destroyed. This loss of luteolin from higher heat cooking is one of the reasons we like cooking methods for bell peppers that use lower heat for a very short period of time.
Although we tend to think about cruciferous vegetables like broccoli or allium vegetables like onions and garlic as vegetables that are richest in sulfur-containing compounds, bell peppers can also be valuable sources of health-supportive sulfur compounds. Several recent studies have taken a close look at the presence of enzymes in bell peppers called cysteine S-conjugate beta-lyases and their role in a sulfur-containing metabolic pathway called the thiomethyl shunt. These enzymes and this pathway may be involved in some of the anti-cancer benefits that bell pepper has shown in some animal and lab studies. They may serve as the basis for some of the anti-cancer benefits shown by green, yellow, red and orange vegetable intake in recent studies, including a recent study on risk reduction for gastric cancer and esophageal cancer.