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Mushrooms, even common button mushrooms, contain traces of carcinogenic compounds in raw form. The same toxin, hydrazine, is also found in portobello mushrooms, and shiitake mushrooms contain a naturally occurring formaldehyde. Both chemicals are heat-sensitive and abolished upon exposure to heat. You might think nothing of eating a few slices of button mushrooms raw, but to get the anti-cancer effects of mushrooms, eat them cooked. A 2009 study published in the International Journal of Cancer found that regular consumption of cooked mushrooms has been shown to decrease the risk of breast cancer by 60 percent.
Related: The Healing Power of Mushrooms
Cooking corn increases its antioxidant activity; when the ability to quench free-radicals was measured, cooked corn outperformed raw corn by between 25 to 50 percent! Cooking corn releases a phytochemical called ferulic acid, which is an anti-cancer superstar. Ferulic acid is present in tiny amounts in most fruits and vegetables, but it is found in very high amounts in corn. Cooking corn helps increase your body’s absorption of ferulic acid by a gargantuan 500 to 900 percent.
Tomatoes are known for their high levels of lycopene, a potent antioxidant, but lycopene levels jump through the roof when tomatoes are cooked. Cornell University conducted a study in which the ability to absorb lycopene cooked at varying temperatures was measured; tomatoes were heated for 2 minutes, 15 minutes, and 30 minutes. Levels of these disease-fighting warriors went up with each incremental increase in heating.
Choking hazards aside, there are poisonous compounds present in raw beans; for instance, raw kidney beans contain a toxin that, at a level as low as 1 percent, causes death in rats within two weeks. All raw beans contain lectins, potentially toxic protein compounds that can damage the heart, kidneys, liver, and intestines; and inhibit cell digestion—yet are destroyed upon cooking. Then you can enjoy the many health benefits of beans, whether you choose a comforting bowl of three-bean chili or top a fresh salad with cooked black beans or chickpeas. That’s a pretty simple list to remember.
Another handy fact to keep in mind is that steaming veggies and making vegetable soups changes the plants’ cell structures so that fewer of your own enzymes are needed to digest the food, not more. When you steam vegetables or make vegetable soup, the temperature is fixed at 212°F—the temperature of boiling water. Both of these cooking methods avoid the formation of heat-created toxins called acrylamides. The same cannot be said for higher-heat cooking techniques such as roasting and baking. However, roasting/toasting at low temperatures below 200°F does not create a significant level of harmful compounds.