Packed full of antioxidants, vitamins, minerals and fiber, vegetables are a valuable component of a healthy diet. Because some forms of cooking -- especially high-heat methods -- can damage nutrients and beneficial compounds, raw vegetables may seem superior to their cooked counterparts. However, cooking bestows some benefits of its own by breaking down indigestible cellulose, making the cooked-versus-raw debate more complex than meets the eye.
Benefits
Because raw vegetables haven't been subject to heat or draining after boiling, they retain all of their original nutrients and antioxidants. According to Martha Filipic, writer for the Ohio State University Extension Chow Line, cooking tends to reduce levels of heat-sensitive vitamin C in vegetables, making raw vegetables a superior source of this nutrient. In broccoli, cooking damages myrosinase, an enzyme that may play a role in cancer prevention. Similarly, cooking carrots reduces their levels of polyphenols, which may slash cancer and cardiovascular disease risks.
Drawbacks
Despite retaining more nutrients, raw vegetables also have drawbacks compared to cooked versions of the same food. Filipic notes that the process of cooking cruciferous vegetables, such as broccoli and cabbage, forms a compound called indole, which helps ward off precancerous cells. Cooked tomatoes, despite losing some vitamin C, contain a more usable version of the nutrient lycopene. Physician and author Joel Fuhrman, M.D., notes that cooking can also destroy some anti-nutrients present in raw foods that inhibit absorption of minerals.
Research
A large body of research shows health-protective effects of both cooked and raw vegetables, although raw vegetables do appear to have some specific advantages in terms of disease prevention. A literature review published in the September 2004 issue of "Cancer Epidemiology, Biomarkers and Prevention" found that while both cooked and raw vegetables lower the risk of gastrointestinal cancers and possibly breast cancer, raw vegetables, on the whole, have a more significant protective effect against these diseases. Another study published by Li Tang, et al. in the April 2008 edition of the same journal found that raw cruciferous vegetables, but not their cooked counterparts, may lower bladder cancer risk. Likewise, a 2003 study appearing in "Nutrition and Cancer" found that raw vegetables, but not cooked vegetables, appear to decrease the risk of breast cancer.
Considerations
Consuming vegetables in both raw and lightly cooked forms may be the best route for reaping their benefits. As Dr. Fuhrman explains, conservative cooking methods such as steaming and stewing for soup can break down the cellulose in vegetables, making them more digestible without damaging significant amounts of nutrients. Cooking vegetables gently may be superior to methods such as frying, barbecuing and baking.
References
- Ohio State University Extension: Chow Line; Eat Lots of Produce, Raw and Cooked; Martha Filipic; August 2009
- "Cancer Epidemiology, Biomarkers and Prevention"; Raw Versus Cooked Vegetables and Cancer Risk; Lilli B. Link, et al.; September 2004
- "Cancer Epidemiology, Biomarkers and Prevention"; Consumption of Raw Cruciferous Vegetables is Inversely Associated with Bladder Cancer Risk; Li Tang, et al.; April 2008
- "Nutrition and Cancer"; Raw and Cooked Vegetables, Fruits, Selected Micronutrients, and Breast Cancer Risk: A Case-Control Study in Germany; Karl-Heinrich Adzersen, et al.; 2003
- Dr. Fuhrman; Raw Vs. Cooked?; Joel Fuhrman, M.D.
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