Does Cooking Vegetables Destroy Vitamins? It Depends…

raw food vegetable fruit on forks

We know that the way you cook your fruits and vegetables can change its nutritional contents. Cooking can break down some valuable nutrients, but in other cases can enhance the availability of others. So, raw vegetables of not always pack in more nutrition than their cooked counterparts. So what should you do? Today’s New York Times provides a nice reminder of the effects of cooking.

A study of 200 Germans who ate a raw food diet showed that they had higher levels of beta carotene, but below average levels of lycopenes. As you may know, lycopenes are in tomatoes (and watermelon),and cooking breaks down the thick cell walls of the plant, allowing the nutrient to come out. Water-soluble nutrients (think vitamins B and C, as well as polyphenolics) appear to be the most vulnerable to processing and cooking.

Canned peas and carrots lose 85-95% of their natural vitamin C. After 6 months, frozen cherries may lose as much as half of anthocyanins, the nutrients found in the dark pigments of fruits and vegetables. Cooking removes about two-thirds of the vitamin C in fresh spinach. Depending on the cooking method, loss of vitamin C during home cooking can range from 15% to 55% (University of California, Davis research). But vitamin C levels are often higher in frozen produce compared with fresh produce. Vitamin C levels can drop during the transport and storage of produce.

What about fat-soluble compounds such as vitamins A, D, E, and K and the antioxidant carotenoids? Boiling is better for carrots, zucchini, and broccoli than steaming, frying, or serving them raw. Frying vegetables is the worst method for nutrient preservation. Of course, each cooking method has tradeoffs. For example, boiling carrots can significantly increase carotenoid levels (compared to raw carrots). But raw carrots have more polyphenols than do cooked ones.

And microwaving? Surprisingly, microwaving can increase the concentrations of certain vitamins. Steaming and boiling drop vitamin C levels of broccoli by 22% and 34%, respectively. Microwaving and pressure cooking foods retain 90% of their vitamin C.

In summary, there is no single cooking or preparation method that is optimal for vegetable nutrient preservation. As long as you eat your vegetables, you are on the right track to better living. Mix it up: Steam, boil, eat raw, bake, and grill. Eat a variety of fruits and vegetables on a regular basis, and worry less about the method of cooking. I’m Dr. Michael Hunter, and I love grapes and watermelon!

The small print: The material presented herein is informational only, and is not designed to provide specific guidance for an individual. Please check with a valued health care provider with any questions or concerns. As for me, I am a Harvard- , Yale- and UPenn-educated radiation oncologist, and I practice in the Seattle, WA (USA) area. I feel genuinely privileged to be able to share with you. If you enjoyed today’s offering, please consider clicking the follow button at the bottom of this page.

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Reference: NY Times 25 October 2013

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Harvard AB Yale MD UPenn Radiation Oncology Radiation Oncologist, Seattle area

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