How does cooking affect the nutritional value of food?

Janis Jibrin, MS, RD
Nutrition & Dietetics
When it comes to nutrient loss from cooking, the main foods that are affected are fruit and vegetables. (Meat and other proteins need to be cooked, and their mineral content stays intact. They also need to get hot enough to destroy microbes.)

Heat diminishes vitamins and phytonutrients (beneficial plant compounds other than vitamins or minerals) in fruits and vegetables. The longer they cook, and the higher the temperature, the greater the nutrient destruction. Even chopping food can begin to erode some of the nutrients. (So it’s best to eat foods soon after chopping.)

However, when it comes to certain phytonutrients, chopping and cooking actually makes these phytonutrients easier for our bodies to absorb. For example, light cooking enhances absorption of carotenoids (found in tomatoes, butternut and other winter squash, and dark green leafy vegetables and herbs, like parsley, spinach and kale) and isothiocyanates (found in cruciferous vegetables like broccoli, Brussels sprouts, and cabbage.)

For example, you absorb more of the carotenoid lycopene, a powerful antioxidant from spaghetti sauce than from raw tomatoes. Chopping broccoli and other cruciferous vegetables releases their cancer-fighting isothiocyanates, and lightly cooking furthers the process. (But too much cooking destroys the compounds.)

Bottom line: it’s fine to cook vegetables, just keep the cooking time to about 5 minutes if possible and use moderate heat.
Margaret Floyd
Nutrition & Dietetics
Most food preparation, including chopping, cooking, baking, juicing, and so on, actually reduces the nutritional value of the food. Cooking food damages some of the more delicate nutrients. The barbecue adds lots of flavor but that delicious charcoal flavor that makes it so distinctive comes at the cost of added carcinogens. Even something as simple as chopping diminishes the nutritional value of produce. This is just part of eating, and unless you're going to eat entirely raw foods, it's something you minimize where possible and learn to live with. Cooking minimally, chopping things right before you eat them, and eating as raw as you can are some good and easy strategies for dealing with this challenge.
Eat Naked: Unprocessed, Unpolluted, and Undressed Eating for a Healthier, Sexier You

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Eat Naked: Unprocessed, Unpolluted, and Undressed Eating for a Healthier, Sexier You

Eat Naked with Margaret Floyd for a Sexier You Are you fed up with counting calories? Confused by all the diet hype? Want to eat delicious, real food and look and feel great? Leading...

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Cooking & Health

Cooking & Health

Most Americans don't prepare meals from scratch, and many eat out frequently. Reconnecting with food by cooking it can improve not only taste but health. How you cook can make a difference not only to taste, but nutrition. Boiling ...

broccoli or cabbage can destroy antioxidants. Microwaving or cooking on a griddle can preserve them. Stir-frying can be a good, quick way to prepare food too. Frozen and fresh vegetables have similar nutrient levels (not always similar taste). Canned foods do not. Some foods require adequate cooking time to ensure safety. If you think you don't have time to cook, a little planning can go a long way. Veggies may be pre-cut when time permits, and beans or pasta can be prepared in advance without loss of flavor or nutritional value. Many recipes may be modified to lower fat or sugar variations.

Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.