April 16, 2009
Best Cooking Methods To Retain Antioxidants

Artichokes are indestructible whereas cauliflower, peas, and zucchini took heavy losses.

Some vegetable cooking methods may be better than others when it comes to maintaining beneficial antioxidant levels, according to a new study in the Journal of Food Science, published by the Institute of Food Technologists. Results showed that, depending on the vegetable, cooking on a flat metal surface with no oil (griddling) and microwave cooking maintained the highest antioxidant levels.

Fruits and vegetables are considered to be the major contributors of nutritional antioxidants, which may prevent cancer and other diseases. Because of their high antioxidant levels and low-calorie content, consumers are encouraged to eat several servings of fruits and vegetables daily.

Researchers at the University of Murcia and the University of Complutense in Spain examined how various cooking methods affected antioxidant activity by analyzing six cooking methods with 20 vegetables. The six cooking methods were boiling, pressure-cooking, baking, microwaving, griddling and frying. Their findings showed the following:

• The highest antioxidant loss was observed in cauliflower after boiling and microwaving, peas after boiling, and zucchini after boiling and frying.
• Green beans, beets, and garlic were found to keep their antioxidant levels after most cooking treatments.
• The vegetables that increased their antioxidant levels after all cooking methods were green beans (except green beans after boiling), celery and carrots.
• Artichoke was the only vegetable that kept its high antioxidant level during all the cooking methods.

Griddle- and microwave-cooking helped maintain the highest levels of antioxidants, produced the lowest losses while “pressure-cooking and boiling [led] to the greatest losses,” says lead researcher A. M. Jiménez-Monreal. “In short, water is not the cook’s best friend when it comes to preparing vegetables.”

Eat more raw vegetables and you can avoid losses in all but a few vegetables. Cook grean beans, celery and carrots. Then eat all the rest raw.

You can also read a review of the beneficial compounds found in Brassica vegetables.

Share |      Randall Parker, 2009 April 16 10:18 PM  Aging Diet Studies

Vincent said at April 17, 2009 8:56 AM:

What about broccoli? I love broccoli.

Alec Rawls said at April 17, 2009 11:28 AM:

Are anti-oxidants water soluble, like vitamins? Vitamins are not lost so long as you still use the water. Does that work with anti-oxidants?

Anton said at April 17, 2009 12:11 PM:

No, eat carrots and celery raw. Cook your peas (but in the microwave it appears)

Barbara in Va. said at April 17, 2009 1:06 PM:

Sorry, Anton, but the article says "vegetables that increased their antioxidant levels after all cooking methods were green beans ..., celery and carrots." It also says "Cook green beans, celery and carrots. Then eat all the rest raw."

Cook your celery and carrots if your goal is to increase antioxidants. I'll keep eating mine raw for the most part as I like them better that way and am far more likely to eat them raw than cooked. You do have to eat them to get the benefits of the antioxidants.

David Nishimura said at April 17, 2009 2:01 PM:

I'd like to get a look at the actual article. One big question regards definitions: was "frying" deep-frying or stir-frying? did "boiling" entail using loads of water that was then discarded? Steaming appears to have been omitted as an option.

Nor do antioxidant levels offer us a complete measure of the beneficial effects of vegetables. Keep in mind that the vegetables consumed as part of the classic Mediterranean diet are quite thoroughly cooked.

Keva Silversmith said at April 17, 2009 4:31 PM:

I'm curious how a vegetable can actually increase its antioxidant content by being cooked. Intuitively it seems like a vegetable could only have its nutritional value subtracted - how can it become more nutritious than when it was pulled out of the ground?

pond said at April 18, 2009 5:50 AM:

Steaming was not considered? I steam mine, then drink the broth as well.

Vitamin C is destroyed by high temperature, which means pasteurized orange juice contains so little of it, and the recommendation is to eat oranges rather than drink the pasteurized juice.

mark baard said at April 18, 2009 6:53 AM:

How do you griddle without oil, as the report suggests?

Brett Bellmore said at April 18, 2009 7:46 AM:

"how can it become more nutritious than when it was pulled out of the ground?"

If the existing nutrients become more digestible. You've got to eat food to benefit from the nutrients, but they don't do you any good if they're still in the food when it inevitably exits the other end of your digestive tract.

Randall Parker said at April 18, 2009 8:41 AM:

Keva Silversmith,

In some cases the antioxidants are bound up inside of cell wall fiber that can't be digested. So, for example, you will absorb more lycopene from tomato paste than from whole tomatoes. The grinding that turns the tomatoes into a paste breaks up the cell walls and makes more lycopene bioavailable.

That brings up a larger point: cooking is not the only way to free up carotenoids in carrots. Grinding will work as well.

Another point: Eating your veggies with some oil will improve absorption of oil soluble antioxidants. Lycopene is an example where some olive oil is a good thing to combine with tomato paste in a dish.

Alec Rawls,

Whether cooking will break down an antioxidant depends on the individual antioxidant. They vary in their temperature stability. Sorry, I do not have the details on which are stable.

David Nishimura,

Agreed there are other benefits of vegetables. Lower glycemic index and minerals are among those benefits. Though even cooked vegetables have way more antioxidants than, say, a can of Coca-Cola. Compared to other foods vegetables are still great no matter how they are cooked.

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