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Cook Vegetables without Losing NutrientsDifferent cooking techniques make a tremendous difference in the retention of different nutrients in plant foods. Let's take a look at the results of different cooking methods in the nutritional content of broccoli.
Nutrients in BroccoliSome people love its taste, and some people hate its taste, but every nutritional expert agrees that broccoli is one of the most nutritious of all plant foods. A single 3-1/2 oz (100 gram) serving of raw broccoli only sets you back 34 calories, but it provides thiamine (vitamin B1), riboflavin (vitamin B2), niacin (vitamin B3), pantothenic acid (vitamin B5), pyridoxine (vitamin B6), folic acid, vitamin C, vitamin E, vitamin K, lutein, zeaxanthin, beta-carotene, calcium, iron, magnesium, and fiber. It is also one of the best natural sources of a group of cancer-fighting compounds known as the glucosinolates.
A high intake of broccoli is known to reduce the risk of prostate cancer in men and the risk of heart disease in both sexes. The only downside to eating broccoli is that it is well known for causing malodorous flatulence, because of the high sulfur content of its cancer-fighting compounds.
Different methods of cooking broccoli have different effects on nutrient retention. There is no single best method of cooking that preserves all of its nutritional value.
Vitamin C in Cooked Broccoli
Scientists at Zhiejiang University in China measured vitamin C in broccoli after several different cooking methods. They found that:
- 33% of vitamin C was destroyed by boiling,
- 24% of vitamin C was destroyed by stir-frying,
- 18% of vitamin C was destroyed by microwaving, but
- Steaming broccoli caused no significant loss of vitamin C.
Heating broccoli does not destroy vitamin C, but contact with hot liquids seems to dissolve vitamin C.
Sugars in Cooked Broccoli
If you have ever eaten broccoli the same day it was harvested, you probably noticed that it is a naturally sweet vegetable. These sugars break down if broccoli is held in refrigerated storage for weeks or months before being sold as "fresh" broccoli in the market. Certain cooking methods preserve far more of these natural sugars than others.
- A 100 gram serving of raw broccoli contains about 4 grams of natural sugars.
- A 100 gram serving of steamed or microwaved broccoli contains about 3 grams of natural sugars.
- A 100 gram serving of boiled broccoli contains about 2 grams of natural sugars.
- A 100 gram of stir fried broccoli contains about 1 gram of natural sugars.
Many stir fry sauces include sugar to make up for the natural sweetness lost in frying the vegetable.
Glucosinolates in Cooked Broccoli
And what about the cancer-fighting compounds in cooked broccoli. What does cooking do to them?
- Boiling removed about 40% of the cancer-fighting compounds in broccoli.
- Stir-frying removed about 55% of the cancer-fighting compounds in broccoli.
- Steaming had no effect on the cancer-fighting compounds in this favorite vegetable.
For broccoli, steaming preserves the greatest nutritional content. But what about for other vegetables?