Steaming Outshines All Cooking Methods for BroccoliResearchers in the Department of Agriculture at Zhejiang University in Hangzhou, China have published what might be the best-documented study to date on broccoli and the cooking methods that are best at preserving its nutrients. After carefully reviewing the results from 34 previous studies, these researchers went on to compare 5 different cooking methods for broccoli and their impact on nutrient content. All cooking methods were carried out for 5 minutes on 200 grams (approximately 2 cups) of chopped broccoli. The methods included: boiling, stir-frying in soy oil, microwaving, steaming, and a stir-frying-plus-boiling combination in which the raw broccoli was stir-fried for 2 minutes and then boiled for 3 minutes.
The researchers went on to analyze the nutrient content in 6 areas: protein, sugar, chlorophyll, glucosinolates, carotenoids, and vitamin C. Proteins and sugars were best retained by steaming, with microwaving doing the next best job in this macronutrient area. But the most dramatic were results in the 4 other nutrient areas, which you will find summarized in the following chart:
|Cooking Method||Chlorophyll (% Decrease)||Vitamin C (% Decrease||Glucosinolates (% Decrease||Total Carotenoids (% Decrease|
|Steaming||almost unchanged||no significant loss||almost unchanged||no significant loss|
|Stir-Frying-Plus-Boiling||18%||24%||55%||no significant loss|
|Microwaving||16%||16%||60%||no significant loss|
All we can say is, "Wow!" When taken as a whole, the differences here between steaming and other cooking methods are even greater than we would have predicted. This is especially true in the area of glucosinolates, the sulfur-containing compounds in broccoli that can be converted by the body into related sulfur-compounds called isothiocyanates that have been shown to have cancer-preventive effects. The difference between steaming and all other cooking methods in this phytonutrient area is striking. And while chlorophyll is not ordinarily discussed as a food nutrient, some studies have shown that chlorophyll retention in a cooked food may be partially representative of that food's overall nutrient quality. That speaks amazingly well for steaming as a cooking method for broccoli.Also striking to us is the minimal amount of nutritional difference between broccoli that has been steamed for 5 minutes and raw broccoli. These researchers found no significant difference between raw and steamed broccoli in all of the four categories measured above. That finding makes us confident that steaming is by far your best cooking method for broccoli and can do an outstanding job in preserving its nutrients.