Posted by Beyond Health on Nov 3rd 2025

Steaming: a Healthy Way to Prepare Vegetables

Although we recommend eating most of the diet raw, a number of studies have shown that steaming preserves more nutrients than other forms of cooking, and in certain instances can even increase or release nutrients over and above what you’d get from eating the vegetables in question raw.

Glucosinolates are compounds found in cruciferous vegetables (like broccoli, cauliflower, and Brussels sprouts) that protect against cancer. Scientists suggest that 3-5 servings a week of cruciferous vegetables provide a substantial cancer protective benefit.

But to become properly activated, glucosinolates need to be mixed with the plant enzyme myrosinase. This mixing happens when you bite into your broccoli or Brussels sprout and crush the cellulose walls that otherwise keep the glucosinolates and myrosinase separated.

But cooking can destroy myrosinase, and who wants to eat raw broccoli? Fortunately, according to a recent article in Tuft’s Health and Nutrition Letter, scientists at the University of Illinois looked at different ways of cooking broccoli and found that myrosinase was retained after steaming broccoli as long as five minutes. (It was destroyed after only one minute of boiling or microwaving.)

Further, a study published in the Journal of Agricultural and Food Chemistry found that lightly steaming broccoli increased total glucosinolates by 30% compared to raw, although boiling or frying led to substantial losses (frying caused an 84% loss of glucosinolates).

But what if you get distracted and steam your broccoli longer than 5 minutes? Here’s something that a 2012 study confirms will work: Even though you may have cooked away the myrosinase in the broccoli, you can cheat and get it from another source. The researchers ate their broccoli with raw broccoli sprouts, and that did the trick. While you may not have broccoli sprouts on hand, you may have mustard, horseradish or wasabi, all of which are myrosinase sources and will work as well. So will any raw cruciferous vegetable, like radishes, cabbage or arugula.

Another study mentioned in the Tufts article found that steaming spinach (5 minutes) and broccoli (15 minutes) preserved folate, while boiling destroyed more than half of this B vitamin. And a 2009 Chinese study found that steaming preserved chlorophyll, vitamin C and soluble proteins in broccoli although all of these were lost in microwaving, boiling and stir-frying.

The Tufts article also referenced research done at Cornell University showing that in many cases cooking increases or releases nutrients. They found that cooking carrots, spinach, mushrooms, asparagus, peppers and cabbage provided more antioxidants, such as carotenoids and ferulic acid, to the body than when these vegetables were eaten raw. Vegetables need only light cooking for this effect to occur: spinach needs only a minute, kale five minutes; and less cooking will help to retain other nutrients that are damaged by heat.

Once your vegetables are steamed, you’ll want to add some fat in order to absorb the fat-soluble vitamins they contain, like the carotenes and vitamin K. May we suggest some coconut oil and a sprinkle of Celtic salt? Yum!

References: