Discover Steaming: a Healthy Way to Prepare Vegetables

Why Steaming Vegetables Can Be Better Than Eating Them Raw

Although we recommend eating most of the diet raw, research shows that steaming is the best cooking method for preserving nutrients—and in some cases, it can actually increase the availability of powerful protective compounds compared to eating vegetables raw.

Cruciferous Vegetables, Cancer Protection, and a Key Enzyme

Cruciferous vegetables—such as broccoli, cauliflower, and Brussels sprouts—contain compounds called glucosinolates, which are strongly protective against cancer. Scientists suggest that 3–5 servings per week of cruciferous vegetables provide substantial cancer-protective benefits.

For glucosinolates to become biologically active, they must interact with a plant enzyme called myrosinase. This interaction occurs when you chew raw vegetables, breaking down the cellulose walls that keep glucosinolates and myrosinase separated.

The problem?
Heat can destroy myrosinase—and most people don’t relish eating raw broccoli.

Steaming: The Sweet Spot

Fortunately, research summarized in Tufts University’s Health & Nutrition Letter found a solution.

Scientists at the University of Illinois tested various cooking methods and discovered that:

• Steaming broccoli for up to 5 minutes preserves myrosinase

• Myrosinase is destroyed after just 1 minute of boiling or microwaving

Even better, a study published in the Journal of Agricultural and Food Chemistry found that lightly steaming broccoli increased total glucosinolate content by 30% compared to raw.
In contrast:

• Boiling caused major losses

• Frying caused an 84% loss of glucosinolates

Overcooked Your Broccoli? There’s a Fix

If you accidentally steam broccoli longer than five minutes, all is not lost.

A 2012 study showed that even when broccoli’s own myrosinase is destroyed, you can restore glucosinolate activation by eating it with another myrosinase-rich food, such as:

• Raw broccoli sprouts

• Mustard

• Horseradish

• Wasabi

• Raw radishes

• Raw cabbage

• Arugula

In other words, you can “borrow” the enzyme from another food.

Steaming Preserves Folate and Vitamin C

Additional findings highlight steaming’s advantages:

• Steaming spinach (5 minutes) and broccoli (15 minutes) preserved folate, while boiling destroyed over 50% of this B vitamin.

• A 2009 Chinese study found that steaming preserved chlorophyll, vitamin C, and soluble proteins, while microwaving, boiling, and stir-frying caused significant losses.

Cooking Can Increase Antioxidant Availability

Research from Cornell University found that cooking can actually increase the bioavailability of antioxidants in many vegetables.

Light cooking increased absorption of compounds such as carotenoids and ferulic acid from:

• Carrots

• Spinach

• Mushrooms

• Asparagus

• Peppers

• Cabbage

Only minimal cooking is needed:

• Spinach: ~1 minute

• Kale: ~5 minutes

Longer cooking times reduce heat-sensitive nutrients, so light steaming is key.

Don’t Forget the Fat

Once vegetables are steamed, add a healthy fat to absorb fat-soluble nutrients like:

• Carotenoids

• Vitamin K

We suggest:

• A drizzle of coconut oil

• A sprinkle of Celtic sea salt

Simple. Delicious. Nutritionally optimal.