How to prepare broccoli to retain its nutritional value.

How to Prepare Broccoli to Retain Nutritional Value

It comes of no surprise that, like all of the World’s Healthiest Foods, broccoli has many different way of supporting our health! What is surprising is that how it is prepared can add even greater nutritional value to this already highly nutritious and popular vegetable.

Preparation Makes a Difference

Did you know that cutting the florets into smaller pieces and the stems into thin slices and letting them sit for 5 to 6 minutes before cooking will enhance their cancer protective properties? Cutting broccoli into smaller pieces breaks the cells and activates an enzyme called myrosinase. The myrosinase converts some of the sulfur-containing chemicals found in broccoli (call glucosinolates) into other sulfur containing chemicals (called isothiocyanates) which research has shown to contain cancer preventive properties not found in the glucosinolates . Studies have actually pinpointed specific mechanisms, like changes in cellular genetic processes, which are involved in increasing cancer protection.

Since myrosinase is specifically activated by ascorbic acid (vitamin C), sprinkling your sliced broccoli with a little lemon juice, an excellent source of vitamin C, before letting it sit may also help increase myrosinase activity. Once broccoli is heated, even if it is just lightly steamed, the myrosinase enzyme will become inactivated. For this reason, the slicing of broccoli 5-6 minutes before steaming will enable the enzyme to go to work and convert some of the sulfur-containing compounds prior to steaming.

Increase Assimilation of Nutrients

This may raise the question of whether it would not be preferable to let the broccoli sit and eat it raw allowing the enzymes to continue functioning. While, of course, this is an option, we prefer to recommend slightly cooking broccoli. Light cooking tends to soften fibrous materials aiding digestion and increasing the potential assimilation of nutrients.

One study has shown that although there may be more vitamin C in a stalk or florets of raw broccoli, we absorb the vitamin C a little better once the broccoli has been steamed or boiled. In a carefully controlled study, the availability of vitamin C from raw broccoli was compared to the availability from cooked broccoli, orange sections and orange juice. All foods forms of vitamin C showed equal bioavailability, except for the vitamin C from raw broccoli, which was less well absorbed.

Lightly Cooked

Of key importance is the definition of “lightly cooked”. Lightly cooked broccoli has a bright green color and has not been steamed or boiled for more than 3-5 minutes. Overcooking any vegetable will decrease its nutritional value.

Broccoli and Your Thyroid

The same cancer-preventing compounds that slicing helps activate in broccoli (isothiocyanates) may decrease thyroid function under certain circumstances. The jury is still out, however, on exactly how this process works, or how problematic it is for everyday eating. However, to err on the safe side, individuals with pre-existing and untreated thyroid conditions might want to avoid eating broccoli. The consumption of steamed broccoli that has not been cut would logically lower isothiocyanate intake, but even in this case, intestinal bacteria could produce the isothiocyanates once the steamed broccoli reached their area of the intestine.

We recommend that individuals with thyroid problems talk with their healthcare providers about the best way to proceed in this circumstance. For all individuals with healthy thyroid function (except those allergic to broccoli, of course) we recommend incorporating this magnificent food into your healthy eating plan, raw or steamed!

This page was updated on: 2004-11-18 21:16:50
© 2002 The George Mateljan Foundation