There are a few examples of plant enzymes having physiologically relevant impacts on the human diet, and the formation of sulforaphane in broccoli is one of them.
You’ll hear folks in raw food community waxing poetic about enzymes, the importance of preserving the activities of plant enzymes, which are destroyed by cooking. Skeptics, on the other hand, indignantly assert that we have no use for plant enzymes, since we are animals and make all the enzymes we need. Well, both sides are wrong. There are two known examples of plant enzymes serving physiologically useful functions, and the production of sulphuraphane is one of them.
One of our most powerful phytonutrients, it is formed by an enzyme in broccoli. You cut or chew or chop raw broccoli, or broccoli sprouts, and the enzyme is released and gets to work making us a big batch of phytonutrient goodness.
Cooking inactivates the enzyme, though, so steamed broccoli doesn’t have any. So why have experiments show detectable sulphuraphane levels in the blood and urine of people who eating only cooked broccoli? Now I’m really confused. Were they sneaking raw broccoli on the side?
No! (how cool is this?) Good bacteria that reside in our gut have the raw broccoli enzyme too! So as soon as the cooked broccoli gets down there, the bacteria makes sulphuraphane for you. And the way they figured this out is that you incubate cooked vegetable juice with fresh human feces and whallah, sulfuraphane was born.
Not as much though. To get the same amount of benefit in a cup of raw broccoli you’d have to eat 10 cups of cooked broccoli, so I encourage people to try to eat their broccoli raw or, alternately, chop the broccoli up first raw, wait 40 minutes for the enzyme to do its business and then you can cook the heck out of it because the enzyme’s job is already done.. So the next time you want to make like broccoli soup put it in the blender raw, blend, then wait, then cook. Safer too, since you’re not trying to blend hot liquids at the end.
Or if you don’t want to wait, you know those prepackaged bags of prechopped broccoli in the produce aisle? More expensive, but more convenient, and maybe even healthier, because it’s been building up anticarcinogens the whole time in the store.
For more on raw food controversies, I encourage everyone to go to their local library and check out Davis and Melina’s Becoming Raw which does the best job to date of summing up the available science on the matter.
To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring watch the above video. This is just an approximation of the audio contributed by veganmontreal.
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If you're new to sulforaphane, check out my recent videos Broccoli Versus Breast Cancer Stem Cells and Sulforaphane: From Broccoli to Breast. For more videos on raw food diets check out Raw Food Diet Myths, Best Cooking Method, and Raw Food Nutrient Absorption. And for more on keeping our good bacteria happy, see these 9 videos on gut flora, including one on how the phytonutrients in flax seeds go through a similar transformation in our gut, Just the Flax, Ma’am. Then of course there are hundreds of other videos on 1200 or so topics. Note that one of the sources for this video is open access, so you can download it by clicking on the link above in the Sources Cited section.