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.
Sometimes the Enzyme Myth Is True
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You’ll hear folks in the 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’re 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 sulforaphane is one of them.
One of our most powerful phytonutrients, it is formed by an enzyme in broccoli. You cut or chew or chop up broccoli or broccoli sprouts, and the enzyme is released and it 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 shown detectable sulforaphane levels in the blood and urine of people 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 sulforaphane for us. And the way they figured this out is that you incubate cooked vegetable juice with fresh human feces and voila! Sulforaphane is born.
Not as much, though. To get the same amount of benefit in a cup of raw broccoli, you’d have to eat ten cups of cooked broccoli. So, I encourage people to try to eat their broccoli raw, or, alternatively, 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 broccoli soup, put it in the blender raw, blend, 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 pre-chopped 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 summarizing the available evidence.
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.
Please consider volunteering to help out on the site.
- Vermeulen M, Klöpping-Ketelaars IW, van den Berg R, Vaes WH. Bioavailability and kinetics of sulforaphane in humans after consumption of cooked versus raw broccoli. J Agric Food Chem. 2008 Nov 26;56(22):10505-9.
- Getahun SM, Chung FL. Conversion of Glucosinolates to Isothiocyanates in Humans after Ingestion of Cooked Watercress. Cancer Epidemiol Biomarkers Prev. 1999 May;8(5):447-51.
Images thanks to Jawahar Swaminathan via Wikimedia Commons, and Whole Foods.
You’ll hear folks in the 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’re 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 sulforaphane is one of them.
One of our most powerful phytonutrients, it is formed by an enzyme in broccoli. You cut or chew or chop up broccoli or broccoli sprouts, and the enzyme is released and it 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 shown detectable sulforaphane levels in the blood and urine of people 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 sulforaphane for us. And the way they figured this out is that you incubate cooked vegetable juice with fresh human feces and voila! Sulforaphane is born.
Not as much, though. To get the same amount of benefit in a cup of raw broccoli, you’d have to eat ten cups of cooked broccoli. So, I encourage people to try to eat their broccoli raw, or, alternatively, 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 broccoli soup, put it in the blender raw, blend, 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 pre-chopped 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 summarizing the available evidence.
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.
Please consider volunteering to help out on the site.
- Vermeulen M, Klöpping-Ketelaars IW, van den Berg R, Vaes WH. Bioavailability and kinetics of sulforaphane in humans after consumption of cooked versus raw broccoli. J Agric Food Chem. 2008 Nov 26;56(22):10505-9.
- Getahun SM, Chung FL. Conversion of Glucosinolates to Isothiocyanates in Humans after Ingestion of Cooked Watercress. Cancer Epidemiol Biomarkers Prev. 1999 May;8(5):447-51.
Images thanks to Jawahar Swaminathan via Wikimedia Commons, and Whole Foods.
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Sometimes the Enzyme Myth Is True
LicenciaCreative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)
URLNota del Doctor
If you’re new to sulforaphane, check out my videos, Broccoli Versus Breast Cancer Stem Cells, and Sulforaphane: From Broccoli to Breast. For more on raw food diets, check out my videos Raw Food Diet Myths; Best Cooking Method; and Raw Food Nutrient Absorption. And for more on keeping our good bacteria happy, see all my 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.
Note that one of the sources for this video is open access, so you can download it by clicking on the link in the Sources Cited section, above.
For more context, check out my associated blog posts: The Best Detox; Broccoli Boosts Liver Detox Enzymes; and How Probiotics Affect Mental Health.
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