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Prolonged Liver Function Enhancement From Broccoli

The boost in detoxifying enzymes triggered by cruciferous vegetable consumption may last for weeks!

January 30, 2013 |
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Supplementary Info

Sources Cited


Images thanks to Dhaluza and David.Monniaux via Wikimedia Commons, [puamelia] / Flickr



This study on cooked meat and the risk of breast cancer in Long Island women added to the accumulating evidence that consumption of meats cooked by methods that promote carcinogen formation may increase risk of postmenopausal breast cancer," but also offer a clue as to how we may be able to mediate that risk. Modest increased risk was found in older women eating the most grilled or barbecued and smoked meats over their lifetime—about 47% increased odds of breast cancer, but those same women who also had a low fruit and vegetable intake had a higher odds ratio of 1.74, 74% greater odds. Now low fruit and vegetable consumption may just be a marker for unhealthy habits in general, but maybe there's something in fruits and vegetables that's protective. Check out this fascinating study. To review ''The consumption of cooked meat appears to predispose individuals to cancer and the consumption of cruciferous vegetables is thought to protect against cancer, but if you remember it's in a rather unique way by boosting the activity of the detoxifying enzymes in our livers. For example, if you feed people broccoli and Brussels sprouts, they clear caffeine quicker. Meaning if you eat a lot of these healthy vegetables you have to drink more coffee to get the same buzz because your liver is so revved up. Same thing with the cooked meat carcinogens. If you have a side of broccoli with your meat you can significantly decrease carcinogen levels in your body. In period one they had subjects consuming cooked meat meals containing known amounts of these carcinogens, and this is the amount of the carcinogens they were absorbing into their bloodstream and then peeing out. In period 2 they ate the same amount of meat, but added broccoli and Brussels sprouts. Notice there's a significant drop in the amount of these meat mutagens circulating within their bodies. Now this wasn't a surprise, that's what cruciferous vegetables do—boost our livers ability to clear chemicals from our body. But this is what blew people away. In period three, again same amount of meat but they took away the veggies, yet their liver function appeared to remain enhanced two weeks later. So there appears to be a prolonged beneficial effect of cruciferous vegetable consumption. So you can eat broccoli days or even weeks before the big barbeque and still retain a little protection, though of course if you grilled veggie burgers,  it would be even better, as apparently no matter how you cook plant-based foods—even if you deep fry them, no detectable heterocyclic amines are formed.

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 Jonathan Hodgson.

To help out on the site please email

Dr. Michael Greger

Doctor's Note

To review what I had covered previously about the remarkable detoxifying effect of cruciferous vegetables, see my videos The Best Detox and Sometimes the Enzyme Myth Is True. You can overdo it, but apparently only at extremely high doses (see Liver Toxicity Due to Broccoli Juice, Overdosing on Greens, and How Much Broccoli Is Too Much?).

Wasn't the protective effect of fruit and vegetable consumption against cancer called into question, though? See my video EPIC Study.

What other foods may mediate the effects of the mutagenic compounds in cooked meat? See the last two videos Cancer, Interrupted: Green Tea and Cancer, Interrupted: Garlic & Flavonoids. What are these heterocyclic amines? You must have missed my four-part video series starting with Estrogenic Cooked Meat Carcinogens!

What are the health effects of that caffeine buzz? See Coffee and Cancer and What About the Caffeine?

More about the implications of frying veggie burgers here: Carcinogens in the Smell of Frying Bacon, an update of which I'm going to give in my next video—stay tuned!

For some context, please check out my associated blog posts: Broccoli Boosts Liver Detox Enzymes

If you haven't yet, you can subscribe to my videos for free by clicking here.

  • Frances Morey

    I once took cranberry capsules to ward off urinary tract infections. After a week or so I developed red spots all over my body’s lower half–called the doctor. He asked what was new and I described my cranberry food supplement addition. He advised me that each cranberry capsule has the chemistry of a pound of cranberries and that I had apparently set up a sensitivity to them in my body. He told me to stop taking them and be careful to not eat cranberry products since my body may have a reaction to them that could be worse. Once since then I drank 4 ounces of cranberry juice and the spots returned. I now avoid all ingestion of cranberries.

    • Frances Morey

      I know this comment is off topic but it is an interesting experience with food supplements.
      Thanks for the broccoli endorsement–even if I have become a vegan it is interesting. It may deter even cancers caused by other sources as well.
      Dr. Colin Campbell once spoke at a book signing here in Austin. He mentioned that cancer causes are ubiquitous, and we encounter them in many ways. He said that they are like a seed. Whether they implant, root and grow depends on what you feed them. He pointed out that cancer prefers the casein protein as food. I decided to cut out dairy.

  • PaulB

    Great post MIchael. I think the only point I would make about grilling veggies is that while you don’t need to worry about HCAs, you do need to be concerned about advanced glycation endproducts like acrylamides. Depends of course how long, how hot and how dry the grill is.

  • James

    I think this explaines why my caffeine craving has increased since becoming mostly vegan. Any less harmful alternatives to caffeine, or shall I just have a broccoli chaser with my espresso?

    • WholeFoodChomper

      I believe Dr. G would recommend green tea as a healthier alternative. See his videos on the topic.

      • rainmaker

        or Chai

    • isamk

      hi James! I went cold turkey 2 yrs ago and have never had a drop of coffee since. I was sick detoxing it out of my body for a week…food for thought as to just how addictive coffee really is….I do not miss ot at all and if I need a “pick me up” I drink water! I also drink lots of green juices – my fave is sliced “coins” of ginger & curcuma that I bring to a boil, turn off and mascerste over night or at least for a few hours before drinking….deicious! tastes way better than any coffee I remember…..

  • Alicia (vegan epicurean)

    Perfect timing I was just discussing liver function with a friend yesterday.

  • Mike Quinoa

    Don’t forget the stalks are equally nutritious. I like to slice the stalks in such a way that I create broccoli “coins.”

    • Thea

      Mike: Good point. I’ve made those “coins” you are talking about in the past. I enjoyed them.

      Here’s another tip for people: I’ve recently started enjoying ‘broccoli slaw’. It is a packaged food – where manufacturers are slicing broccoli stems into super-thin sticks and adding some carrots. For someone who is not a fan of chopping, eating the broccoli slaw is a great way to get some broccoli.

    • R Ian Flett

      I read years ago that the broccoli stalks are higher in alkaloids somewhat toxic to the liver. These alkaloids are produced as deterrents to insects crawling towards the nutritious tips. Perhaps it needs more research.

      • Thea

        R Ian Flett: I appreciate the info, but what a bummer! I’m going to research this some. If true, it will make it harder for me to get my broccoli on. (sigh) Thanks for taking the time to write this.

      • broccolibill

        the alkaloids are the protective part, and this is the whole plant… thankfully our stomachs are nice and acidic to help us break it down

  • Sam

    Could this not indicate that the elevation in the enzymes is due to the body reacting to a sort of toxic ingestion?

  • Katrina Dresaj

    Is there a difference between raw and cooked broccoli? Its often served raw on salads, but some authors suggest its dangerous to eat raw, while others claim its necessary to eat it raw to obtain its most important beneficial effects.

    • Toxins

      Raw broccoli can both be beneficial, while cooking deactivates certain compounds such as sulforaphane, it enhances others. There is not toxicity seen with eating raw broccoli unless consuming over 100 cups per day which is not feasible on a normal diet.

  • mark

    I always tell my carnivorous friends they can be “virtual-vegans” if they merely have a big salad & a big side of broccoli with their steak-&-potatoes dinner; but I thought of it as tricking them into noticing how good the broccoli is. Who knew it was no trick?