Greens rank highest in chemical antioxidant assays (such as ORAC, TEAC, TRAP, and FRAP), but which vegetables lead the pack when cellular antioxidant activity is measured?
Image thanks to Daderot via Wikimedia Commons.
In choosing the healthiest foods, you may notice that everywhere you look, everyone seems to have a different "top ten" list of the most antioxidant-rich foods, with probably dozens of competing commercial products swearing theirs is the "best of the best". Some are probably just making stuff up, but genuine competing estimates arise from people citing old data,
[J. Agric. Food Chem. 2004, 52, 4026-4037, "Lipophilic and Hydrophilic Antioxidant Capacities of Common Foods in the United States"]
where they only test a few dozen foods, or a few hundred, but other disparities arise from different labs using different tests.
There are four in common usage: ORAC, TEAC, TRAP, and FRAP. USDA likes ORAC. These researchers
[Nutrition Journal 2010, 9:3 "The total antioxidant content of more than 3100 foods, beverages, spices, herbs and supplements used worldwide"]
used FRAP, in part because it's one of the quickest methods, which is important if you're doing 3,000 foods. Each has their pros and cons, but the problem with all of them is that they're just measuring how good a particular food is at altering a chemical oxidation reaction in a test tube. It's not done in a biological system.
But for the first time ever, scientists at Cornell took 27 vegetables
[J. Agric. Food Chem. 2010, 58, 6621-6629, "Cellular Antioxidant Activity of Common Vegetables"]
and measured their cellular antioxidant activity: their ability to quench free radicals within cells, by testing various vegetables on cultures of human liver cells. Sure, some phytonutrient may be a great antioxidant outside the cell, but what if it can't get inside the cell? That's where we need it!
If you do the standard ORAC test, this is what you find: spinach at the top, cucumber at the bottom. No surprise; dark green leafy leads the pack. But again, this is a chemical assay, measuring how these foods slow down some oxidation reaction in a test tube, a reaction that actually doesn't even occur in nature. But hey, look, it's the best we had: until now. Any guesses as to who was able to unseat spinach? Here's the cellular antioxidant activity. Cucumber is still at the bottom. But now, beating everyone else: beets! Number one, spinach, isn't even in the top ten any more. All the cruciferous moved ahead: Brussels sprouts, broccoli, cabbage, cauliflower. And hey, look, between the beets and the red bell pepper, it looks like the greens got beat out by the reds.
To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video. This is transcript contributed by Bruce A. Hamilton.
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Please feel free to post any ask-the-doctor type questions here in the comments section and I’d be happy to try to answer them. Be sure to check out all the other videos on antioxidants and don't miss all the videos where we rank foods. And there are 1,449 subjects covered in the rest of my videos–please feel free to explore them!
Check out my associated blog post for more context: Which Common Fruit Fights Cancer Better?