Full Transcript Recommended flavanols and food sources 0:03 [music] 0:07 >> There are recommended daily intakes of essential nutrients like vitamins to 0:11 prevent deficiencies, but recently the first dietary 0:15 recommendation for a bioactive food compound was published. Bioactives are 0:19 food compounds that are not necessary for basic human needs, but may have 0:24 health benefits. For example, plant metabolites called 0:28 flavonoids. Flavonoids are a type of polyphenol, of which the most commonly 0:33 consumed are flavan-3-ols, also known as just flavanols. 0:37 A review of the literature suggested that the intake of 400 to 600 mg a day 0:42 of flavanols would be beneficial for cardiometabolic protection, potentially 0:47 helping to improve blood pressure, cholesterol, and blood sugars. 0:51 Note it specified that these are food guidelines, not supplement guidelines. 0:55 Though really they're more like beverage guidelines as tea, green or black, would 1:00 be by far the easiest way to reach those levels. Though there are also certainly 1:05 some in a variety of berries and cocoa. However, there is an enzyme called 1:10 polyphenol oxidase that can break down polyphenols like flavanols. That's what
How polyphenol oxidase browns fruit 1:15 causes certain fruits and vegetables to brown when you cut into them like 1:19 bananas and potatoes. Why would a plant do that to itself? 1:24 Apparently as a defense mechanism, part of the plant's own immune system. 1:29 When exposed to oxygen, polyphenol oxidase can oxidize polyphenols into 1:34 breakdown products with antimicrobial activity. 1:39 So when a banana gets bruised or you cut open an avocado, the polyphenol oxidase 1:44 can start oxidizing polyphenols into defensive compounds that can clump 1:48 together and form a brown compound called melanin. The same class of 1:53 compounds that darkens the skin of a banana darkens our skin, too. 1:57 Okay, no problem. We can just not eat brown bananas. As that's visual evidence 2:03 that many of the polyphenols have been lost. 2:06 But, what if you mixed that banana, which you know is filled with a 2:10 polyphenol oxidase enzyme, into a smoothie [clears throat] 2:13 with polyphenol-rich foods like berries or cocoa? Might you end up with less 2:19 nutrition? Big chocolate-funded researchers sought to find out. They put 2:24 about a half a cup of cocoa's worth of cocoa flavanols into a smoothie 2:29 containing banana compared to the same amount in a berry smoothie with no 2:34 bananas. Here's a measure of how many of the 2:37 chocolate flavanols made it into the bloodstream within hours of drinking the 2:41 chocolaty berry smoothie compared to the same amount of cocoa blended into a 2:47 banana smoothie. It's almost as if you hardly put any cocoa in there at all,
Banana smoothies reduce cocoa flavanols 2:52 presumably because the banana enzymes chopped up all the chocolate goodies. 2:58 Let's not presume, though. They blended up the chocolaty banana smoothie again, 3:04 banana, almond milk, and cocoa flavanols, and then just measured the 3:07 amount of flavanols as the smoothie sat for an hour. Check it out. The cocoa 3:12 flavanols plummeted. More than a 90% drop. A half-life of like 10 minutes. 3:18 So, every 10 minutes or so, the levels drop in half. 3:21 How do they know for sure it was the polyphenol oxidase enzyme? Because when 3:25 they added specific enzyme blockers, they blocked the effect. 3:30 Okay, no problem. If you're adding bananas to your smoothies, can you just 3:34 chug it quickly before the enzyme does its job? And presumably, the enzyme 3:38 would be deactivated when it hit the acid bath of the stomach, but let's not 3:42 presume. You don't know [clears throat] until you put it to the test. I love 3:48 that the researchers did all these extra steps. This time, they made study 3:52 participants alternate sips between a straight banana almond milk 3:57 smoothie and like chocolate milk, cocoa flavanols plus almond milk. So, there 4:01 was no pre-mixing in the blender between the banana enzyme and the flavanols, 4:06 just mixing in the stomach. Here's how many cocoa flavanols make it into your 4:10 bloodstream when sipping the chocolate milk alone. 4:13 Mixed in the stomach with banana and you get this, 37% less in your bloodstream, 4:20 which shows that the banana enzyme can still do some polyphenol damage in the 4:24 stomach. And yes, in simulated stomach acid conditions, the polyphenol oxidase 4:29 enzyme is indeed down but not out. So, yeah, if you drink a smoothie with 4:34 banana in it, it's better to not let it sit around, but even if you drink it 4:38 immediately, you may still get less polyphenols in your system than if you 4:42 would have skipped the banana. But, banana makes smoothies so rich and
Bananas still affect absorption in the stomach 4:47 creamy. Anything we [clears throat] can add to the smoothie to counter the 4:51 banana enzyme's effects? That's exactly what I'll cover 4:55 next. There is one food that has more 5:00 polyphenol oxidase activity than a banana, and it's a vegetable that's not 5:05 a potato. What vegetable turns brown that's not a 5:09 white potato? A white mushroom. White button mushrooms are packed with that 5:13 polyphenol munching enzyme, even more so than bananas. Uh now, for those of you 5:19 thinking, "Don't worry, I don't expect to be putting mushrooms in my smoothies 5:23 anytime soon." Some people add avocado to smoothies or or make a chocolate 5:28 avocado pudding. Here's a question. What if you eat 5:31 mushrooms with a meal packed with polyphenol-rich foods? Might they mix in 5:36 your stomach and decrease the absorption of the anthocyanins in red cabbage or 5:40 the berries in dessert, for instance? You could also imagine having some 5:43 potatoes or eggplant in a meal. But, note this is for fresh produce, the 5:49 enzyme is destroyed by cooking. And remember we should be cooking our 5:53 white mushrooms anyway because of the agaritine, right? So, problem solved. 5:58 Who wants to cook their bananas though? What else can we put in a smoothie? My
Other high-enzyme foods and smoothie ingredients 6:03 favorite is mango, which you can buy frozen when it's not in season. Do we 6:08 have to worry about it having polyphenol eating enzymes? Well, what happens when 6:12 you cut open a mango? Does it go brown? No. So, it's probably fine. And indeed, 6:18 when researchers measured polyphenol oxidase activity in a bunch of fruits 6:22 and vegetables, mango had 500 times less than banana. 6:27 The apple doesn't surprise me since it goes brown so fast, but what's with the 6:31 beet greens? Better to use something like kale for your green smoothies 6:35 instead, where enzyme activity is undetectable. 6:39 This study raises so many interesting questions. 6:43 Should you not add bananas to your oatmeal? I no longer add it to my 6:47 cran-chocolate-pomegranate breakfast bowls since I don't want to 6:51 lose any of the polyphenols. But what if you're not making something 6:55 chocolatey? The study only tested the effects of the enzyme on cocoa 6:59 flavanols. Like they didn't check [snorts] to see if mixing bananas with 7:03 berries would affect the berry phytonutrients, but the presumption is 7:07 that it would. And what does this mean for bottled smoothie drinks that you buy 7:13 off the shelf in the store? Well, if they've been pasteurized, then 7:17 it should be okay since the heat should destroy the enzyme. 7:20 That's why vegetables are blanched before they're frozen to destroy the 7:24 enzymes. Even just heating banana to 70° C, which is like the temperature of hot 7:30 tea for 2 minutes in the presence of vitamin C and citric acid, which might
Cooking, pasteurization, and ways to inhibit browning 7:35 come from lemon juice, would suppress the enzyme by 80%. 7:39 I'm not suggesting drinking hot smoothies, but rather that depending on 7:44 the ingredients, pasteurized smoothie drinks may not share the same problem as 7:48 fresh made smoothies. What about just the vitamin C and citric 7:52 acid alone, like putting lemon juice in your smoothie? 7:55 Only cuts the enzyme activity down by 13%. 7:59 Works wonders on a cut apple though, slashing enzyme activity nearly in half, 8:05 which explains why lemon juice can keep your fruit salad from turning brown. 8:10 Anything we can add to a banana smoothie to inhibit the enzyme? Sulfites used to 8:15 be put on fresh fruits and vegetables until they were banned in 1986 following 8:20 cases of sulfite induced asthma. They're still used in dried fruit though to 8:26 prevent browning. What about natural agents? 8:29 Onion extracts can prevent the browning of pears, both fresh and cooked onion 8:34 juice, but there's got to be a better option 8:38 for your smoothie. Pineapple seems to help keep apples from 8:42 browning and bananas too, but that was after soaking in pineapple 8:46 juice for 3 days, so it's not clear if it would work right away. There was a 8:51 study comparing lemon juice and white wine to prevent browning in pastry 8:55 dough. You've heard of hard cider, hard seltzer. The lemon juice beat out the 9:00 wine though, so better a lemon squeeze than drinking a hard smoothie.
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