There are lots of things we want to do in life. Climb a mountain, write a song, watch our grandchildren grow up. But guess what? We can’t do any of those things if we don’t have our health.
Welcome to the Nutrition Facts Podcast. I’m your host Dr. Michael Greger. And I’m here to bring you evidence-based research that takes the mystery out of the best way to live a healthier, longer life.
It’s time for the nutrition facts grab bag, where we look at the latest science on a whole variety of topics. First up, I’ll let you in on a little cooking secret, my very own method for cooking greens.
In a review of more than a hundred articles about the effects of cooking on vegetables, they tried to find the sweet spot. On the one hand, heat can destroy certain nutrients; on the other hand, by softening the tissues, they can become more bioavailable. Researchers settled upon steaming as the best cooking method to preserve the most nutrition. You’re not dunking it in water or oil where the nutrients can leach out, and you’re not reaching excessive dry heat temperatures. But they acknowledge that of all the common cooking methods, we know the least about pressure cooking.
There are all these fancy new electric pressure cookers on the market, including the Instant Pot, with more five-star ratings than even How Not to Die: I’m jealous! These pressure cookers are great for cooking dried beans with just a touch of a button. But what happens to the nutrition? The antioxidant content of presoaked black beans boiled for an hour normally. Compare that to pressure cooking for 15 minutes. Even more. In fact, six times more! Wow. Here I was pressure cooking just because I liked the texture better (the canned ones can be a bit mushy), and I was spending lots of money on cases of canned beans, whereas dried beans are just so dirt cheap. So wait, cheaper, tastier, and healthier? That’s quite a combo. Okay, but what about pressure-cooking vegetables?
Vitamin C is one of the more heat-sensitive nutrients. Sauté spinach or amaranth leaves in a pan for 30 minutes, and about 95 percent of the vitamin C is destroyed, whereas 10 minutes in a pressure cooker wiped out only about 90 percent. But who pressure cooks spinach for 10 minutes? And sautéing for half an hour? And even then, not much effects on beta carotene levels either way.
Vitamin C is but one of many antioxidants. What about the effects of pressure cooking on overall antioxidant capacity? Here’s the cooking methods they compared. So, for the carrots, for example: 12 minutes of boiling, compared to five minutes of pressure cooking, compared to six minutes of microwaving. Here’s what they found. Cooking carrots increased their antioxidant potential. In fact, pressure cooking nearly doubled their antioxidant value, whereas peas took a hit no matter how they were cooked.
I’m particularly interested in the greens. The chard wasn’t affected much across the board, but microwaving beat out pressure cooking and boiling for the spinach. Note that pressure cooking beat out the boiling too, though, and pressure cooking is boiling (just at a shorter time at a higher temperature.) But the time appeared to trump the temperature. Significantly less nutrient loss pressure-cooking spinach for three and a half minutes, compared to boiling for eight.
Same for those magical cancer-fighting glucosinolate compounds in cruciferous greens, the healthiest greens like kale, collards, and turnip greens. Here’s where levels started out raw, with three-quarters wiped out by boiling, but less than half with pressure cooking. Now, both got beat by steaming, but that’s because you weren’t dunking the greens in water, which can leach out the nutrients. But even though the pressure-cooked greens were immersed just as much as the boiled greens, only half the nutrient losses, presumably because it was only half the time. Seven minutes pressure-cooked compared to 15 minutes boiled.
Okay, so here’s my idea. This was after 10 minutes of steaming. What if you cut down that time by pressure steaming, like put a layer of water down at the bottom of an electric pressure cooker, drop in a metal steaming basket on top, and then put the greens in and steam under pressure? That’s how I cook the greens I eat every day. I’ve always loved collards in like Southern cooking, or Ethiopian cuisine, and I found I could get that same melt-in-your-mouth texture just steaming under pressure for zero minutes. What you do is set it for zero, so it shuts off as soon as it reaches the cooking pressure, and then quick release valve it immediately to release the steam. The greens turn out perfect, bright emerald green, cooked tender. Give it a try, and let me know what you think.
Next up, we put some refrigerator water filters to the test.
Though many distrust the safety of tap water, a study of 35 brands of bottled water did not find them to necessarily be safer, cleaner, or of a higher quality than water straight out of the faucet. How much is that saying, though? Two studies published back in the 1970s forever changed our perception that drinking water safety was only about waterborne diseases. In fact, it was our fight against microbial contaminants that led to a new kind of contamination in the form of “disinfection by-products.”
The two landmark papers in ‘74 solved the mystery of the source of chloroform in drinking water: we met the enemy and he is us. The chlorination of drinking water ”crucial for maintaining microbiological safety” was interacting with natural organic matter from the water’s source, and creating chlorinated compounds that can not only result in off-flavors and smells, but pose a potential public health risk. More than 600 disinfection byproducts have so far been identified.
After decades of research into the matter, it appears that the lifelong ingestion of chlorinated drinking water results in “clear excess risk” for bladder cancer. There is also some evidence of increased risk of certain types of birth defects, but most of the concern has focused on the bladder cancer link. Forty years of exposure may increase your odds of bladder cancer by 27 percent. The Environmental Protection Agency estimated that between 2 to 17 percent of bladder cancer cases in the United States are due to these disinfection byproducts in drinking water. However, this is assuming the link is cause-and-effect, which has yet to be firmly established.
The best way to reduce risk is to treat the cause. Countries could prevent the formation of disinfection byproducts in the first place through the better initial removal of source water’s “natural organic matter” (or what my grandmother would have called “schmutz”). Some countries in Europe, such as Switzerland, have newer, well-maintained drinking water systems that can distribute tap water free from residual disinfectants. But the cost to upgrade the infrastructure of even a small city here in the U.S. could run in the tens of millions. As the Flint tragedy revealed, we seem to have trouble keeping even frank toxins out of the tap.
Nearly 40 percent of Americans use some sort of water purification device. Two of the most common approaches, pour-through pitchers and refrigerator filters were put to the test, head-to-head against Tucson tap water. Both of the fridge filters (GE and Whirlpool) did similarly well, removing more than 96 percent of trace organic contaminants, edging out the three pitcher filters. ZeroWater brand caught 93 percent, PUR pitchers got 84 percent, but by the time the filters needed to be replaced, Brita was only catching 50 percent. A similar discrepancy was found between PUR and Brita brand filters tested specifically against disinfection byproducts. They both started out about the same at the beginning, but by the end of the filter’s life PUR appeared to do better. Reverse osmosis systems can work even better, but the cost, water waste, and loss of trace minerals doesn’t seem worth it.
The annual cost for purifying your water with the pitcher or fridge filters was calculated out to be about the same, at only around a penny per cup with the exception of the ZeroWater brand, which is up to four times more expensive.
I always figured the “change by” dates on the filters were just company scams to get you to buy more, but I was wrong. Since I drink filtered water mostly just for taste, I used to just wait until the water started tasting funky. Bad idea. Not only do the filters eventually lose some of their removal capacity, bacterial growth can build up inside them, resulting in your so-called “filtered” water having higher bacterial counts than the water straight out of the tap. You’d be actually making your water dirtier rather than cleaner; so, it is important to replace them regularly.
As an aside, I used to think the same thing about the advice to change your toothbrush every three months. Like, which Big Brush executive thought up that one? But no, wrong again. Toothbrushes can build up biofilms of tooth decay bacteria or become breeding grounds for bacteria flumed into the air with each toilet flush before going back into our mouths. Fun Fact: A single flush can spew up “millions of bacteria” that can settle on your nice moist brush. The good news is that rather than buying new ones, you can just disinfect the head of your toothbrush with as little as a 10-minute soak in white vinegar; or even more frugally, vinegar diluted in half with water.
Finally today, we look at how certain foods are linked not only to increased happiness, but also to greater feelings of engagement, creativity, meaning, and purpose in life.
Thousands of papers have been published on the important topic of what determines people’s happiness and psychological health, but what about the potential influence of the different kinds of foods that people eat?
The rising prevalence of mental ill health is causing a considerable burden. And so, inexpensive and effective strategies are required to improve the psychological well-being of our population, and now, we have a growing body of literature suggesting that dietary intake may have the potential to influence psychological well-being. Dietary intake of what? Well, given the strong evidence base for the health benefits of fruits and vegetables, researchers started there.
Cross-sectional studies from all over the world support this relationship between happiness and fruit and vegetable intake. Those eating fruits and vegetables each day have a higher likelihood of being classified as “very happy,” suggesting a strong and positive correlation between fruit and vegetable consumption and happiness, perhaps feelings of optimism, too.
The largest such study was done in Great Britain, where a dose–response relationship was found between daily servings of fruits and vegetables and both life satisfaction and happiness, meaning more fruits and veggies meant more happiness. People who got up to seven or eight servings a day reported the highest life satisfaction and happiness. And these associations remained significant even after controlling for factors such as income, illness, exercise, smoking, and body weight, suggesting fruit and vegetable consumption wasn’t just acting as a marker for other healthy behaviors.
But how could eating plants improve happiness on their own? Well, many fruits and veggies contain higher levels of vitamin C, which is a co-factor in the production of dopamine, the “zest for life” neurotransmitter. And the antioxidants reduce inflammation, which may lead to higher levels of eudaemonic well-being.
Aristotle’s notion of eudaemonia described the highest of all human goods, the realization of one’s true potential, which was the aim of this study. They wanted to know whether eating fruits and vegetables was associated with other markers of well-being beyond happiness and life satisfaction, like greater eudaemonic well-being, a state of flourishing characterized by feelings of engagement, meaning, and purpose in life.
So, a sample of about 400 young adults were followed for about two weeks, and indeed, young adults who ate more fruits and veggies reported higher average eudaemonic well-being, more intense feelings of curiosity, and greater creativity. And they could follow this on a day by day basis. Greater well-being on the days they ate healthier. These findings suggest that fruit and vegetable intake is related to other aspects of human flourishing, beyond just feeling happy.
Not so fast, though. Instead of eating good food leading to a good mood, maybe the good mood led to eating good food? Experimentally, if you put people in a good mood, they rate healthy foods, like apples, higher than indulgent foods, like candy bars. Given a choice between M&M’s and grapes, individuals in a positive mood were more likely to choose the grapes. The results of these studies lend support to a growing body of research that suggests that positive mood facilitates resistance to temptation. Who needs comfort food when you’re already comforted? It’s like which came first, the stricken or the egg? Yes, eating eggs may increase our likelihood of chronic disease, but maybe chronic disease also increases our likelihood of eating unhealthy foods. Which came first, the mood or the food? What we need is a study like this, but instead of looking at well-being and diet on the same day, you see if there’s a correlation between what you eat today, and how you feel tomorrow. But we didn’t have a study like that, until now.
They found the same strong relationships between daily positive mood and fruit and vegetable consumption, but lagged analyses showed that fruit and vegetable consumption predicted improvements in positive mood the next day, not vice versa. On days when people ate more fruits and vegetables, they reported feeling calmer, happier, and more energetic than they normally do, and they also felt more positive the next day. So, eating fruis and vegetables really may promote emotional well-being. Look, single bouts of exercise can elevate one’s mood, why not the same thing with healthy food? How many fruits and vegetables? Seems we need to consume approximately 7.2 daily servings of fruit or 8.2 servings of vegetables to notice a meaningful change.
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To see any graphs, charts, graphics, images, or studies mentioned here, please go to the Nutrition Facts Podcast landing page. There you’ll find all the detailed information you need, plus links to all of the sources we cite for each of these topics.
For recipes, check out my “How Not to Die Cookbook.” It’s beautifully designed, with more than 100 recipes for delicious and nutritious meals. All the proceeds I receive from the sales of my books all goes to charity.
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Thanks for listening to Nutrition Facts. I’m your host, Dr. Michael Greger.