Health! Wealth! Happiness! I’m Dr. Michael Greger and you’re listening to the Nutrition Facts podcast. And while I can’t promise you all of those things, if you take a listen to the evidence-based nutrition found in this podcast, chances are you’ll learn something that you can use to make a positive change in your diet and in your health. My job here is to bring you the information you need to make that reality possible.
Back by popular demand, it’s the Nutrition Facts Grab Bag with the latest news on a whole variety of topics. First up – the health risks related to consuming meat from animals shot with lead ammunition.
I’m often asked in lectures if microwaves are safe, to which I respond: not if you drop them on your foot. But otherwise, it matters what you’re putting in them—sweet potatoes and broccoli, or Hot Pockets and Pop-Tarts. Similarly, when I was exploring the safety of hot sauces, given their potential for lead contamination, I had the same reaction. It matters what you’re putting it on.
When I think toxic pollutants, the first thing I think of is the aquatic food chain. We know, for example, that giving people even just a seven-ounce portion of a high-mercury fish, like tuna or swordfish, once a week—that’s about a can-and-a-half of tuna’s worth a week—can quadruple mercury levels in the blood within a few months. What about lead? A dietary intervention with not one, but five, portions a week, “significantly increased…blood concentrations” of toxic metals, including lead. Even though “the background intake of lead was [found to be] disturbingly high,” the seafood intake increased it by about a quarter. But, “[f]rom a public health perspective,” it’s important to recognize that the amount of seafood that they used in that study “far exceed[s] the intake of most populations.”
Lead can also bioaccumulate in other animals. But, half of our dietary exposure to lead probably comes from plant foods. Animals shot with lead ammunition, though, may present a special case.
We know “[l]ead is toxic and…banned from [most] household items in…developed countries”—except for lead ammunition, “now likely the greatest, largely unregulated source of lead that is knowingly discharged into the environment in [America].” But, not just discharged into the environment, but into the meat itself. “People generally reject the idea of injecting toxic substances into food, except when it involves hunting wild game.”
“Eighty percent of ground [venison]” was found to contain lead. No surprise, given the hundreds of metal fragments that end up in deer carcasses “after being shot” with standard, lead-based rifle bullets—”an impossible number of fragments to pick out by hand, especially because some of these fragments are microscopic.”
Using X-rays, researchers have shown that “[d]uring…penetration, expanding
core bullets typically release hundreds or thousands of fragments.” Or, even millions. Tens of millions of microscopic lead particles per gram; so, one serving could have a billion particles, though they were nanoparticles—extremely tiny, about the size of viruses.
The only good lead, though, is no lead. Even “[v]ery low levels of lead exposure can result in [brain and nerve damage], yet most “hunters [may not be] aware about [the] health risks related to consuming meat from [animals] killed with lead ammunition.
Children may be at risk for losing IQ points, which could reduce their future prospects. A common response from hunters, though, when confronted with the risks of lead exposure, may be, look, “I have been hunting for years, and I am fine.”
To which this physician responds: Ah, “but just imagine how smart you could have been.”
Our next story features some revealing new research on diet and autism. It turns out, the original randomized, controlled trials of gluten- and casein-free diets may have been complicated by parental expectation bias. Here’s the story.
The first randomized, controlled trial to put a gluten-free, casein-free diet to the test for children with autism reported significant improvements in attention problems, less aloofness, fewer needs for routines and rituals, and improved response to learning after a year on the diet—whereas, there was no significant difference reported before or after in the control group.
Same with improvements in social and emotional factors; significantly fewer problems with relationships with their peers, less anxiety, more empathy, and more acceptance of physical contact—but again, no significant changes reported in the control group.
Significantly fewer communication problems too; more facial expressions, better eye contact, more responsive, and fewer things like meaningless word repetition in the diet group—whereas, no significant changes in the control group.
And, in terms of cognitive factors and movement, after a year on the diet, there was significant improvement in the ability to judge dangerous situations, expanded personal interests, and a lower likelihood of being inordinately restless or passive.
Now, the problem with this study is that they relied mostly on parental report. They asked parents questions like these, before and after the year-long trial, to see if they detected any differences.
Why is that a problem? I mean, who better knows the day-to-day functioning of children than their parents? Yeah, they could have had some impartial observer come in before and after to make assessments, blind to which group the children were in, but those would just be like snapshots in time. Who better than the parents to know what was going on with their children?
The problem is the placebo effect. I mean, here the parents are investing “a great deal of time and effort” to maintain these strict diets. I mean, there’s wheat and dairy in so many products, it’s a big shift for most families—and so, they have this hopeful expectation of an effect. So, while the families in the control group did nothing special that year, and reported no significant changes before and after, the families in the diet group put all this work in, and so, when asked if their kids appeared better, their opinions may have been “impacted” by their expectations of benefit. In other words, “placebo effects may have been at play.”
Oh, come on, though; are parents that gullible? Well, “the power of suggestion on the part of the parents can be very strong in situations affecting their children’s behavior.” For example, there was this famous study in which all the children were given “a drink with artificial sweetener,” but half of the parents were told that the drink was sweetened with a boatload of sugar. And, “[t]he parents who thought their children had received the sugar-drink rated their [own] children’s behavior as significantly worse…”
So, in these autism studies, “[it’s] possible that parents [were unconsciously] looking for positive changes in behavior and ignor[ing] or explain[ing] away negative [changes].” So, ideally, what we need are double-blind studies—where kids are given foods made to look and taste the same, but one food has gluten and casein, and the other doesn’t. The kids don’t know which is which; the parents don’t know which is which. Even the researchers, at first, don’t know which is which—until they break the code at the end. “In this way, the behaviors recorded after the [food] challenges couldn’t be impacted by preconceived ideas or biases.”
Okay. So, why didn’t this study do that? “With regard to design”, the researchers conceded, “it might be argued that a double blind…study might have been ideal. With all children on [the] diet, gluten and casein could have been [secretly] administered, for example, in capsules [with wheat flour or powdered milk] during specific altering periods. Then, “[p]arents and caretakers would…have been blind to who was [still] on [the] diet and who” was, unbeknownst to them, actually off the diet, secretly getting gluten and casein. Then, we could eliminate the placebo effect, eliminate that expectation bias. So, why didn’t they do it?
The researchers refused to do it because they were so convinced that gluten and casein were harmful, that from an “ethical “standpoint, they just couldn’t bring themselves to give these kids gluten or casein. The kids in the diet group seemed to be doing so much better, and they had seen cases in which kids appeared to relapse when those proteins were reintroduced back into their diet. And so, they just couldn’t bring themselves to slip them any on the sly.
I understand that, but if they were really so certain that gluten and casein were bad, then by designing a less-than-ideal study, they were potentially dooming scores of other children by failing to provide the strongest possible evidence.
Here’s a question. How do you improve immune function in children and adults under physical or psychological stress? Here’s your answer.
“Natural immunomodulators are getting more and more popular [things that might naturally regulate our immune system]. That popularity, however, often brings over-optimistic claims and mediocre effects.” Such mythical beasts “have been sought [after] for centuries. The current market is full [of all sorts of supplements] promising the golden fleece–inexpensive,” no side effects, yet actively boosting our immune system. Many simply repeat unjustified claims “with hardly any” science to support them.
On the other hand, there is beta-glucan, which has “undergone…10,000 scientific studies…and…clinical trials. Wait, what? Beta-glucan is the fiber in nutritional yeast I talked about before—able to decrease episodes of common illnesses in young children. But what about in adults?
First of all, why can’t they just come up with a vaccine against the common-cold virus? Because there is no single common-cold virus; there are hundreds of different viruses implicated in causing cold-like symptoms. So, that’s why there’s so much interest in finding a general, nonspecific immune booster, across the board.
Beta-glucan supplementation can increase the levels of immunoglobulin A in the saliva within four days, at a daily dose of 400 mg, but not 100 mg. So, the amount found in about two teaspoons of nutritional yeast a day; but not a half-teaspoon. (IgA is an antibody that plays a crucial role in the immune function of our moist membranes, like eyes, nose, and mouth.) One teaspoon’s worth didn’t do much, until they exercised.
Two hours after a strenuous 50-minute bout of strenuous cycling in a hot, humid environment, those who had been on the yeast beta-glucan did get that IgA boost. Beta-glucans failed, however, to boost the antimicrobial activity of white blood cells taken from subjects who had been taking like a tablespoon’s worth a day. What we care about, though, are clinical outcomes. Do those consuming beta-glucans suffer significantly fewer infections?
Okay. How about a double-blind, randomized, placebo-controlled nutritional study to see if yeast beta-glucan can improve our “immune defense system.” A hundred people followed for 26 weeks; 50 getting about a tablespoon of nutritional yeast worth of beta-glucan a day; 50 getting a placebo. And they just counted how many episodes of the common cold they got, and there was “no significant difference.” Now, if you just look at the first half of the time, during cold season, there did appear to be fewer infections in the active group, meaning the beta-glucan group. But, this is what’s called a “post-hoc” analysis, where you go back and look at your data after the fact—which is frowned upon by the scientific community, because it increases the likelihood that your findings are just due to chance. But, those who did end up getting sick while on the beta-glucan did genuinely appear to suffer milder symptoms. A similar, larger study had similar findings. Maybe the severity of the colds was lessened, but, in the main analysis, no significant difference in the number of times people got colds in the first place.
Same in other studies: “no significant differences…in the number of [symptomatic respiratory infection] episodes.” No significant effect on upper respiratory tract infection outcomes. So, overall, pretty disappointing results.
But, wait a second. What about my video about preserving immune function in athletes with nutritional yeast? They found a significant drop in cold symptoms two weeks and four weeks after a marathon at both one teaspoon of yeast worth of beta-glucan a day, and two teaspoons. Yeah, but they had just run a marathon. Okay. But, that’s counteracting the effects of physical stress; what about mental stress?
Stressful life events can impair our moist membrane defenses, such that “psychological stress [has also] been shown to increase susceptibility to the common cold,” getting more colds, and worse colds, than people under less stress. So, let’s see if we can help. And, indeed, those taking about a teaspoon of nutritional yeast a day worth of beta-glucans for 12 weeks were 60% less likely to report experiencing symptoms, like sore throat, stuffed or runny nose, or cough—strongly suggesting that baker’s, brewer’s, and nutritional yeast “beta-glucan is able to counteract the negative effects of stress on the immune system.” And, they experienced 41% greater vigor (which is a measure that encompasses “physical energy, mental acuity, and emotional well-being”). So, they just felt better, too.
Put all the studies together, and yeast beta-glucans do appear to have immune-strengthening effects, at least in children, and those under physical or mental stress.
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 the sources we cite for each of these topics.
Be sure to check out my new How Not to Die Cookbook. It’s beautifully designed, with more than 100 recipes for delicious, health-promoting meals, snacks, beverages, desserts. Not just every recipe is healthy—every ingredient of every recipe is healthy, all green-light whole plant foods. And, of course, all the proceeds I receive from the sales of my books all go to charity.
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Thanks for listening to Nutrition Facts. I’m Dr. Michael Greger.
This is just an approximation of the audio content, contributed by Allyson Burnett.