Doesn’t it seem like when it comes to nutrition there are more opinions than facts to go around? Every day we hear new theories about diets, and supplements, and the best foods to eat. My role is to take the mystery out of good nutrition, and look at the science. Welcome to the Nutrition Facts Podcast. I’m your host Dr. Michael Greger. And I’m here to bring you an evidence-based approach to the best way to live a healthier longer life.
Our focus today is on improving children’s diet. Did you know that only one in 500 children eats the equivalent of a single leaf of Romaine lettuce a day? If we could increase the intake of whole fruits and vegetables, we could cut down on a wide range of childhood diseases. In our first study, we look at the effects of sulforaphane; the compound found in broccoli on autism.
You may remember my series of videos about the engine-of-aging enzyme, TOR. Well, kids with autism tend to have higher TOR activity in their bodies, and this “hyperactive TOR signaling” may actually play a role in causing autism, making TOR a potential target to treat autism or even theoretically reverse it, if we could target downstream TOR signaling, like between TOR and S6K1. Well, that’s actually one of the ways broccoli compounds kills off prostate cancer cells by inhibiting the “signal transduction between TOR and S6K1.” Breast cancer too; sulforaphane is “a potent inhibitor” of breast cancer cells, because “it targets downstream elements of the TOR pathway.”
So, if we gave broccoli to those with autism, if it blocks TOR, maybe it would block some of the synaptic dysfunction that contributes to the features of autism. And, that’s in addition to blocking autism pathways four other ways: “oxidative stress and lower antioxidant capacity, the mitochondrial dysfunction,” the brain inflammation. And, not just in a petri dish: “sulforaphane can cross the blood-brain-barrier.” You eat broccoli, and sulforaphane “quickly reaches your brain to exert its protective effects”; in theory, but you don’t know, until you put it to the test.
But now, you can understand why such a study could attract researchers from leading institutions: Harvard, Hopkins, and get published in one of our most prestigious journals: PNAS (the Proceedings of the National Academy of Sciences). But what did they find? Well, first, what did they do? A “placebo-controlled, double-blind, randomized trial, young men (aged 13–27) with moderate to severe autism received sulforaphane from broccoli sprouts, or an indistinguishable sugar pill.” They “were dosed according to body weight.” Those under 100 pounds got about a tablespoon of broccoli sprouts worth of sulforaphane a day, which is about a cup’s worth of broccoli. Between 100 and 200 pounds got about two cups of broccoli’s worth, or two tablespoons of fresh broccoli sprouts, and the big boys got three cups’ worth a day, or a little under a quarter-cup of broccoli sprouts. Why didn’t they just use actual broccoli, or actual sprouts? Because then you couldn’t have a blinded study; the patients, doctors, and parents would know who’s getting the special treatment and who’s not, and that could introduce bias just through the placebo effect. So, instead, no one knew, until the end, who got the sulforaphane, and who just got nothing in a pill.
They chose dietary sulforaphane because of its “capacity to reverse” oxidation, dysfunction, and inflammation. Yeah, but when put to the test, did it actually work? Well, the placebo didn’t. Give people with autism nothing, and nothing much happens. But, effectively, secretly sneak them some broccoli, and “substantial improvement in behavior, social interaction and verbal communication.” But, it all disappeared once the broccoli stopped.
Similar findings for a “Social Responsiveness Scale”, significant improvements until the treatment was stopped, and then caught right back up to how poorly those in the placebo group continued to function. And, these weren’t just scores on a page. “The substantial improvements were conspicuous;” the doctors could see them; their parents and caregivers could see the improvements. No drug has ever been shown to have these kinds of effects. And, look, these were young men, starting at age 13. One could imagine it working as well, or even better, for younger children, because their brains are still developing.
And look, what’s the downside? “Broccoli sprouts are widely consumed all over the world without any reports of adverse effects.” Now, remember, we’re talking about whole foods, not broccoli or sulforaphane supplements. Remember, I did videos about them. Broccoli sprouts work; commercial broccoli sprout supplements hardly at all. Broccoli has sulforaphane, florets more than the stems.
Broccoli sprouts have like ten times more, but broccoli pills, powders, and supplements have little or none. So, broccoli and cruciferous vegetables for all kids, autism or not and hey, maybe pregnant women as well, for potential “prenatal prevention” of autism in the first place.
In our next story, the equivalent of a dusting of nutritional yeast is put to the test for the prevention of common childhood illnesses.
In 1989, the late Charles Janeway gave a presentation that was to revolutionize our understanding of the immune system. He proposed that we must have some ancient, innate first-line-of-defense. We knew about vaccinations for centuries, how our bodies can learn from past infections, but he figured that’s not good enough. Our body must have evolved some way to recognize foreign invaders the first time they invade. He proposed that the way our immune cells discriminate between self and non-self. Our own cells vs. invading microbes may arise from pattern-recognition receptors; we’re just born with the ability to “recognize patterns of microbial structure.”
For example, there’s a unique component of fungal cell walls that naturally stimulates our immune system, called beta-glucan. Our own cells don’t produce it, but fungal pathogens, like candida, do. Candida is a type of yeast that can cause serious blood infections; so, it’s a good idea our immune system recognizes it right off the bat. So yeah, you could stimulate your immune system injecting candida into your veins but then, you also might die. Luckily for us, non-disease-causing yeasts, like Saccharomyces cerevisiae, which is what baker’s yeast is, and brewer’s yeast, and nutritional yeast, also have that same molecular signature, that beta-glucan. So, the drug industry is all excited about capitalizing on this “powerful immunostimulatory response” to develop new anti-infection, anti-cancer therapies. Yeah, but does it have to be injected into the vein? What happens if you just eat some nutritional yeast?
Our digestive tract is our largest point of contact with the outside world, more surface area exposed than our lungs and skin put together. And so, not surprisingly, most of our immune cells are concentrated along our intestinal wall. But, they don’t just stay there. Once they’re tipped off to what’s happening in the gut, they can go off to defend other parts of the body. That’s why you can give an oral cholera vaccine, for example, and end up with cholera-fighting immune cells in your salivary glands, pumping out antibodies into your saliva to protect against infection.
So, what if we sprinkled some nutritional yeast on our kids’ popcorn for a snack? Might that help marshal defenses throughout their bodies? Adults tend to just get a few colds a year, but “the average school child” can come down with a cold every other month. And, what can we really do about it? Modern medicine has “little to offer for” run-of-the-mill common colds. Nevertheless, doctors still commonly prescribe antibiotics, which can do more harm than good. “Clearly, there is a need for effective, safe, and inexpensive treatments.” And, “β-Glucan may be just the right solution.” But, you don’t know, until you put it to the test.
So, researchers performed “a randomized, double-blind, placebo-controlled trial” of about a half-teaspoon of nutritional yeast worth of beta-glucan in children who suffered from like repeated respiratory infections, and after a month, found a significant increase in salivary lysozyme levels, compared to control. Lysozyme is an important protective immune component of our eyes, nose, and mouth. But, a larger follow-up study reported the opposite findings; an apparent drop in salivary lysozyme levels. Though the researchers claimed this was “accompanied by pronounced improvements in general physical health,” no data is given.
But the only reason we cared about the lysozyme levels, though, was because we were hoping it would result in fewer infections. But, that had never been directly studied, until now.
The title kinda gives it away, but basically, a “randomized, double-blind, placebo-controlled trial” was performed to see if just a dusting of nutritional yeast worth of beta-glucan a day could reduce the number of episodes of common childhood illnesses. “During the 12-week course of the study, 85% of children in the placebo group experienced one or more episodes of infectious illness.” 85% got ill in the sugar-pill group, but just taking like an eighth of a teaspoon of nutritional yeast worth of beta glucans, or even just a 16th of a teaspoon’s worth, appeared to cut illness rates in half. And, those on the yeast that did come down with a cold only suffered for about three days, compared to more than like nine days in the placebo group.
The researchers conclude that by giving kids the yeast beta-glucans, we “could decrease the incidence and severity of infectious illness during the cold and flu season,” and thereby benefit the parents as well.
Finally, today we look at how PBDE flame-reducing chemicals in the food supply may contribute to attention and cognitive deficits in children.
The results of the CHAMACOS study were published recently (the Center for the Health Assessment of Mothers and Children of Salinas Valley California) investigating the relationship between the exposure to flame-retardant chemical pollutants in pregnancy and childhood, and subsequent neurobehavioral development. Why California? Because California children’s exposures to these chemicals are among the highest in the world, considered to be endocrine disruptors and neurotoxins. What did they find? Both prenatal and childhood exposures to these chemicals were associated with poorer attention, fine motor coordination, and cognition (particularly verbal comprehension) by the time they reached school age. This study, the largest to date, contributes to growing evidence suggesting that these PBDEs, (flame-retardant chemicals) have adverse impacts on child neurobehavioral development. And, the adverse effects may extend into adolescence, again affecting motor function as well as thyroid gland function, something that may extend into adulthood.
These chemicals get into the moms, then get into the amniotic fluid, and then into the breast milk. And the more that’s in the milk, the worse may be the infants’ mental development. Breast is still best; but, how did these women get exposed in the first place?
The question: is exposure mostly from diet, or from dust? Researchers in Boston collected breast milk samples from 46 first-time moms, vacuumed up samples of dust from their homes, and questioned them about their diets. They found that both were likely to blame. Diet-wise, a number of animal products were implicated. That’s consistent with what’s been found worldwide. For example, in Europe, these flame-retardant chemical pollutants are found mostly in fish, meat, and other animal products. It’s similar to what you see with dioxins: fish and other fatty foods, with a plant-based diet offering the lowest exposure.
Well, if that’s the case, then do vegetarians have lower levels of flame-retardant chemical pollutants circulating in their bloodstreams? Yes, vegetarians had about 25% lower levels. Poultry appeared to be the worst. USDA researchers compared the levels in different meats, and the highest levels were found in chicken and turkey, with less in pork, and even less in beef. California poultry had the highest, consistent with strict furniture flammability codes, but it’s not like chickens are pecking at the sofa. Chickens and turkeys may be indirectly exposed through the application of sewer sludge to fields where feed crops are raised, contamination of water supplies, the use of flame-retardant materials in poultry housing, or the inadvertent incorporation of fire-retardant material into the birds’ bedding or feed ingredients.
Now fish have been shown to have the highest levels overall, but Americans don’t eat a lot of fish, and so they don’t contribute as much to the total body burden in the United States.
Where did the vegans end up? Well, we know the intake of many other classes of pollutants is almost exclusively from the ingestion of animal fats in the diet, so, what if you take them all out of the diet? Well, it works for dioxins. Vegan dioxin levels appear markedly lower than the general population, but what about for the flame retardant chemicals? This tendency for chemical levels to decline the longer one eats plant-based suggests that food of animal origin contributes substantially, but note the levels never get down to zero; so, diet is not the only source.
The USDA researchers note that there are currently no regulatory limits on the amount of flame-retardant chemical contamination in U.S. foods, but look reducing the levels of unnecessary, persistent, toxic compounds in our diet is certainly desirable.
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Everything on the website is free. There’s no ads, no corporate sponsorship. It’s strictly non-commercial. I’m not selling anything. I just put it up as a public service, as a labor of love – as a tribute to my grandmother, whose own life was saved with evidence-based nutrition. Thanks for listening to Nutrition Facts. I’m your host, Dr. Michael Greger.