RHR Research Review: Dietary Interventions for Cancer, Vitamin D, Walking, Tocotrienols, Sleep Apnea, ADHD in Kids, Mental Health, and Nanoplastics

In this episode, we discuss:

• Whether ketogenic diets might protect against colorectal cancer
• Influence of protein intake on diffuse midline gliomas
• Vitamin D supplementation for protection against COVID-19
• What difference the pace of walking makes in terms of health and longevity
• Therapeutic potential of tocotrienols
• The impact sleep apnea has on biological age
• Behavioral and emotional benefits of micronutrients in kids with attention-deficit/hyperactivity disorder (ADHD)
• Improvements in mental health during the COVID-19 pandemic among those who had exposure to the outdoors
• Health effects of plastic nanoparticles from food and beverage containers

Show notes:



Hey, everybody, Chris Kresser here. Welcome to another episode of Revolution Health Radio. This week, I’m going to do another solocast research review.

Whether Ketogenic Diets Might Protect Against Colorectal Cancer

Let’s start with a study that investigated whether ketogenic diets might protect against colorectal cancer. It’s called “β-Hydroxybutyrate Suppresses Colorectal Cancer.” This is an important study because colorectal cancer kills about 50,000 Americans each year. It’s one of the most common cancer types, [and] it’s the third leading cause of cancer mortality in the [United States]. The researchers put mice on diets with varying ratios of carbohydrates and fat, and the majority of the mice on the most ketogenic diets, with the most ketogenic diet being 90 percent of calories as fat, didn’t develop tumors or cancer at all. On the other hand, all of the mice on the lower-fat, higher-carbohydrate diets eventually developed tumors. This is pretty remarkable, and what made it even more stunning was that when the researchers switched the mice who had developed cancer on the lower-fat, higher-carbohydrate diets to ketogenic diets, they actually observed slower rates of tumor growth and proliferation in those mice. So it seemed to have a treatment effect as well as a preventative effect.

When the study authors looked into the mechanisms, they found that beta-hydroxybutyrate, which is a molecule that’s produced in the liver in response to a ketogenic diet or fasting, was responsible. Beta-hydroxybutyrate can work as an alternative fuel source to glucose in people who are doing ketogenic diets, but it seems that it also has an effect on slowing the growth of cells by activating a surface receptor called [hydroxycarboxylic acid receptor 2] (HCAR2). And then HCAR2 stimulates the expression of a growth-slowing gene called HOPX. The researchers then did in vitro studies with human cells and found that the beta-hydroxybutyrate has the same growth-slowing effects on those cells via the human versions of HCAR2 and HOPX. So this is a really important study. It suggests that ketogenic diets and perhaps beta-hydroxybutyrate supplements may not only help prevent colorectal cancer, but they might even be useful in treating it once it’s already there.

Influence of Protein Intake on Diffuse Midline Gliomas

However, before we all switch over to a ketogenic diet, I just want to note that the research on diet and cancer is really mixed. Some cancers do seem to benefit from low-carb and keto[genic] diets, whereas others don’t. And some research suggests that, for certain cancers, they might be more influenced by protein intake, specifically the intake of methionine, which is an amino acid. A good example is a recent study called “Loss of MAT2A compromises methionine metabolism and represents a vulnerability in H3K27M mutant glioma by modulating the epigenome.”

This study looked at deadly brain cancers called diffuse midline gliomas (DMGs), and they found that these cancers are uniquely dependent on methionine, which is an amino acid found in proteins, lean meats, poultry, egg whites, [and] particularly lean proteins. Whereas glycine is the amino acid that tends to be found in the more gelatinous cuts of meat. DMG tumors are the second most common cancers in children behind only leukemias. But unlike leukemias, which tend to have relatively high survival rates when they’re detected early and well treated, DMGs are, unfortunately, especially deadly. Most kids [who] are diagnosed with them die within a year. This study found that DMG tumors are highly dependent on methionine, and when researchers put mice with these tumors on a methionine-restricted diet, their life expectancy increased by 50 percent. This is also an important finding because DMG cancers are difficult to treat. They don’t tend to respond well to chemotherapy, and, as I said, they affect children. The mortality rate is really high. So having another tool to address these cancers is really useful.

I mostly bring this up to show you that, when it comes to cancer, there really is no “one-size-fits-all” dietary approach. We still have a lot to learn about the way that different cancers respond to different diets. I’m really encouraged by the studies showing that ketogenic diets and beta-hydroxybutyrate seem to make a really big difference for colorectal cancers. I’m also encouraged by the study showing that methionine-restricted diets can benefit kids with DMG cancer. I think what we need in the case of diet and cancer is a specific approach that probably depends on the type of cancer, and then even [on] the individual [who] has that cancer. So I’m glad to see studies that are making this more specific so that we can eventually have a really individualized, tailored approach to dietary interventions with cancer.

Vitamin D Supplementation for Protection Against COVID-19

The next study is about vitamin D supplementation and protection against COVID[-19]. I like to revisit this occasionally because if you’ve been following my work for any length of time, you know that this is a topic [that] I’ve covered at length. I did a presentation on it in March 2021 at the IHH-UCSF Symposium on Nutrition and Functional Medicine, and it’s a topic I’ve been following very closely in the research literature since then. This study was called “Efficacy and Safety of Vitamin D Supplementation to Prevent COVID-19 in Frontline Healthcare Workers. A Randomized Clinical Trial.” This [one] is great. A lot of the early studies on vitamin D and COVID[-19] were observational in nature, and we didn’t have a lot of experimental evidence. But this is a randomized trial, so the results [are], of course, a little bit more reliable than a purely observational study. It was a double-blind, parallel, randomized trial of healthcare workers from four hospitals in Mexico, and they were randomly assigned to receive [either] in the treatment group, 4000 IU of vitamin D per day, or a placebo. This was a 30-day intervention period.

The [healthcare workers] who received vitamin D had a 77 percent lower risk of testing positive via [polymerase chain reaction] for SARS-CoV-2. This effect was independent of vitamin D deficiency, which means that supplementation benefited even those who were not clinically deficient in vitamin D going into this trial. I’m not surprised by these results. Like I said, I’ve been tracking this topic for a long time, and there’s a huge body of evidence now linking adequate vitamin D levels or vitamin D supplementation to better outcomes with COVID-19. In fact, in my presentation at UCSF back in 2021, I made 10 arguments in favor of maintaining optimal vitamin D levels as a means of protecting against COVID-19. [Note: I misspoke when I said 10 reasons—I meant to say 9!] Number one is [that] most observational studies do support a role. So while we can’t rely on these studies exclusively, when you have many different observational studies coming from many different parts of the world with many different study design types, and they’re all pointing in a similar direction, it’s definitely a sign that there might be a signal there.

[Number two is that] the observational evidence meets most of Hill’s Criteria for Causality. I’m not going to go into detail on this here, but I’ve spoken about these criteria before. They are a way that researchers can determine whether observational evidence is more likely to be causal. And when these criteria are met, it’s much more likely that there is a causal relationship between two variables. They’re associated together in an observational study. Number three is that the majority of experimental evidence supports a connection. As I said, a lot of the early evidence for vitamin D was observational in nature. But we have seen randomized controlled trials like the one that I just mentioned, over the past several months especially, and those have also generally shown a benefit for vitamin D. Number four [is that] there are well-established plausible mechanisms that explain the connection. We know that vitamin D stimulates antiviral peptides that reduce inflammation [and] it protects the vascular endothelium. There are many, many mechanisms that are well-established for vitamin D that could explain its benefit for COVID[-19]. Number five [is that] vitamin D supplements have been shown to protect against other upper respiratory tract infections. Number six [is that] the populations at highest risk for COVID[-19] are also those that are at highest risk of vitamin D deficiency. Number [seven is that] supplementation with vitamin D at appropriate doses is safe, effective, affordable, and accessible to nearly everybody, especially if there is government support. Number [eight is that] supplementation with vitamin D would be prudent even without the COVID-19 pandemic because we have an epidemic of vitamin D deficiency, and vitamin D deficiency is associated with everything from obesity to metabolic issues, to cardiovascular disease, to osteoporosis, to cognitive issues and dementia, neurodegenerative disorders, etc. There [are] so many chronic inflammatory conditions that vitamin D is associated with and there’s such a high rate of vitamin D deficiency, that it just makes sense for people to be paying attention to their vitamin D levels. And number [nine is that] normalizing vitamin D levels would be expected to provide a benefit even if or when the virus mutates again. We’ve seen several different versions of SARS-CoV-2 now, [with] Omicron and the recent Omicron variants being the latest iterations, and it’s almost certain that these mutations will continue. And unlike vaccines, which tend to be designed specifically for a variant, vitamin D works by supporting our own endogenous immune defenses, and that would be expected to provide a benefit regardless of what variant is dominant at any given time.

So what is the optimal level of vitamin D? For many years, I’ve argued that a range of 40 to 60 nanograms per milliliter is ideal, and I still think that’s a generally good range. But some evidence suggests targeting the upper end of that range, let’s say 50 to 60 [nanograms per milliliter], might be better while the coronavirus is still circulating. How do you do that? Well, there’s a wide individual variation [in] response to supplementation and food and sunlight, which are the major ways of getting vitamin D. But studies suggest that, in general, somewhere between 3000 to 5000 IU per day is a good target for most people who are generally healthy and well. For people who have chronic inflammatory conditions or people who are obese, those conditions can actually reduce the production, absorption, and utilization of vitamin D, whether it’s from sunlight, food, or supplements. So some research suggests that a dose of 10,000 IU per day is necessary for folks in that category to establish that level of 50 to 60 [nanograms per milliliter] and maintain it over time. It’s best, if you can, to get tested to confirm that your levels are not going too high. Studies have shown that doses up to 15,000 IU per day are safe and well-tolerated for about six months. So if you can’t get tested right away, you can get started [by] taking a dose of 5000 to 10,000 IU per day. And then if you can get your doctor to test you [in] a few months or even order an at-home test, that would be good. It’s generally a good idea to do that a couple of times a year to make sure your levels are where you would like them to be and [that] they’re not too low and they’re not too high.

One other thing to note is that, just like all other nutrients, vitamin D requires the presence of other nutrients to be absorbed and utilized. Magnesium is probably the best example. It acts as a cofactor in several different enzymatic reactions in the liver and the kidneys that involve vitamin D, and it’s also required for the biosynthesis transport and activation of vitamin D. This is important because studies suggest that 60 percent of Americans don’t get enough magnesium on a daily basis. So if you’re not getting enough magnesium, even if you’re taking vitamin D or getting sun exposure, you very well may end up being vitamin D deficient if you’re not getting enough magnesium. I’ve definitely seen this in my clinic over the years. Magnesium deficiency is even more common in patients who are at the highest risk of COVID-19 and who are also most likely to be vitamin D deficient. Those are people with obesity, diabetes, hypertension, and other metabolic issues. Those folks need to pay particular attention to their magnesium status and their vitamin D status simultaneously.

What Difference the Pace of Walking Makes in Terms of Health and Longevity

The next study was really interesting. I think this is the first study of its kind. We know from a lot of research that walking benefits our health tremendously. There’s just something about walking for human beings, I think because we’ve been doing it for so long, even before we were fully human, that is very good for our physiology and our health. But up until this study, I’d never seen any research on what difference the pace of walking makes in terms of health and longevity. This one was called “Investigation of a UK biobank cohort reveals causal associations of self-reported walking pace with telomere length.” These researchers looked at genetic data of over 400,000 adults in the UK biobank and they found a clear link between not just walking, but the pace of walking and biological age. They collected data from wearable risk-based activity trackers, and they found that people who walked habitually at a faster pace had longer telomeres. Telomeres, you might know, are the caps at the end of each chromosome, and they hold repetitive sequences of noncoding DNA that protect the chromosome from damage. Each time a cell divides, [the] telomeres become shorter. This continues to happen until the telomeres become so short that the cell can no longer divide. This is called replicative senescence, and it’s thought to be a key marker of biological aging.

Conversely, anything that lengthens telomeres may reverse the effects or at least slow the effects of biological aging. And that’s what the researchers in this study found that brisk walking does. In fact they estimated, based on the data, that a lifetime of brisk walking could lead to the equivalent of 16 years younger biological age by the time we’re in midlife. In other words, if you start [doing a lot of brisk walking] early in your life, [then] by the time you reach middle age in your 50s or 60s, according to your telomeres, you might be 16 years younger than what your age on paper would suggest. The good news is [that] you don’t need to walk a marathon, so to speak, to get this benefit. Previous research that the same scientists have done found that as little as 10 minutes of brisk walking per day is associated with longer life expectancy, and brisk walkers have up to 20 years longer life expectancy than slower walkers. It’s a really fascinating paper. I will say, [these are] observational data. We don’t know if there’s a causal relationship between brisk walking and longer lifespan. There are certainly lots of mechanisms [that] could explain a causal link. But it’s also true that there could be some confounding factors like, maybe people who walk briskly do other things that extend their lifespan, [or] maybe they tend to have healthier diets than slow walkers or be less likely to smoke or drink alcohol. They did try to control for some of these confounding factors, but as I’ve discussed before, that’s not always easy to do completely.

Nevertheless, given the previous research on this topic, I think it’s certainly an interesting finding and [that] walking in general, and certainly brisk walking, [is] probably really good for us as human beings.

Therapeutic Potential of Tocotrienols

The next [study] is an introduction to tocotrienols. You may have seen me mention tocotrienols in some of my Friday Favorites newsletters recently. You may also have heard my full podcast episode with Dr. Barrie Tan, who is one of the pioneers of tocotrienol research and the scientist who discovered tocotrienols in palm and annatto, which are two of the biggest sources of tocotrienols. I am really excited about the therapeutic potential of tocotrienols. I first became aware of them about 10 years ago. I was creating the second digital education program [that] I ever created, which is called High Cholesterol Action Plan. It still exists, and it’s a product that’s designed for people who have high cholesterol or dyslipidemia and are looking for natural solutions to manage that. I was researching natural compounds that are able to reduce [low-density lipoprotein] (LDL) particle number and [apolipoprotein B] (ApoB). If you’ve followed my work for a while, [then] you’ll know that’s more important than reducing LDL cholesterol. It’s the LDL particles that really drive [the] risk for atherosclerosis and heart disease, not so much the cholesterol inside the particle.

A lot of natural substances are known to decrease cholesterol, but there are a lot fewer substances that actually decrease LDL particle number. In that research, I came across delta- and gamma-tocotrienols and started using them in my practice and have been using them for many years, and have had great success with them. They’re effective, they’re well-tolerated, they don’t tend to produce any side effects, and there [are] no long-term risks. They also have a bunch of other benefits that we’re going to touch on here like being anti-inflammatory and reducing oxidative stress. I’ve been using them for many years and yet the other day, when I was searching my own website for articles on tocotrienols, I couldn’t believe that I hadn’t actually written one. And I hadn’t done a podcast on tocotrienols either. So I’m now setting out to remedy that. I want to tell you a little bit more about these compounds. Because most people, even patients [who] I work with, have never heard of them [and are] not familiar with them at all.

Let’s back up and talk a little bit about what tocotrienols are. Vitamin E, as a family of compounds, was originally discovered 100 years ago in 1922, by researchers at UC Berkeley who were studying fertility in rats. They found that vitamin E was required for conception and carrying a pregnancy to full-term. So at that point, vitamin E became an essential nutrient. Essential, meaning the body can’t manufacture it on its own and we need to get it from diet. Vitamin E was originally called “anti-sterility factor X” for this reason, but then they renamed it tocopherol, which means “to carry a pregnancy” in Greek. There are four forms of tocopherol that have Greek names: alpha, beta, delta, and gamma. Tocopherols, especially alpha-tocopherol, became synonymous with vitamin E, and they’ve been the major subject of research and they’re almost always included in vitamin E supplements or multivitamins that contain vitamin E. However, in the early 2000s, a different family of vitamin E isomers called tocotrienols was discovered. Like tocopherols, tocotrienols also have four forms: alpha, beta, delta, and gamma. But as researchers learned more about tocotrienols, they discovered some pretty amazing properties and differences from tocopherols.

The first is that tocotrienols are 40 to 50 times more potent as antioxidants than tocopherols. Second, studies over the past several years have shown that supplementing with alpha-tocopherol, which again is what you will find in most vitamin E supplements and multivitamins, can actually increase the risk of heart disease and cancer, which is, of course, exactly the opposite effect that people are trying to get when they take vitamin E, which is typically known as an antioxidant. On the other hand, tocotrienols have the opposite effect. They not only don’t increase the risk of heart disease and cancer, [but] they actually decrease cardiovascular disease risk factors and have several protective effects against cancer. Third, tocotrienols have a much wider range of action and benefit than tocopherols. I’m just going to name a few here. They help protect our brain as we age by reducing oxidative stress in neurons. They help maintain healthy metabolic function, [including] everything from reducing abdominal fat to lowering triglycerides and blood pressure. They protect against oxidative damage and reduce inflammation. They’ve been shown to reduce C-reactive protein (CRP), interleukin-6, [tumor necrosis factor alpha] (TNFα), [and] a whole bunch of other inflammatory cytokines and increase endogenous antioxidant capacity. They promote healthy lipid profiles and cardiovascular function in general. They improve insulin sensitivity, glucose tolerance, and other factors in metabolic health. They reduce fat deposition in the liver, so they’re being used in people with non-alcoholic fatty liver disease. They support bone health, particularly in menopausal women. They protect the skin and the eyes. In fact, tocotrienols are particularly active in the macula. So there [are] studies showing they can help protect against macular degeneration. They support immune function and have several protective effects against cancer including inhibiting tumor growth and reducing tumor size, reducing the multiplication of cancer cells, and reducing angiogenesis by inhibiting [vascular endothelial growth factor] (VEGF), all of which are really important mechanisms for chemoprotection.

Over the years, I’ve come to believe that tocotrienols are among the most potent and safe natural compounds that we can use to optimize our health and performance and extend our lifespan. I will be sharing more about how to use them for different health goals and protocols in the near future. As you may have heard, I’m launching my own supplement line called Adapt Naturals in July. After 15 years of treating patients and extensive clinical research, I’m really excited to bring these to you. I’m starting with a bundle of five products called Core Plus that are designed to provide all the nutrients and support I think most of us need to thrive and flourish in the modern world. Perhaps not surprisingly, now that you’ve heard me talk about tocotrienols and my enthusiasm for them, they will be included in the bundle. Stay tuned for more information about this.

Hear my thoughts and insights on some recently published studies that I’ve found especially interesting in this episode of Revolution Health Radio. #chriskresser #educator #cancer #vitaminD #kidsADHD #tocotrienols

The Impact Sleep Apnea Has on Biological Age

The next study is about sleep apnea and how it can accelerate aging if it’s not treated. On the other hand, if it is treated, that impact goes away. The study is called “Epigenetic age acceleration in obstructive sleep apnoea is reversible with adherent treatment.” The researchers found that sleep apnea increases biological age. They had an algorithm and markers for assessing biological age. But they found that if sleep apnea is treated with a continuous positive airway pressure (CPAP) device, [it] will reverse the impact of sleep apnea on biological age. For those [who] don’t know, sleep apnea is a sleep-disordered breathing characterized by a number of involuntary breathing events during a single night of sleep that can often seem like gasping for air or choking, [and] periods of not breathing. If you sleep with someone who is doing that, they [may] very well have apnea, or if you notice yourself doing that, [then] you might have apnea. There are two major types of apnea, obstructive and central. Obstructive apnea is far more common. It’s really important to know that 75 percent of people with sleep apnea are undiagnosed. It’s a very common disorder. One in five Americans have mild obstructive sleep apnea and one in 15 have moderate to severe obstructive sleep apnea.

This is a big deal because there [are] so many studies on sleep apnea’s relationship as a risk factor with other chronic inflammatory disorders like obesity, diabetes, heart disease, dementia, Alzheimer’s [disease], etc. We would often test people for sleep apnea when they came into the clinic, and I would say, very consistent with these statistics, seven or eight out of 10, at least, didn’t know they had it when they tested positive. And when it was corrected, it was an absolute game changer for people. These were people who were doing everything right, they were eating a good diet, they were exercising, managing stress, etc., and they just couldn’t get past a plateau and couldn’t reach their health goals, whatever [those] were. Then [we corrected the] sleep apnea, [and] all of a sudden, they felt like a different person. They were able to bust through that plateau. Why is this? Well, sleep apnea, as I described, is basically a deficit of oxygen. You’re not getting enough oxygen. And every cell in the body needs oxygen. In fact, we can go quite a while without eating, up to a month in some cases, [and] we can go several days without drinking water, [but] we can’t go more than a few minutes without breathing. That indicates the importance of oxygen. If we’re not getting enough oxygen to our cells, that’s going to really wreak havoc on our bodies and lead to a lot of different problems.

You can’t really diagnose sleep apnea from symptoms. I’m going to tell you how we can diagnose it in a moment. But there are some characteristic symptoms of sleep apnea. These are not specific to sleep apnea, of course; they can occur with other conditions as well. But if you notice that you’re having a lot of these as I go through this list, then it [may] very well make sense to get yourself tested. Waking up with morning headaches [is] often a reaction to oxygen deprivation. [Other signs are] excessive daytime sleepiness, lack of energy, [and] irregular breathing during sleep—gasping for air, choking, [and] long pauses of not breathing. Snoring [is] a big one. Frequent nocturnal urination [is another] because generally, people with sleep apnea are not sleeping deeply. Depression, GI reflux, and a large neck size can [all] be telltale sign[s].

The gold standard way to test for sleep apnea is a sleep study in a sleep clinic. These are not that fun, I can tell you, I’ve had one. You need to get a recommendation from your doctor. Then you need to go into the sleep clinic [and] spend the night there. You get hooked up to all kinds of different electrodes, and you’ve got wires all over the place, and then you’re sleeping in this foreign place, in a room with all these wires attached to you. It always seemed weird to me [because] I don’t know anyone who would go into that kind of situation and sleep well. So I always wondered about sleep studies from that perspective. Nevertheless, they are still the gold standard, and the best option if your insurance will cover it, your doctor will order one for you, and you’ve got a good sleep clinic nearby. However, there is another option that’s become available more recently called the WatchPAT home test. This is [a U.S. Food and Drug Administration]-cleared at-home sleep apnea test. One of the advantages [of] it is that you can do it at home. So you’re sleeping in your own bed, in your own environment, [and] it’s a lot more representative of your typical sleep patterns. I think you can make a strong argument for that. That makes a lot of sense to me.

The other thing is that it’s just one wire. You wear something on your wrist, and then there’s a wire that goes from that wrist device [that] you thread through your shirt, and then you put the sensor under your sternal notch. Then there’s one [wire] that goes from the wrist device to your finger, and you put your finger in this little device. So you only have two wires on one side of your body. I’ve done it myself, as well. It’s much less invasive and more comfortable than a sleep study in a clinic. I think, for that reason, it might even be a more accurate indicator of how you’re sleeping. It’s cheaper, as well, especially if your insurance doesn’t cover it, and just far less of a hassle, far less cumbersome. So those are a couple of ways to get tested for apnea.

If you do have apnea, usually, you will be prescribed the CPAP machine that we talked about before. This is essentially a way of making sure that your cells are getting enough oxygen. You wear a mask and it makes noise. It’s pretty intrusive, and a lot of people hate them. Even though they recognize that they get far better sleep and a big health benefit from doing it, the compliance tends to be pretty low because they are quite invasive. I want to be clear that this study showed that the CPAP did reverse the biological aging caused by sleep apnea. There are other treatments for apnea that usually dentists will administer. One is called a mandibular advancement device. It brings the lower jaw forward, and the reason that helps is often, the airway can be obstructed if the lower jaw is too far recessed and impinges on the airway. It makes [the airway] more narrow, and it makes it harder for someone to breathe and get oxygen. So these mandibular advancement devices look almost like a retainer, but they’re bulkier, and they bring your lower jaw forward and keep it in place while you’re sleeping. Some studies show some mandibular advancement devices are equivalent to CPAP in their ability to treat apnea, although I would say generally, most studies suggest that CPAP devices are superior. I have no idea if a mandibular advancement device would have the same impact on reducing the biological aging effect because I don’t think that’s been studied. But if you can’t tolerate a CPAP [machine] or you don’t want to use one, you might at least consider one of these devices as an alternative. It would definitely be better than not treating the apnea at all. And a lot of dentists are doing this now. You can just search for “sleep apnea dentist” in your area, and you [will] find somebody who specializes in that.

Behavioral and Emotional Benefits of Micronutrients in Kids with ADHD

The next study was on micronutrients for ADHD in kids. Kids with ADHD and emotional dysregulation were randomized to take a micronutrient formula, and they were three times more likely to show symptomatic improvement on blinded clinician ratings compared to those in the placebo group. Fifty-four percent of kids who were taking the supplement showed improvement versus just 18 percent in the placebo group. The name of this study [is] “Micronutrients for Attention-Deficit/Hyperactivity Disorder in Youths: A Placebo-Controlled Randomized Clinical Trial.” One of the things I really liked about this study [is that] it was triple blinded. That means that neither the parents nor the children nor the clinicians knew what treatment was being administered and were not able to guess better than chance. Especially with a condition like ADHD, where subjectivity and bias could potentially affect the results of the study, it’s important to do this. So they really did a great job with that.

There were 135 kids, and they were randomized into two groups. One received the placebo [and] the other received the formula that contained all essential vitamins and minerals. [The treatment group] took them for eight weeks, [and] the placebo group took placebo for that length of time.

I mentioned “essential” earlier in the podcast. In this context, what essential means is [that it’s] not just really important; it means that these are nutrients that the body cannot produce on its own and has to obtain through diet or supplements. These are things like vitamin A, vitamin D, vitamin C, iron, calcium, zinc, [and] copper. We’re not talking about phytonutrients like flavonoids, or things like quercetin, or resveratrol, or some of the more newly discovered phytonutrients that certainly have a lot of health benefits and can really improve our overall health and well-being but they’re not absolutely essential in the sense that we can’t survive without them.

Another interesting effect that was observed in this study is that, beyond the behavioral and emotional benefits, children who were taking the micronutrient blend actually grew six millimeters in height more than kids who were not taking the supplement. And this was in [just] eight weeks. The reason this is important is [that] one of the biggest concerns about ADHD medication, stimulants specifically, is that they can stunt growth. And this does happen. I’ve seen it in my practice. There are lots of studies about it, and there’s discussion about what the mechanism is. One may be that stimulants suppress appetite and kids don’t eat as much. This may explain why taking a micronutrient blend is helpful. It might make up for the nutrients that the kids who are taking these medications are not getting. There are other studies, which we’ve talked about in the past, that show that there’s a strong link between nutrition and behavioral health. That shouldn’t be a surprise to us. It’s true in adults. We all know [that] if we eat a crappy diet and aren’t getting enough nutrients, it’s going to affect our behavior and our mood. But surprisingly, that’s been a controversial concept with kids up until fairly recently. This study is great because it does provide more evidence for the benefit of these micronutrients and how necessary they are. This is not a small difference. It was a three-fold difference, 54 percent versus 18 percent.

I was really happy to see this study [since] it adds to the already significant body of research suggesting this connection between nutrition and behavior. ADHD can be a serious condition [in children]. They’re at risk for more serious problems in adolescence and adulthood, academic failure, delays, driving problems, they have higher rates of accidents in the car, they have difficulties with peers in social situations, [and] they’re more likely to engage in risky sexual behavior and substance abuse. So anything that we can do to help these kids, especially helping them with natural interventions that don’t have side effects and aren’t going to do things like stunt growth, is really, really important. I don’t say that to imply that medication isn’t helpful and even necessary in some cases with kids. Especially for kids who don’t have success with these other methods. I think ultimately, treating ADHD is [the] most important [thing], however you do it because the statistics show that untreated ADHD becomes such a risk factor for so many other problems later in life. But this is a great option for parents. There are a bunch of different formulas out there that are specifically formulated for ADHD and [contain the] nutrients that are particularly important.

If you haven’t heard my podcast with Dr. James Greenblatt on a functional approach to ADHD, definitely listen to that. He was the pioneer of Functional Medicine treatment for ADHD, and he’s a wealth of knowledge. I had him on my show recently. Just search for Chris Kresser, ADHD, and Greenblatt, and you should be able to find that pretty easily.

Improvements in Mental Health during COVID-19 among Those Who Had Exposure to the Outdoors

Okay, just a couple [of] short ones to wrap things up here. The next [study] was [on] exposure to the outdoors and mental health during the [COVID-19] pandemic. The study was called “Perceptions of green space usage, abundance, and quality of green space were associated with better mental health during the COVID-19 pandemic among residents of Denver.” The study title says it all. The researchers found that people in the Denver area who had more access to green space had much better mental health during the pandemic. And really, that shouldn’t surprise us, right? We know from so much research, from our evolutionary history, and just from our own personal experience that we do better as human beings when we have some connection to nature.

The good news is that even if you live in a city, spending time in parks can have the same effect. You don’t necessarily need to be 50 miles out in the backcountry, in the middle of nowhere, in nature. Although if you’re lucky enough to have access to that, that’s my preferred method. But just taking a walk in a neighborhood park or a regional park or something like that can have the same effect. Even just having houseplants or having a little window planter with some green plants [has] also been shown to make a difference. Sometimes these small changes can really add up to make a big impact.

Health Effects of Plastic Nanoparticles from Food and Beverage Containers

[The] last [topic] is the health effects of nanoparticles from plastic food and beverage containers. This is one of the realities of our modern life. We have this huge proliferation of toxins in our environment, and we don’t really know what the impact is because it hasn’t adequately been studied. This is a big concern. It’s definitely something that I think we need more research on, and I’m glad to see these papers for [that] reason. It’s a reason why we, in my family, tend to follow what we call the precautionary principle, where we reduce our exposure as much as we can to things like this because we don’t yet know what the health effects are. The first study was looking at the health risks due to micro- and nanoplastics in food. This is one of the biggest concerns with plastic in the food supply is that these little nanoparticles are teeny, teeny, teeny, [they] get into our system, and because they’re so small, they can cross membranes and get pretty much everywhere in the body. This study found that five grams of these teeny plastic particles on average enter the human gastrointestinal tract per person per week. This is roughly the equivalent of eating a credit card-[sized] amount of plastic each week.

There are various agencies that have set thresholds on how much plastic is okay for us to be ingesting in that way. Depending on the agency, some might say that that’s an acceptable amount. But the point of this study was [that] we don’t really know what’s acceptable because there hasn’t been enough research to guide us on what the impacts [are] of ingesting that amount of plastic. Particularly in the form of nanoparticles, which, as I said, could potentially be more dangerous than eating an actual credit card, for example, which the gut would probably just excrete, recognized as a foreign presence. You’re not going to absorb any of that in the bloodstream. It’s going to stay in the gut, and you’re just going to excrete it out. But with nanoparticles, it’s a different story. These are in plastic cups, they’re in plastic-lined Styrofoam cups, they’re in plastic bags, [and] they’re in the nylon cooking bags that some people use for sous vide cooking.

That’s the second study I want to tell you about. It looked directly at nylon cooking bags and plastic-lined cups. What they found was that heat in particular is bad mixed with plastic. Usually, with colder temperature liquids or foods, the plastics are not going to leach as much. But in this study, they found that [with] nylon cooking bags in the slow cooker, 35 trillion plastic nanoparticles leached into the liter of water in each bag. And when the team put hot liquid in 12-ounce plastic-lined Styrofoam cups, the kind[s] that are used to keep beverages warm for 20 minutes, 5.1 trillion plastic nanoparticles per liter leached out. They do point out that both materials released considerably fewer nano-sized particles into room temperature water. So, again, heated water makes a bigger difference.

The researchers noted that, even with these trillions of particles getting into the water, it still didn’t exceed the levels that have been indicated for safe human consumption according to the U.S. Food and Drug Administration. I’ve got to tell you, I don’t really trust those thresholds. Like I said, I think we’re still early in understanding the impacts of these compounds, and we know from research on other compounds like bisphenol A that even low levels of exposure can be harmful, and they can produce different types of harm than high levels of exposure. So I think it’s best to employ that precautionary principle and be careful with plastics. Use stainless steel water bottles or use glass mason jars to store your food, or glass Tupperware dishes. Don’t put nylon plastic bags in hot water and then put food in those plastic bags and consume that food or beverage. A lot of this [seems like] common sense, but maybe not, because plastics can be really convenient. You have to put food in a bag in sous vide or else it just turns into watery mush. But I stopped using sous vide as a cooking technique for this reason, once I started to read the research on this, which is a shame because it’s really convenient. And also, food cooked in sous vide is delicious. But I think there’s just too much that’s not known about the impact of these plastics at the nanoparticle size, and ingesting tens or hundreds of trillions of them on a regular basis may not be a great idea.

So that’s the research review and solocast for this week. [I] hope you enjoyed it. Like I said, stay tuned for further announcements about ADAPT Naturals, the Core Plus supplement bundle that’s going to be launching in July. I can’t wait to tell you more about it. Please keep sending your questions in. We’re not doing a lot of Q&A episodes these days, but I do use your questions to inform topics that I choose for these research reviews and also for the interviews that I do. So that’s ChrisKresser.com/podcastquestion, and I’ll see you next time.