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RHR Research Review: MS, Teen Prediabetes, Sleep Deprivation & Fat, Cognitive Decline, Leisure & Loneliness, and Sunscreens


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In this episode of Revolution Health Radio, Chris Kresser reviews some of the most interesting recently published studies and shares his thoughts and insights on them. Chris examines studies related to dairy and multiple sclerosis, alarming rates of prediabetes in teens, the relationship between sleep deprivation and abdominal fat, rates of cognitive decline in older populations, using leisure time to reduce loneliness, and carcinogens in sunscreen.

In this episode, we discuss:

  • Antibody reactivity to dairy proteins in people with multiple sclerosis
  • Alarming rates and potential causes of prediabetes in teens
  • Statistics showing that insufficient sleep contributes to abdominal fat accumulation
  • The increase in cases of cognitive decline in older people
  • How leisure time can reduce the loneliness that negatively influences well-being, particularly during the COVID-19 pandemic
  • Carcinogens in sunscreen and the safest sunscreen options

Show notes:

Hey, everybody, Chris Kresser here. Welcome to another episode of Revolution Health Radio. This week, we’re going to do another research review episode. I recorded the first one of these a few weeks ago, and we got a lot of great feedback about it, so I am considering making it a regular feature.

Antibody Reactivity to Casein Protein in People with Multiple Sclerosis

The first study is about milk and [multiple sclerosis]. The study was called Antibody Cross-Reactivity Between Casein and Myelin-Associated Glycoprotein Results in Central Nervous System Demyelination. That’s a mouthful. And it was published in PNAS. I think this is a really important study because the researchers found that casein, which is a protein in cow’s milk, can trigger inflammation in the myelin sheath around the nerves in the brain. If you think about our nervous system [as] a bundle of wires, which it kind of is, the myelin sheath is like the insulation around those wires. It helps prevent short circuits, so to speak, and also helps with [the] conduction of nerve impulses. The researchers suspected that the reason this happened was molecular mimicry. What this means is that the body produces antibodies to casein, which is the protein in milk, [and], for whatever reason, in people with [multiple sclerosis], and I would argue other autoimmune diseases at times, I’ll come back to that, see this casein protein as a foreign invader, as something that should not be present. It produces antibodies against that protein in a similar way [to how] our body would produce antibodies against a virus or bacteria or something else that is pathogenic and doesn’t belong.

But the antibodies that are produced against this casein protein also end up attacking proteins in the myelin sheath around the nerves. That’s this phenomenon of molecular mimicry, where antibodies that are produced originally against one compound or antigen end up cross-reacting and attacking our own self-tissue. This can happen with gluten. That’s probably where molecular mimicry is best known, in cases of celiac disease or non-celiac wheat or gluten intolerance. But this study shows that it’s also happening with milk proteins in people with multiple sclerosis. So this is, I think, really interesting in light of Terry Wahls’ work and also the Autoimmune Protocol. Those of you [who] are familiar with this know that, in the autoimmune disease community, [and] particularly in the Functional Medicine, Functional Health, and ancestral health spaces, there’s been a dietary protocol for addressing these conditions. It’s been around for many years. Sometimes it’s referred to as AIP. That’s one protocol, [the] Autoimmune Protocol.

Dr. Terry Wahls, who suffered from [multiple sclerosis] herself and made a remarkable recovery, also has her own version of this diet. It involves removing all dairy products from the diet as well as other foods like peppers, nightshades, nuts and seeds, grains, legumes, etc. Because all these foods either can trigger gut issues that disrupt the immune system, or they can cause antibody production, which then triggers this molecular mimicry phenomenon that we’re talking about right now. There has been some published peer-reviewed research supporting AIP. In fact, I’ve had Dr. Wahls on the podcast a few times to talk about her groundbreaking research in this area. But beyond Dr. Wahls’ work and a few other papers, there hasn’t been a lot of formal research supporting AIP and [the] removal of dairy products for people with autoimmune disease. So this study adds to that, and in particular, for patients with multiple sclerosis, suggests that consuming dairy proteins may actually exacerbate the condition or even contribute to it developing in the first place. [However,] that was not studied in this study, and I have some questions about that.

I just want to mention a couple of things here. The first is that, while this study does show that dairy proteins can contribute to or exacerbate [multiple sclerosis], it does not suggest that dairy proteins are harmful [to] everybody. That’s an important distinction. It’s tempting to come to that conclusion. But that is not at all what this study suggests. There may be features [in] people with autoimmune disease that make them susceptible to this kind of molecular mimicry from dairy proteins that people who do not have autoimmune disease don’t have, and it may even be particularly specific to people with [multiple sclerosis]. So remember, with diet, there’s no “one-size-fits-all” approach. There are always people who say, “This food is bad for everybody; that food is good for everybody.” And certainly, we can say that sugar, refined sugar and flour, industrial seed oils, and foods like that are bad for everybody and certain foods are good for everybody. But there’s a limited number of those. When it comes to choosing the best diet for ourselves as individuals, there really is no “one-size-fits-all” approach. It’s important to consider a whole bunch of different variables, and also do a lot of experimentation to find [the] best diet for you. Nevertheless, I think this is a very interesting study, and it contributes to a lot of anecdotal evidence and some published, peer-reviewed evidence suggesting that dairy proteins and dairy products, in general, may not be a good idea for people with autoimmune disease.

Alarming Rates of Prediabetes in Teens and Potential Causes

The next study looked at rates of prediabetes in teens over the last two decades. It’s called Trends in Prediabetes Among Youths in the US From 1999 Through 2018, and it was published in JAMA Pediatrics. The statistics in this study are, frankly, quite alarming. They suggest that one in five teens now have prediabetes. Let that sink in for a moment. One in five teens now has prediabetes. This is a horrific failure of public health. We know from a huge body of evidence that people with prediabetes progress to full-fledged type 2 diabetes [at] an annualized rate of 5 to 10 percent. And 70 percent of individuals that are diagnosed with prediabetes will eventually develop diabetes. So this makes it extremely likely that without intervention, if someone is diagnosed with diabetes as a teenager, they will almost certainly go on to develop full-fledged type 2 diabetes. And probably quite early in their life, given the statistics that I just mentioned. This is a huge problem because we know that people with type 2 diabetes have a higher risk of heart and blood vessel damage and heart attacks, nerve damage, kidney damage, eye damage, [and] foot damage. They develop osteoporosis at a higher rate, they have a decreased quality of life, and they have a much higher risk of Alzheimer’s [disease] and dementia later in life.

If you recall from the first research review [that I did], I shared a study that suggested that our blood glucose levels as early as age 35 will predict our Alzheimer’s disease risk later in life. If a growing number of teens are being diagnosed with type 2 diabetes at that age, then imagine what that’s going to do to the risk of Alzheimer’s [disease] and dementia 30, 40, [or] 50 years later in their life. The researchers in this paper did not speculate on the cause of these increased rates of prediabetes in teens, but I will speculate on it. If you look at other studies, you see that the average American, and I would extend this to other industrialized countries (it’s not quite as bad, but they’re catching up), the average American gets 60 percent of their calories from ultra-processed foods. Not just processed foods, [but] ultra-processed foods. These are highly refined foods like pizza, cookies, crackers, cakes, sugar-sweetened beverages, all the processed and refined junk that you see at fast-food restaurants and convenience stores, and things like this. These sources now comprise more than half of the calories that people eat. And this is true for teenagers, as well. It may be even more true for teenagers. I haven’t seen specific studies on the percentage of calories from ultra-processed foods in this age group, but there are definitely trends in food consumption in teens that match or exceed what we see in adults. So one problem is diet. A huge problem.

Number two is lack of physical activity. Studies have shown that school-aged children, including teens, are sedentary for eight or more of their daily waking hours on average, and most are engaging in excessive screen time. So sedentary time is a unique problem. It’s not just [a] lack of exercise or physical activity. Someone could exercise for a half-hour a day, but if they’re sedentary for the rest of that day, then there’s still going to be an increased risk of diseases like type 2 diabetes. It’s not enough just to get a short period of exercise each day. If you’re sitting for an extremely long period of the day, then that confers its own unique risk. I’ve written and talked a lot about this over the years, and I’m sure this isn’t the first time you’re hearing about it. But it’s definitely, in my mind, a contributor to this increase in prediabetes risk in teens.

The third cause of this, in my estimation, is lack of sleep. We know that there’s now an epidemic of sleep deprivation in teenagers, which is, in part, caused by excessive screen use. Bringing phones into the bedroom [and] texting during the night, but also just busier schedules, more activities, more homework, and just general trends. If a teen is not getting enough sleep, we know that even a single night of sleep deprivation can cause insulin resistance the next day. It can cause an increase in food intake, [and] it can cause a decrease in judgment around food choices. And that’s just from one night. So imagine what happens over an extended period of not getting enough sleep. You put all those three factors together—extremely poor nutrition, high rates of sedentary time, and an epidemic of sleep deprivation—then that can certainly explain this alarming increase in prediabetes in kids and teens, and this is something that I’m really passionate about. We need to get our act together here. It’s one thing with adults; it’s obviously a very bad pattern with adults. But with kids, we’re setting them up for a lifetime of suffering and chronic disease, and that’s just not okay. Hopefully, this can be a wake-up call, and we can really make some progress toward supporting teens in making better choices.

Insufficient Sleep as a Contributor to Abdominal Fat Accumulation

Along similar lines, the next study looked at how sleep deprivation increases abdominal fat. It’s called Effects of Experimental Sleep Restriction on Energy Intake, Energy Expenditure, and Visceral Obesity, and it was published in the Journal of the American College of Cardiology. This was a randomized, controlled crossover study, which is a really great study design. Kind of [a] gold standard. They found that lack of sufficient sleep led to a 9 percent increase in total abdominal fat area and [an] 11 percent increase in abdominal visceral fat compared to getting enough sleep. As I just mentioned, this is a huge issue because such a large percentage of people now don’t get enough sleep. The most recent statistics suggest that a third of Americans get fewer than six hours of sleep. That’s up from just a few percent back in the 1960s. This has been a trend over the past 50 years, [and] it’s getting worse and worse. I want to read you a quote from Dr. Verand Summers, who was the lead author of the study. “Our findings show that shortened sleep, even in young, healthy and relatively lean subjects, is associated with an increase in calorie intake, a very small increase in weight, and a significant increase in fat accumulation inside the belly. This suggests that inadequate sleep is a previously unrecognized trigger for visceral fat deposition and that catch-up sleep, at least in the short-term, does not reverse the visceral fat accumulation. In the long-term, these findings implicate inadequate sleep as a contributor to the epidemics of obesity, cardiovascular and metabolic diseases.”

I want to highlight one part of that quote that I think is especially important, which is that catch-up sleep does not reverse the visceral fat accumulation. What he means by that is, let’s say you go three, four weeks without getting enough sleep, [and] you’re particularly sleep-deprived. And you accumulate some visceral or abdominal fat during that period. Then for the next three or four weeks, you try to make up for that sleep deprivation by sleeping a little bit extra. What this study suggests is that extra catch-up sleep does not actually reverse the abdominal fat accumulation. I’m not saying this to scare you because look, there are situations in life where it might not always be possible to get as much sleep as we want. [There could be] some traumatic event, car accident, illness, or just a particularly difficult time at work, or if you’re an entrepreneur, something related to your own business. There are many different reasons that people may go a period of time without getting enough sleep. The idea here is not to make us feel guilty about [the] things we can’t control. I mention this because, in many cases, the amount of sleep we get comes down to choices that we do make and that we do have control over. Staying up late browsing the internet, watching TV, not making it a priority to get into bed early and get seven or eight hours of sleep. That’s a far more common cause of not getting enough sleep, at least in the [United States] and other developed countries. I hope that this study shows how important it is to get that sleep because, if we don’t, that visceral abdominal fat accumulation can start and may not be easily reversible. That’s one of the key findings of this study.

It’s really important to continue to make sleep a very high priority in our life and to protect that [priority] against a lot of the encroaching threats to sleep, particularly screen time, as I’ve discussed a lot before. Using screens really close to bed[time] can suppress melatonin production and give us [the] nighttime second wind that a lot of people experience [that] then make[s] it less likely that we’ll go to bed in the first place. It’s really important as a starting place to prioritize sleep and make enough time for sleep, and make it a huge priority in your life. Then, second, to follow good sleep hygiene practices. In the last research review, we talked about a study showing that even moderate light exposure during nighttime sleep can increase insulin resistance the next day. That’s a good example [of why] we want to sleep in a cool, dark room [and] we want to get rid of anything that emits light, like a digital alarm clock or a phone. You can have a nightlight with [an] amber or red tint if you need to be able to see to get up and go to the bathroom or something like that. We want to not use screens within an hour of bed[time], [and] we want to make sure that our sleep environment is quiet. All the things that we’ve talked about in the past, that’s the best way to do it and make sure that we get enough sleep.

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

The Increase in Occurrence of Cognitive Decline in Older Populations

The next study looked at cases of cognitive decline in older people and found that they’ve doubled in the last 10 years. This study was called Time Trends and Incidence of Reported Memory Concerns and Cognitive Decline: a Cohort Study in UK Primary Care, and it was published in the Journal of Clinical Epidemiology. The researchers looked at 1.3 million adults between 65 and 99 years old, and this was between 2009 and the end of 2018, so roughly a 10-year period. They found that for every 1,000 people that were observed for a year in 2009, there was one new case of cognitive decline being recorded. By 2018, for every 1,000 people that were observed for a year, there were three new cases of cognitive decline being recorded. So this is a tripling in risk from 0.1 percent to 0.3 percent. As you’ll note, absolute risk is still relatively low. We talked about the difference between absolute and relative risk [in] the last Research Review [episode of the podcast] and we’ve talked about [it] before. But in this case, I would argue that the implications are still significant. Although the absolute risk is relatively low, we saw a tripling in that risk. This study also showed that 46 percent of people reporting a memory concern and 52 percent of people reporting cognitive decline would go on to develop dementia within three years.

We also know that cases of Alzheimer’s disease are rising rapidly, and memory issues and cognitive decline can be early signs of Alzheimer’s [disease]. So this study and [also] the earlier one about higher rates of prediabetes and teens are certainly disturbing. But they can also be viewed as opportunities or wake-up calls. The reality is we know how to address this stuff. We know what to do; we just need to make it a priority and take action. I was hoping [that] the COVID-19 pandemic would spur us forward in this regard because we saw during the pandemic that people with diabetes, obesity, and other chronic conditions were at higher risk of a severe outcome. I had hoped that would lead to more public health focus and attention on these chronic lifestyle diseases and we’d see a greater effort within the public health infrastructure to address them. Unfortunately, that did not happen. There was just a lot more focus on the short-term steps that we could take to address the pandemic and not really much focus on the underlying health issues that dramatically increase the risk of severe outcomes with COVID-19. It’s up to us now to take those steps forward, and studies like the one before about the increase in rates of prediabetes in teens and then this one about [the] increase in cognitive decline in elderly people should be that wake-up call. [They] should be that motivation to help us move forward here.

How Leisure Time and the Flow State Can Reduce Loneliness

The next study was a really interesting one and it looked at this question [of], “Is free time overrated?” It’s called Relationships of Leisure Social Support and Flow With Loneliness in International Students in Taiwan: Implications During the COVID 19 Pandemic, and was published in Leisure Sciences. What the researchers set out to look at in this study is how to mitigate the negative impacts of loneliness. I’ve talked about the effects of social isolation and loneliness before. In fact, I mentioned it in my first book, The Paleo Cure. Loneliness and social isolation are greater predictor[s] of early death than body mass index, alcohol consumption, and even smoking 15 cigarettes a day, which is just remarkable. I don’t think most people are aware of that. It’s certainly not something that tends to come up in the discussion of the most important factors that determine our health span. But it definitely is, and a lot of researchers in this space are aware of this. The study authors found that engaging in meaningful, challenging activities during free time can reduce people’s loneliness and increase their positive feelings, even if they don’t have more social connection during that period. This is an attempt to answer the question, “How can we mitigate the impacts of loneliness when social connection isn’t available?” This, of course, was an issue during [the] COVID-19 pandemic when a lot of people were locked down and stuck on their own. COVID[-19] certainly worsened loneliness and social isolation for a lot of people, and we’re now seeing a lot more research in this area.

This study challenged the notion that free time is always desirable or optimal. The researchers found that people who had meaningful and challenging experiences, even on their own, were less lonely. This doesn’t surprise me at all. It definitely fits with my personal experience. I always have something that I’m engaged in and trying to learn and master. Lately, during the winter, that [thing has] been skiing. I love skiing, but I’m not a ski racer or anything. But I take it pretty seriously and I work with a coach, and I ski with a friend who takes video of me and I take video of him and we send it to our coach and the coach makes a lot of suggestions. I’m always trying to improve my skiing, and that keeps me really engaged and makes it more meaningful and fun. I’m often working on some kind of art-related project [like] photography [or] creating art for my home, [or] maybe I’m learning a new musical instrument. Last year, my goal was to get back to being fluent in Spanish, which I used to be, but I’ve fallen out of practice [with]. I’m always trying to engage in these kinds of experiences that will help me grow. I’ve found [that] in my own life, these [experiences] just make my life so much better. So I was really interested to see this study because that’s exactly what the study results found, as well.

When we’re engaged in what we’re doing, we enter what psychologists call the flow state. To achieve a flow state, an activity has to require a pretty good amount of skill. Not so difficult that it’s impossible, but it has to really demand our attention and require a fairly high level of skill. We have to be focused on it and not distracted. The activity needs to be meaningful in some way and will often involve or provoke a sense of timelessness. We’ve all experienced this before. If you like rock climbing or you’re engaged in playing music, or making a painting or something like that, and [then you’re] surprised or shocked by how much time has passed while [you’re] doing that. That’s [the] flow state. Of course, the activities that induce flow differ from person to person, but the most common ones are sports or outdoor activities, making art, playing music, or writing. Or routine repetitive activities like chopping wood or washing the dishes can also induce a flow state.

I think the message from this study, regardless of whether [or not] you’ve been suffering from loneliness, but especially if you are, is to regularly do activities that put you in a flow state. I think this leads to a life well-lived and a more enjoyable and satisfying life, regardless of your social connections. But I think the contribution of this study that’s interesting is that, even when you’re feeling a sense of social isolation, whether it’s related to the pandemic or something else, these kinds of activities can help increase your life satisfaction, even when you’re not able to immediately increase those social connections. [It’s a] really fascinating study, and [I’m] looking forward to seeing more research along these lines.

Carcinogens in Sunscreen and the Safest Sunscreen Options

The last study for today looked at carcinogens in sunscreen. Summer is coming, which means warmer [temperatures] and, for a lot of us, more time outdoors and more sun exposure. So I want to be sure you’re choosing the best and safest sunscreen if you’re going to be outside in the sun and using sunscreen. Scientists have discovered at least two different compounds in sunscreens that are carcinogens, benzene and benzophenone. The problem is that neither of these compounds appear[s] on product labels, but [it] can be introduced during the manufacturing process or by chemical reactions within the sunscreen. In one study, for example, benzene was found in 43 out of 224 sunscreens and in 8 of 48 after-sun products. The [U.S. Food and Drug Administration] itself suggests that no level of benzene is safe, and it’s not permitted in these or any other products. So when products are discovered that contain benzene, they need to be removed from the market because it’s such a potent carcinogen.

In fact, I just saw a headline the other day that two popular antiperspirants were recalled off of the market due to [discovering] that they contained benzene. Benzene is a known carcinogen in humans according to the [Centers for Disease Control and Prevention], the Department of Health and Human Services, the World Health Organization, and other regulatory agencies around the world. So this is definitely a concern when we see these in sunscreens. But benzene and benzophenone are not the only chemicals of concern in conventional sunscreens, as I’ve discussed before. [Ultraviolet] (UV) filters like oxybenzone are also problematic. Oxybenzone is a compound that is not stable when it’s exposed to UV radiation, which is bizarre that [it] would be put in sunscreen because, of course, people are using sunscreen when they’re exposed to UV radiation. Oxybenzone forms reactive oxygen species. These are popularly referred to as free radicals and can cause oxidative damage, which is definitely a precursor to cancer. One UV filter, [phenylbenzimidazole sulfonic acid] (PBSA), has been shown to induce DNA damage in human skin cells after exposure to [UV] rays.

And beyond the local effects from [the] formation of these free radicals or reactive oxygen species, systemic toxicity is a concern because these UV filters get absorbed into the bloodstream. Our skin is a very porous barrier, which means that whatever we put on our skin, we should assume [is] going to get absorbed into our blood. From an evolutionary perspective, we didn’t have a reason to evolve a very tight, effective skin barrier because we weren’t putting stuff on our skin for the vast majority of our evolutionary history. Our gut barrier, when it’s intact, actually works pretty well in that regard, but our skin does not. So whatever we put on our skin can end up in our bloodstream. That’s one of the reasons [why] it’s so important to use healthy personal care products. Systemically, with these UV filters, one of the primary concerns is their potential for endocrine disruption. Hormone imbalances. There are several animal and in vitro studies that have found adverse developmental and reproductive effects of these UV filters. That’s important for all of us, but even more important for kids and young people. Putting these sunscreens on our kids as they’re still developing their endocrine systems might be especially harmful.

The safest option for sunscreen is one that is a non-nanoparticle zinc oxide product. If that doesn’t make any sense to you, I’m going to direct you to the Environmental Working Group website. They have a guide to sunscreens [that lists] the best sunscreens that don’t contain these UV filters and benzene and benzophenone, and that are zinc oxide-based and don’t have nanoparticles. They’re just the cleanest, safest products. Environmental Working Group, we’ll put a link to it in the show notes. You can also Google “Environmental Working Group guide to sunscreens” and you should be able to find it. They’ve also got good tips in general on how and when to use sunscreen and how to make good choices when shopping for sunscreen.

Okay, everybody. That’s it for now. Keep sending your questions in to ChrisKresser.com/podcastquestion, and we’ll see you next time.

This episode of Revolution Health Radio is sponsored by Thrive Market.

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