A streamlined stack of supplements designed to meet your most critical needs - Adapt Naturals is now live. Learn more

RHR Research Review: Cancer, Alzheimer’s, Statins, Light & Sleep, Candida, and Screens & Kids


Last updated on

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 cancer and artificial sweeteners, metabolic indicators of Alzheimer’s risk, statins and heart disease, light exposure during sleep, Candida, and screen time in kids.


In this episode, we discuss:

  • Artificial sweeteners and cancer risk
  • Early-life metabolic markers and how they might indicate later in life Alzheimer’s disease risk
  • Effectiveness of statin drugs in reducing heart disease
  • Impact on metabolic and cardiovascular function by light exposure during sleep
  • Candida and other high-damaging yeast strains’ correlation with inflammatory gut issues
  • Social media impact on kids and teens

Show notes:

Chris Kresser:  Hey, everyone, Chris Kresser here. Welcome to another episode of Revolution Health Radio. This week, we’re going to do something different that I don’t know if I’ve ever done [before]. I certainly [at least] haven’t done it in a long time. It’s going to be a news and research review episode where I go over some of the most interesting studies that I’ve come across in the past couple of weeks that have been recently published and tell you my thoughts on them. So let’s dive in.

Artificial Sweeteners and Cancer Risk

The first is a study suggesting an association between consuming artificial sweeteners like aspartame and increased cancer risk. This was published in PLOS Medicine on March 24. The title was “Artificial Sweeteners and Cancer Risk: Results From the NutriNet-Santé Population-based Cohort Study.” We’ll put a link to all these studies in the show notes on the website. The researchers found a higher risk of cancer in people consuming artificial sweeteners, especially aspartame and acesulfame-K. The increase was statistically significant but on the smaller end of the scale. It was about a 13 percent higher risk of cancer. As you recall from some of my previous shows looking at research methodology, we need to be careful with epidemiological studies like this [one], especially when the effect sizes are small. We’ve talked about this in the context of studies suggesting a link between, let’s say, red meat and cancer. We have to apply that same skepticism to studies like this [one] suggesting a link between artificial sweeteners and cancer.

Having said that, this research is in line with previous studies suggesting a link between artificial sweeteners and cancer, and there are some mechanisms that have been established, like the effect of artificial sweeteners on the gut microbiota and how that could affect our immune system since the gut plays such an important role in the immune system. So I think with artificial sweeteners, given what we know, the precautionary principle applies. There are many other ways for people who are trying to avoid sugar to get a little bit of sweet taste. There are sweeteners like stevia, allulose, monk fruit, and many more that can provide a little bit of a sweet taste but seem to do that in a safer way. They’re natural. Not that natural is always better, but when you have these artificial sweeteners, you have to ask, “What is the effect?” Because these have not been found in nature. They have never been consumed before, and we really don’t know enough yet about what their impact is. [However], some of the studies that we’re seeing like this suggest that they may be problematic, and not just for this reason. There are also studies that show that artificial sweeteners mess with our brain circuitry that affects our regulation of food intake and perception of sweet tastes, and can actually lead to increased calorie consumption, although I don’t think that link is entirely clear yet.

So that was an interesting study. And if you’re trying to limit sugar, I think you should go for those other sweeteners rather than these artificial ones.

Metabolic Markers Earlier in Life and Alzheimer’s Disease Risk

The next study looked at lipid and blood sugar levels at age 35 and then looked forward in time to see how those correlated with Alzheimer’s disease risk later in life. [It’s] a very interesting study. I want to give the researchers props for this because instead of just looking for drugs that people with Alzheimer’s [disease] could take, which is what a lot of the focus on Alzheimer’s research is [on], they are looking at factors [that] actually contribute to Alzheimer’s. And not only that, they’re looking well in advance. So this is really a preventive medicine study, and I was surprised and pleased to see it. It’s called “Midlife Lipid and Glucose Levels are Associated with Alzheimer’s Disease,” and it was published in the journal Alzheimer’s & Dementia. The researchers are from Boston University School of Medicine, and they found that low [high-density lipoprotein] (HDL) levels and high triglycerides as early as age 35 are associated with a higher incidence of Alzheimer’s disease later in life. They also found that high blood sugar levels, blood glucose, measured between the ages of 51 and 60, is associated with the risk of Alzheimer’s disease in the future. I think this is very significant. Alzheimer’s disease is the fifth leading cause of death in Americans aged 65 years or older, and there are now almost 6 million cases of Alzheimer’s disease. This is projected to triple to 14 million cases by 2060.

When I speak to patients and talk to people, we all know that our lives are going to end at some point. At least we know that now; who knows what the future holds. But that’s what we understand at this point. But when it comes to how our life ends, I think Alzheimer’s [disease] and dementia are rightfully feared, almost more than any other cause of death, and that’s because of the devastating impact that Alzheimer’s disease can have not only on the person who’s suffering from it but perhaps even more so on their family and friends. So anything that we can do to protect ourselves from Alzheimer’s [disease] and dementia is really critical to understand. And what this study is telling us is that our metabolic health, our lipid numbers, like HDL cholesterol and triglycerides, and our blood sugar, which are, even though HDL cholesterol and triglycerides are lipids, they are more metabolic markers than cardiovascular markers, because it’s really our metabolic health that drives them. So our blood sugar, HDL and triglycerides, earlier in life, as early as 35 years old, actually predict our risk of Alzheimer’s [disease] later in life.

So this means that everything we’ve been talking about [like] the importance of eating a nutrient-dense whole-foods diet, of moving enough, getting enough sleep, [and] managing stress, is absolutely critical, and it’s too late to start thinking about this when you’re in your 60s, or certainly in your 70s. Taking early steps to stay healthy and manage all these risk factors is critical to reducing the risk of these conditions later in life. Ben Franklin once said, “An ounce of prevention is worth a pound of cure,” and that definitely seems to be the case here with Alzheimer’s disease, which is not really the dominant paradigm way of understanding the condition. Mostly, you’ll hear a lot of discussion about genetics and APOE4 and things like that. The implication is that if you get Alzheimer’s [disease] and dementia, it’s just bad luck and genetic risk. We know now from pioneering work [by] people like Dale Bredesen, who I’ve had on the show a few times, you can search for his name in Revolution Health Radio and my name, and those shows will come up. He and others, [like] Dr. David Perlmutter, have been instrumental in helping us to understand that these are not conditions that are driven primarily by genetics. They are driven by environmental factors, and those environmental factors are within our control. So if you’re interested in this topic, I’d encourage you to go listen to those podcasts that I did with Dr. Dale Bredesen as a starting point, and there’s so much to learn there that, unfortunately, you probably aren’t going to hear about from conventional medical sources.

Effectiveness of Statin Drugs in Reducing Heart Disease

The next study found that reducing cholesterol with statin drugs may not be as effective for lowering heart disease as previously thought. This study was called “Evaluating the Association Between Low-Density Lipoprotein Cholesterol Reduction and Relative and Absolute Effects of Statin Treatment: A Systematic Review and Meta-Analysis.” This was published in JAMA Internal Medicine. Researchers from RCSI University of Medicine [and] Health Sciences found that the link between [low-density lipoprotein] (LDL) (so-called bad cholesterol), heart attack, and stroke was not as strong as previously thought. I guess that depends on who you ask because, as you know, I’ve been sharing research that disputes this link for more than 10 years. This study suggests that lowering LDL cholesterol using statins had an inconsistent and inconclusive impact on cardiovascular disease outcomes like heart attack, stroke, and all-cause mortality. It also suggested that the overall benefit of taking statins may be small and will vary depending on an individual’s personal risk factors.

This was a meta-analysis of 21 trials, and the researchers found that the absolute risk reduction from taking statins was 0.8 percent, less than 1 percent, for all-cause mortality. That’s the risk of death from any causes, which is really the most important endpoint we need to be looking at [in] these kinds of studies. It was [a] 1.3 percent reduction for heart attack, and it was [a] 0.4 percent [reduction], less than one-half of a percent, for stroke. I want to take a moment here to explain the difference between absolute and relative risk reduction because it’s a critical concept to understand when you’re evaluating the efficacy of any type of intervention. A relative risk reduction looks at how much risk is reduced by an intervention relative to no intervention or a different intervention. It’s often a placebo in a randomized controlled trial. So let’s say two people out of 100 in the placebo group had a heart attack, and then one person out of 100 had a heart attack in the intervention group. That’s a pretty impressive relative risk reduction on paper, at least. It’s a 50 percent risk reduction because you went from two people experiencing the event to one person experiencing the event. But when you look at the absolute risk reduction, it went from having a 2 percent chance to having a 1 percent chance, and that is much less impressive.

Typically, when you read news stories about that study, you’ll see a headline that says, “Such and such drug reduces the risk of heart attack by 50 percent.” It sounds very impressive, but when you look at the absolute risk reduction, you generally see that it’s much lower. It’s more like going from a half percent risk to a quarter percent risk. Now, you might argue, “Well, okay, but still, it’s a risk reduction. So why wouldn’t I take that treatment?” As you know, treatments are almost never completely benign. They come with side effects and risks and costs. All that has to be weighed against the risk reduction and evaluated to determine if that very small, absolute risk reduction outweighs the potential increase in side effects, adverse effects, costs, etc. That’s why it’s so important to understand the difference between absolute and relative risk reduction. I’m going to read the conclusion of the researchers from this paper: “The results of this meta-analysis suggest that the absolute risk reductions of treatment with statins in terms of all-cause mortality, myocardial infarction, and stroke are modest compared with the relative risk reductions, and the presence of significant heterogeneity reduces the certainty of the evidence. A conclusive association between absolute reductions in LDL-C levels and individual clinical outcomes was not established, and these findings underscore the importance of discussing absolute risk reductions when making informed clinical decisions with individual patients.”

I couldn’t have said it better myself. I just want to highlight again that in the 21 trials they reviewed, the results were all over the map. As they said in that conclusion, that really reduces the certainty of even the minimal findings in this study, the 0.8 percent reduction for all-cause mortality, [the] 1.3 percent [reduction] for heart attack, and [the] 0.4 percent [reduction] for stroke. Even those minimal numbers are uncertain given the variability of the results in all the different studies.

Impact on Metabolic and Cardiovascular Functions by Light Exposure During Sleep

The next paper [looked] at exposure to light during sleep and how that impacts metabolic and cardiovascular function. This [is] a fascinating paper. It’s called “Light Exposure During Sleep Impairs Cardiometabolic Function,” and it was published in the journal PNAS. They found that exposure to even moderate ambient lighting during nighttime sleep compared to sleeping in a dimly lit room harms your cardiovascular function during sleep and increases your insulin resistance the following morning. So just one night of exposure to moderate room lighting during sleep impairs the regulation of blood sugar and heart function. This is a really, really important paper. If you’ve followed my work for any length of time, going all the way back to the first book I published in 2013, you’ll know that I’ve been beating on this drum, talking about the importance of sleeping in a dark room and reducing your exposure to artificial light at night because so much research has shown that exposure to light at night disrupts our circadian rhythm, and our circadian rhythm controls so many different processes in our body, including blood sugar regulation and metabolic function, as this study has shown.

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

What’s interesting about this study is two things. Number one [is] that even moderate lighting disrupts our cardiometabolic function, and number two is that disruption will happen in just one night of being exposed to moderate room light. We’re not talking about months and months and months of that exposure impacting our cardiovascular and metabolic health; we’re talking about one single night [of exposure] impairs regulation of blood sugar and insulin and causes insulin resistance the next day. This is a really impactful finding. So I want to give you some tips for reducing your light exposure at night. One is to use blackout shades and curtains that completely block light from coming into your room. This is really important, especially if you live in an urban environment, or on a street that has street lights, or where you have any kind of light leaking into your room. If you can’t do that for any reason or that’s not effective, then get a sleep mask. This is maybe the best couple [of] bucks you can spend. I wear one, even at home, and even though I have blackout shades because it blocks out even more light. I also take one with me everywhere that I travel because I can never be sure of how much control I’m going to have over a room where I go.

Next [tip] is, if you do need to turn lights on, [then] make it a dim light close to the floor. This would be, [for instance], a nightlight that you can plug into an outlet in your room. And when you get a nightlight, the color temperature of the light is important. You can buy amber or red-orange lights now, and those are far less stimulating for the brain because of the spectrum of light. Do not use a bright white or blue-tinted light because that’s the type of light that suppresses melatonin production and stimulates cortisol production and messes with our circadian rhythms. Another tip is to use an analog alarm clock if you need an alarm clock that doesn’t emit any light, instead of a digital clock that has the glowing fluorescent green numbers on it. That’s one of the first things I do if I go to a hotel room is throw a towel or something over the alarm clock or I just unplug it because I don’t generally need them. And last but not least, don’t bring your [smart]phone into your room. And if you do, put it in sleep focus [mode] or in airplane mode so it’s not emitting any light or making any noise.

Candida and Inflammatory Bowel Diseases

[The] next study is really interesting, as well. This was a fascinating week on the research side. The researchers found that Candida in the gut is associated with inflammatory bowel diseases like Crohn’s [disease] and ulcerative colitis. The study was called “Immune Regulation by Fungal Strain Diversity in Inflammatory Bowel Disease,” and it was published in Nature, one of the most respected journals. The researchers were from Weill Cornell Medicine, which is a prestigious group. Why do I mention this? Well, just a few years ago, talking about Candida and the idea that Candidacauses problems in the gut would have been labeled as full-on quackery. It’s probably the fastest way to get yourself eye-rolled out of a conventional medical conference or something like that. But interestingly enough, in the past few years, we’ve seen many studies now confirming that fungal species like Candida can and do cause all kinds of different problems in the gut.

In this case, researchers studied people with ulcerative colitis [and] inflammatory bowel disease and found that certain strains of yeast, which they called “high-damaging strains,” produced a potent toxin called candidalysin that damages immune cells. They also found that patients with [inflammatory bowel disease] are more likely to have higher Candidalevels. Interestingly, Candida didn’t cause inflammation in people with a healthy gut. But it did in people with ulcerative colitis or existing gut inflammation. I want to highlight this because it’s an important point. It’s not true that we should have zero Candida or yeast in our gut. Yeast is a normal resident of the digestive tract, and, when you have a healthy gut with a healthy gut microbiome, that’s not a problem if the levels of the yeast are low or normal. This is similar to any other ecosystem like a garden or an ecological environment. There are always going to be pathogens in the environment. But if the health of the overall environment is strong, then those pathogens will not be able to take root and grow out of control. But if the environment is compromised in some way, then that’s when problems can ensue, and that definitely was shown to be the case in this study.

Another interesting finding here is that treating mice with steroids to suppress intestinal inflammation failed in the presence of these high-damaging Candida albicans strains. In other words, [in] patients who had these high levels of yeast, prednisone, which is one of the most common treatments for ulcerative colitis, just didn’t work. This may explain why steroids don’t work for some [patients with inflammatory bowel disease]. So, [it’s] a really important study. Unfortunately, I don’t think that most patients with ulcerative colitis or [inflammatory bowel disease] are being tested for Candida. We do that, of course. I’ve done that for years with all patients coming into the clinic, do[ne] stool testing to screen for fungal overgrowth, and I can’t tell you how many times we’ve found fungal overgrowth, including Candida but also other high-damaging species, in patients not just with [inflammatory bowel disease] but with many different gut conditions.

Social Media Impact on Kids and Teens

The last study looked at social media impacts on kids and teens and found that they differ depending on their age. This study was called Windows of Developmental Sensitivity to Social Media, published in Nature Communications. Researchers out of the University of Cambridge in the UK found that girls experienced a negative link between social media use and life satisfaction when they’re 11 to 13 years old, and boys when they’re 14 to 15 years old. They also found that higher social media use during these periods predict[ed] lower life satisfaction 12 months later, whereas, at other times during adolescence, the link was not statistically significant. These differences suggest, of course, that sensitivity to social media use might be linked to developmental changes, [and] possibly [to] changes in the structure of the brain or to puberty, which occur later in boys than they do in girls.

In an interview about the study, Professor Sarah-Jayne Blakemore, Professor of Psychology in Cognitive Neuroscience at Cambridge and the co-author of the study, said, “It’s not possible to pinpoint the precise processes that underlie this vulnerability. Adolescence is a time of cognitive, biological, and social change, all of which are intertwined, making it difficult to disentangle one factor from another. For example, it’s not yet clear what might be due to developmental changes in hormones or the brain, and what might be down to how an individual interacts with their peers.” The same week that this study was published, a survey by Common Sense Media found that daily screen time for kids and teens increased sharply during the pandemic and has reached new highs. Overall screen time for kids increased by 17 percent from 2019 to 2021, which is more than in the prior four years. The most alarming finding was the growth in Instagram, Snapchat, and Facebook use among kids 8 to 12 years old, despite laws that require users of these platforms to be at least 13 years old to prevent these companies from harvesting data from kids.

This shouldn’t be surprising. Instagram is planning to launch a new service called Instagram Kids, which directly targets children. But to me, it’s deeply disturbing. We can note that [the] increase in social media use of kids 8 to 12 years old overlaps with the vulnerable window of 11 to 13 years old for girls. So if you’re a concerned parent, check out my podcast episode “Managing Screen Time for Kids.” I’ll link to the show notes or you can Google it. Then there are also some books, The Art of Screen Time: How Your Family Can Balance Digital Media and Real Life by Anya Kamenetz, Screenwise by Devorah Heitner, and Raising Humans in a Digital World: Helping Kids Build a Healthy Relationship With Technology by Diana Graber. Those are three recommendations. You’ve probably heard me talk about this before or seen me write about it, [since] this is an issue that I’m very passionate about. I’m the father of a 10-year-old girl, and this is something I pay a lot of attention to and think about a lot. I think this new study raises a really important point, which is that there are times during our development as kids in the adolescence and teenage years that we’re particularly vulnerable to some of the downsides of social media, particularly with services like Instagram, TikTok, Snapchat, and Facebook, which are in many ways designed to exploit those vulnerabilities.

Even Facebook’s own research, now that they own Instagram, has shown that they’re very much aware of the negative impact that Instagram can have on kids. They know that the algorithms have been optimized to pull girls in at times when their self-esteem is low and that liking pictures and posts on Instagram has a toxic effect on girls’ self-esteem. Internal documents have shown that they’re very much aware of this and yet they’ve made no changes to address it. And in fact, they’re going in the other direction by launching a service called Instagram Kids that [is] directly targeting children who really shouldn’t be using these platforms at all, according to what the current research says. So, [it’s] a really important new study that I wanted to tell you about, along with the Common Sense Media survey that showed an increase in screen time use. For me as a parent, and also as a clinician and someone who works with a lot of kids, my recommendation is to delay the use of these services beyond that important developmental window. Or if your kids are already using these services, put some controls and boundaries in place to limit their usage. Because it will really support their mental and emotional health as they grow.

Okay, everybody. That’s it for now. I hope you enjoyed this episode. Let me know what you think. Send your thoughts in to ChrisKresser.com/podcastquestion. If you like this format, [then] I will probably keep doing it. It’s fun for me, and it’s a good way for me to keep you posted on all the available research. I will talk to you next time. Thanks for listening.

This episode of Revolution Health Radio is sponsored by LMNT.

As a member of our community, LMNT has a very special offer for you. Claim your free LMNT Sample Pack – you only cover the cost of shipping. Get yours at DrinkLMNT.com/Kresser