SGU Episode 540
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| SGU Episode 540 |
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| November 14th 2015 |
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| (brief caption for the episode icon) |
| Skeptical Rogues |
| S: Steven Novella |
B: Bob Novella |
C: Cara Santa Maria |
J: Jay Novella |
E: Evan Bernstein |
| Quote of the Week |
We ignore public understanding of science at our peril |
| Links |
| Download Podcast |
| Show Notes |
| Forum Discussion |
Introduction
You're listening to the Skeptics' Guide to the Universe, your escape to reality.
What's the Word ()
- Formication
News Items
Low Calorie Sweeteners ()
S: Alright, so we have some interesting news items this week. We're gonna start with one about low-calorie sweetners. You know, like, aspartame, sucralose--
E: Stevia?
S: Stevia...I hate stevia.
E: That stuff'll kill ya. (laughter)
S: So there was a recent, systematic review of pretty much all of the studies looking at any information about using so-called low-energy sweeteners, or LES, and changes in total energy intake or in weight and body mass. Very interesting because this has been controversial over many years and it's a good, sort of, review of the different kinds of scientific evidence and how we use them.
So, here's the question: if you drink diet soda sweetened with aspartame or sucralose, versus drinking sugar-sweetened drinks, versus drinking, let's say, water, what's the net effect on your calorie intake and your weight? Right, now the common-sense, sort of knee-jerk response is, "Well, if you're replacing 3- or 400 calories of sugar-sweetened drinks per day with zero-calorie drinks, you should be skipping out on 3- or 400 calories." You know, it seems pretty obvious.
But, of course, life is always more complicated than that. Because the body is complicated and there's all kinds of feedback mechanisms and unintended consequences. It turns out that the answer may be far more complicated. For example, psychologically, people may think, "Oh, I'm having a diet soda; I can afford to have that cheesecake." (laughter) You know, it's called compensation.
E: To rationalize it.
S: Yeah, you compensate by increasing your caloric intake elsewhere because you feel like you've earned it, because you're--
C: It's like how, at Starbuck's, I get non-fat milk so I can add whip! (laughter)
S: So, compensation definitely exists; the question is how much? Is it enough to offset the reduction in the sugar that you're missing out on?
There are some biological mechanisms as well. For example, the GI tract has sweet receptors. What are they doing? Does that affect your appetite?
J: Why does that have sweet receptors?
S: Well, because the GI system detects things like what you eat and affects your behavior. It send signals--hormonal signals--to your brain. It's also--there's this idea of learning: that you're tricking the brain by giving it something sweet that doesn't have calories that your brain then begins to disassociate the sensation of sweetness with caloric intake. And that can result in you craving more calories overall.
E: Right.
S: Right? Does that make sense?
E: Yeah.
S: That's the question and it may not be as obvious as it at first seems. So there have been several kinds of studies looking at this question, and you've probably seen headlines over the last 10 years: "Diet sodas make you obese," or whatever. Everytime one of these studies comes out, the press presents it as if this is the final, definitive word on whether or not low-energy sweeteners are good or bad for you.
C: And, also, sometimes they're funded by, like, "THE AMERICAN BEVERAGE ASSOCIATION." (laughter) I've seen that happen a couple times recently and you're like, "I don't know about that."
J: (affected) "Isn't it delicious?" (laughter)
S: There are animal studies. Animal studies have the advantage of we can control everything that they do and everything that they consume. These are mostly done in rats. You can either feed them--you can sweeten their water with either sugar or low-energy sweeteners, or you can force the pills down their throat, and then you give them food that is sweetened, like, it's a little bit of sweetener in it.
And what these studies generally find is that, if you force-feed rats a lot of low-energy sweeteners, they may actually over-consume lightly sweetened food. So that's--most of the headlines that you see, and it says, you know, "Low-energy sweeteners make you obese," probably most of them were rat studies.
A couple of problems with these studies: one is that, you know, rats aren't people and the laborotory situations that they're putting the rats in are very contrived. There may be lots of reasons why the rats will consume more feed that have nothing to do with human behavior. That data may be suggestive but it really isn't definitive in terms of its application to people.
The next type of study is observational. Right, so you're not randomizing people to eating low-energy sweetener or not, you're just seeing what they're doing and what their weight is. Or you might do cohort studies where you follow them going forward. And those generally show conflicting results.
C: It seems like there would be so many confabulating factors there.
S: Yeah, that's the weakness of observational studies--is that they're confabulating. And the authors of this new review argued that you can't make cause-and-effect claims because it's quite possible that people who are overweight choose to drink diet drinks because they're trying to lose weight. You know, they're not overweight because they're drinking the soda; they're drinking the soda because they're overweight. So, yeah, the confounding factors make it impossible, really, to make any kind of cause-and-effect conclusion from those studies.
So now we get to the most clinically relevant types of studies, where you do experiments on people and you randomize them, and you might even blind them to whether or not they're drinking sugar-sweetened or low-energy-sweetener-sweetened beverages, and then follow their behavior. And those studies find, in this systematic review, that drinking low-energy sweetener results in a decrease in caloric intake and weight.
C: Oh, wow!
S: So those studies are broken down into short- and long-term. Short term studies are basically one meal. Right, you give people--you pre-load them with either sugar, or water or aspartame, and then you let them eat as much of a meal as they want and you see how much they eat.
C: So that's just caloric intake. You can't look at weight after one meal, right?
S: Yeah, that's just energy intake, exactly.
C: Okay.
S: And they find that there is compensation; that people do eat more if they drank the low-energy sweetened beverage, but not enough to make up for the decrease in the sugar calories. And so there still is a net decrease in caloric intake. And they said any effects of having had the low-energy sweetener probably wouldn't last much beyond that next meal, anyway, so this data is helpful.
But there are also long-term studies. Long-term studies last anywhere from days to three years. The longest studies last up to three years. Looking at people, again randomized, and perhaps even blinded to whether or not they were drinking sugar-sweetened, low-energy-sweetener sweetened, and then also compared to just drinking water. And they found, long-term, again, there was an overall decrease in energy intake and an overall decrease in weight with the low-energy sweetener--even when compared to water, which is what I found most surprising in this data.
C: Oh, wow!
S: Because there's no calorie difference between the two; between water--zero-calorie water and zero-calorie diet soda. But still there was a little bit of an advantage to the sweetened zero-calorie beverage. But there was a clear advantage over drinking sugar. Which, again, one of those situations where the science confirms your initial assessment, the sort of common-sense assessment that says, "Yeah, not drinking 500 calories of sugar a day is a good thing for your energy intake and your overall weight.
So, whatever compensatory mechanisms are in there, whether they're psychological or biological, they're not offsetting the reduction in calories by avoiding the sugar. It's still a good idea, you know, to not drink sugary drinks if you're trying to manage your weight.
B: Of course.
C: But what if when you get--when you're accidentally served a Diet coke, as opposed to a regular Coke at a restaurant, it tastes like you've been poisoned!
S: So you just don't like the flavor of it.
E: ...or the surprise.
C: I cannot handle it. It's disgusting. It's so gross. I don't know, I think it's one of those things where it's like an acquired taste, and I've not--
S: It is, it's an acquired taste, in my experience, and I've had many other people make this observation to me. I think there are just differences in people's tastes, so that could be just genetic for you. But many people have the experience that, at first, they don't like it, it doesn't taste sweet enough, or something, there's just something not right about it. And then, after a while, they can't stand going back to sugar-sweetened drinks because they taste so syrupy and heavy and thick, and they prefer the diet drinks.
C: Yeah.
S: That was my personal experience. I can't stand sugar-sweetened drinks now. I only drink the calorie-free ones. And other people have made the same observation to me. So I think, yeah, the taste thing is personal and also acquired. And also, before we begin getting emails about this, the evidence does not support that there's any cancer risk, or any other health risk from aspartame or sucralose; they're totally fine. We are not gonna do a deep dive on that--
E: (laughing) Oh, gosh.
S: --just to say, "Don't believe the Internet." There's just a lot of misinformation about them on the Internet. The data actually doesn't support any health risk--
E: Dosage matters!
S: Yeah.
C: (chuckles)
S: Like, in the studies, even like with saccharine--saccharine got a bad rap as causing cancer, but the amount they were giving the rats in those studies was orders of magnitude more than you would ever consume. And the FDA, and also the European Union and other regulatory agencies set safety limits on how much you can consume by body weight, and it's typically, again, it's about a couple of orders of magnitude more than what a typical person would consume, so, it's just not something worth worrying about.
You can drink your diet sodas; you don't have to worry that they're making you fat, according to this latest systematic review. They really did look at--they tried to look at every single study published, of any kind on this question; it was pretty, pretty thorough. Not saying there isn't room for even more rigorous clinical studies, but the data's pretty rigorous, you know, that we have so far.
The other last interesting thing I want to talk about is that you read so many self-help books and nutrition gurus, you know, they're talking about this diet advice or that, or how to avoid aspartame, et cetera, and they usually justify their recommendation with wild extrapolations from basic science. You know, it's like, "We have sweetness receptors in our gut and that causes A to B to C to D, and therefore it's not good for you."
E: There you go.
S: It's like, yeah, but you know we rarely can take our basic science knowledge and then extrapolate four or five steps to net health effects. You can't do that. That almost never works out. You have to study in people what the net health effects are. Because like here, yeah, sure, those mechanisms are in play, but they're just less than the effect of eating less sugar. It all comes down to magnitude. Even if the effects are real and there isn't something compensating for it, it just may not be clinically relevant. So, until you do the clinical studies, you just can't make those kinds of statements. But that is like almost the entire nutrition industry. You know, self-help industries based upon these wild extrapolations from basic science. That is just not reliable.
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Mafia hitman claims to be missing piece in JFK assassination ()
Fossilized Brains ()
Who's That Noisy ()
- Answer to last week: Architectural Instrument
Questions and Emails
Question #1: Anxiety ()
I would like to begin this message by telling you that I love the show and have been a loyal subscriber since 2008. However, Jay mentioned something in the last episode that I would like to correct. He stated that people who needed anxiolytic medication didn't have the 'brass balls' to do things such as go to space and that they allowed their emotions to overcome them in such a way that they would be unsuitable for such a rigorous environment as the ISS. I would like to point out that Isaac Newton's notebooks record his anxiety, fears, and depression during his college years, as well as suicidal thoughts. Nicola Tesla almost certainly suffered from social anxiety. Scientists often work in collaborative teams these days, but there are many quiet, meticulous, solitary tasks that a person with anxiety is exceptionally good at completing. Our tendency to double and triple check things can be a good trait for lab work, as does the anxious brain's tendency to keep churning our every word and action after the fact. I know that it is a common trope in pop culture to portray those of us who suffer from what is essentially a lack of seretonin as nervous wrecks, but I assure you, we are quite capable. There are many medications that can remediate this chemical imbalance and settle our thoughts, but the anxious person can offer something to a team, just as it benefits with both introverts and extroverts, or autistic and other neuro-atypical people. Jay, I'm sure you didn't mean to stigmatize anyone or to downplay the accomplishments of those with psychiatric illnesses. And there is a concern about being stranded and without the trusty SSRIs, a la The Martian, where it might be harder to function. But, in the future, remember that every team needs diversity. People whose brains function differently can be an asset as well as a risk. Sincerely, Someone who worries an awful lot http://www.space.com/26799-nasa-astronauts-psychological-evaluation.html
Question #2: Meat Consumption ()
Toni, I tried to find some specific statistics on meat consumption. 2010 statistics from the USDA http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3045642/ 'Results: Overall meat consumption has continued to rise in the U.S., European Union, and developed world. Despite a shift toward higher poultry consumption, red meat still represents the largest proportion of meat consumed in the U.S (58%). Twenty-two percent of the meat consumed in the U.S. is processed. According to NHANES 2003–2004, total meat intake averaged 128 g/day. The type and quantities of meat reported varied by education, race, age, and gender.' 22% of 128g/day = 28 grams of processed meat per day on average, less than the 50grams in the study. Given this, I think we gave a reasonable bottom line interpretation of the implications of the study. Regarding meat and total health outcomes, I did refer to it on the show, here's the link:http://www.biomedcentral.com/1741-7015/11/63/abstract I did link in the show notes to my blog article which contains this link and others. Regards, Steve Dear Steve, 'Given this, I think we gave a reasonable bottom line interpretation of the implications of the study.' Yes, indeed. The statistic you provided puts the WHO study into context. Now I'm a vegetarian thinking, if only people would eat more processed meat.. But, as I clearly have no case anymore, I concede my position and thank you for taking the time to respond. This was fun. Kind regards, Toni
Interview with Simon Singh ()
Science or Fiction ()
Item #1: A new report describes a method for adding quantum dots to standard lithium ion batteries, allowing a cell phone to fully charge in 30 seconds. Item #2: A study looking at medications stored aboard the ISS finds that, on average, drugs in microgravity degrade at twice the normal rate. Item #3: Scientists have created the first porous liquid, a liquid with holes, allowing it to dissolve large amounts of gas.
Skeptical Quote of the Week ()
"We ignore public understanding of science at our peril" - Eugenie Clark
S: The Skeptics' Guide to the Universe is produced by SGU Productions, dedicated to promoting science and critical thinking. For more information on this and other episodes, please visit our website at theskepticsguide.org, where you will find the show notes as well as links to our blogs, videos, online forum, and other content. You can send us feedback or questions to info@theskepticsguide.org. Also, please consider supporting the SGU by visiting the store page on our website, where you will find merchandise, premium content, and subscription information. Our listeners are what make SGU possible.
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