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Saturday, February 4, 2017

Taking Apart Bad Diet Studies: Sugar-Free Edition

A few weeks ago, I wrote this take down of some recent commentary on the dangers of low-calorie sweeteners. That post is a good place to start on this subject because it covers the most common objections to consuming sweeteners like Splenda, and it's full of references to the peer-reviewed literature.

But this is a hot topic in nutrition these days, so I want to return to it now by picking apart one study in particular, which suggests that low-calorie sweeteners don't aid weight loss. The paper was published in PLoS One in November and its authors argue that

Low-calorie sweetener use is independently associated with heavier relative weight, a larger waist, and a higher prevalence and incidence of abdominal obesity suggesting that low-calorie sweetener use may not be an effective means of weight control.
Even if everything in the above sentence is correct, the authors have done nothing more than find an association (and a weak one at that, as we'll see) between low-calorie sweeteners and obesity. But there's much in the paper's conclusion that is problematic, so let's dive into the details and briefly explain why.

Methods

To perform this study, the researchers utilized body composition and diet data from the Baltimore Longitudinal Study of Aging, which you can read more about here. The present study includes 1,454 men and women from the BLSA who are at least 20 years old. Their height, weight and sweetener use were assessed at several points between 1984 and 2012, and the study participants were followed for an average of 10 years.

There's nothing especially challenging about measuring a person's weight or height, but assessing how much food they eat is really hard to do. So how did the BLSA acquire the numbers on sweetener consumption?

Dietary intake was assessed using a 7-day dietary record
Oh, boy. Food surveys. The details on the collection methods are here. But in essence, the BLSA researchers ask people to track what they eat over 7-day periods, selecting from 41 different food groups, including low-calorie sweeteners.

The authors of the PLoS paper followed 1,455 participants from this study. They compared those who reported consuming sweeteners to those who didn't to see which group fared better. Simple, right? Nope.

Food Frequency Surveys Are Garbage

We've known for years now that surveys of what people eat are useless. They consistently under report consumption of certain food groups and over report consumption of others, for example. We know this because studies have been done in which people are fed carefully measured diets then allowed to report back what they ate on food frequency surveys.



In this study from 2000, people wildly misreported what they were consuming. They did so poorly that the authors concluded that "Our data indicate that the food-frequency questionnaire may be unreliable and inadequate for assessing ... macronutrient intakes." Mind you, this study involved only 19 subjects and lasted just six weeks. The BLSA data, so far, cover more than two decades and include more than a thousand individuals! If 19 people can't accurately report what they ate over a month and a half, there's no way 1,500 people can do the same over 20 plus years.

These questionnaires are so awful, in fact, that this 2005 article in Cancer Epidemiology says they've created a crisis in nutrition research, primarily because human memory is faulty after only a few days. People can remember what they ate yesterday, maybe, but by the end of the week, they begin substituting what they actually ate with "general knowledge about foods, most probably based on beliefs (even hopes) about one's usual or characteristic diet."

These general limitations on food frequency questionnaires are enough to sink any diet study that relies on them. But let's look at a specific issue with this study of low-calorie sweetener consumption.

Sweetener Use Varied Over Time

Clinical trials can be a powerful method for discovering scientific facts, because you can control different variables to see how they affect the outcome of the trial. You could, for instance, put people on identical diets but feed only one group artificial sweeteners and see what happens. The PLoS researchers tried to mimic this method, but they couldn't because "[l]ow-calorie sweetener use by participants fluctuated over time..."

The authors describe the statistical methods they employed to account for this variable, in which they try to compare how much sweetener people say they are consuming to their weight and waist circumference throughout the study. But if people are changing their consumption patterns throughout the study, there's no meaningful way to track how sweeteners are affecting their health.

As Gary Taubes has pointed out, there is often a time delay between a dietary intervention itself and the effect that the intervention exerts on your health. Maybe sweeteners do stunt weight loss. Or maybe they encourage weight loss, if you replace three regular sodas with three diet sodas everyday for three months. The point is, you have to accurately track how much of a sweetener people consume over a given period of time to test either hypothesis in a meaningful way.

What did they find?

So with all these caveats about statistics out of the way, what did this study find? If you look at table 1 in the paper, you can see that the group who consumed sweeteners had a BMI of 26.4 at baseline. This number increased to 26.8 by the end of the study, a whopping .4 increase over the course of a decade! Depending on your height and lean muscle mass, this increase in BMI represents probably less than 1/2 pound of body fat for most people. Even if every single data point in this study is accurate, cutting artificial sweeteners out of your diet will contribute a minuscule amount of weight loss to your overall goal to get slim and sexy.

Parenthetically, both groups in the study consumed more than 230 grams of carbohydrate on a daily basis! And approximately half of the people in both groups had poor glucose tolerance, which almost certainly has something to do with their ability to lose weight. Studying the obesity-promoting effects of low-calorie sweeteners in this context doesn't make much sense, because everyone is eating a fattening diet. Whatever influence sweeteners have is probably dwarfed by the overall effects of the diet.

Conclusion

In summary then, there's way too little reliable data available and far too much modeling going on in this study, especially when there is better research available. The worst part is that you can get the result you're looking for even if your model is bad! I suspect that that's what happened in this case, and that's why I remain unconvinced that low-calorie sweeteners have anything to do with weight gain.


Wednesday, February 1, 2017

Lousy Study Links E-cigarette Use To Heart Disease

E-cigarettes have been widely used for going on 15 years now. In that time, multiple studies have demonstrated that the smoking alternatives are far safer than cigarettes, and much more effective for smoking cessation than nicotine gum or patches.

So with a relatively impressive body of research available to justify "vaping" - the cool kid term for smoking an e-cig - any study that contradicts this ever-growing consensus should ping your poser radar.

Why? Because the new study is probably garbage, as is this new paper published in the Journal of the American Medical Association. The study found that e-cigarette users, "vapers," experienced a temporary shift in heart rate variability also seen in regular cigarette smokers.



Naturally, the conclusion drawn from these results is that e-cigs may cause the same kinds of damage to the heart that tobacco cigarettes do. That's nonsense for a number of reasons, the most important of which is explained by Steve Milloy of JunkScience.com:

Transient physiological effects do not translate into little-understood heart disease which is a natural long-term degenerative process.
Trying to draw conclusions about the long-term effects of vaping based on the results of such a limited study is useless. It's like arguing that a single cheeseburger will make you fat because it temporarily spikes your insulin immediately after you eat it, which coincidentally was also argued this week.

Anyway, heart disease takes decades to develop. Analyzing heart rate variability and oxidative stress one time in 40 people, only 23 of whom were e-cigarette users, is beyond useless. This is why governments spend millions of dollars financing decades-long studies of people with heart disease or who are at risk of developing the condition. It really takes that long to understand what actually causes chronic disease.

Let's briefly put this measly, poorly-designed study in the context of our broader understanding of e-cigarette science. Public Health England said just last fall that e-cigs are 95% less harmful than traditional cigarettes. That review covered dozens of studies published mostly in the last decade, and nearly every one of them comes down on the side of e-cigarettes being a safe alternative to tobacco.

These studies cover everything from lung cancer risk to smoking cessation and secondhand risk to bystanders. Yet we're all supposed to gasp in horror because of elevated adrenaline levels in 23 people, one time.

Nonsense.



Monday, January 30, 2017

Will Trump Be Bad for Science? His Cabinet Appointments Suggest Not

As President Trump settles into office and begins filling cabinet positions, we're starting to get a sense of how the new administration will influence science policy in America.

American Council on Science and Health president Hank Campbell has some interesting thoughts on Trump's cabinet picks as they relate to science:

When it comes to science and health, someone has clearly thought about these nominees, and they are also in line with the stated goals that got the President elected. These selections are certainly not anti-science, unless you are framing science through political or social goals.
A few quick thoughts:

Campbell rightly criticizes the EPA for the propagandizing they've engaged in over the last eight years, but acknowledges that they've also done some good research, especially on fracking in my opinion. Since Trump has been vocal about the importance of increased energy production and ordered the EPA to tone down their environmentalist preaching on twitter, I anticipate the agency will improve under the new president.

The Department of Energy will no longer preach the blessings of alternative energy, nor will they force all of us to pay for it, under the direction of former Texas governor Rick Perry. Greenpeace is breaking out in hives. Snort.

Francis Collins is staying on as director of the National Institutes of Health. He's a great science communicator and a great researcher besides. He's also been a voice of reason in the religion vs. science debate, mainly because he's convincingly argued that the two aren't mutually exclusive.

It's still early. But so far, so good. Trump could have done a lot worse with these cabinet picks.








Sunday, January 29, 2017

Never Mind the Muslim Ban; Trump should Focus on Obesity

This week President Trump has been making headlines with his rapid-fire series of executive orders, particularly with his efforts to start building a wall on the Mexican border and institute a ban on Muslim immigration to the United States.

Whatever you think of these controversial policies, there are other issues President Trump should focus on that have yet to receive any attention from the new administration--particularly obesity.

The exact number of Americans who are or will become obese can be manipulated depending on what political agenda is in question. But what's clear is that Americans are getting fatter than we used to be and our diets are becoming increasingly unhealthy.

Am J Clin Nutr
vol. 86 no. 4 899-906


So what should be done about this situation? The public health mullahs will urge Trump to shake his fists at the food industry for poisoning children with breakfast cereals and soda, then push for a federal tax on sugar. We're better than that sort of unhelpful nonsense by this point, hopefully.

Nonetheless, Trump has an opportunity to do something about obesity, and that something is very simple: he could cancel the USDA's policy of scolding fat people while subsidizing their bad habits. With good nutrition advice in hand, Americans may start making choices that ultimately eliminate obesity as a public health issue.

We Finally Know What Makes Us Fat

For decades, the federal government has promoted a low-fat diet, arguing that it helps us both shrink our waistlines and prevent heart disease. This message was dutifully picked up by the media, food industry and medical establishment in the 1970s, even though the relationship between high-fat diets and poor health was always tenuous. In recent years, though, an overwhelming amount of evidence has been collected that conclusively shatters whatever link there was between poor heart health, obesity and a high-fat diet.

Study after study confirms this assertion: not only will saturated fat keep you slim and your heart healthy, it's probably your body's preferred source of fuel, as opposed to the "heart healthy" whole grains we've been told to consume all our lives by clueless nutritionists and smug public health bureaucrats.

These are the kinds of claims that were made almost exclusively by isolated, rebellious voices in medicine just 15 years ago, figures like Robert Atkins and other such diet doctors. They were largely correct in their recommendation that people ought to avoid carbs and load up on fat and protein, though they were easily dismissed with the overwhelming majority of researchers denouncing their work.

What Can Trump Do About It?

 With prominent Harvard scientists now vocally defending saturated fat and bestselling books warning us about the dangers of consuming sugar, Trump has an opportunity to put his agenda to work promoting good nutrition advice that was previously suppressed by mainstream medicine. The president recently told every federal agency to halt the release of new regulations so his administration has a chance to review them, and I can think of no better setup for Trump to eliminate the USDA's "My Plate" dietary recommendations.

Released every five years since 1980, the USDA's dietary guidelines have hardly changed. They exclude any research that doesn't fit the agency's predetermined agenda and contradict research published by other federal agencies. More importantly, these haphazardly assembled guidelines are the foundation for every other iteration of the "eat less, move more" low-fat diet advice you're likely to see.

Instead of letting the USDA regularly issue outdated, scientifically dubious guidelines, Trump could make sure the agency is giving Americans accurate information about which foods constitute a good diet. He could also push to end federal agricultural subsidies for corn and soybeans, which artificially depress the price of junk foods everyone agrees are unhealthy. Some of the president's earlier comments about letting the free market work in agriculture give me hope on this second point, but we'll have to wait and see.

Conclusion

In the past, the government did an excellent job of promoting an unhealthy diet based on junk science. With a newly-elected populist president now directing the show, Washington could help reverse America's upward obesity trend by just leaving us alone. Following the decades-long debate over saturated fat, consumers are responding to the new science with changing preferences and food companies are happily catering to their customers' new demands.

If Trump keeps his agencies out of the way, we may have found our solution.







Saturday, January 7, 2017

In Defense of Artificial Sweeteners for 2017


The new year has arrived! Naturally, everybody everywhere has pledged to start a new diet and join their local gym.

Following this temporary nationwide shift in diet and exercise habits, every major news outlet is running silly advice articles promising readers the weight loss results they want if they tweak their habits in just the right way.

Most of this advice is typical pop-science boilerplate, unworthy of anyone's valuable time. But there's one bromide I've seen repeated more than usual this January: the claim that artificial sweeteners will make you fat.

I've seen everyone from HuffPo health writers to bona fide nutrition experts smugly asserting that your diet soda will stunt your weight loss effort and even push your weight in the wrong direction.

Bullshit.

With that eloquent thesis laid out, we're going to go through every fallacious reason people give for swearing off artificial sweeteners, and we're going to rely on the best science that's available.

Artificial sweeteners stimulate your appetite

If you're a fly. None of us are flies, so we could move on to more interesting facets of this debate. But disingenuous health writers also like to point out that overweight, diabetic people are more likely to drink diet soda than slimmer, metabolically healthy people. That's got to tell us something about the negative effects of sugar substitutes.

Of course, we could discount every diet ever conceived as ineffective since only fat people and diabetics go on diets to slim down. Or as the authors of a recent PLoS One article put it, " ... findings from observational studies might be biased by residual confounding ... as overweight/obese people are more likely to consume [artificial sweeteners] in an attempt to control weight." This didn't stop the authors from cautioning against consuming sugar substitutes, of course.

Some dieters do gain weight when they switch to sugar substitutes, but that's because they eat more than they otherwise would, assuming they can get away with an extra slice of pizza because they're abstaining from Code Red Mountain Dew. Though that's no reason to blame artificial sweeteners for stimulating your appetite.  

Impaired self-control

According to this study, low blood sugar predicted a lack of self-control in a series of tasks that involved regulating emotion and suppressing negative thinking. Consuming a sugary drink helped participants in this study perform better on subsequent self-control tasks.

The paper is interesting and underscores the importance of properly regulating blood sugar, a point stressed by advocates of low-carb and paelo diets, mind you. However, the geniuses at The Conversation took this as evidence that sugar substitutes impair self-control since they didn't spike blood glucose the same way the sugary milkshake used in the study did.

It's widely accepted that high blood sugar is the primary cause behind weight gain. Therefore, you should obviously avoid sugar substitutes because they don't spike your blood glucose like sugar does. Think through that a few times, then read on.

Artificial sweeteners are full of chemicals

I won't patronize anyone by smugly harping on the obvious retort that everything is full of, or rather composed of, chemicals. But this objection to artificial sweeteners is usually grounded in the ambiguous claim that the especially nasty chemicals in your diet Coke somehow damage your metabolism by harming your gut health.

The best support that can be mustered for this link between poor gut health and artificial sweetener consumption is this paper in Nature, in which the researchers altered the microbiota of mice by feeding them saccharine and increasing their glucose intolerance. The problem, though, as the researchers state is that "... human individuals feature a personalized response to [artificial sweeteners], possibly stemming from differences in their microbiota composition and function..."

The authors go on to argue that the changes they saw in these mice likely occur in humans as well, however, because they found "significant positive correlations between [artificial sweetener] consumption and several metabolic-syndrome-related clinical parameters ..." To find that correlation, they relied on self-reported data around artificial sweetener consumption. Of course we all know how awfully unreliable food frequency surveys are.

These limited results leads us on a search for better studies, preferably those in which the researchers didn't study rodents and then infer that people have the same reaction to artificial sweeteners.

Clinical Studies

A few papers of this sort have been published, but the results are mixed. Some studies show no effect whatsoever, others indicate that sugar substitutes  can help people lose a modest amount of weight. None implicate artificial sweeteners as culprits in causing weight gain.

The naysayers handle this as expected. They claim that dieters who switch to diet soda lose less weight than dieters who drink only water, though the difference is clinically insignificant--only 2.6 lbs in the cited study. If you're severely overweight or obese, losing two pounds won't do much for your health, and it's certainly less than you had in mind when you thought up your weight loss resolution.





I hope you see the theme here. The research returns an inconclusive result or suggests--as does common sense-- that sugarless, calorie-free sweeteners aid weight loss. Yet again and again we're told to avoid sweeteners.

N=1?

One point worth acknowledging is that everyone is indeed slightly different. Some people stuff their faces with junk food, for instance, and maintain the slender figure everyone else wants. So it's at least possible that some people gain weight when they eat sugar substitutes while others don't. But exceptions prove rules more often than they refute them.

Let me borrow a cliche from psychology and point out that humans aren't individually all that special. Being the narcissists we are, we like to think that we're the special case that bucks the trend. But that's usually hubris. There'd be no point in studying nutrition if everyone was so different from one another.

Conclusion

What seems most reasonable given the evidence we've discussed is this: there is some small sliver of the population that doesn't react well to sugar substitutes. This is true of vaccines, anti-depressants and a variety of other medical interventions. That fact, however, is not a good foundation for a blanket condemnation of sugar substitutes.

So as we head into another year, let's quit wasting everyone's time with speculative suggestions and make the changes we know will help us lose weight. There are certain foods that should be avoided generally, but Splenda probably isn't one of them. Unless someone wants to provide some better evidence.