Two weeks ago, researchers from the University of Texas claimed that diet soda may promote weight gain, and research released Tuesday suggested that there may be a link between diet soda consumption and increased vascular events (heart attacks and strokes). Such claims about the sugar-free beverages have the potential change the way Americans look at dieting and weight loss.
There's one problem, however: they're not true. There is very little evidence to support the assertion that diet soda is responsible for weight gain or poor cardiovascular health.
Whenever scientists postulate that a certain product or behavior can harm your health, remember that they can't demonstrate it by conducting observational studies, which prove very little about the subjects they investigate. In this case, both studies simply found that people who consume diet soda may also gain weight or experience heart attacks or strokes, not that drinking diet soda causes the latter two. At first glance the association does seem to suggest a causal link, but there are any number of variables that can explain observations of this nature.
Consider a hypothetical study in which scientists discover that girls who quit high school are more likely to become pregnant than girls who graduate. One conclusion the researchers could draw is that dropping out of school causes pregnancy. Most observers wouldn't accept that conclusion because they recognize that dropping out doesn't literally lead to pregnancy; there's some other factor that better explains the situation, such as basic biology.
The same is true of the two real studies cited above. Diet soda doesn't cause weight gain or vascular events; people who consume it tend to suffer from these health problems in spite of the fact that they're forgoing sugary beverages. This is a better explanation of the data for two reasons. First, neither study found a mechanism by which the artificial sweeteners in diet soda can cause weight gain or vascular events. Several theories have been proposed over the years, but none have held up.
A recent review of the primary sweetener used in diet soda, Aspartame, found that "The weight of existing evidence is that aspartame is safe at current levels of consumption as a nonnutritive sweetener." The federal Food and Drug Administration (FDA), certainly no friend to the beverage industry, agrees. "Aspartame was first approved in the United States in 1981 and is one of the most widely used artificial sweeteners. When metabolized by the body, aspartame is broken down into two common amino acids, aspartic acid and phenylalanine, and a third substance, methanol. These three substances are available in similar or greater amounts from eating common foods."
More importantly, however, sugar unquestionably causes weight gain and damages the cardiovascular system, and the average American's diet is loaded with it. Unlike the studies linking diet soda to negative health outcomes, numerous clinical trials, which are far more reliable than observational studies, have demonstrated that avoiding sugar is one of the best ways to prevent obesity and most of its related health effects. For those reasons, sugar is the much more likely culprit than the sweeteners in diet soda.
To be fair, none of the researchers involed in either study said their results are conclusive. But given the above facts, the associations they found don't stand up to scrutiny. As JunkScience.com's Steve Milloy summarized it, "Weak correlation + poor-quality exposure data + unaccounted-for confounding risk factors + “unclear” biologic mechanisms = Junk science."
The media also deserve a lashing for their coverage of these studies. While the researchers themselves were slightly more cautious about their conclusions, the media took the possible links between diet soda and poor health and ran with them. CBS's coverage of study on weight gain was titled "Diet Soda Can Lead To Weight Gain," and the network's health expert told viewers that she recommends her patients avoid the "chemicals" in diet soda and drink regular beverages sweetened with sugar. The Daily Mail told readers that "Just one can of diet fizzy drink can increase risk of heart attack or stroke." These are certainly possible conclusions, but they're not the best ones based on all the evidence.
We should always be open to the possibility that the accepted wisdom about proper nutrition is flawed. In fact, it often is. But in the case of diet soda, we don't have good enough evidence to throw out the standard advice. And no amount of shrill news coverage or unsound science will serve as a proper replacement.
Photo Credit: Wikimedia Commons
The Discussion
Since you've previously mentioned the need for better science journalism, let's address a few things.
First, association and causation. While I commend your catchy example, I want to ask how you can show that sugar causes weight gain, while aspartame is only associated. The link to clinical trials shows a study regarding which diet works best. None of the diets specifically note a reduction in sugar intake - only changing ratios of carbs, proteins, and fats.
The second link, however, found drinking diet sodas daily was strongly associated with vascular risk, even when controlling for protein, carbohydrate, fat, and sodium intake, as well as physical activity. [to be continued]
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Look at this:
http://rheumatology.oxfordjournals.org/content/50/7/1244.short
aspartame is good for osteoarthritis in mice.
Maybe the FDA should call it a drug.
Cell phone radiation prevents Alzheimer's disease in mice
http://www.popsci.com/technology/article/2010-01/cell-phone-exposure-reverses-alzheimers-and-boosts-memory-mice
Everything is good for something.
Thanks for pointing me to the link.
The vascular event study pivots on the recall of 163 people who once said they generally drink one or more diet sodas per day. With a cohort this small, it doesn't matter what you try to control for, your results will be not be truly significant.
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Cameron,
Please supply links to the new diet soda study...I could not find a reference for it.
I may be the same old tired two year old study by the same people.
Thanks
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Fine, your analysis of causation vs linkage remains unchallenged. Way to learn your stats. But why not discuss some of the processes at hand when your body breaks down aspartame instead of breaking down cane sugar? Why not mention that formaldehyde is a byproduct of aspartame that may be generated when you consume diet sodas?
Just because there's no study to prove causation (it is extremely difficult to show causation in science) it doesn't mean the linkage is irrelevant. The media is never a great place to look for health advice and accurate accounts of research papers. It's unfortunate to me that instead of offering an analysis of the research that is there, you chose to throttle an obviously overblown conclusion.
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A study done on rabbits at the Biological Research Institute in Babes-Bolyai University in Rumania, shows damage to the ventromedial hypothalamus (VMH) using an electron-microscope. The VHM controls leptin production required in resisting diet-induced obesity. In layman’s terms, the very part of your brain that signals you to stop eating is being destroyed by Aspartame. Since aspartame has been in the diet since 1981 this might explain why the population is getting fatter, since it is destroying the body’s own biological feedback system!
Download the study in PDF format from the following link:
http://journals.usamvcj.ro/vet
Another study on rats at King Saud University found half the rats given Aspartame died.
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Great article. I've found caffeinated diet soda is a great substitute for coffee-- it's cheap (in bulk), you can store it in your dorm room, and you can grab one on your way out in just a few seconds. Even instant coffee requires some preparation and clean-up.
It's a shame "science reporting" is an oxymoron these days. The media rarely reports all the information necessary, and they never explain the difference between observational studies and experiments. But it makes one wonder: Why do respected universities like U Texas waste money on poor experiment designs? Clearly, it can't just be the media's fault.
The unfortunate reality is that a large number of "scientific" studies, particularly about diet and health, uncover weak correlations and the media and sometimes health organizations present them as causation. This is encapsulated in the phrase "risk factors," which are NOT causes but rather correlations. To use one egregious example, the entire premise of lowering cholesterol to prevent heart attacks is based on a false assumption of causation.
I am the last person to advocate increased government intervention - Normally. But it is increasing clear that private, non-profit and governmental agencies are not adequate in policing their own. Has the media gone wild - obviously yes. Where has truth gone in media reporting - to op-ed news at best or out the window for sensationalism to outright lies in reality. I would never advocate censorship. But after the fact fines of false reporting would be another matter. Would it be acceptable? Absolutely not! And a media firestorm in protest, twisted truth of purpose and disingenuous reports of censorship and 1st amendment right violations. But, the truth remains that the media is disingenuous for sensationalism. Now junk news on junk science.
It may not cause weight gain or cause cancer but drinks and foods containing aspartame are toxic and deadly. Aspartame was developed as a chemical weapon. Watch Sweet Misery and see how Donald Rumsfeld and Ronald Reagan are responsible for poisoning millions.
http://topdocumentaryfilms.com/sweet-misery-a-poisoned-world/
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And I shall continue to enjoy my occasional Diet Coke and Lime.
Also, Cameron, speaking of reportorial responsibility, you cite Steve Milloy and his website JunkScience.com. A little homework would seem to indicate that the outlet's scientific bona fides should be seriously called into question, to say the least...
http://www.guardian.co.uk/environment/2006/sep/19/ethicalliving.g2
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Kathleen is absolutely right. Aspartame has proven consequences for one's health, and it would be foolish to pretend otherwise.
Moreover, diet soda doesn't quench thirst, which is the original point of drinking liquids in the first place. Why put empty calories into your body when they don't even make you less thirsty? Soda — diet or not — is a losing proposition on both ends unless you really need the caffeine and don't have coffee handy.
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Hi Cameron,
Hate to burst your bubble but Aspartame is 'not' the safe sugar alternative the FDA presents it to be and they know it.
First, back around 1967-69 problems where noted with people who ingested products containing aspartame. In fact, it was proven to cause brain damage & was widely & openly discussed on major news and programs like 60 Minutes. However, the FDA neglected the findings.
Second, having worked in a major medical facility for years I am aware of the FDA food pyramid. Knowledgeable & honest people will tell you the pyramid is based on the most successful lobbysists of the time.
I hear Mothers shopping with their children say: it contains Aspartame, it's not good & leave product on the shelf; just like we did.
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There are other studies that show that diet sodas encourage overconsumption of other foods. http://articles.latimes.com/2011/jul/01/news/la-heb-diet-soda-weight-gain-20110701
I've seen one that indicated people get the idea they are "saving" calories and inadvertently end up eating more than they would otherwise eat, if they stuck to water, tea, or the occasional sugary soda or juice. Another one I saw looked at how artificial sweeteners impact the taste buds, and it attempted to show correlation with preferences for less healthy food. As to one can causing a stroke or heart attack - give me a break! It's a pattern associated with general unhealthy habits, or it could be people with diabetes and heart disease trying to reduce calories.
I wholeheartedly agree that media reports often make irresponsible leaps from association to causation, but your assessment of these studies is equally outrageous. The Northern Manhattan study you cite above, for example, seems to find some remarkable correlations between diet soda consumption and cardiovascular events, all while controlling for numerous baseline risk factors (e.g. obesity, diabetes). The authors call for further studies with designs capable of exploring a potential causal relationship here, and highlight some compelling basic science research that suggests that such a relationship could potentially exist. Absolutely nowhere do the authors make the kinds of causal claims you are alleging.
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Here's the conclusion to my study: Diet soda is gross and how people can consume it regularly is beyond me.
Let's be clear about the actions of the scientists and media.
From the abstract: "Conclusion: Daily diet soft drink consumption was associated with several vascular risk factors and with an increased risk for vascular events. Further research is needed before any conclusions can be made regarding the potential health consequences of diet soft drink consumption."
The scientists show a correlation and explicitly reject any conclusions about causation. This is very reasonable science; it tells other scientists that this might be a good place to *look for* correlations.
As usual, the media have totally scrambled the science. But you can't tell scientists not to publish science the media will scramble: science would stop completely.
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Great article, and on my favorite beverage. I feel much better about the Coke Zero in my hand at this very moment.
Absolute nonsense! The high sugar content and that additive that makes you thirsty all the time will actually make people fat over time. One of the requirements for the program I'm on is to cut out all sodas. I've dropped 180lbs since.
If you're interested in my story please head over to Zdiets.net
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I know of a bevaerage that is great for weight loss, causes no known health problems and is (usually) cheap to boot: water. Good article. Nicely debunked media hype and lax science.