Diet soda increases risk of stroke and dementia – does it?

diet soda increases risk

Two recent studies published in respected journals seem to indicate that diet soda increases risk of stroke and dementia. Not to give a free pass to sugary drinks, one of the studies seemed to indicate that either artificially sweetened or sugar filled drinks might be linked to a higher risk of Alzheimer’s disease.

Typical of the popular press and your average website, they accept the findings of these studies without any serious critique of these studies. US News blares a headline that says, “Health buzz: drinking diet soda linked to stroke, dementia risk, study says.” Thankfully, many of the headlines use the qualifier “may be linked,” but I’m afraid most people will overlook that nuanced discussion of these studies.

But what does the actual science say? Do these studies provide us with robust evidence that cutting out diet soda will suddenly decrease our risk of stroke, dementia or Alzheimer’s disease? Probably not, but let’s see what this data actually tells us.

 

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Pepsi and aspartame – an unscientific decision

Unless you’re a follower of the junk science presented by the pseudoscience shill, Joe Mercola and other crackpots, you probably didn’t think much of the artificial sweetener called aspartame (or by its more common trade name, Nutrasweet). You might have wondered if it was safe, but your skeptical mind probably rejected any safety issue not because most of the negative information came from bad sources–like Mercola.

Now that you’re here, reading this story, probably because you just read something about Pepsi and aspartame – because the giant soft drink bottler decided to remove it from their diet sodas. They did replace aspartame with–oh wait for it–two other artificial sweeteners. Obviously, Pepsi did it for marketing/public relations reasons, but the decision itself is based on bad information (on the internet, of course), rather than real science.

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Artificial sweeteners linked to obesity–poor evidence

artificial-sweetenersThis article was written by Linda Tock, an American living in Denmark, who has an extensive research background in the biomedical sciences. She has a Master’s Degree in Environmental Chemistry and Health, and will be pursuing a Ph.D. Ms. Tock has a fascination for Daphnia, an interesting planktonic crustacean, that is an important organism in studying pollution and environmental stresses. She’s also a passionate Boston Red Sox fan, so she had to endure a difficult year.

So I received a message from a friend of mine, wanting my opinion on this news article, which loudly proclaims that artificial sweeteners are linked to obesity. Because it was a genuine question regarding the science behind the study, and not a ‘concern troll’ about my preference for diet cola, I went and looked at the study itself to see what the fuss was about.

According to the abstract in the article published in the journal Nature,

Non-caloric artificial sweeteners (NAS) are among the most widely used food additives worldwide, regularly consumed by lean and obese individuals alike. NAS consumption is considered safe and beneficial owing to their low caloric content, yet supporting scientific data remain sparse and controversial. Here we demonstrate that consumption of commonly used NAS formulations drives the development of glucose intolerance through induction of compositional and functional alterations to the intestinal microbiota. These NAS-mediated deleterious metabolic effects are abrogated by antibiotic treatment, and are fully transferrable to germ-free mice upon faecal transplantation of microbiota configurations from NAS-consuming mice, or of microbiota anaerobically incubated in the presence of NAS. We identify NAS-altered microbial metabolic pathways that are linked to host susceptibility to metabolic disease, and demonstrate similar NAS-induced dysbiosis and glucose intolerance in healthy human subjects. Collectively, our results link NAS consumption, dysbiosis and metabolic abnormalities, thereby calling for a reassessment of massive NAS usage.

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Aspartame is safe according to the scientific consensus

This article has been completely updated with new information and can be found here. Comments are closed on this article, but please comment on the new one.

Aspartame (brand name Nutrasweet) is a popular artificial sweetener, approximately 200 times sweeter than common table sugar known as sucrose. Aspartame is a dipeptide of the natural amino acids Laspartic acid and Lphenylalanine–these amino acids or peptides are consumed regular with nearly any animal or plant protein.

When aspartame is ingested, it is hydrolyzed (broken down by water molecules) into its constituent components: aspartate, phenylalanine and methanol, in an approximate 4:5:1 ratio. No aspartame has been found in the bloodstream, since it is so quickly hydrolyzed in the gut, and only the constituent components are absorbed.

To be absolutely clear, there is no difference between aspartic acid and phenylalanine that form aspartame than all “natural forms” of those amino acids that are contained in the proteins of food sources. Continue reading “Aspartame is safe according to the scientific consensus”

Harvard hospital retracts statement about data on aspartame and cancer

This is a story about clinical research, misinterpreting said clinical research, an overaggressive Public Relations department, honest scientists, and good scientific journalism. Let’s start at the beginning.

This week, an article was published in the American Journal of Clinical Nutrition by Schernhammer et al., scientists from Brigham and Women’s Hospital, a teaching affiliate of Harvard University Medical School, that examined potential risks of certain cancers in groups that consumed diet drinks. The study identified, over 22 years, 1324 non-Hodgkin lymphomas (NHLs), 285 multiple myelomas, and 339 leukemias. They then determined their intake of diet sodas (or pop, depending on your location in the United States).

They determined that:

  • Men who had greater than 1 daily serving of diet soda had increased risks of NHLs and multiple myeloma. Women had no observed increased risks.
  • They also observed an unexpected elevated risk of NHL with a higher consumption of regular, sugar-sweetened soda in men but not in women. 
  • Neither regular nor diet soda increased risk of leukemia but were associated with increased leukemia risk when data for men and women were combined.

Based on these results, you might think that diet sodas are dangerous, at least for men. Or maybe just sodas (or pop), whether sweetened with sugar or artificial sweeteners, are dangerous. Or maybe not. The authors themselves conclude:

Although our findings preserve the possibility of a detrimental effect of a constituent of diet soda, such as aspartame, on select cancers, the inconsistent sex effects and occurrence of an apparent cancer risk in individuals who consume regular soda do not permit the ruling out of chance as an explanation.

In other words, there’s really not much there. And that’s not bad in science. They tried to look for something, and they didn’t find anything. Maybe those men who drank sodas heavily had other confounding risk factors like obesity, diet, or other environmental factors. Or it may just be random.

At this point in the story, it’s just one of those published articles that really isn’t much of anything. No one would make much of it, because it really doesn’t provide much evidence that aspartame or sodas are that dangerous. 

Then Brigham and Women’s Hospital puts out a press release with an attention grabbing headline of “The truth isn’t sweet when it comes to artificial sweeteners.” Now, if you saw that headline, you would have assumed that the article provided a solid conclusion that there was a direct causal link between artificial sweeteners and certain cancers. But the article said no such thing, it showed a very weak link, if one at all.

I guess the real scientists at Harvard saw the press release and decided their reputations mattered more than marketing the hospital in an unethical way. But whatever the real story, the hospital issued an “apology”:

It has come to our attention that the scientific leaders at Brigham and Women’s Hospital did not have an opportunity, prior to today, to review the findings of the paper entitled Consumption of Artificial Sweetener and Sugar Containing Soda and the Risk of Lymphoma and Leukemia in Men and Women”, to be published in today’s Journal of Clinical Nutrition (sic). Upon review of the findings, the consensus of our scientific leaders is that the data is weak, and that BWH Media Relations was premature in the promotion of this work. We apologize for the time you have invested in this story.

Uh,  it’s actually the American Journal of Clinical Nutrition, shocking they can’t get that right. Maybe I’m just being picky, but Public Relations should represent the organization better than that. 

Robert Bazell, NBC News reported that “the situation is a great example of why the public often finds science confusing and frustrating. After being asked some hard questions – and just before the report was to be released —  the hospital changed its tune.”

Bazell further reports that “the conclusion was so weak that the researchers had to submit it to six journals before they found a seventh, the American Journal of Clinical Nutrition, that would publish it. Few reporters read that journal. If it was not for the frightening headline no one would have known about this study.”

This study was a well-intended one that could have found a causal link if there was one, because of the way it sought out information. But it did not find the link, and that is how research is done. Sometimes, you find evidence of the null hypothesis, that artificial sweeteners don’t do anything.

And just in case there’s any confusion, Bazell reported that the lead author Schernhammer, when asked whether the published “research proves that aspartame is dangerous, she answered emphatically, ‘No, it does not.'”

The vast weight of evidence shows aspartame is safe. This doesn’t add to that weight, it just doesn’t support that it causes cancer. And it proves one more thing. Do NOT use press releases as your scientific proof source. They aren’t worth anything, because they aren’t written by scientists, and they are used to promote the facility. 

Drink your diet soda. Or pop. Your choice.

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