Soft drink giant PepsiCo recently announced its plans to stop sweetening Diet Pepsi with aspartame in response to growing consumer concern, yet the company, regulators and many medical authorities say the potential detrimental effect of the artificial sweetener on human health is overblown. So, what's really going on here and who should you believe?

The tricky thing is that there's lots of conflicting information out there on the safety of aspartame, and there's almost as much conflicting information out there on the scientific quality of that primary information. In short, it's a rabbit hole of never-ending argument.

The full history of Aspartame is one plagued by controversy almost since the day in 1965 when it was accidentally discovered by a chemist named James M. Schlatter. He was working on an anti-ulcer drug and found that his concoction had a pleasant, sweet taste. After a few more years of testing, the pharmaceutical company that employed Schlatter, G.D. Searle & Co., decided to take advantage of the damaged reputation of the existing sugar substitutes of the time (cyclamate was banned in 1969, giving saccharine a virtual monopoly, but it too was plagued by health concerns and building calls for a ban) and petition for the approval by the American Food and Drug Administration for aspartame to be sold as a food additive.

That petition was filed in 1973 and was technically approved the following year, but approval was then delayed when concerns surfaced about the methods and research procedures Searle used to prove the safety of aspartame.

What followed for the next seven years was a series of audits, inquiries and even a grand jury investigation into both the safety of aspartame and the internal practices at Searle. While a board of inquiry declared in 1980 that more testing was required of aspartame due to concerns of possible carcinogenicity, the FDA commissioner found errors in the board's calculations of the potential risks and overruled its decision. In 1981 FDA Commissioner Arthur Hull Hayes Jr. ruled that aspartame was safe and approved its use as a tabletop sweetener and in dry goods; it was later approved for use in soft drinks in 1983.

While the initial science behind aspartame's safety was eventually validated, the climate of controversy and suspicion under which aspartame came to market has never abated and has flared up at certain times over the last three decades.

In 1985, Senator Howard Metzenbaum, who led an investigation into Searle and aspartame's safety prior to its approval, introduced the Aspartame Safety Act of 1985 to provide for further study in response to the widespread popularity of aspatame-based NutraSweet. The bill came out shortly after the Centers for Disease Control conducted a study on short-term negative side effects of aspartame use and found no reason for concern, which may have played a role in the bill failing to become a law. A lawsuit attempting to remove aspartame from shelves on health grounds also failed around the same time.

When the internet became a global phenomenon in the 1990s, an anti-aspartame community was able to better connect, coalesce and grow exponentially. A study published in 1996 by long-time aspartame critic Dr. John Olney and publicized by Metzenbaum suggested a possible correlation between the incidence of brain tumors and the introduction of aspartame to the market several years earlier.

The company producing Nutrasweet and the FDA both pointed out problems with Olney's study and it was widely criticized in scientific, academic and regulatory circles, but the mass media latched on to the fear factor over potential health concerns associated with aspartame, arguably exaggerating Olney's main conclusion, which was simply that more study of the effects of aspartame was called for.

Now, nearly two decades later, the influence of the internet on the aspartame debate has snowballed, and the web is filled with a dizzying array of claims, conspiracy theories, debunkings, and debunkings of those debunkings. Depending on what Google result you click on, you could find claims that aspartame is linked to the Nazis, the Illuminati, or that it causes multiple sclerosis, a claim that the National Multiple Sclerosis Society now lists on the "disproved theories" page of its website.

So how can we pull anything resembling the truth about aspartame, especially its effects or lack thereof on human health, from this tsunami of rhetoric spanning three decades?

Here's what we think we know with a pretty high level of confidence. While there's plenty of reason to doubt either the competence or the motives of both the aspartame manufacturers and the regulators from time to time, the science still speaks for itself, and it has yet to prove a conclusive link between aspartame and cancer, or even between aspartame and lesser health effects like headaches.

Of course, science has not completely disproven the existence of such a link either. Such is the nature of scientific inquiry – it's very difficult to prove a negative. All we can do is study something as rigorously as possible, and then continue to study it more. That process has been ongoing for almost four decades with aspartame, and the science has yielded a few false positives (including an oft-cited 2005 study linking high doses of aspartame intake in rats to brain tumors), a lot of data pointing to aspartame as a benign additive, and some studies that call for further study, which continues to be ongoing.

Today, the National Cancer Institute, the National Institutes of Health and the European Food Safety Authority (EFSA), among others, all consider aspartame to be safe for human consumption in the amounts currently recommended (one exception being those with the medical condition phenylketonuria, who should probably steer clear altogether).

"This opinion represents one of the most comprehensive risk assessments of aspartame ever undertaken," said Dr. Alicja Mortensen of the EFSA, following a full risk assessment in 2013. "It’s a step forward in strengthening consumer confidence in the scientific underpinning of the EU food safety system and the regulation of food additives."

While aspartame's early political history may leave reason to doubt its safety, the scientific consensus that has been amassed since then points in the other direction.

However, the science also suggests that aspartame might not be all that great for one of its initial purposes, which was to help people diet and lose weight. There's conflicting data in this area, with some studies supporting the notion that artificial sweeteners can be a miracle weight loss tool, others showing no impact, and even some that suggest they may have the opposite effect.

There are also new concerns, published in a study last year, that indicate artificial sweeteners could be messing with the microbiomes in our guts and leading to problems like glucose intolerance. This research is pretty new and only applies to animals so far; it probably needs more research to see if humans might also be affected in similar ways.

So, to wrap this all up, don't believe the hype that aspartame is killing you, whereas large amounts of the high-calorie sugar sweeteners it replaces just might. In fact, you'd probably be better off just restricting sweet stuff from your diet and choosing water or tea over Diet Pepsi or Diet Coke.

Like most things, there's no reason to fear aspartame in moderation, but we should continue to question past findings and study it more as our science and technology improves. That's just the way science works. Maybe some day I'll eat these words, but right now there are decades of research backing them up.

So what's to become of Diet Pepsi? In a conference call with industry analysts in February, before officially initiating the move away from aspartame, the company's CEO for the Americas hinted at the issue:

"The number-one thing we see from consumers is a complaint about aspartame. Aspartame is just one sweetener, but it's the one that seems to get most of the negatives in the press and on YouTube. And as you research it, that's where the negatives are coming."

The company also says aspartame is safe in the frequently asked questions section of its website, but now it's switching to sucralose, (aka Splenda) in response to those "negatives."

This naturally leads to the question, how safe is sucralose? It's generally accepted as safe, but a few seconds of Googling will lead to other opinions ... but that's an entirely different article.

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