Until a week or so ago, I drank soda. I was grabbing a can a day from the fridge at work-- sometimes two (mostly diet). Then I read the studies cited below, and I flat-out quit. Cold turkey, 100 percent.

Americans still drink a lot of soft drinks. Many of us wonder, which is worse: the sugar in regular soda, or the chemicals in diet?

Now, a pair of university studies has some disquieting answers to those key questions about carbonated beverages. I'll be interested to hear if you react the same way I did.

A lot of people drinking lots of soda.

First, the background. Researchers at Boston University produced two studies using data from the Framingham Heart Study, which is the nation's longest-running epidemiological study, dating back to 1948. The Franklin study is credited with helping scientists make many key discoveries about preventing heart disease over the past seven decades.

It's a big pool of data, and it originally focused on 5,209 people living in Framingham, Massachusetts--and then picked up the next generation, and the next. By studying their health and habits, researchers have produced more than 1,000 academic papers about how life choices affect health.

The soda researchers used this data to correlate residents' health with whether they drank regular soda, diet soda, or neither. It all resulted in two separate academic studies that came out almost simultaneously over the past month. We'll call them the "sugary drinks study" and the "diet drinks study."

Sugary drinks? A bad (and unexpected) problem.

The first study looked at about 4,000 of the Framingham participants, according to a university press release, identifying those who drank "more than two sugary drinks a day of any type--soda, fruit juice, or other soft drinks--or more than three per week of soda alone."

While most of us would anticipate these people might have had higher BMI or difficulty losing weight, the study found other correlations you might find shocking, because they're about an entirely different part of the body--the brain. Among the correlations:

  • Multiple signs of accelerated brain aging
  • Smaller overall brain volume
  • Poorer episodic memory
  • Shrunken hippocampus

All four correlations are "risk factors for early-stage Alzheimer's disease," the summary notes. This first study was published in the journal Alzheimer's & Dementia last month.

Diet drinks? Sadly, another unexpected problem.

Unfortunately, for soda lovers, the news isn't much better if we switch to diet drinks. Writing in the medical journal Stroke this month, another team of Boston University researchers focused on 4,372 Framingham study participants, looking for those who had either suffered a stroke, or had been diagnosed with Alzheimer's disease.

The result? Participants who had drank a single diet soda per day were "almost three times as likely to develop stroke and dementia."

Again, we are talking about correlation, not necessarily cause and effect. It could be the case, for example, that people who drink lots of soda simply happen to have these kinds of health outcomes for entirely unrelated reasons.

Or, it might be that drinking copious amounts of soda indicates that the subjects also made some other choices, which in turn lead to those health outcomes.

But at least for me personally, as soon as I started reading studies suggesting any connection between either excess sugar or diet soda and dementia--well, it put a quick stop to a casual habit I've had for decades.

So, what can I get you to drink?

I've been a marathon runner and a boxer in years past. Granted, I've added a few pounds over the last little bit. (New dad, new startup; it happens.) Yet I've clung to the idea that with a few lifestyle changes I'd be able to lose the weight, get in better shape, and handle a few minor, associated health issues.

But these two studies--early and tentative as they might be--gave me serious pause. It simply had never never occurred to me that extra sugar or things like acesulfame potassium or sucralose or aspartame could potentially mess with your brain.

I mean, your brain!

So what do I drink instead? Water, mainly. Coffee and tea. Red wine in the evenings, and a little beer. I acknowledge the latter two beverages aren't optimal either, but at least they're things people have been consuming for centuries. We can state their health effects with some confidence. Heck, you can even point to benefits when it comes to the red wine.

But when it comes to sugary drinks and diet sodas, even if you take these studies at face value, who really knows the effects for sure? Human beings have only been drinking soda for less than a century; diet soda for far less than that.

As the researchers themselves point out, "more research is needed to determine how--or if--these drinks actually damage the brain, and how much damage may be caused by underlying vascular disease or diabetes."

Again, it's those words: "actually damage the brain."

I'm no longer willing to take the risk, and so after reading these studies, I've sworn off soda. I'll be curious to hear in the comments how you react.