UNC Healthy Heels

PART I: The Science 

Linked to obesity, regular sodas have gotten a pretty bad rap causing many to turn to diet soda as the healthier alternative for their sweet, fizzy fix. So…

Is diet soda really healthier than regular?   

In this blog, I will explore the science of diet soda to help answer this question. Let’s start by examining diet soda’s main ingredient: the sometimes-controversial, almost-too-good-to-be-true, calorie-free sweetener…

Are the artificial sweeteners in diet soda safe?

Concerns about the safety of artificial sweeteners have led to decades of public debate. The simple answer is YES; they are safe. The FDA lists all artificial sweeteners commercially used in the U.S. as safe. The artificial sweetener, saccharin, was linked to bladder cancer in labs rats in the 1970’s, prompting a warning label for all saccharin products, but the FDA rescinded the warning in 2000 after epidemiological studies showed no link between saccharin and bladder cancer in humans. Much of the concern about the artificial sweetener-cancer link stems from this early saccharin controversy.

Today, most diet drinks contain either aspartame or Splenda. Aspartame came under fire during the 1990’s with a study suggesting that it may be linked to brain tumors, but this was later disproved. In 2005, a European Food Safety Authority (EFSA) study found aspartame to be carcinogenic in rats. Both the FDA and EFSA have since reviewed the study and concluded that there is no evidence to support aspartame as a human carcinogen.

Besides this research, there is an abundance of anecdotal evidence questioning aspartame’s safety. For example, some consumer watchdog groups suggest that formaldehyde, a byproduct of aspartame, creates toxic effects in the body. But many naturally occurring foods, including fruit juice, also produce formaldehyde when broken down in the body as part of the natural digestion process with no adverse effect. Although no studies have measured side effects from aspartame consumption, some cited side effects include digestive problems, headaches, dizziness, and headaches.

What we do know for sure is that aspartame contains phenylalanine. People with the rare genetic disorder phenylketonuria (PKU) cannot break down this amino acid and should avoid aspartame.

Splenda, the other common diet soda sweetener, was approved as a general sweetener in 1999 after the FDA reviewed more than 100 studies examining its safety. So, looks like Splenda and aspartame are A-ok when it comes to cancer risk.

Now that cancer risk is off the table (for now, at least), let’s look at whether diet soda fulfills its intended purpose…

Does diet soda help with weight control?

Many soda drinkers choose diet to save calories in order to control their weight. But, recent research suggests that the artificial sweeteners in diet soda may actually lead to weight gain in addition to other metabolic disorders.

Susan Swithers, professor of behavioral neuroscience at Purdue University, just published a review of multiple studies on diet soda, weight, and metabolism. Here’s the gist of her findings:

• Multiple studies show a correlation between diet soda consumption and weight gain
• Artificial sweeteners are many times sweeter than sugar and trigger the release of certain hormones to digest sugar
• When no sugar shows up, the body gets confused and stops releasing as much of these hormones whenever it tastes something sweet, whether sugar or not
• This hormone disruption may cause increased sweet craving, weight gain, and reduced ability to process real sugar

She reports that these changes occur even in occasional diet soda drinkers (3 sodas a week) and that the metabolic disruption can lead to metabolic syndrome, Type II diabetes, and even heart disease. Wow. Is anyone else flashing to that scene in “Mean Girls” when Regina George finally discovers that her diet bars are actually the cause of her weight gain?

Before you blame diet coke for your Beyonce curves, keep in mind that Swithers’ article is based on a review of lots of studies, and it isn’t conclusive. Many of these studies show a correlation between diet soda and these negative health outcomes, but that does not mean that diet soda caused those things (correlation ≠ causation!). At the very least, these findings are food for thought, something to consider when staring down the cold drinks section of Student Stores.

Ok, let’s review….

1. Artificial sweeteners do not cause cancer in humans–YAY! They are safe to consume.

2. Aspartame is dangerous for folks with the genetic disorder PKU.

3. Artificial sweeteners in diet sodas are correlated with weight gain and some metabolic disorders, but we don’t know for sure if drinking diet soda causes them.

Stay tuned for PART II next Tuesday, when I will move beyond the physical realm–since we folks at Student Wellness like to think of health in the holistic sense–and examine the diet soda debate from a psychological perspective.