Examining Diet Soda

Drinking diet soda instead of regular soda is like smoking cigarettes to avoid taking meth. It doesn't make sense. At least, that's how I feel now. After buying a few Coke Zeros recently, I thought I would research the health implications of diet sodas and was surprised by what I found. 

More Diet Soda = More Obesity. And Diabetes.

Sharon Fowler, MPH, and her colleagues at the University of Texas Health Science Center-San Antonio collected data on consumers of diet soda for 8 years and presented their findings at the annual meeting of the American Diabetes Association in San Diego. The surprise finding was that those drinking only diet sodas had a much higher prevalence of obesity than those who drank the sugary versions of the soda. As Fowler tells WebMD, "There was a 41% increase in risk of being overweight for every can or bottle of diet soft drink a person consumes each day" [Source 1]. Concerning diabetes, in a study performed by the Journal of American Medicine, the daily consumption of diet soda was associated with a 67% increased risk of developing type 2 diabetes. 

The authors of the study did note that diet soda consumption wasn't likely the primary cause of the weight gain. But not only does diet soda have this high degree of correlation to obesity, it can also be unhealthy itself and lead to poor dietary decisions. To understand this, we should take a closer look at the main ingredient of diet drinks- Aspartame.

Aspartame: what is it? 

Two forms of Aspartame

Aspartame, the main sweetener in U.S. diet drinks, is distributed under several trade names- such as NutraSweet® and Equal® -and is approximately 200 times sweeter than sugar. So little of it is necessary to achieve a sweet taste within a beverage that it's caloric contribution is negligible. Upon ingestion, aspartame is catabolized into smaller molecular components, principally aspartic acid, phenylalanine, and methanol. Whereas phenylalanine and aspartic acid are both commonly encountered naturally in the body (the former is an essential amino acid in mammals), methanol is toxic and only 10mL of it will cause blindness while 100mL can cause death. Is the concentration of methanol resulting from aspartame metabolism unhealthy? Very likely not, but methanol is there, and that's a health concern to be aware of. 

In a survey of U.S. consumers performed by the FDA, the average aspartame intake was found to be approximately 200mg per day, or, 7% of the ADI (with ADI essentially being the recommended maximum daily consumption allowed to avoid health risk). A widespread controversy surrounding aspartame is that it's linked to an increased risk of various cancers. In a study published in 2006, however, the National Cancer Institute compared individuals who consumed aspartame-containing beverages to those who didn't. They found that increasing levels of aspartame consumption were not correlated with any risk of lymphomas, leukemias, or brain tumors in men or women.

My conclusions on aspartame- it seems like a perfectly acceptable artificial sweetener except for the fact that it's metabolized into methanol. Even though the quantity of methanol would likely be negligible, it's a toxic chemical that I want no part in voluntarily consuming.

So, despite my aversion to methanol consumption, the trial of diet soda seems to pass the aspartame test. But what about the affect of diet drinks on one's dietary choices.

Diet Soda: same great soda taste, but, well, even more calories. Just in a different form.

The main point of this entire blog entry is to reveal the hypocritical nature of diet soda consumption. There's a documented "Sweet Tooth" Syndrome induced by diet soda consumption wherein a person is more inclined to desire and consume sugary foods following diet coke consumption. Though the Diet Coke in your hand may have zero calories, the cookie likely to follow it has quite a few.

In a paper published by Behavioral Neuroscience, adult male Sprague-Dawley rats were given a differential experience in terms of foods provided with varying sweetness and caloric content. Here's the quote:

 "We found that reducing the correlation between sweet taste and the caloric content of foods using artificial sweeteners in rats resulted in increased caloric intake, increased body weight, and increased adiposity, as well as diminished caloric compensation and blunted thermic responses to sweet-tasting diets. These results suggest that consumption of products containing artificial sweeteners may lead to increased body weight and obesity by interfering with fundamental homeostatic, physiological processes."

The effect is similar in humans. In a study performed by the University of California- San Diego, 12 women were scanned by functional MRI while sipping water sweetened with either real sugar (sucralose) or artificial sweetener (sucralose). Though the women's palates couldn't tell the difference (sucrose and sucralose are registered the same by taste buds) the brain could register a difference. In the study, the sugar activated the pleasure-related regions of the brain more intensely than Splenda. To paraphrase, the artificial sweeteners got the brain all excited, but didn't deliver the goods. Another study by the researchers found a similar effect, where rats fed yogurt with real sugar and artificially-sweetened sugar consumed much more of the latter. They suspect that the sweeteners inhibit the brain's ability to regulate its caloric consumption. 

In addition, as anyone who regularly consumes diet soda will tell you, they're highly addictive. A fairly high concentration of caffeine combined with the seductive claim of being a zero-calorie indulgence can lead individuals to consume several daily. A study was performed where rats were fed artificial sweeteners in order to elucidate the addictive nature of the sweeteners. Not only did the rodents gain weight to the point of obesity, when given the option of consuming cocaine or diet soda, they preferred the... diet sodas!

Finally, though diet soda may replace regular soda in the diet, it is itself replacing actually healthy beverages like water. Try obtaining your caffeine fix from healthier sources, like coffee or tea, and stay away from diet soda.

Sources:

[1] Denoon, Daniel J. "Drink More Diet Soda, Gain More Weight?" http://www.webmd.com/diet/news/20050613/drink-more-diet-soda-gain-more-weight . WebMD.com

[2] Better Health: Smart Health Commentary. "Do Diet Sodas Make You Fat?" http://getbetterhealth.com/do-diet-sodas-make-you-fat/2009.12.21#more-13550

[3] Scientific American. "Artificial Sweeteners Confound the Brain- May Lead to Diet Disaster." http://www.scientificamerican.com/article.cfm?id=artificial-sweeteners-confound-the-brain