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Diet soda is sugar-free or sugar-reduced soda marketed to those that want to reduce sugar intake in soda, but find water too nasty and boring. To make diet soda taste sweet, even if they have minuscule sugar, companies rely on artificial sweeteners (such as aspartame, saccharin, and sucralose) or naturally-derived stevia. These sweeteners are many, many times sweeter than sugar, but they don't ever taste quite as good. These sweeteners, since they are not sugars, are often the source of problems people have with diet soda.
There are many types of diet soda but they all seem to taste the same. The black cans of Coke Zero and Pepsi Zero (we'll call them "Coke Zero") have been marketed as something that tastes like the original drink, better than the silver ones, and there are drinkers that swear that Coke Zero tastes better, but it doesn't appear that people know the difference between Diet Coke and Coke Zero.
Despite being very well studied, being used for 30 years, being deemed safe for consumption (except for people with the genetic disorder phenylketonuria) by more than 90 regulatory agencies around the world, and showing no evidence of risks in humans despite decades of usage, aspartame tends to be the go-to ingredient people hate about diet soda and the subject to conspiracies about the sweetener industry. Aspartame has been blamed for everything big and scary including Alzheimer's disease, cancer, diabetes, blindness, headaches, seizures, multiple sclerosis, dementia, strokes birth defects, and Gulf War syndrome. It's gotten so bad that Pepsi caved to public pressure and removed the ingredient.
There has been another circulated claim that drinking diet soda tricks the brain and deprives one of sugar despite drinking something sweet, so the body makes up for it by intensifying sugar cravings. Therefore according to the claim, people end up eating more sweet foods than if they just drank regular soda. This has been derived from a few studies that found a mere correlation between obese people and consuming diet drinks. Correlation does not demonstrate causation, and this hasn't been demonstrated in more controlled trials. In the absence of any obvious mechanism, it is hypothesised that the apparent correlation between diet soda and diabetic or pre-diabetic conditions is due to "residual confounding by other dietary behaviors, lifestyle factors, or demographic characteristics", i.e. it's not diet soda that is responsible but other factors that the study did not control for. Consuming diet soda to try to cut down sugar is a viable part of the effort to avoid the negative health consequences of too much sugar, and research shows that people who drink diet sodas as part of a calorie-controlled diet lose weight.
A similar, but somewhat more plausible, "backfire effect" mechanism hypothesis states that drinking diet soda tricks your brain into thinking you've consumed sugar, and so your endocrine system readies itself for the supposed incoming sugar assault by producing insulin. Since no sugar is actually forthcoming, your cells have to ignore this extra insulin, which reduces insulin sensitivity over time and eventually gives you Type 2 diabetes. Studies of this hypothesis show mixed results.
Better than water?
It is claimed by the diet soda industry that consuming diet soda is better than drinking water at promoting weight loss, with a 2014 University of Colorado study apparently showing this. However the study, which was funded by the diet soda industry, has been criticised: it failed to adequately control for all relevant factors, and the study forced people who normally drink diet soda to give up diet soda and drink water as well as pursuing other weight loss techniques, while the group which kept drinking diet soda in contrast had an easier time. Willpower is generally considered a finite resource, and it's really hard to give up lots of things at once; an experiment which forced people who don't drink diet soda to quit drinking regular-sugar Coke might have given a different result.
Diet soda and Mentos
Diet Coke and Mentos eruption is a cool and well-known phenomenon, and it works best with diet drinks because there's a pretty creamy brown color and you don't have to worry about the sugary residue that's left behind. No, this combination does not kill children. This is very ill-advised to ingest the two yourself, however. If you do, your mouth will be forced open and gas and frothing soda will spill out of your mouth, and there's a lot of physical discomfort involved.
There are also rumors about mixing Diet Coke with other things causing an explosion, including ham.
- Diet sodas cause strokes or dementia: as with other claims of bad effects, this has been shown by the occasional study, based on correlation but there's no obvious mechanism or evidence of causation.
- One-calorie drinks contain more calories than they claim: Snopes investigated the claim "Diet Coke (or Diet Pepsi) contains more calories than claimed, but the company gets away with the deception by paying a yearly fine" and unsurprisingly found it false.
- Diet Coke is somewhat effective as a spermicide: it can kill sperm but it's really not recommended. (It can probably kill goldfish too.)[citation NOT needed]
- Diet cola and other caffeinated drinks don't hydrate you: false, as with regular cola, tea, or coffee.
- Diet sodas are good for your teeth: false, while not as bad as regular sodas since they don't have sugar, they are still very acidic and will dissolve your lovely shiny enamel.
- Huffingon Post. (January 11, 2012). Diet Coke vs. Coca-Cola Zero: What's The Difference?. Retrieved August 25, 2019.
- Novella, S. (April 29, 2015). Pepsi Removing Aspartame. Science-Based Medicine. Retrieved August 25, 2019.
- Hall, Harriet. Artificial Sweeteners: Is Aspartame Safe?. Science-Based Medicine. Retrieved August 25, 2019.
- Kasprak, A. (October 31, 2108). Can Drinking One Diet Drink a Day Triple the Risk of Dementia and Strokes?. Snopes. Retrieved August 25, 2019.
- Bon Secours. (January 19, 2014).Drinking Diet Soda To Lose Weight May Backfire, Study Warns. Retrieved August 25, 2019.
- Novella, S. (July 19, 2017). New Review of Artificial Sweeteners. Science-Based Medicine. Retrieved August 25, 2019.
- Diet Soda Intake and Risk of Incident Metabolic Syndrome and Type 2 Diabetes in the Multi-Ethnic Study of Atherosclerosis (MESA), Jennifer A. Nettleton et al, Diabetes Care 2009 Apr; 32(4): 688-694. https://doi.org/10.2337/dc08-1799
- Diet Sodas Cause Weight Gain? Not so Fast, WebMD
- Healthline, How Artificial Sweeteners Affect Blood Sugar and Insulin
- Diet soda helps weight loss, industry-funded study finds, CNN, May 27, 2014
- Dispelling 3 diet soda myths, Fox News, October 27, 2015
- Mikkelson, D. (November 9, 2006). Mentos and Coke Death. Snopes. Retrieved August 25, 2019.
- Ham in Diet Coke Explodes?, Snopes.com
- Can Drinking One Diet Drink a Day Triple the Risk of Dementia and Strokes?, Snopes.com, 31 Oct 2018
- 1 Calorie Diet Sodas Rumor, Snopes.com, 26 Aug 2013
- Can Coca-Cola Prevent Pregnancy?, Snopes.com
- Debunking Diet Soda Myths, Calorie Control Council (warning: trade body so don't entirely trust them, but their references seem to check out)
- Sugar Free Drinks: Are They Safe For Teeth?, Colgate