The ongoing myth of diet soda/artificially sweetened consumable products being unhealthy has been popularized by popular and unreliable blogs and sites with little to no research to back their claims. Those that do include small amounts of evidence, often tend to be of an anecdotal nature. Example: 10 Reasons to Give up Diet Soda

Diet sodas typically include one or more of the following artificial sweeteners: Aspartame, Sucralose, Acesulfame-Potassium. These sweeteners provide a similar level of sweetness and sugary satisfaction as compared to sugar, but with a significantly lower caloric density. This can aid in weight loss as it provides a substantially lower calorie substitute to regular sugar infused sodas.

2 studies published almost a decade ago on the US National Library of Medicine attempt to conclude that diet sodas negatively effect the body, but are both flawed. (Studies 1, 2)

Although both studies provide evidence that their subjects have increased health risks such as diabetes and increased blood pressure after the period of drinking diet soda, they did not hold other important factors constant.

Firstly, the diet of the subjects were not recorded or controlled. This means that all the other factors that could have increased the health risks were not accounted for. They could have been eating more calorically dense foods, assuming that consuming the diet soda would offset the increase calories they consumed, they could have been eating more candy or exercising less. The list could go on...but simply put, if their diet was not controlled, how could the researchers expect to have an accurate and reliable conclusion?

A more reasonable explanation to the overall consensus of the media believing diet sodas are unhealthy is the fact that typically unhealthy or overweight people tend to make up the majority of the diet soda market.

However, more current (but also older) clinical research concludes that paired with a controlled diet, diet sodas do not negatively affect health. (Studies 1, 2, 3, 4, 5)

The only downside is the effect it has on dental health. Both diet and non diet sodas do pose a threat to dental health, but if maintained and cleaned regularly, it shall pose no threat. In this regard, regular sugary soft drinks do pose a greater threat to dental health as compared to diet sodas. (Studies 1, 2)

To conclude, diet soda is not unhealthy, and to be consumed with proper dental care. It can very well aid in weight loss as it provides a much less calorically dense alternative as compared to regular sugary sodas.