For me, diet soda is not good for our health. The thing is that people are getting used to it since it is very tasty not knowing its long term effects. I had stop drinking diet soda and soda itself last 2014, and won’t ever drink it. Diabetes and other autoimmune diseases are increasing and the main culprit is sugar, eventhough the label of the soda is zero sugar, do not be fooled by their marketing strategies, there is still sugar in that and it is more harmful than normal sugar and it comes in the form asparteme and high fructose corn syrup. I remembered reading an article online wherein there is a location in Mexico wherein all the people are diabetic simply because the water is expensive compared to the soda drink. Hopefully, people would wake up that we should not let our bodies depend or hunger/urge for soda drinks, and if they do, take it moderately and have lots of bodily movements and exercise.
Although I don't think it has any serious health consequences, but I still have reservation. As it does add to weight gain and also it weakens the bone as per the expert. Further I must say that why not we stick to natural form of sugar and when it comes to diet. Why we can not have organic and natural way to stick to. It must be noted that the more synthetic food you take, the more complex the mechanism of the body will be the and the mechanism of the body may not be able to read properly to the dietary intake and it may result in issues like weight gain, over-eating etc.
Be it sweeteners, soda or any other stuff that we take, are all artificial and not the natural and hence it adds complexity to the body and it may not find a way to properly absorb into out body. So although severe risk like cancer by these food may be low or rare, but the complexity will likely develop by taking this form of diet.