First, the reason that I went digging into this again is because I watched a video lecture from NIH Grand Rounds titled, Artificial Sweeteners and Obesity: More than an Association? The speaker was Kristina Rother, MD. You can see the presentation here.
In her presentation, Dr. Rother made mention of a "number"; the amount of aspartame or sucralose a person could consume every day for the rest of their life (based on body weight) and stay below the threshold for any negative side effect. I subsequently searched for this 'threshold' information, and then emailed the Food and Nutrition Information Center with the USDA to find it. I am going to share some links, but the main one - of which I have just been speaking - came with these instructions:
The Food and Agriculture Organization of the United Nations has an online, searchable database that lets you search for detailed information on Food Additives. If you search for a particular additive and then click on the PDF symbol in the “Specification” row, you will see the ADI value at the top of the PDF on that additive.
To get your answer about how much sweetener you can safely (according to available science) consume, you have to click on the PDF symbol. ADI stands for Acceptable Daily Intake.
I want to note, and you'll see it in the aspartame pamphlet, that some people have a genetic condition which prevents their body from adequately breaking down an amino acid in aspartame called phenylalanine. People with this condition cannot use aspartame (often sold in blue packets), but its the amino acid that is the problem not the aspartame. If you have this condition, you already know it; its quite serious.
Another concern that people have expressed with regard to aspartame is a story/myth about military personal serving in the middle east who drank diet soda and became ill. This was likely due, if even true, to the fact that aspartame is not a heat stable substance. You might have noticed that I use sucralose (yellow package) when I bake, and that is why.
If you have heard aspartame stories that sound terrifying, read this Snopes response written by an evaluator at the FDA.
The third most common artificial sweetener, is saccharin. I don't use saccharin (pink packets) because it is super, super sweet, not because I think I will get bladder cancer. I also don't use the more expensive sweeteners, stevia and truvia - I get plenty of fiber from whole grains and buying a sweetener because it has fiber seems silly to me.
The American Cancer Society and the National Cancer Institute both have webpages dedicated to artificial sweeteners and I find these organizations credible.
So here are the links that I found either on the USDA Food and Nutrition Information Center webpage or that were provided by email correspondence with nutrition information assistant Valerie Stoner.
To look up the Acceptable Daily Intake of food additives, such as aspartame, click here. You will have to search for the additive you are interested in and click on the pdf symbol.
To see the National Cancer Institute's fact sheet on artificial sweeteners and cancer, click here.
To see the American Cancer Society's aspartame information, click here.
The International Food Information Council also provides information on aspartame and sucralose.
I hope you find the information in these documents helpful. The decision to use artificial sweeteners is a personal one. Some people use them to avoid consuming excess amounts of sugar (in any form); and as discussed in a previous post, the amount considered 'in excess' is under review.