I don't think you will find a scientific double blind study because
1. they cost money
2. manufacturers who fund a study hope to use the diet substance and have no interest in publishing negative business information
3. consumer advocates usually have hotter hot buttons than diet drinks.
You should be able to find lots of antedotal accounts, i.e. stories of how the substance effected one person/family/group. But genetics can have a huge effect on side effects.
Antedotally, we gave up on both soda and diet sodas for the following reasons:
1. they are addictive. Harder to give up on colas than smoking.
2. they cause hi-low cycling of moods and energy levels,
3. they increase appetite and so consume more calories than drinking equavalent non diet drink
4. they reinforce a drug addiction habit: I don't feel perfect, I will take some XYZ and I'll feel better.
5. they are not natural and thus less than best for our bodies
6. they increase headache frequency and durations.
7. they tend to increase long term problems with teeth and joints.
Your body chemistry is different, but those are the common results of a 2 culture family.
Best advice:
1. drink water,
2. if not water, add weak teas. Not too much or will dehydrate body. Watch for allergic reactions with teas. Celestial seasons is notorious for adding XYZ which may have an unexpected allergy reaction.
3. if not weak teas, try the mexican solution. Pour a small, about 1/8th at most, better is 1/10, or a good squirt of fruit juice in water.
4. If non of above, go with filtered water.
5. NB: Hot water works better than cold water in satisfying thirst.