Nutrasweet (aspartame) is the most prevalent sweetener in soda. And it is a known neurotoxin; people with PKU cannot break it down and must eat a special diet until they are mature; when the issues moderate, but do not go away. There's a PKU warning on sodas with aspartame.

In the large quantities used to sweeten soda, it is not beyond the realm of possibility that it could trigger similar symptoms in vulnerable people without PKU. For years, stories of severe headache and epilepsy triggering in people without known issues have been making the rounds and shouted down.

But there's a lot of money in aspartame. The person who worked for the company who makes it, G D Searle, guided it through the FDA and then rose high in government afterward: Donald Rumsfeld.

Would such an alliance suppress bad side effects of a highly lucrative chemical to make more money for themselves?

Such a question answers itself.