Is there such thing as too little sodium??

Yes. Im not an expert but I have been studying this. Your body needs a certain amount, I guess just dont add it to your food in huge amounts like me lol

It's possible to get too little salt, particularly if you're training really hard, as a certain level is required to rehydrate successfully. For instance, I'm somewhat prone to muscle cramps. On the advice of the nutritionist at the martial arts school I was training at, I raised the overall level of salt in my diet and made a point of eating either table salt or using rehydration salts whenever I got cramp.

Overall result: I no longer cramp during training and, as a nice bonus, I no longer wake up in the middle of the night with scream-inducing cramps in my calf muscles or feet.

This is very much a Your Mileage May Vary situation, though. Some people really do need to have very little salt in their diet and will experience serious negative health effects (most notably high blood pressure) if they over-do it. Meanwhile a handful of people require inordinately high levels to maintain both their physical and mental well-being (salt deficiency has been linked to depression, among other things).

Most people just need to eat an amount that's proportionate to the activity they're doing and that satisfies their body's needs, but it can take some trial and error and is subject to a fair bit of variance from person to person.

(Note: I have no training in medicine or nutrition, don't take my advice over that of trained professionals, etc., etc.).