system
Given the following post, respond as if you're commenting on Reddit:
human
Why are potassium supplements so regulated ?

So a grown male should get around 4500mg of potassium a day. 
When I was looking for supplements I noticed that most of them only have around 50-100mg per pill and found out that it is because set regulations from the FDA.


I get that too much potassium can be lethal, but I don't understand where the logic in regulating the supplement is, when you could just eat 200 grams of pistachios and get 40 times the amount of a normal supplement dose. 
Wouldn't that be equally dangerous ? Could you kill yourself if you eat a lot of spinach, pistachios and avocados for example ?
gpt
Quite simply, the 50-100mg potassium supplements are not likely to increase your potassium level by any biologically relevant amount, and that's totally intentional.

Any potassium pill large enough to measurably raise your serum potassium is restricted to prescription-only, because it's potentially deadly. A lot of older people have poor kidney function. High potassium can be very rapidly fatal and if you can't pee out the potassium you're in trouble.

So you can get a 10 mEq (750mg) or 20 mEq (1,500mg) potassium pill, but it'll be a prescription.

Taking 20 mEq (1,500mg) of potassium in pill form is much more deadly than eating 1500mg of potassium in avocado or potato or pistachio form. Pills are absorbed into your body very rapidly, while foods are digested slowly, so with food you have more time to get rid of excess K. (and your body may or may not even absorb all of the K in a solid-food meal)