Yes. Anything more than 2000 mg, aka two freaking grams, is likely to cause diarrhea. Because that’s the symptom of a Vit C overdose. It will cause your body to flush water and with it other water soluble vitamins. Unless you are lactating or a blood test says you need more there is no reason to consume more than 120 mg a day. And with the Standard American Diet [SAD] you will get plenty of vit c because so many things are fortified with C that not getting the RDA is very difficult.
So by taking 3 grams a day you, waste money, flush other vitamins potentially creating new issues, spend too much time on the pot.
Vit C is clinically proven to prevent scurvy. And that’s about it. Its benefits are extremely over stated by people trying to take your money. Airborne is a scam.