The bottom line: "Whey protein is a good source of protein, but most of us do not need to worry about eating more protein," Majumdar says. When taken in the recommended dose, whey protein is generally safe to consume, according to the Mayo Clinic . But there can be potential side effects, from abnormal heart rhythms, to stomach or intestine symptoms, so be careful if you're taking it for the first time. "If someone has a history of kidney stones, they may put themselves more at risk when consuming a diet high in animal protein , including whey," Majumdar says. And if you're someone who has a milk allergy, then you should avoid whey, because it is milk, after all.