Grass-fed whey protein is derived from the milk of grass-fed cows, as opposed to conventional whey protein which comes from cows that may be fed grains or other feeds. The idea behind grass-fed whey is that the cows are raised on a natural diet of grass, which researcher believe leads to a healthier and more nutrient-rich milk.

Advocates of grass-fed whey claim that it contains higher levels of certain nutrients like omega-3 fatty acids and conjugated linoleic acid (CLA), which are beneficial for health. Additionally, grass-fed whey may have higher levels of certain vitamins and minerals due to the cows' diet.