Just like how grass fed, organic, and pasture-raised meats are more nutritious (and more eco-friendly), the same goes for whey protein powder. What a cow eats impacts the nutritional content of its milk and meat.
Commercially raised cows (as opposed to grass fed) are fed grains for the majority of their life in order to quickly (and unnaturally) fatten them up.
Aside from unsanitary and inhumane conditions that are usually the (sad) reality of these types of animal feedlots, it also produces meat and milk that have a different fatty acid profile, not to mention certain micronutrient differences.
Main Nutritional Differences
The number one nutritional difference of grass fed whey vs regular whey is in the fatty acid composition.
Grass fed whey contains more omega 3 fatty acids (known for being anti-inflammatory), while grain-fed whey is generally higher in omega 6’s. A diet excessively high in omega 6 fatty acids (as is the case in a typical American diet) has been linked with a myriad of chronic and degenerative diseases rampant in today’s society.
Grass fed beef and whey are also higher in conjugated linoleic acid (CLA), which is a type of omega 6 fatty acid known to help reduce body fat.
There is some disagreement among Nutritionists as to whether or not grass-fed whey is worth the extra cost, and many claim that it is. Even aside from the nutritional differences, it is commonly understood and accepted that whey from grass-fed cows is better for the environment and superior in terms of the conditions in which the cows live.