The inspiration for this article comes from two absolute truths: One – you learn something new every day; and two – if you don’t know the answer it is best to say so rather than make something up! Recently I was asked a great question during a Nutrition Boot Camp workshop. I was discussing the importance of eating animal protein. I was asked if it is so important how do cows and other animals that don’t eat meat grow so large. I had never really thought about it, so it provided an excellent learning opportunity.

First, a little background. What is protein? It is one of the six core nutrients that we humans require for life (the others being fat, carbohydrates, vitamins, minerals, and water). Protein is the structural basis of our body. It builds and repairs tissues and cells. It makes our hormones, enzymes, neurotransmitters, and antibodies. As you can see, protein is pretty important stuff! And remember, our body is essentially one big chemical factory and these processes go on continuously. Therefore, we need a constant supply of protein which is why I recommend to my clients that they consume protein with each meal and that it is approximately 30-35% of their diet. One of the factors I believe behind all the chronic diseases, such as obesity, diabetes, cancer, and heart disease is that most people do not consume enough healthy protein. In fact, if you do the math of the government recommended 2000 calorie diet, it comes out to approximately 60% carbohydrate, 30% fat, and 10% protein. If you’d like to read more about the connection between high carbohydrate diets and disease I strongly recommend Gary Taubes book Good Calories, Bad Calories.

How do we get protein? It comes from both animal and plant sources. Animal sources include meat, fish, poultry, milk, cheese, and eggs. Plant sources include whole grains, legumes, nuts, and seeds. When we consume a “protein” it is broken down in our body to amino acids. Believe it or not, depending on what book you read you will get a different number for how many amino acids there actually are! But, for discussion purposes here we’ll use the number 23 with nine of them being classified as “essential”. Anytime you hear the word “essential” in nutrition means you have to eat it (your body does not make it). Animal proteins are considered complete proteins meaning they contain all the essential amino acids. Plant proteins are not, which is why you hear the famous “rice and beans” combination to provide a complete protein. People and animals that do not eat meat are therefore dependent upon getting the right mix of incomplete proteins from plant sources and mixing them together properly to build essential amino acids.

Now comes the big question – how do cows or other animals get complete proteins? Particularly since unlike humans they don’t have access to the Internet and all other kinds of sources to tell them exactly what foods to eat in what combinations so they can get the exact nutrients they need!

I did some research and found out some interesting facts. First, I came across a very succinct answer at Here’s a summary:

“Grass it mostly cellulose. And cows, like us, can’t digest cellulose. So where do cows get all their nutrients? Cows have four separate stomach compartments. The rumen (one of the compartments) serves as a fermentation vat where microorganisms, such as bacteria and protozoa, break down the feed (hay, water, saliva, etc.) These microbes break down the cellulose into energy sources that the cow can digest (volatile fatty acids), and build protein, which again, the cow can digest. The rumen is quite huge (about 160 liters), and in an average cow, there are about 100 times as many bacteria as there are humans on earth.”

Then I found another interesting fact. In nature grasses are not cleaned and purified. What do I mean by that? They contain small bugs, grubs, larvae, etc. that the animals consume along with the grass! These small bugs are complete proteins! So, many of these so called “herbivores” (plant only eating animals) may in fact be eating small animals on the plants!

Bernard Rosen, PhD is a Nutrition Consultant and Educator. He works with individuals, groups, and at corporations to create individualized nutrition and wellness programs. His office is in Thiensville. To learn more or to schedule an appointment, e-mail at, call (262) 389-9907 or go to