There are two answers to this question. Let me start with the simple one. When you eat protein, like a piece of steak, the cow protein is broken down by stomach acid and enzymes in the stomach into shorter chains of amino acids. Those shorter chains are then passes into the small intestine where enzymes chop them into even smaller pieces. They then stick to the wall of the small intestine, are chopped into individual amino acids and are absorbed into the blood stream. The individual cells will absorb the amino acids they need and make the proteins. (In this case moo protein to you protein.) Think of the amino acids as scrabble tiles. It makes no difference what word the tile was last used in when you want to use it for your word. The same goes for the amino acids, once they are digested it makes no difference where they came from. Before they are digested it is a different story.
There are complete proteins and incomplete proteins. Complete proteins contain all twenty of the amino acids while incomplete ones are missing some. Animal proteins like meat, eggs, and dairy are complete proteins while most plant proteins are incomplete. From this it would seem that animals are the best sources of protein. However, some animal products contain large amounts of saturated fats which are not good for you. Grain fed beef has an inflammatory effect on the body which is bad. So go with plant proteins? Soy contains compounds that mimic estrogen and some studies show negative effects while others don’t. Many other plant proteins are incomplete so you have to eat a combination to get all of the amino acids you need. So what to do?
- Eat small servings of lean meat 3oz. (about the size and thickness of the palm of your hand.)
- Limit your beef intake.
- Limit your processed meats even more. (Bologna, hot dogs, etc.)
- Eat a variety of plant sources.
- Choose low fat dairy anytime you can.
- This chart will tell the amounts of protein in many foods. PLEASE note the serving size many times we eat several servings at once. Also pay attention to the number of calories in a serving as well. http://www.todaysdietitian.com/pdf/webinars/ProteinContentofFoods.pdf
Remember you are aiming for about 30grams of protein each meal, breakfast especially. Choose the leanest meat and lowest fat dairy possible. Limit grain fed beef. Eat a variety of plant based protein sources.