Proteins: Molecular Wonders in Three Dimensions

I grew up in a solid middle-class family, largely of German descent, in a city of modest size in central Nebraska. Like a lot of such families, our diet was based on meat and potatoes. It was an unwritten but religiously observed law in our home that two meals each day would include both meat and potatoes. The meat was turkey twice a year, ham on occasion, chicken or pork from time to time, but mostly beef. The potatoes were usually boiled or boiled potatoes subsequently sliced and fried. My brother and I also drank a lot of whole milk, at least a quart a day each and frequently more (skim milk was available, but no one gave much thought to “reduced fat” or “low fat” milk back in those days). On farms, a lot of people just drank what the cows had on tap. Between the meat, potatoes, and the whole milk, we got a lot of protein in our diet, which is good; we also got a lot of saturated fat in our diet and that is not so good. Adequate protein in our diet is essential for good health. Proteins in our diet break down to provide essential amino acids. Amino acids are the building blocks of proteins. The amino acids that are essential in our diet are those that our bodies cannot make or cannot make in adequate quantity for optimal health. For dietary proteins, two things matter: amount and quality. The amount of protein is a simple quantitative matter; it is measured in grams per day. The amount you need depends on several factors: your gender, age, size, level of exercise and other physical activity, and whether you are pregnant or lactating, for example. The quality of protein is not so easy to evaluate. Getting the essential amino acids in your diet is more important than getting the others. The highest quality proteins are those that contain an abundance of all the essential amino acids. Meats and dairy products are among the best sources of high-quality proteins.