What I learned about proteins

In my Introductory Nutrition class this week, we learned all about proteins. I use the plural term because the singular protein is misleading – there are possibly unlimited quantities of unique types of proteins in living things. Most of the proteins in humans are made from combinations of only 20 amino acids. Of those twenty we usually hear about the 9 Essential amino acids, which are:

  • histidine
  • isoleucine
  • leucine
  • lysine
  • methionine
  • phenylalanine
  • threonine
  • tryptophan
  • valine

You’ve probably heard of two of the popular ones: phenylalanine in energy drinks, and tryptophan in your turkey on Thanksgiving (but not in your Tofurkey if you’re a Veg.). The nine are called essential because you need to get them from food sources since they aren’t manufactured in the body. The body makes the remaining 11 of the 20, so these are Nonessential (alanine, arginine, asparagine, aspartic acid, cysteine, glutamic acid, glutamine, glycine, proline, serine, tyrosine). Unless you have some sort of deficiency that your doctor has told you about, you don’t need to take a vitamin for any of those nonessential ones.

Proteins, like carbs and fats, contain carbon, hydrogen, and oxygen, but unlike those two nutrients, proteins also contain nitrogen and their structure is decided by DNA. Proteins will “uncoil and lose their shape and function when they are exposed to heat, acids, bases, heavy metals, alcohol, and other damaging substances”.1 This is called denaturation. Some examples are when egg whites are whipped, when milk mixes with another acid like lemon juice, and when eggs and meat are cooked.

Proteins function as they are supposed to function when there is sufficient carbohydrates and fat. When there is not enough energy in our diet from carbohydrates, our bodies have to use proteins for energy. That means those proteins are being taken away from their job of building new proteins. So it seems backwards to believe that more protein in the diet means more protein for our bodies. The more protein we give our body (over the daily requirement), the less protein gets created because the already-present proteins lost their jobs and got new ones.

While I’m on the topic of carbs vs. proteins: when you don’t consume enough carbs, the body produces an alternative fuel called ketones and your body goes into ketoacidosis. This causes dehydration and bad breath (smells like nail polish remover) and creates a highly acidic environment, which breaks down our immune system, leaving our bodies wide open for bacteria and viruses to grab hold. High acidity messes up basic body functions, causes loss of lean body mass, and damages many body tissues. I quote from my textbook: “untreated ketoacidosis can be fatal”1. When there are too few carbohydrates our body takes amino acids from the blood, muscles, heart, liver, and kidneys. Doing this over a long period of time “can cause serious, possibly irreversable, damage to these organs”1.

Incomplete proteins are ones in our diets that don’t have all essential amino acids. Complete proteins are ones that do. Vegetarians and vegans know that they have to combine certain proteins to make a complete one. Beans + rice are a complete protein because the amino acids that beans lack, rice has, and vice versa. Soybeans themselves are complete, and therefore tofu and tempeh, as are quinoa (pronounced keen-wah) and amaranth and buckwheat. You don’t have to eat a complete protein in one sitting, though, you could eat the rice as a snack and then the beans as dinner and that would still give your body the complete protein it needs for the day. Other good complete protein examples are these below, and they are called complementary proteins:

  • rice + lentils
  • rice + black-eyed peas
  • hummus (garbanzos + sesame seeds)
  • peanut butter + bread (this is super good news for me…PBJ!)
  • barley + letil soup
  • corn tortilla + beans
  • spinach salad + pine nuts + kidney beans
  • lentil soup + slivered almonds
  • sesame seeds + mixed bean salad

How much protein should you eat? For most people, it’s .8g per kg of body weight, so take your weight, divide by 2.2 and that gives you how much you weigh in kilograms. Then take that and multiply it by .8 and that tells you how many grams of protein you need. Here’s mine:

120lbs ÷ 2.2 = 54.5 kg
54.5 kg × .8 = 43.6

Remember when I blogged about that software program that tracks my nutrients? I never have a hard time getting in my protein for a given day, and I actually easily go over 43.6 grams on a regular basis. It’s important not to go over your amount if you are not bodybuilding, training for marathons, or doing some other kind of rigorous activity every day. My textbook says that on average, American women eat 65-70g/day while men eat 88-110g/day, which is more than adequate.

Men’s and athletic magazines claim you have to take amino acid supplements to build muscle and gain weight. Not true: “there is little evidence that taking individual amino acids or protein supplements orally can build muscle or improve strength2; and because this stuff is so expensive and you are already getting 1.5-2 times as much protein as you already need, save your money and stop getting the supplements, you don’t need them! Too much protein can be harmful: “three health conditions that have received particular attention are heart disease, bone loss, and kidney disease1.

You don’t have to worry about too little protein — that is shown in diseases like marasmus or kwashiorkor – where the children have swollen bellies. You don’t see that in America, do you? So stop fretting about getting enough protein; even vegetarians and vegans aren’t deficient!


1. Thompson, Janice & Manore, Melinda. Nutrition: An Applied Approach, 3rd Ed. Copyright (c) 2012 Pearson Education, Inc.
2. Manore, M. M, N.L. Meyer, and J. Thompson. Sport Nutrition for Health Performance, 2nd Ed. Copyright (c) 2009 Human Kinetics.


One response to this post.

  1. I AM OBSESSED WITH PROTEIN! HA HA! I eat far too much but oh well.


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