|Last update November 11, 2021, article reviewed & updated multiple times since August 8, 2001.|
What You Need to Know
How Does Excess Protein Turn Into Carbohydrates In The Body?
In our last discussion of protein and amino acids, the building blocks of proteins, we discussed the digestion of protein and the waste products produced in the body by the digestion and utilization of protein. I told you the important fact that the protein parts of every cell in the body are being destroyed continually, and need to be replaced continually. I pointed out that the blood contains amino acids at all times, and that the body is able to keep a fairly uniform balance of protein-building materials.
We also discussed the destruction of proteins in the body, which gives rise to two classes of waste products, nitrogenous wastes that contain nitrogen, primarily urea, and the non-nitrogenous wastes that don’t contain nitrogen. It is the non-nitrogenous waste products and the nitrogen balance in the body that we are going to talk about today.
Last time I promised you an early Halloween. Read on, friends.
Nitrogen Balance In The Body
When the building up and the breaking down of proteins in the body are equal, the amount of nitrogen eaten as protein is equal to that excreted in the form of nitrogenous waste products. This is called nitrogen balance, and except during pregnancy, this is the normal state of health. Since protein foods are the only source of nitrogen, all nitrogen waste products come from protein, and are, as we discussed last time, excreted by the kidneys. But when the loss of body proteins exceeds the synthesis of new proteins, there will be more nitrogenous waste products. This situation is called negative nitrogen balance.
Negative Nitrogen Balance
A negative nitrogen balance can be the result of either too much breakdown of protein or insufficient intake of protein. Recall from last time that we discussed how the body’s muscles can act as an emergency source of protein if insufficient amounts are eaten. In negative nitrogen balance, the body will break down its own muscle tissue and transport the amino acids gathered from that muscle destruction to the more vital organs. In long term, low-fat dieting without sufficient protein intake, the dieter will be in a state of negative nitrogen balance.
A long-continued or severe negative nitrogen balance is serious. In addition to consuming its own muscle protein, the body will begin to consume its own blood proteins to supply the proteins needed in the important organs because protein breakdown is continually taking place, as we have already discussed. Since antibodies will not be produced because there isn’t enough protein to build them, bacterial infections may result. Ultimately, the edema (tissue and abdominal swelling) of starvation that is seen in third world countries takes place, and if protein is not provided the person will die. The truly sad part is that there may be food lying all around the starving person, but no amount of fat or carbohydrate foods can solve the problem.
An excess of protein construction over protein destruction leads to an increase in living tissue. This is most evident during growth. The diet of a child (or of a pregnant mother) should be higher in protein than the diet of other adults because the creation of more living tissue is what is desired. If more protein is eaten than is needed, more nitrogen will be excreted, and a new balance will be established. Since increased amounts of nitrogen, wastes occur with increased protein intake, and since increased amounts also occur when there is a negative nitrogen balance with kidney disease, some people think there is a connection between the two causes of increased nitrogen waste in the urine. This leads to the still-unproven idea that too much protein in the diet causes kidney problems.
The healthy body has a strong tendency to be in nitrogen balance irrespective of the amount of protein eaten. As a result, the storage capability for protein in the body is very limited. Since it cannot be stored, and since the body does not throw it away as excess protein waste product, something else must happen to it.
The Protein Horror Story
Let’s back up a little and work our way back to this point. In our first discussion of protein, we learned that protein is made of carbon, hydrogen, and oxygen with the addition of the key ingredient nitrogen, and some other elements that don’t concern us right now. Think back to our discussion of carbohydrates. Carbohydrates, we learned, are made from carbon, hydrogen, and oxygen, but without nitrogen. When we write a chemical symbol for carbohydrate, we write CHO; when we write a chemical symbol for protein, we write CHON.
Among the many functions that take place in the liver is a process known as deamination (dee-amin-NATION). This consists of the removal of the nitrogen part of the amino acid. Remember that it is the nitrogen part of the protein that is crucial, and it is the nitrogen component that is the reason that we must eat protein. Now let’s look at deamination. It takes the CHON and removes the N.
Okay class, you clever girls and boys, tell me what we get when we remove N from CHON. We get CHO, right? And, what is CHO? It stands for carbohydrate!!
Excess Protein Turns Into Carbohydrates In The Body
Horror of horrors, this CHO portion of the protein is transformed into glucose in the liver in a process called gluconeogenesis (gluco-NEO-genesis; gluco=sugar; neo=new; genesis=creation). The glucose is then available to be transformed into glycogen by the liver, just like the glucose from “regular” carbohydrates that we discussed in previous articles. (If you are a new reader to these pages, you can find previous articles in here.)
We are already familiar with the fact that body fat comes from the storage of carbohydrates as fat. Remember that excess glucose is converted to body fat by the liver. So, the unhappy news is that, on average, about 58% by the weight of the protein we eat converts to glucose, and if the body doesn’t need that glucose for energy, it can and does convert it to body fat.
What this means is that of every 100 grams (3 1/2 ounces by weight) of protein you eat, about 58 grams of it becomes sugar. We are talking about the weight of the protein itself, not the weight of the protein food. A 3 1/2-ounce piece of meat weighs 100 grams, but it only contains about 20 or 25 grams of protein, depending on the kind of meat. The piece of meat would give about 10 to 14 grams of actual carbohydrates, not 58 grams. The fact is that, on average, 58% of all protein converts to sugar, and is therefore the major source of what we in the low carb world call hidden carbs.
But don’t panic! Join me next time when I will talk more about proteins and carbohydrates, and how to calculate the optimal amount of protein consumption.
The Science of Low-Carb & Keto Diets
|About Dr. Beth Gruber
Dr. Gruber is a graduate of the Southern California University of Health Sciences and has been in private chiropractic practice in Long Beach, California since 1964. She also received both a Bachelor’s Degree and a Master’s Degree from California State University at Long Beach. She has written on health-related subjects for over 30 years, for several different publications. She lives in Southern California with her husband of 33 years. Both she and her husband follow and live the low-carb lifestyle full time.
Dr. Beth Gruber talks about how protein works in the body. Article 10 of the Science of Low-Carb & Keto Diets series. The liver converts an average of 58% of the protein we eat into carbohydrates, and that the carbohydrates-from-protein are handled by the body just like "regular" carbohydrates. It is broken down into glucose by the simple water-related steps of hydrolysis; it is used for fuel to run the body; it is converted to glycogen and stored. If there…