The non-essential amino acid glycine is needed to generate muscle tissue and also for the conversion of blood glucose into energy. It is referred to as being ‘non-essential’ because the body can manufacture its own glycine, and is therefore not an essential component of your diet. Other uses to which glycine is put by the body includes the maintenance of a healthy nervous system, and is necessary for the proper functioning of the digestive system.
Amino acids play three essential roles in the human body:
1. They are the building blocks of proteins: proteins comprise about half of the dry weight of the majority of your body cells, and without them there would be no life. They are produced using monomers known as amino acids, and there are about 20 different amino acids used to make the vast variety of proteins that make up the human body. Proteins are needed to form enzymes, the catalysts that permit the majority of chemical reactions within our bodies, and also genes, the building blocks of DNA.
2. More relevant here, amino acids play an important role in the production of ATP (adenosine triphosphate) from ADP (adenosine diphosphate) by phosphorylation with creatine phosphate. The more creatine phosphate available, the more ATP can be produced. Since ATP is the molecule responsible for the generation of energy, then the more ATP available the more energy is generated. Although creatine is available from many food sources, it is destroyed by cooking, and over half of what you use is made from the three amino acids, glycine, arginine and methionine. The energy produced in this way is very short-lived, and last only a few seconds – more on that later.
3. Glycine is heavily involved in the production of collagen, which is the substance that maintains the flexibility of your skin and other connective tissues while still maintaining their strength and firmness. Without glycine your skin would become slack due to the degrading effect of sunlight, free radicals and oxidation.
The non essential amino acid, glycine, is believed to offer other benefits to the human body, but it is the second of those above, the production of ATP, which interests us here. ATP is an extremely important nanomolecule, second in importance to the body only to DNA, and possibly also RNA since the two are linked. RNA makes copies of your DNA structure for use in cell division and growth.
When a cell expends energy for whatever reason, such as when I am typing this, or when your heart beats, or even when your liver synthesizes a protein, one of the phosphate groups is removed from the adenosine triphosphate molecule, and converts it to adenosine diphosphate (ADP). The ATP is then said to be ‘spent’, just as your energy is spent when you are tired and can exercise no more.
The ADP is then immediately reconverted to ATP in the mitochondria, a part of every cell in your body. A cell can contain hundreds, or even thousands, of mitochondria, the number depending upon that particular cell’s need for energy. Hence, cells in your muscles, or in your liver where most of the body’s chemistry takes place, contain thousands of mitochondria whereas those in your scalp contain a lot less. Once changed to ATP, a phosphate is again lost when energy is expended, and so the cycle continues.
Glucose is needed allow the ADP to be converted to ATP, hence the need for sugars, or the carbohydrates from which they are manufactured in your body. Each cell can contain up to a billion molecules of ATP, although the couch potatoes among you probably have a lot less! Your store of ATP molecules last about 2 to 5 seconds before being changed to ADP although more rapidly for athletes that expend a lot of energy. Then the energy stored in the form of glycogen in the liver kicks in for another 4 – 6 seconds.
Additionally, you cannot expend more energy that the (eventual) sugars that you take in your diet, which can be in the form of ordinary ‘sugar’ (sucrose), fruit (fructose), glucose, carbohydrates that are metabolized into sugars, or any other member of the sugar family (e.g. lactose, maltose, etc.).
Glycine is one of what are called glucogenic amino acids, which refers to their ability to provide glucose to the blood. Because it helps to maintain proper blood glucose levels, it is often prescribed for conditions that are caused by low glucose levels, such as hypoglycemia that shows symptoms of fatigue and tiredness, and also anemia and what is known as CFS (chronic fatigue syndrome).
The one activity of the human body, in fact that of any mammal, for which ATP is essential, is the heartbeat. Without that no mammal could survive, or any other creature that relies on a circulation system for life. The only reason you heart has to beat is to pump your blood around your body, and it is your blood that contains the oxygen and nutrients needed to sustain life. Your cardiovascular health relies on lots of ATP being available to power each and every heartbeat.
Analysis of the heart during the final stages of heart failure has revealed that there is a general decrease in the myocardial arginine: glycine amidinotraferase (AGAT) gene expression, which is indicative of the necessity of this enzyme for proper heart function. The enzyme is responsible for the first stage in the biosynthesis of creatine from glycine.
Creatine is well known to athletes, and while it is available naturally from some food sources, it can be destroyed during cooking, and at least 50% of the creatine needed by the body is produced in the liver, pancreas and kidneys. It is creatine phosphate that is broken down into creatine and phosphate, the latter of which is used by the mitochondria to regenerate ATP from ADP.
The study carried out on the reduced AGAT levels found in heart failure patients indicates the importance of glycine to heart health. Without a good supply of glycine, there will insufficient creatine produced biochemically to generate the phosphate needed to for the ATP to produce the energy required to keep the heart pumping with the required strength. The energy provided by the mitochondria is used locally by the cells in which it is produced, and within a few seconds of that production. As explained earlier, ATP stores are used up within 2 – 5 seconds, and glycogen stores within another 4 – 6 seconds.
That is why sprinters cannot keep running at maximum speed for more than around 10 seconds or so, because the immediate availability of glycine, and hence creatine, are insufficient to last longer than that. That is one reason why they have to finish those 100 meters as fast as possible, because otherwise they would run out of energy. Other than trying to win, of course!
However, when it comes to the heart, ATP stores are essential, and the cells in your heart require a constant supply of ATP from creatine, which itself depends upon your intake or biosynthesis of glycine. Since dietary sources are insufficient to meet all your needs, and destroyed by cooking, a glycine supplement is the only way to ensure a sufficient intake. You cannot undernourish your heart and remain healthy.
ATP biosynthesis is essential if that of glycine theoretically is not, but the fact that 50% of your glycine requirement has to be produced by your body and the other 50% is sensitive to heat during cooking, a supplement of glycine could be essential to many people.