Total protein: what the test shows and why it matters for athletes
Total protein is one of the simplest and oldest indicators of a biochemical blood test. For a person who trains and monitors protein intake, the name sounds intriguing: it seems the test should show whether there is enough protein in the diet. In reality it tells about something else — about water balance, the immune system, the liver and kidneys. The editorial team examines what this indicator consists of and how to use it.
What the total protein test measures
Total protein is the summed concentration of all proteins in blood serum. They include hundreds of different molecules: transport proteins, immunoglobulins (antibodies), coagulation factors, enzymes, hormones of a protein nature, acute-phase inflammation proteins. However, the bulk is made up by two groups — albumin and globulins.
In most laboratories the reference ranges of total protein for adults lie approximately in the range of 60–85 g/L; the specific values are stated on the form. The indicator is measured mostly by the biuret method, based on the reaction of peptide bonds with copper salts — it is simple, cheap and well standardized.
Blood proteins perform a multitude of functions: they maintain oncotic pressure and hold water in the vessels, transport hormones, drugs, minerals and lipids, provide immune defense and blood coagulation, and maintain the acid-base balance. Therefore total protein is an integral indicator that reflects the state of several systems at once.
At the same time, precisely because of its integral nature, total protein rarely gives a specific answer. A change in one fraction may be compensated by another: for example, a decrease in albumin in chronic inflammation is often accompanied by a rise in globulins, and the total number stays within the norm.
Albumin, globulins and the A/G ratio
To make total protein more informative, it is supplemented with albumin. The difference between them is called globulins, and the ratio of albumin to globulins — the A/G ratio. These calculated indicators can be obtained at no additional cost from an ordinary biochemical analysis.
| Indicator | How it is obtained | What it reflects |
|---|---|---|
| Total protein | Measured directly | The summed concentration of proteins, hydration status |
| Albumin | Measured directly | The synthetic function of the liver, inflammation, protein losses |
| Globulins | Total protein minus albumin | Mainly immunoglobulins and inflammation proteins |
| A/G ratio | Albumin / globulins | The balance between fractions; usually greater than one |
Globulins are a heterogeneous group. They include alpha globulins (among which there are many acute-phase proteins), beta globulins (in particular transferrin, which carries iron) and gamma globulins, the main part of which is made up by immunoglobulins. Therefore an increase in globulins often points to activation of the immune system.
A reduced A/G ratio can be the result of either a decrease in albumin or an increase in globulins. The doctor assesses which of the parts has changed and, taking this into account, decides whether additional studies are needed.
Important: the A/G ratio on its own, without context, has no diagnostic value. It only helps to notice an imbalance that is worth explaining.
Protein electrophoresis: when a breakdown is needed
If total protein or globulins deviate noticeably from the norm without an obvious cause, the doctor may order serum protein electrophoresis. This method separates the proteins in an electric field into fractions, and the result looks like a curve with several peaks.
Each fraction changes in certain conditions. The alpha fractions rise in acute inflammation, the beta — in particular in iron deficiency due to an increase in transferrin, while the gamma fraction rises in chronic infections, autoimmune diseases and liver diseases.
Of special significance is a narrow «sharp» peak in the zone of the gamma or beta globulins — the so-called M-spike, or monoclonal protein. It may indicate the proliferation of a single clone of plasma cells. The diagnostic criteria for such conditions, in particular myeloma, are established by the International Myeloma Working Group (Rajkumar et al., 2014).
For young healthy athletes electrophoresis is not needed routinely. But it is worth remembering: if a person has high total protein without dehydration or pronouncedly elevated globulins, the doctor may propose precisely this simple test.
Total protein in athletes
The most common misconception is that total protein in the blood shows whether the athlete eats enough protein. The ASPEN position stand (Evans et al., 2021) emphasizes that plasma proteins are not reliable markers of nutrition: they depend far more on inflammation, hydration, the liver and kidneys than on the diet.
Protein needs for people who train are determined by body mass and goals, not by a blood test. The ISSN position stand (Jäger et al., 2017) recommends for most physically active people approximately 1.4–2.0 g of protein per kilogram of body mass per day, distributing it evenly between meals. A blood test is not needed for this.
Instead, training substantially affects protein concentration through the water balance. After intense work, in the heat, when cutting weight, the plasma volume decreases and total protein temporarily rises. In those trained for endurance, on the contrary, an increased plasma volume may give a slightly lower concentration at rest (Convertino, 1991).
- Pre-season screening:total protein and albumin as part of basic biochemistry.
- Assessment of hydration:together with hematocrit, sodium, urea.
- Frequent infections, chronic inflammation:globulins and the A/G ratio as an additional hint.
- Taking drugs with a load on the liver:protein indicators as part of monitoring the synthetic function.
Preparation for the test and typical mistakes
Total protein is more sensitive to the conditions of taking blood than many other biochemical indicators. Body position, the duration of tourniquet application and hydration can change the result to such an extent that it goes beyond the norm in a healthy person.
- Give blood in the morning, on an empty stomach, after a day without intense training.
- Drink water as usual, do not allow dehydration and do not drink a large volume of fluid immediately before the test.
- Sit for 10–15 minutes before blood is drawn: in an upright position the concentration of proteins rises.
- Avoid prolonged application of the tourniquet and «working the fist» during the draw.
- Compare results from a single laboratory.
One of the typical mistakes is trying to «fix» low total protein by increasing protein in the diet on the eve of the test. Short-term changes in nutrition have virtually no effect on the indicator, and the cause of the deviation must be sought elsewhere.
The second mistake is not paying attention to a normal total protein value with an altered albumin. It is precisely the combination of the two indicators and the calculated globulins that gives the most information; a single total figure can conceal substantial changes.
Editorial conclusions
Total protein is the summed concentration of all serum proteins, the basis of which is made up by albumin and globulins. By calculating globulins and the A/G ratio, one can obtain more information at no additional cost.
In athletes the indicator depends most of all on hydration and the conditions of taking blood, not on the amount of protein in the diet. Protein needs are determined by body mass and goals.
Persistent deviations of total protein or globulins without an obvious explanation are grounds for discussing additional studies with a doctor, in particular protein electrophoresis.
We also recommend reading our materials on the causes of total protein deviations from normal, on albumin in an athlete's test, and on protein needs during strength training.
References
- Evans DC, Corkins MR, Malone A, et al. The use of visceral proteins as nutrition markers: an ASPEN position paper. Nutr Clin Pract. 2021;36(1):22–28.
- Jäger R, Kerksick CM, Campbell BI, et al. International Society of Sports Nutrition position stand: protein and exercise. J Int Soc Sports Nutr. 2017;14:20.
- Convertino VA. Blood volume: its adaptation to endurance training. Med Sci Sports Exerc. 1991;23(12):1338–1348.
- Rajkumar SV, Dimopoulos MA, Palumbo A, et al. International Myeloma Working Group updated criteria for the diagnosis of multiple myeloma. Lancet Oncol. 2014;15(12):e538–e548.
- Sanchis-Gomar F, Lippi G. Physical activity – an important preanalytical variable. Biochem Med (Zagreb). 2014;24(1):68–79.
- Kratz A, Lewandrowski KB, Siegel AJ, et al. Effect of marathon running on hematologic and biochemical laboratory parameters, including cardiac markers. Am J Clin Pathol. 2002;118(6):856–863.
- Rifai N, Horvath AR, Wittwer CT (eds). Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. Elsevier.
Andriy Melnyk
A strength-sports coach and author of programs for beginner and intermediate levels. Writes about training planning.
