Haemoglobin reveals your physical condition

Haemoglobin can tell us a lot about our health. Red blood cells transport oxygen to tissues more efficiently when haemoglobin levels are in order.

Anna does not always have the energy to climb the stairs. She loses her breath easily and sometimes suffers from chest pains and headaches. At times, she is tired without any obvious reason.

Meanwhile, Urho is full of energy. This is not surprising, as he has twice the volume of blood Anna has. Urho's red blood cells also contain a greater amount of the iron-rich protein haemoglobin that binds oxygen. In other words, his haemoglobin level is good.

The more blood you have, the more red blood cells there are to transport oxygen to the tissues. And oxygen is what the mitochondria in the cells need to generate energy, for example, for muscles and the brain.

“A high haemoglobin level makes moving easy,” says Juha Peltonen, research director at the University of Helsinki unit for sports and exercise medicine.

Many suffer from low levels of haemoglobin like Anna. According to estimates, as many as one-third of the global population suffers from anaemia of one type or another, the most common of which is iron deficiency anaemia. With low iron levels, red blood cells remain small and pale, and too few in number.

Iron deficiency anaemia is more common among women than men, since menstruation and pregnancies reduce iron levels. That is the reason for Anna’s tiredness as well.

Regular measurements?

The assessment of haemoglobin levels is perhaps the most common type of blood test. A blood sample taken from the tip of a finger is an easy way to determine haemoglobin levels.

“Haemoglobin is a good yardstick for measuring the body’s condition,” says Ulla Wartiovaara-Kautto, head of the Haematology Department at Helsinki University Hospital.

For women, the range of normal haemoglobin values is 117–155 grams per litre and, for men, 134–167 grams per litre. Levels below these reference values indicate anaemia, but haemoglobin levels that are too high are not good either. Haemoglobin makes the blood thicker, which may result in clots and infarctions.

If anaemia develops slowly, the body may adapt to it. However, anaemia can also be a sign of cancer or another serious disease.

As a consequence, should haemoglobin levels be routinely monitored in all people? Pregnant women have their blood tested regularly. Wartiovaara-Kautto believes comprehensive screening makes no sense since asymptomatic anaemia is a rare condition.

“If you have symptoms, the haemoglobin level should of course be measured without hesitation.”

Iron and vitamins

Anna’s mother Anneli is low on vitamin B and folate. She suffers from megaloblastic anaemia, which makes red blood cells larger than usual. At the same time, the cells contain a low amount of haemoglobin, which makes their oxygen-carrying capacity poor.

Megaloblastic anaemia is common among people over 60 years of age, and it can cause memory problems and affect the ability to walk.

In developing countries, iron deficiency anaemia is caused especially by malnutrition and parasites. In the West, it can be caused by malabsorption, such as coeliac disease, or bleeding in the digestive tract.

Iron is absorbed less efficiently from vegetables than meat, which is why Wartiovaara-Kautto recommends iron supplements to vegetarians. Coffee and dairy products inhibit iron absorption, while vitamin C boosts it.

While Anna uses iron supplements to help her anaemia, Anneli receives vitamin B12 as injections. The injections make Anneli’s red blood cells mature and condense normally again. Anneli had not noticed any symptoms of anaemia, and she is happy that the ailment was discovered before it had caused any serious damage.

Oxygen for athletes

Urho is preparing for an important sporting competition and wants to find a way to improve his performance. As a runner, he is particularly interested in oxygen uptake.

Mitochondria in cells use oxygen to fuel muscle cell functions. People in poor physical condition have fewer mitochondria, and their mitochondria have less capacity to provide energy. They may not be able to utilise all the oxygen transported in the blood.

For athletes, the picture looks different. Their performance is limited the most by insufficient oxygen supply for their muscle cells.

“Athletes’ muscles are sleeping giants. To wake up, they need oxygen,” says exercise physiologist Peltonen.

Before the oxygen gets into Urho’s cells, it has to be imported from the air into his lungs, the pulmonary alveoli and pulmonary capillaries, and further into the arteries, capillaries and eventually into the tissues. For most of the journey, oxygen hitches a ride in red blood cells. Each cell can transport hundreds of oxygen molecules at a time.

At rest, cells consume roughly 25% of the oxygen they receive, but high-intensity exercise can make them spend as much as 85% of the available oxygen.

Determining haemoglobin mass

Haemoglobin levels are normally measured by determining its concentration in a decilitre or litre of blood. That value provides an overview of the person's physical condition, but it is not a very good indicator of how much oxygen blood is able to carry.

“For athletes, considering the overall volume of blood and the mass of haemoglobin is more important,” Peltonen stresses.

Determining haemoglobin mass is more arduous than the traditional measurement technique. In the sports and exercise medicine special unit, it is examined by having the study subject inhale pure oxygen mixed with “a couple of cigarettes’ worth of carbon monoxide”, as Peltonen puts it.

Subsequently, the amount of carbon monoxide in the haemoglobin is determined from a blood sample. The greater the haemoglobin mass of the subject, the greater the amount of haemoglobin that binds carbon monoxide, correspondingly making its blood concentration smaller.

Exercise boosts haemoglobin levels

Similar to blood volume, total haemoglobin mass varies considerably by person, from 300 grams to two kilograms. In addition to the size of the person, the mass is affected by gender, genes, exercise activity and the environment. Out of environmental factors, particularly the altitude of a person’s place of residence has an impact.

Even casual sports enthusiasts can increase their blood volume and haemoglobin mass by exercising. Running, cycling, cross-country skiing and other endurance sports are a particularly good fit. First, the volume of plasma expands. After this, the total haemoglobin mass increases.

Peltonen estimates that people who have an active lifestyle can gain 100 grams of haemoglobin in a year, improving their oxygen uptake as well as their speed and endurance.

Where does this extra blood go?

“Blood vessels are flexible, and, besides, you could fit all of the blood in the body into one leg. Blood pressure distributes it all over the body and ensures there’s enough for all parts,” Peltonen says.

The power of high altitudes

Urho wonders if he should head to the hills. For athletes who have trained for a long time, increasing haemoglobin mass becomes difficult at sea level. This is why many competitive athletes spend time at high-altitude camps. With less oxygen in the air, the kidneys boost the production of the erythropoietin (EPO) hormone, which stimulates the formation of red blood cells.

According to Juha Peltonen, high-altitude training that is designed and implemented well can improve results as effectively as illegal doping. Indeed, the vast majority of endurance athletes regularly train at high altitudes. The unit for sports and exercise medicine assists endurance athletes in the Finnish national team in preparing for high-altitude training.

“When oxygen distribution is efficient, the level of performance may improve by a few percentage points. In sports, that can make the difference between first and 12th place,” Peltonen says.

However, care is needed in high altitudes.

“High-altitude training is not easy. The potential is great, but there is also the risk of ruining months of effective training.”

For Urho, that would be a nightmare.

Anna has no intention of running at high altitudes, but after fixing her haemoglobin level she will retrieve her exercise gear from the farthest corners of the cupboard. Maybe this winter she will have the energy for physical exercise! 

Depleting iron reserves

Deficiency in ferritin, the body’s stored iron, causes symptoms resembling anaemia in some people, even though their condition has not advanced to actual anaemia. In such cases, the cause underlying the ferritin deficiency should be identified and the deficiency corrected before it develops into anaemia. Ferritin deficiency is treated with iron tablets or drops. If the iron is absorbed poorly, one option is a therapeutic iron preparation administered intravenously.

The body’s iron reserves are measured by the concentration of ferritin in plasma. If the ferritin value is below 30 μg/l, there is reason to suspect iron deficiency. In athletes, the figure should be more than 50 μg/l.

Iron deficiency is common but does not cause symptoms in everyone. In 2019, the Finnish Red Cross Blood Service published a study on the iron stores of blood donors that showed that many study subjects had low iron reserves even though their haemoglobin levels were high enough for donating.

However, based on a related survey on health and lifestyle habits, the participants considered themselves to be just as healthy as other blood donors.

Anaemia and ethnic backgrounds

Anaemias connected to ethnicity, which occur among people with an immigrant background, are a new phenomenon for Finnish doctors. These anaemias are often misdiagnosed.

In the case of thalassaemia, for instance, red blood cells are small, which might make the doctor prescribe an iron supplement if they think the patient is suffering from iron deficiency anaemia. However, the situation may be the opposite: in thalassaemia patients, an excessive amount of iron easily accumulates in the body.

Currently, the treatment of anaemias associated with certain ethnic backgrounds has been centralised in a clinic specialised in rare haematological diseases at Helsinki University Hospital.

“We take a family-centred approach to treat hereditary haematological diseases since more than one family member usually has the same disease. It’s easier to engage teenagers in treatment when they don’t have to move from the paediatric department to the adults’ side,” says Ulla Wartiovaara-Kautto.

In sickle cell disease, which is caused by a gene defect, the patient's red blood cells are shaped like a crescent moon and break down prematurely. These cells form clots and scratch the walls of blood vessels, causing severe pain. In the worst cases, sickle cell disease is fatal.

The disease can be treated by carrying out blood transfusions once a month. However, a medication exists that enables people who suffer from the disease to live an almost normal life without transfusions. This treatment reduces the breakage of red blood cells and increases the production of spare haemoglobin.

The product is not on the reimbursement list for medicinal products of Social Insurance Institution of Finland, Kela, even though products essential for treating many other hereditary diseases are.

“The medication is not expensive, but for low-income patients, the expense can be overwhelming. Patients who cannot afford the medication can easily end up with a visit to intensive care. This is much more costly to society,” Wartiovaara-Kautto points out.

The article has been published in Finnish in the 9/2019 issue of the Yliopisto magazine. 

From bone marrow to blood vessels

In adults, red blood cells are formed in the marrows of the sternum, ilium and femur. In children, they are formed in all flat bones and, during the foetal period, in the liver and spleen. If a disease endangers the formation of red blood cells in bones, the adult liver and spleen can also start manufacturing them.

“The bone marrow can be understood as the childhood home of red blood cells. Their ‘mother’, an erythropoietic stem cell that divides, resides there. Both white and red blood cells as well as platelets are formed from the mother. The blood cells enter circulation only after they have matured,” says Wartiovaara-Kautto.

The diameter of a normal red blood cell is seven micrometres, and it is shaped like a biconcave disc. The mature red blood cells are the only human cell type without a nucleus. A third of the cell is composed of haemoglobin.

Each red blood cell contains hundreds of haemoglobin molecules, each of which binds four oxygen molecules. The life cycle of a red blood cell is 120 days, or roughly four months. In that time, it carries countless loads of oxygen from the lungs to the tissues.

The average volume of blood is approximately four litres in women and five in men. In large male athletes, the volume can be as high as 10 litres.

Blood circulates roughly four times through the entire body every minute. That means that the heart pumps out 15–30 litres of blood in the same timespan. The largest pumping volume of the heart ever measured in humans is over 40 litres per minute.

“That is a massive figure. Just try and fill four ten-litre buckets from the tap in a minute. It isn’t easy,” says Research Director Juha Peltonen.