Oxygen is crucial for several processes in your body. But if you want oxygen to reach your cells, you require iron. Iron is one of the key minerals, which greatly impacts your physical performance.
Iron is an integral part of hemoglobin, a molecule found in red blood cells, which takes part in transporting oxygen from the lungs into the organs through the bloodstream.
Iron is also found in the muscles in myoglobin, a molecule similar to hemoglobin. Myoglobin is responsible for the transport of oxygen within the muscle cell — from the cell membrane to the mitochondria, which require oxygen to produce energy.
In your body, iron is responsible for several processes, such as:
- body growth.
- neurological development,
- cell function,
- synthesis of certain hormones.
How much iron do you require, when must you be especially mindful of its intake, what affects iron absorption? Learn all this in this blog.
Daily iron requirements
A male body contains about 3.6 grams of iron, while the female body contains a little less. You lose iron every day, mostly by eliminating it through sweat and skin cells. Men lose only 1 milligram of iron per day, while women, due to menstrual bleeding, lose an additional 0.5 milligram.
The bioavailability of iron (the amount of iron your body can absorb) is limited and your body cannot absorb all the iron it gets from food. That's why your daily requirements of iron are much greater than the amount you lose.
The daily iron requirements for an averagely-active man are 10 mg, while due to blood loss during their period women need a little more, namely 15 mg.
Since exhausting physical activity drains iron stores more quickly due to an increased production of red blood cells, sweat, and tissue inflammation, active individuals have higher iron requirements — as their energy requirement increases, so does their iron requirement.
Your iron requirements also depend on the type of sport you practice, your exercise intensity, dietary habits, and individual physiological features.
The following groups of athletes are especially likely to develop iron deficiency:
- female athletes due to iron loss during menstruation;
- endurance athletes, as prolonged exercise leads to increased iron loss with sweat, urine, and digestion. Furthermore, such efforts increase oxygen consumption, which requires more hemoglobin to transfer oxygen into the muscles;
- athletes who train at high altitude — lack of oxygen at high altitudes increases production of red blood cells;
- athletes who mainly follow a vegetarian or vegan diet. Plant-origin foods contain non-heme iron, which has lower absorption rates than heme iron found in animal-origin foods;
- athletes with an insufficient energy intake;
- children and young athletes, as growth and body development further increase their iron requirements.
Iron deficiency
Since iron deficiency reduces the transport of oxygen, this leads to fatigue, increased risk of injury, and poor performance in training and races.
The symptoms of iron deficiency include:
- weakness,
- paleness,
- poor concentration,
- weakened immune system.
Iron deficiency usually develops when the body doesn't receive enough of this essential mineral from food, can't absorb it well, or loses more iron than it gets.
Some common causes of iron deficiency:
- Insufficient intake from food: Iron deficiency often occurs when you don't consume enough iron-rich foods. This is especially common for vegetarians and vegans.
- Poor absorption: Even if your iron intake is sufficient, you can develop iron deficiency if absorption in your body is not efficient enough. This often occurs in case of digestive issues, celiac disease, or Chron's disease.
- Increased requirements: Some groups of people have increased iron requirements. This includes pregnant women, lactating women, growing children, and athletes.
- Bleeding: Both internal bleeding or strong menstrual cycles in women cause iron loss and gradually lead to iron deficiency and disease — certain diseases, such as sickle cell anemia, influence iron levels in the blood.
Iron deficiency may reduce hemoglobin production. This can reduce the amount of oxygen transported to the muscles, resulting in a reduction of VO2 max and endurance.
If you want to increase your VO2 max with dietary supplements, check out our guide!
And if you're looking for a great iron supplement, Iron+ 4Endurance Pro contains iron bisglycinate, also known as chelated iron. This type of iron has high bioavailability and your body tolerates it well, which means it provides the best possible effect without unwanted side effects.
Iron+ 4Endurance Pro is the ideal source of iron for endurance athletes — high iron content without digestive issues.
Iron is essential for endurance athletes, especially female athletes. Iron deficiency, among other things, hinders your VO2 max, which is why you must be mindful of your iron intake.
Iron in foods
Iron in foods is found in two main forms: heme iron (from animal sources) and non-heme iron (from plant sources). Both forms are important for your dietary needs, but they differ in terms of bioavailability and absorption rates.
Heme iron:
- Source: Heme iron is found in animal sources, such as red meat, poultry, fish, and seafood.
- Absorption: Heme iron is better absorbed than non-heme iron.
- Bioavailability: Heme iron has better bioavailability and is more efficient in increasing body iron levels.
Non-heme iron:
- Source: Non-heme iron is found in plant sources, such as legumes, cereals, nuts, seeds, and vegetables, such as beetroot.
- Absorption: Non-heme iron has lower absorption rates than heme iron.
- Bioavailability: Non-heme has lower bioavailability than heme iron.
Iron food sources:
| Food | Iron content (mg) per 100 g |
| Raw beef liver | 9.75 g |
| Linseed | 8.20 g |
| Cocoa powder | 4.10 g |
| Oats | 2.76 g |
| Spinach | 2.62 g |
| Dried plums | 2.30 g |
| Buckwheat porridge | 2.11 g |
| Veal | 2.00 g |
| Beef thigh | 1.90 g |
| Egg | 1.83 g |
| Beetroot | 1.53 g |
| Rocket | 1.50 g |
| Wild blueberries | 0.74 g |
| Chicken breast, fillet | 0.64 g |
| Strawberries | 0.64 g |
| Turkey breast, fillet | 0.59 g |
| Kaki | 0.37 g |
| Farmed Atlantic salmon | 0.34 g |
| Farmed rainbow trout | 0.27 g |
When we talk about iron content in foods, which also applies to other nutrients, you must first consider how much of this food you regularly consume.
For example, linseed is on the top of the list in terms of iron content, but you rarely consume 100 grams of linseed in a meal, and in fact its consumption is much lower. It's easier to consume 200 grams of veal steak, which grants you about 4 mg of iron.
Don't forget that heme iron, found in foods of animal origin, has better absorption rates than non-heme iron, found in foods of plant origin.
Do you want to increase your iron levels? Try to consume more iron-rich foods.
Iron absorption
The absorption of iron is a complex process, and many factors can have a positive or a negative influence on iron absorption. Understanding these factors is essential to maintain adequate levels of iron in your body.
Several factors influence iron absorption, among which:
- Type of iron: As mentioned, foods contain two types of iron: heme and non-heme iron. Heme iron, found in foods of animal origin, has better absorption than non-heme iron, found in foods of plant origin.
- Vitamin C: Vitamin C (ascorbic acid) increases iron absorption in the intestine. That's why we recommend that when consuming iron-rich foods you also consume foods rich in vitamin C, such as citrus fruits, strawberries, paprika, and broccoli.
- Presence of animal protein: Protein in food can improve iron absorption.
- Calcium: Calcium from dairy products and other sources can reduce iron absorption.
- Phytates: Phytates or phytic acid, found in some plant sources, such as legumes, wholegrain cereals, and nuts, may reduce iron absorption.
- Oxalates: The oxalates found in plant food (such as spinach, chard, or rhubarb) may reduce iron absorption.
- Dietary fiber: A high intake of dietary fiber may influence iron absorption. But the effect depends on the type of dietary fiber and other factors.
- Medical conditions: Certain medical conditions, such as celiac diseases, Chron's disease, infection with the bacteria Helicobacter pylori, may reduce iron absorption.
- Certain medicaments: Medicaments may reduce iron absorption.
- Polyphenols: Polyphenols found in tea, coffee, cacao, red wine, certain vegetables, legumes, and soy protein may reduce iron absorption.
In case your iron levels are too low, you should ingest foods that boost iron absorption in combination with iron-rich foods or iron supplements.
For example, wash down a capsule of iron with a glass of lemonade. At the same time, when consuming iron, be careful to avoid foods that inhibit iron absorption.
| Boosts iron absorption | Inhibits iron absorption |
| vitamin C | calcium |
| vitamin A | phytic acid |
| animal protein | oxalates |
| heme iron boosts non-heme iron absorption | polyphenols |
| dietary fiber | |
| certain medical conditions | |
| certain medicaments |
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Ferritin
Ferritin is a protein in the body responsible for iron storage. Its role is to bind and store iron in the cells, mostly liver, spleen, and bone marrow. By doing so, ferritin maintains adequate blood iron levels.
Measuring blood ferritin levels is used to detect conditions related to blood iron levels. Low ferritin levels may indicate an iron deficiency, while high ferritin levels may indicate excessive storage of iron in the body.
Too much iron
Iron is essential for the optimal function of your body, but you can still consume too much of it. If you intake too much iron, you can cause the development of oxidative stress.
An excess of iron that is not used or stored remains free in the body. Free iron ions may damage your cells, DNA, and protein due to their oxidation reactions, which is linked to various chronic conditions, including cancer, hearth diseases, Alzheimer's disease, and diabetes.
Excessive intakes of iron may damage your digestive tract, liver, and pancreas and cause other cardiovascular diseases. But it's impossible to consume too much iron with food, as your body gets rid of excess iron.
On the other hand, you must be careful with iron supplements, as they allow you to consume too much iron too quickly, which can harm your body. This is why it's important to verify your blood iron levels with a blood test and consult your physician or dietician before supplementing iron.
Conclusion
Among many nutrients that play a key role in your endurance, iron is definitely one of the most important ones.
It is an essential mineral that performs several functions in your body, and it is especially important for athletes due to its role in oxygen transport, energy metabolism, and immune function.
Since athletes often have higher iron requirements and their nutrition, due to their high intake of carbohydrates during high-intensity training and races, is often poor in nutrients, you should consider supplementing iron, but not before running a blood test.
There are many iron supplements available on the market, but they differ greatly in terms of type of iron, iron content, and additional ingredients, which all affect iron absorption.
Iron+ 4Endurance Pro contains iron bisglycinate, also known as chelated iron. This type of iron has high bioavailability and your body tolerates it well, which means it provides the best possible effect without unwanted side effects.