Iron

The term myoglobin is related to iron. What does it mean?

Myoglobin is a muscle protein that, in addition to its protein component, contains an organic nitrogen compound heme, in which a divalent iron atom is bound. The main function of myoglobin is to transport oxygen from the blood to the mitochondria, where cellular oxidation takes place. Iron in myoglobin represents approximately 10% of its total content in the organism.

You write that iron from plant sources is poorly absorbed. I am interested in how poorly, because, for example, quinoa or millet seem to be excellent sources of iron.

When considering the individual components contained in food, it is necessary to distinguish the chemical form in which they are present and the other substances with which they are associated. The body can utilize different forms of bonds, but the fact remains that the level of their bioavailability varies. Iron is a typical example here, as most of the iron in animal foods is bound to porphyrin, and this bond is referred to as "heme iron," whereas in plants, this bond is absent, leading us to define it as "non-heme iron." Heme iron is relatively well-utilized, with absorption through the intestinal mucosa membranes also being higher (reported to be around 10-20%). The bioavailability of non-heme iron is significantly lower, which is caused not only by its binding to an active carrier but also by the presence of antinutritional factors (phytic acid in grains and sprouts, oxalic acid in spinach, lignins in plant cell walls, tannins in tea or coffee; fiber and calcium can also have antagonistic effects on iron).

Good day,

I am currently dealing with a dilemma. How should one proceed in a situation where athletes are recommended to have a higher ratio of plant-based proteins, but on the other hand, as a cyclist, I struggle with iron deficiency, for which it's advised to consume it predominantly in heme form, essentially excluding a higher ratio of plant-based proteins? Should preference be given to digestibility or iron? Personally, I resolved it by consuming predominantly plant-based proteins and supplementing iron through supplements (it seems like the lesser evil to me), but I am interested in your opinion :).

Thank you.

When considering constructively, it is always necessary to address the importance of individual nutritional rules in relation to individuality. Recommendations regarding the ratio of plant-based to animal-based proteins are general and do not have clearly defined boundaries or limits. In practice, it should not be a problem to implement a diet containing approximately half plant-based proteins, as you can provide a reasonable amount of heme iron from the resulting animal sources. Additionally, you can "assist" by including strong bone broth, which is very rich in minerals. If you also ensure a higher intake of vitamin C, which improves iron metabolism, in addition to an overall adequate iron intake (regardless of its source and form), the body should not suffer from a deficiency even under significantly higher physical exertion (and in such a situation, you will still have the option of supportive supplementation as a reserve).

Hello,
I am interested in whether it is true that women generally have a greater need for iron. The stated value is up to 33mg. For men, various sources agree on 14mg.
Thank you.

This is true and applies to women throughout the life period from adolescence to menopause, when there are relatively significant losses of iron during the monthly cycle. With increasing physical exertion (= athletes), this value continues to rise, but it is always individual.