Iron deficiency can arise in bees due to reduced supply, decreased intake, or due to iron being extracted by one or more factors. The cause of iron deficiency can always be traced to certain circumstances in the environment. In the case of reduced supply, we must not only consider a different composition of pollen, but also a lower iron content in the nectar or water that bees drink.
Iron may be extracted by the Varroa mite, for example. Judging from data published about weight loss of bees parasitized by Varroa, this could account for the external extraction by mites of 15-25% of the bee's iron.
Influence of other minerals
An iron deficiency is not necessarily due to reduced supply or absorption of the iron itself. An iron deficiency may also be a consequence of an increased supply of other minerals. These other minerals take the place of iron in certain enzymes. These are physical biochemical adaptations. There are clear indications that these types of process play a role in the insecticides that are criticized. This is explained in more detail in the Research section of this website.
It is important to remember that iron deficiency in bees is not necessary due to insufficient iron in the environment. In certain circumstances, the poor solubility of iron may play a role, as well as the form in which the iron occurs.