Vitamin A, also known as retinol, is present in milk, liver, egg yolk, butter and other foodstuffs and as carotene in vegetables that have a yellow-orange colour, such as carrots and pumpkins.
This vitamin is accumulated in the liver where it is transformed into retinoid. Given that vitamin A, as such, has no effect on our organism, it is the retinoids that are responsible for the physiological activity of the vitamin.
Retinoids take part in three processes: in cell death, in cell differentiation and in cell proliferation.
Clean and programmed death
Two types of death occur in cells: necrosis and apoptosis. Necrosis defines a pathological death, i.e. a death caused by a lack or deficit within the cell such as lack of oxygen or food.
On the other hand, apoptosis is the pre-programmed death of a cell. A number of cells have to die in order that our organism function correctly: for example, when the feet of a foetus are developed in the womb of a mother, at first the fingers are united by a membrane. This membrane has to disappear and, so, the cells thereof have to die off so that the hands may develop correctly. This cellular death is programmed in the embryo genes and has a concrete function. This is apoptosis.
All cells, in fact, have the necessary information to be able to undergo apoptosis but, of course, not all cells have to die. Both internal and external stimuli are what initiate this mechanism in those cases where it is necessary. Various modulating substances are involved amongst which are the retinoids.
Amongst these retinoids, researchers from the University of the Basque Country chose retinam