Vitamin Supplements

The vitamin is also found in the retina of the eye. It forms part of a substance called rhodopsin which enables us to distinguish black and white objects in low light. We have two separate visual systems in the eye, colour, and black and white. During the daytime they work together, but in a dim light, we cannot distinguish colours and must rely on the black and white system. There are types of receptors at the back of the eye called rods and cones. The cones interpret colour and the rods give us our black and white vision. Rhodopsin, composed of protein and retinol, is found in the rods. Light entering the eye causes a chemical reaction in the rods and is said to ‘bleach’ the rhodopsin. This change causes electrical impulses to leave the eye and travel to the brain, and we see an image. The bleaching process destroys the rhodopsin and it must be re-formed if we are to see the next image clearly. Read the rest of this entry »

Vitamin A is the generic, or family name which covers the active vitamin, retinol, and the provitamin, carotene. Retinol is found in animal products and carotene is found in fruit and vegetables. Carotene is described as a provitamin because it does not turn into an active vitamin until it has been eaten and digested. The conversion to retinol occurs in the wall of the intestines before reaching the bloodstream. Retinol and some of the unchanged carotene is carried in tiny droplets of oil which enter the blood after leaving the intestines and pass to the liver. Vitamin A is stored here before it is transported to other parts of the body. Being fat soluble it cannot mix directly with the watery medium of the blood, but the liver forms special protein carriers for the vitamin so that it can be transported into the main bloodstream. Read the rest of this entry »