Hippocrates, the famous Greek doctor, first recognized night blindness sometime around 300 BC. He recommended eating raw liver as a cure for the condition. Another eye disease, “xerophthalmia” (dry cornea and conjunctiva), was thought to be related because of a nutritional deficiency that was corrected by cod liver oil.
In 1917, a German researcher was successful in reversing both of these eye conditions in malnourished children with a diet including whole milk or butter. Through the intensive research conducted later, “fat-soluble vitamin A” was identified. A Nobel Prize was distributed to one physician, Dr. Wald, who in 1964 found that the retina contains vitamin A. And that vitamin A comes from carotenoids in fruits and vegetables.
Vitamin A isn’t one nutrient; instead, it is a general term for many chemicals. Retinoids consist of retinal, retinol, retinoic acid, and related chemicals. Provitamin A carotenoids include beta-carotene and other carotenoids, which our body can convert into retinal. Among the many hundreds of carotenoid made by plants, only 10% are considered to be provitamin-A carotenoids, the ones that are turned into vitamin A in our bodies.
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Vitamin A’s important roles in our bodies include:
1. Vision
2. Development: Essential for the development and formation of ears, eyes, heart, brain and limb
3. Red Blood Cells: Helps move iron from storage to red blood cells, which carry oxygen in the body
4. Immune Function: Essential for normal immune function, maintaining the body’s first line of defense (skin, mucus lining of airways, urinary system), and for development of white blood cells
5. Gene Expression: Vitamin A helps prevent cancer by inducing tumor suppressor genes called “retinoic acid receptors” (RAR).