Carrot is a root vegetable known for its reddish, orange-colored large taproot. Although the vegetable is cultivated for the taproot, its leaves are also eaten. The vegetable was discovered in the middle east, and it has been bred selectively to reduce fiber content, making the vegetable softer and more palatable.
Colorful carotenoids
Apart from being portable, the orrange or the reddish hue is the source of beta cartoon. A carotenoid, that is not only responsible for plant health but also for the humans who consumed the vegetable. There are more than 500 types of carotenoids found in plants giving deep red, yellow, and blue colors to different parts of it.
Broad classification of carotenoids
Broadly speaking, carotenoids are of 2 types: xanthophyll, that contains oxygen atoms in their structure and carotenes that contain no oxygen in their hydrocarbon structure. Beta carotenes belong to the latter group. It is the most popular of all the carotenoids that has great importance in vision, suppression of cancer, and metabolic stress. It was isolated chemically at the beginning of the 19th century and has been used for food coloring since 1950.
Retinol and retinal
Beta carotene is called the pro-vitamin A as it is the precursor of the vitamin: retinol and retinal, the alcohol and the aldehyde form of vitamin A are formed from the beta carotene play a very important role in eyesight. Without vitamin A, it is impossible to for the photochemical reactions to occur and will lead to complete loss of eyesight. Deficiency of the vitamin cause night blindness, clinically called a xeropthalmia.
Formation of retinol and retinal
Initally the long molecules of the beta carotene is broken into half in the small intestines to form 2 molecules of retinal by one enzyme beta carotene dehydrgenase. Retinal is the aldehyde form of the vitamin A. With enzyme retinal reductase, the retinal is reduced to retinol. This is absorbed in the intestines and tranported to the liver to be stored in the esterified form of retinol.
This retinol is transmitted to the retina when required and this is oxidized in the retinal epithelial cells by retinol dehydrogenase to retinal. This is the useable form of the vitamin A that performs all the reactions that enable vision.
Rods and Cones
In the retina, there are 2 types of cells that take part in the vision: rods and cones. As the name suggest, rods are cells cylinder in shape reponsible for low light and night vision. Whereas, the cones are conical cells responsible for the absorption of color of wider spectrum and for color vision. The rods stores a chemical which is called rhodopsin. Rhodopsin is the combination of retinal and a protein opsin. Due to the action of photons on rods, rhodopsin breaks down into retina and protein opsin. In the dark, the reaction reverses and retinal and opsin combines to form rhodopsin.
Vision in the light and in the dark
When in a lighted environment, the cones are very active. Photons incident on the rods, rhodopsin, breaks down into opsin and retinal which creates the impression of bright, colored surroundings. in this case the pupils are narrowed to prevent excess light from entering the eye creating a sensation of pain and discomfort.
While entering an area of darknes from lighted one, there is a sudden sense of blindness as the cones have been active, which are not accustomed to the low light. It takes some time for the opsin and the retinal to combine to form rhodopsin to enable hypersensitivity to low lighted environment. The pupils in the dark get dilated to allow more light and slowly the vision in the dark is restored. It is not a colored one, it is colorless, shady but the contours of the objects in the surroundings.
Case for consumption of carrots
These instances show that, the indespensibility of retinal in vision and that brings the equal importance of food sources of vitamin A. Carrots are the best source of vitaminA. It is important to know that most of the retinal in the reactions are further oxidized to retinoic acid and excreted. This cause for ample consumption of the carrots that provide vitamin for frequent replenishment of vitamin A.
Culinary variants
One can explore ones culinary skill with this red root vegetable. Making a salad with peeled raw carrots along with cucumber, onions, boiled beet root, lettuce, spinach, parsley is the best way to consume it, keeping the nutritional value intact. There are other ways like sauteed carrots, pickled carrots, fried carrots are next popular items. Carrot soup garnished with spices is tasty and equally nutritious.
A caution against too much consumption of carrots
Too much consumption of carrots will lead to yellowing of the skin, a clinical condition, that is called carotenemia. Although it is not serious it might lead to indigestion.
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