Vitamin A, Retiniol, Carotene-ß
Vitamin A (or Vitamin A Retinol, retinal, and four carotenoids including beta carotene) is a vitamin that is needed by the retina of the eye in the form of a specific metabolite, the light-absorbing molecule retinal, that is necessary for both low-light (scotopic vision) and color vision.
Vitamin A also functions in a very different role as an irreversibly oxidized form of retinol known as retinoic acid, which is an important hormone-like growth factor for epithelial and other cells.
In foods of animal origin, the major form of vitamin A is an ester, primarily retinyl palmitate, which is converted to the retinol (chemically an alcohol) in the small intestine.
The retinol form functions as a storage form of the vitamin, and can be converted to and from its visually active aldehyde form, retinal.
The associated acid (retinoic acid), a metabolite that can be irreversibly synthesized from vitamin A, has only partial vitamin A activity, and does not function in the retina for the visual cycle.
All forms of vitamin A have a beta-ionone ring to which an isoprenoid chain is attached, called a retinyl group. Both structural features are essential for vitamin activity.
The orange pigment of carrots – beta-carotene – can be represented as two connected retinyl groups, which are used in the body to contribute to vitamin A levels. Alpha-carotene and gamma-carotene also have a single retinyl group, which give them some vitamin activity.
None of the other carotenes have vitamin activity. The carotenoid beta-cryptoxanthin possesses an ionone group and has vitamin activity in humans.
Vitamin A can be found in two principal forms in foods:
- Retinol, the form of vitamin A absorbed when eating animal food sources, is a yellow, fat-soluble substance. Since the pure alcohol form is unstable, the vitamin is found in tissues in a form of retinyl ester. It is also commercially produced and administered as esters such as retinyl acetate or palmitate.
- The carotenes alpha-carotene, beta-carotene, gamma-carotene; and the xanthophyll beta-cryptoxanthin (all of which contain beta-ionone rings), but no other carotenoids, function as vitamin A in herbivores and omnivore animals, which possess the enzyme required to convert these compounds to retinal. In general, carnivores are poor converters of ionine-containing carotenoids, and pure carnivores such as cats and ferrets lack beta-carotene 15,15'-monooxygenase and cannot convert any carotenoids to retinal (resulting in none of the carotenoids being forms of vitamin A for these species).
7 Health Benefits of Vitamin A
03. Bones and Teeth
When converted into retinoic acid, vitamin A effectively maintains healthy bones and teeth. Dentin, which also requires vitamin A, forms the hard layer of material within our teeth, thereby ensuring their strength. Vitamin A also plays an important role in replacing worn out or old tissue with newer tissue to ensure healthy bones and teeth.
04. Urinary Stones Urinary calculi, or solid particles in the urinary system, may cause pain, nausea and vomiting when stones are formed. Vitamin A produces a mineral compound within the body called calcium phosphate that prevents the formation of these solid particles.
05. Cancer As a powerful antioxidant, vitamin A fights against oxidative stress, or "cellular rust," within our bodies, thus protecting us from health problems such as cataracts, atherosclerosis, chronic obstructive pulmonary disease, and cancer.
06. Skin The antioxidant properties of vitamin A combat free radicals that can damage the skin through oxidative stress. By maintaining proper moisture retention, the skin is not only protected from common dryness, but also keratinization (the process in which the epidermis hardens into a heavy material that makes up hair and nails), psoriasis (a skin disease marked by red, itchy or scaly patches), acne, and even wrinkling.
07. Reproductive System Vitamin A is known to be essential for the reproductive process for both males and females
Table 1 : List of Vegetables high in Vitamine A
Vegetables, Vitamin A TOP10 (Source: USDA National Nutrient data base) | ||||
순위 | Vegetables | Contain/100g | RDA | |
1 | Powder paprica | 52,735 IU | 1,055% | |
2 | Powder , Red peppers | 41,610 IU | 832% | |
3 | Sweet Potatoes | 19,218 IU | 384% | |
4 | Carrots | 16,706 IU | 334% | |
5 | Kale | 15,376 IU | 308% | |
6 | Butternut Squash | 11,155 IU | 223% | |
7 | Mustard Green | 10,500 IU | 210% | |
8 | Spinach | 9,377 IU | 188% | |
9 | Coriander (Dry) | 8,424 IU | 168% | |
10 | Lettuce | 7,405 IU | 148% | |
Table 2 : List of Fruits high in Vitamine A
Fruits , Vitamin A TOP10 (Source: USDA National Nutrient data base) | |||
Rank | Fruits | Contain/100g | RDA |
1 | Noni | 15,620 IU | 312% |
2 | Dried Apricots | 3,604 IU | 72% |
3 | Cantaloupe | 3,382 IU | 68% |
4 | Passiflora edulis | 1,274 IU | 43% |
5 | Papaya | 1,094 IU | 22% |
6 | Aci Berry | 1,002 IU | 21% |
7 | Tomatoes | 833 IU | 17% |
8 | Mangoes | 765 IU | 15% |
9 | Guavas | 624 IU | 21% |
10 | Peaches | 326 IU | 7% |
Table 3 : List of herbs high in Vitamine A
Herbs Vitamin A TOP10 (Source: USDA National Nutrient data base) | ||||
순위 | Hurbs | Contain/100g | RDA | |
1 | Comfrey | 18,000 IU | 360% | |
2 | Mjorana | 8,069 IU | 161% | |
3 | Dill | 7,718 IU | 154% | |
4 | Sage | 5,900 IU | 118% | |
5 | Basil | 5,275 IU | 106% | |
6 | Thyme | 4,751 IU | 95% | |
7 | Chive | 4,352 IU | 87% | |
8 | Peppermint | 4,248 IU | 85% | |
9 | Tarragon | 4,200 IU | 84% | |
10 | Spearmint | 4,054 IU | 81% | |
Table 4 : List of Foods high in Vitamine A
Foods, vitamin A TOP3 (Source: USDA National Nutrient data base) | ||||
Rank | Vegetables | contain/100g | RDA | |
1 | Liver, animal | 62,526 IU | 1,250% | |
2 | Moringa | 16,300 IU | 326% | |
3 | Green Peas | 2,100 IU | 42% | |
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