Vitamin A and Beta Carotene

Vitamin A
Recommended daily intake (DV-Daily Value):

For men (age group 19 +) - 3,000 IU (International Units); For women (age 19 +) - 2,310 IU

Suggested optimal amount (DV):

For men (19 +) - 10,000 IU; For women (19 +) -10,000 IU

Toxicity can occur as low as 15,000 IU +.

Toxicity symptoms: Dry skin, nausea, headaches, fatigue, irritability, liver damage.

Uses: Plays an important role in eye protection, helps maintain good vision and normal vision in dim light. Forms and maintains normal structure and functions of mucous membranes to assure healthy eyes, skin, hair, gums, and various glands. Supports the immune system. Promotes bone growth and teeth.

Food sources: Carrots, fortified skim milk, pumpkin, sweet potatoes, dark green leafy vegetables (like spinach and kale), winter squash, tuna, halibut, cantaloupe, mangoes, apricots, broccoli, watermelon, and fortified breakfast cereals.

Beta-Carotene

Daily value (DV) for men: Not established.

Suggested average amount: 3,300 IU.

Toxicity and symptoms: None known.

Uses: Helps protect against cancer, cardiovascular disease, and cataracts.

Food sources: Carrots, mangoes, sweet potatoes, winter squash, leafy vegetables such as spinach, kale, collard greens, turnip greens, fresh parsley.

Vitamin A and Beta-Carotene

Where you get it: Liver and carrots (richest sources), dark green leafy vegetables (spinach, collards, mustard greens), yellow vegetables (squash,    pumpkins, sweet potatoes), yellow fruits (peaches, apricots).

What it does for you: keeps your eyes healthy; prevents night blindness; is essential for body growth and normal tooth development; protects and maintains linings of the throat and respiratory, digestive, and urinary systems; helps with protein and glycogen synthesis.

Too little can cause deficiency that contributes to night blindness, stunt growth and development in children, promote tooth pitting and decay, create rough, dry, scaly skin and cause reproductive disorders. Taking more than suggested tolerable dosage per day over a long period of time can lead to headaches, blurred vision, loss of hair, dry skin (with flaking and itching), drowsiness, diarrhea, nausea and enlargement of liver and the spleen.

Vitamin A is probably the most important vitamin to your body. That certainly qualifies it as interesting. But more astounding is this: You need vitamin A to live but can't make it on your own, so you eat plants. And here's the rub: Plants don't have any vitamin either.

Confused? Don't be. This little chemical conundrum is what makes vitamin A so exciting-and so important.

Every living animal, including man, the wildest animal of all, needs vitamin A to live. Vitamin A, as a scientist would say, is the product of animal metabolism, which means that your body-and the body of every species of mammal, bird, and fish-manufactures vitamin A internally through the physiology of life and living.

Most of the vitamin A you need comes from the food you eat, particularly plants. Yet, plants themselves don't have any vitamin A. Their chemical counterpart is a similar substance called carotene, a yellow-colored, fat-soluble substance that gives the characteristic yellow-orange color to carrots. (Carotene got its name because it was first isolated from carrots more than 100 years ago.) As a result, the ultimate source of man's vitamin A comes from carotene synthesized by plants. Our bodies, and the bodies of other animals, take the carotene and through the wonders of our metabolic chemistry sets, turn it into vitamin A. In other words, plants have the ingredients for vitamin A and later it's being converted by the body into actual vitamin A.

A little bit of history of vitamin A

Early remedies using vitamin A surfaced in ancient China, where the Chinese made vitamin A- rich concoctions to treat night blindness. Later, in Greece, Hippocrates, the father of modern medicine, did pretty much the same when he prescribed various preparations of liver because liver, too, is rich in vitamin A. (Night blindness, or nyctalopia, is a condition in which your eyes lose their ability to adequately adjust to dim light.)

Definitive discovery of vitamin A came in 1913, when four scientists operating independently in two labs discovered vitamin A by demonstrating that there was an essential substance in fatty foods. Elmer V. McCollum and Marguerite Davis of the University of Wisconsin discovered vitamin A in butter fat and egg yolks, while Thomas B Osborne and Lafayette B. Mendel of the Connecticut Experiment Station discovered it in cod liver oil. In those two experiments, the four scientists found that the absence of vitamin A caused eye problems in animals. Two years later, McCollum and Davis fine-tuned their research to directly link vitamin A deficiency with night blindness.

Following the pioneer work, vitamin A attracted the attention of scientists all over the world within two short decades. In 1920, an English scientist proposed the official "vitamin A" name. It was previously called fat-soluble vitamin A. Other scientists discovered similar substances in other foods, like sweet potatoes and corn. These substances would later be called carotene. The true defining moment in the history of vitamins and nutrition in general came in 1931, when a Swiss researcher isolated the active substance in halibut-liver oil and analyzed for its chemical content. His work resulted in vitamin A being the first vitamin ever to have its chemical structure decoded. For this, researcher Paul Karrar received the Nobel Prize.

Science today has much to say about vitamin A and carotene. More than 600 carotenoids are found in nature, and 50 of them have the potential for vitamin A activity. The most common are: beta-carotene, alpha-carotene and beta-cryptoxanthin. Beta-carotene is the most efficient and it can be found in orange fruits and vegetables, like mangoes and carrots, and in green leafy vegetables, like broccoli, and vitamin A also found in foods of animal origin.

In a way vitamin A is a misleading name. It's not truly one substance.  
There are several forms of vitamin A, each with varying degrees of potency. The two main types of vitamin A are retinol and dehydroretinol. Then there are the carotenes. These are the precursors to vitamin A, the substances found in fruits and vegetables. Carotenes help us make vitamin A through metabolism.

The four most powerful carotenes vitamin A - are called alpha-carotene, beta-carotene, gamma-carotene, and crypto-xanthine, which is carotene found in corn. Of these four heavy-hitting carotenes, beta-carotene has the highest potential to create vitamin A, alone providing about two-thirds of the vitamin A that your body needs to survive. "These carotenes give some of those fruits and vegetables their characteristic colors. But just because you don't see yellow or orange doesn't mean they're not present. In other foods, like broccoli, for example, the carotene is there. It's just masked by chlorophyll, the substance that gives plants their green color."

As for its utility, vitamin A serves the body in several ways. In addition to its well-known role in maintaining healthy vision and in preventing blindness and night blindness, vitamin A does the following:

• Spurs overall growth. In addition to helping growth at the cellular level, vitamin A indirectly responsible for your sense of taste. Without enough vitamin A, the cells that make up your taste buds dry out, or keratinize, because there isn't enough vitamin A to help those cells properly develop.

• Develops bones and teeth.
• Helps the reproduction of specialized cells. Vitamin A helps epithelial cells develop. These are special cells found in your skin and in the lining of mucous membranes, like those in your throat, digestive system, and of course, your eyes.
• Helps prevent breast cancer. Experts aren't exactly sure how, but vitamin A, either in its retinol or carotene form, seems to play a crucial role in warding off cancer, especially cancer of the epithelial cells.
• Neutralizes free radicals. Beta-carotene and vitamin A seem to possess antioxidant properties. Antioxidants hamstring the body's rampaging free radicals, which are unstable molecules that potentially cause everything from cancer to the effects of aging.

Your body excretes some vitamins, like C or B, when you get too much. This isn't necessarily so with vitamin A, which is high doses should be taken under medical supervision. In fact getting too much can result in vitamin mortality, rather than vitamin vitality. Excess dose of vitamin A can be very dangerous and affects the central nervous system and, in extra-ordinarily large doses, can cause death. Most toxicity occurs through unhealthy and unwise supplementation.

Be careful with beta-carotene. Avoid taking too much beta-carotene, too. Despite its near-mystical appeal, appearance of the skin can change and you may start looking like a walking carrot. Some individuals drink too much carrot juice because someone told them to. Too much won't kill them, however, it will turn their skin an orange-yellow because all that carotene gets stored in the skin.

Seek a variety of food sources. Not only will you get healthier amounts of vitamin A and beta-carotene that way but also you'll be on the road to an overall healthy nutrition that will serve you well. Moreover, eating a varied, healthy diet - especially one rich in produce - will expose you to more of the carotenes than just beta-carotene. Beta-carotene is better absorbed with oil. If eating raw vegetables like carrots and broccoli, it's better to eat them with salad dressings like for example "ranch dressing".

When it comes to taking dietary supplements, most experts agree that you're better off taking them to round out a healthy, nutritious diet - not to take place of a healthy, nutritious diet. That is, except when it comes to vitamin A and beta-carotene. Enormous amounts of vitamin A can be toxic. Too much beta-carotene, while not toxic, can turn your skin orange. The question is, if you want extra A, what do you do?

For starters, talk to your dietitian or physician. After that, consider taking beta-carotene supplements in addition to vitamin A and beta-carotene in foods. Beta-carotene is nontoxic, but look carefully at labels that say vitamin A with beta-carotene.

Don't let your food get fresh air. Although vitamin A and carotenes are relatively hardy, they do lose potency when exposed to the air. Store animal fat products in cold, dark places. And keep fish-liver oils, like cod-liver oil, in dark bottles to preserve their levels of vitamin A and carotene.