FAT SOLUBLE VITAMINS           

• Vitamins are organic compounds                      

• Required in trace amounts

• Perform specific metabolic functions

• Not synthesized by the body or not synthesized in adequate amounts

Fat Soluble Vitamins

• All have similar mechanism of absorption and excretion
• Do not have to be consumed daily
• Excess can be toxic
• Relatively stable during processing

Vitamin A -

• Occurs in preformed state and as a precursor
• Three active forms:
•     Retinol,
•     Retinal
•     Retinoic acid
• In food most preformed vitamin A is found in the form of retinol
• All three forms of vitamin A can be formed from the plant pigments, carotenes
• Most common form is beta-carotene. Vitamin A is susceptible to oxidation, but is relatively heat stable

Absorption and metabolism

• Requires bile salts
• Stored in liver
• Requires a transport protein. Protein deficiency will have a negative impact on Vitamin A status. Zinc deficiency has a similar effect

Functions in vision and maintains the structure of the eye. (Only retinol and retinal function in the visual cycle) Deficiency is night blindness

Epithelial tissue - Vitamin A is necessary for synthesis of substances in mucous produced by epithelial tissue - Deficiency - increased incidence of infection, hard dry keratinized skin.

Deficiency

• Night blindness
• Stunting of growth
• Xeropthalmia
• Problems with skin and epithelial cells that line respiratory, digestive and genitourinary tracts.
• Abnormalities of enamel-forming cells of the teeth.
• Has been suggested to decrease risk of cancer, but data doesn't support this claim

Requirements

Sources: Dark green vegetables, orange-yellow vegetables, whole milk, butter, cheese, eggs, fish liver oils, all liver. Little loss in normal cooking Oxidizes readily with heat

Vitamin A

Intake
Little concern if intake equals 2/3 RDA
Availability in US is about 8,200 IU/day
Problems with intake throughout the world
In world, except China, estimated that 80,000 children become blind each year

Toxicity: Excess carotene does not result in toxicity - should not consume more than 10,000 IU/day of retinal.

Vitamin D

• Cholecalciferol (Vitamin D3)
• Can be produced from cholesterol by the action of ultraviolet light.
• Can be formed from a protovitamin
• Stored in the liver
• Functions in the absorption of calcium and phosphorus
• Acts directly on bone
• Affects reabsorption of calcium and phosphorous by kidney

Requirements

• Impossible to state requirement exactly
• In infants, 135 IU prevents rickets, but 300 - 400 IU results in more rapid growth and earlier eruption of teeth.
• In older children, from 300 to 400 IU favors calcium retention.
• Food and Nutrition board recommends 400 IU from birth to age 22 years.

Requirements

Sources: sunlight, fish, egg yolk, butter, organ meats.

Functions

• Conversion to a hormone that improves absorption of calcium and phosphorous, mobilization of calcium form bone and control of excretion of phosphorus by the kidneys.
• Vitamin D may also play a role in regulation of amino acid levels in the blood and the level of citric acid in tissues and bones.

Vitamin D Deficiency

• Poor growth and lack of normal bone formation in children (Rickets)
• In adults a softening of bone know as osteomalacia can occur.
• Symptoms are similar to a lack of calcium. The calcium is present, but not absorbed efficiently.
• Others include poor tooth development, muscular weakness, listlessness and enlarged skull.

Toxicity - double the recommended intake for a few months can be toxic:

• Intakes of from 3,000 to 4,000 IU/day result in elevated serum calcium levels.
• Intake of over 20,000 IU/day may result in serious toxicity. Symptoms include:
• Vomiting, Diarrhea, Weakness, Loss of weight, Kidney damage

Vitamin E

• Alpha tocopherol
• Widely available in normal diet

Functions:

• Detoxify oxidizing radicals that arise in metabolism
• Stabilize cell membranes
• Regulate oxidation reactions
• Protect Vitamin A and PUFA from oxidation

In animals, Vitamin E has been shown to:

• Be essential for fertility in rats
• Be essential for male potency in rats
• Protect against a form of muscular dystrophy in rats and lambs

In humans, Vitamin E does not:

• Lower high blood lipids or cholesterol
• Decrease hot flashes
• Decrease risk of bladder cancer
• Prevent heart attacks
• Restore or improve sexual potency
• Improve athletic ability

Requirement increases as intake of PUFA increases.

• RDA for men = 10 TE or 15 IU
• For women = 8 TE or 12 IU

Excess intake can impair function of G.I. tract and increase time for blood clotting

Human Deficiency

• Vitamin E is required for normal creatine excretion and for prevention of blood disorders (hemolysis test).
• Not related to: Athletic performance, heart disease, sex drive, muscular dystrophy, sterility or longevity.

Animal Deficiencies

• In rats, males become sterile and pregnant females are unable to carry to term. Also related to nutritional muscular dystrophy.
• In chicks brain lesions have been observed, as well as liver damage and muscular symptoms in mice, pigs, dogs and other animals.

Functions

• No known coenzyme role, nor requirement in any known enzymatic reaction.
• Symptoms in all animals can be prevented by other antioxidants or much lower levels of selenium.
• Several generations of experimental animals have been raised without vitamin E with no adverse effects as long as other antioxidants are present.

Vitamin K

• Phylloquinone - plants K1
• Menaquinone - bacteria K2
• Diet and intestinal bacterial contribute to supply
• Storage in body is minimal
• Functions in normal blood clotting

Sources - green leafy vegetables, cabbage, cauliflower

• Routinely given to newborns after birth
• Safe and adequate intake = 70 to 140 mg/day
• Synthesized by intestinal microflora
• May have secondary deficiency due to administration of sulfa drugs.
• Resistant to heat and oxygen, destroyed by strong acid or alkali

Deficiency

• Deficiencies are rare in all animals.
• Found in chickens fed diets very low in alfalfa.
• In other animals, usually results from prolonged treatment with antibiotics.

Role in Body

• Functions in formation of a protein, prothrombin, in the liver.
• Prothrombin is required for normal blood clotting.
• No known function other than prothrombin formation.

Requirements

• No allowance set be FNB.
• Normally produced by intestinal microflora.
• Deficiencies are possible in premature infants. Infant formulas are fortified to a level of 100 mcg/liter.
• Toxicity does not appear to be a problem in people of normal health. People who are taking medication to control the rate of bllod clooting (anticoagulants - also known as blood thinners) must be carful that they do not consume too much vitamin K or the proper dosage of medication is difficult to determine.

 

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