Description
Use: Assess hypervitaminoses or vitamin deficiency
Special Instructions: Patients must be fasting for a minimum of eight hours. Patients should avoid foods containing vitamin A or carotene for 48 hours (24 hours for patients younger than six months of age).
Vitamin A is a fat-soluble vitamin that has several important functions in the body:
It helps cells reproduce normally (called "cellular differentiation").
It is essential for good vision -- the first sign of a vitamin A deficiency is often poor sight at night.
It is necessary for the proper development of an embryo and fetus.
Vitamin A also helps keep skin and mucous membranes that line the nose, sinuses, and mouth healthy. It plays a role in proper immune system function, growth, bone formation, reproduction, and wound healing.
Vitamin A comes from two sources: a groups of molecules called retinoids (which are derived from animal sources and includes retinol) and another group called carotenoids (which are derived from plants and includes beta-carotene). The body converts beta-carotene to vitamin A. Severe vitamin A deficiencies are rare in the developed world: symptoms can include dry eyes, night blindness, diarrhea, and skin problems.
While vitamin A is essential for good health, it can be toxic in high doses. Never exceed the recommended daily allowance without first talking to your doctor.
Reference Interval: 30-90 µg/dL
Vitamin E is a fat-soluble vitamin. It has eight different variants, each one has its own biological activity.
Alpha-tocopherol (a-tocopherol) is the most active form of vitamin E in humans. It is a powerful antioxidant. It is sold in supplements as alpha-tocopheryl acetate. The synthetic form is labeled "D, L" while the natural form is labeled "D". The synthetic form is only half as active as the natural form.
Antioxidants such as vitamin E act to protect cells against the effects of free radicals, potentially damaging by-products of energy metabolism.
Vegetable oils, nuts, green leafy vegetables, and fortified cereals are common food sources of vitamin E.
Its concentration is measured by means of analysis of a blood sample drawn from the vein in the arm.
Purpose of the test
To measure the level of vitamin E in blood in order to check whether the patient has a convenient level of this vitamin or there is a defect in diet or a disease related with absorption of vitamin E.
Vitamin E deficiency is rare in humans, except in:
1. persons who cannot absorb dietary fat due to an inability to secrete bile or with rare disorders of fat metabolism: Crohn's Disease and Cystic Fibrosis
2. individuals with rare genetic abnormalities in the alpha-tocopherol transfer protein: Ataxia and vitamin E deficiency (AVED)
3. premature, very low birth weight infants: Necrotizing enterocolitits
Reference range values
mg/L (SI: mcmol/L = 2.32 x mg/L)
20-150Y: 5.5-17
1-19Y: Not established
Abnormal findings
Vitamin E deficiency is usually characterized by neurological problems associated with nerve degeneration in hands and feet. It can be due to:
• Problems related with inability to absorb fat: Crohn's Disease and Cystic Fibrosis
• Metabolic inherited problems Ataxia and vitamin E deficiency
Blood levels of vitamin E may also be decreased with zinc deficiency.
Carotene is a type of pigment found in plants, especially carrots and colorful vegetables. The name beta-carotene is derived from the Latin name for carrot, and it gives yellow and orange fruits and vegetables their rich hues. Beta-carotene is also used as a coloring agent for foods such as margarine.
Beta-carotene is converted to vitamin A (retinol) by the body. Vitamin A is needed for good vision and eye health, for a strong immune system, and for healthy skin and mucus membranes. While large amounts of vitamin A in supplement form can be toxic, the body will convert only as much vitamin A from beta-carotene as it needs. That means beta-carotene is considered a safe source of vitamin A. However, too much beta-carotene can be dangerous for people who smoke. (Getting high amounts of either vitamin A or beta-carotene through your diet -- not from supplements -- is safe.)
Like all other carotenoids, beta-carotene is an antioxidant. It protects the body from damaging molecules called free radicals. Free radicals cause damage to cells through a process known as oxidation. Over time, this damage can lead to a number of chronic illnesses. There is good evidence that eating more antioxidants in your diet helps boost your immune system, protect against free radicals, and may lower your risk of two types of chronic illness -- heart disease and cancer. But the issue is a little murkier when it comes to taking antioxidant supplements.