Vitamin A, Best Nutrition Products

VITAMIN A

DESCRIPTION

Vitamin A occurs in two forms: preformed vitamin A, known as retinol, and provitamin A, also known as beta carotene. Vitamin A is also known as “the vision vitamin” for its role in aiding eyesight. Because it is fat-soluble and stored in the liver, it need not be replenished every day.

Vitamin A helps maintain healthy skin, teeth and bones, as well as mucous membranes, such as those in the nose, throat and lungs. It is necessary in the formation of an eye pigment involved in night vision, and is therefore essential for vision in dim light. Vitamin A is needed for proper development of the fetus in the womb.

DEFICIENCY SYMPTOMS

Severe deficiency leads to various physical changes in the eye and will eventually lead to blindness. Marginal deficiency will lead to increased susceptibility to respiratory tract infections and skin problems.

THERAPEUTIC USES

•     certain skin conditions, e.g. acne and psoriasis

Those WHO MAY NEED TO SUPPLEMENT

•     vegetarians

•     diabetics (who cannot efficiently convert beta carotene into vitamin A)

•     those with malabsorption syndromes, e.g. celiac disease or gastrectomy patients.

RECommended DIETARY ALLOWANCE

Age                      Retinol/Vitamin A (mcg/day)

0-12 months……………………………………………… 375

1-3 years…………………………………………………….. 400

4-6 years…………………………………………………….. 500

7-10 years…………………………………………………   500

11+ years (male)……………………………………… 1000

11+ years (female)……………………………………   800

Pregnancy………………………………………………..   800

Lactation, 0-6 months……………………………. 1300

Lactation, 6-12 months………………………….. 1200

BEST FOOD SOURCES

Food                                        Retinol (mcg/100g)

halibut liver oil………………………………….. 900,000

lamb’s liver………………………………………….. 19,900

cod liver oil…………………………………………… 18,000

butter………………………………………………………….. 985

margarine…………………………………………………. 800

cheese, cheddar………………………………………… 363

eggs……………………………………………………………. 190

pig’s kidney………………………………………………. 160

milk……………………………………………………………… 56

mackerel………………………………………………………. 45

beef……………………………………………………………….. 10

sardines, canned………………………………………….. 7

SAFETY

Taken in excess, vitamin A can lead to toxicity because it is stored in the liver. However, it still has a high safety margin in that regular daily intake generally has to exceed 7,500 mcg in women and 9,000 mcg in men before toxic effects are experienced. Vitamin A toxicity is usually fully reversible.  The vitamin A intake of pregnant women should not exceed 3,300 mcg per day (from food and supplements combined) unless directed by a health care professional.

INTERACTIONS & CONTRAINDICATIONS

Vitamins A and D (both fat-soluble vitamins) are found together in many food sources, although they are not actually dependent upon one another for their absorption or utilization. A zinc deficiency can affect the function of vitamin A and vice versa. Vitamin A should not be taken with vitamin-A-derived acne medications. The need for vitamin A is decreased if the individual is using the contraceptive pill.

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