Fat-Soluble Vitamins
د- هديل فاضل فرهود
Fat-soluble vitamins are essential vitamins needed by the body for proper functioning and protection against certain diseases and illnesses. Unlike water-soluble vitamins, fat-soluble vitamins are stored in fatty tissues of the body and do not dissolve in water. With the exception of vitamin D, fat-soluble vitamins cannot be produced by the body and must be obtained through food. Fat-soluble vitamins A, D, E, and K can be found in both plant and animal sources. . Unlike water-soluble vitamins that need regular replacement in the body, fat-soluble vitamins are stored in the liver and fatty tissues, and are eliminated much more slowly than water-soluble vitamins , they generally pose a greater risk for toxicity than water-soluble vitamins when consumed in excess. Eating a normal, well-balanced diet will not lead to toxicity in otherwise healthy individuals. However, taking vitamin supplements that contain mega doses of vitamins A, D, E and K may lead to toxicity.
Vitamin A
Vitamin A is the term for the biologically active compound retinol & its provitamin (precursor) carotenoids. , has many functions in the body.
Vitamin A is supplied primarily by certain foods of animal origin like dairy products, fish and liver. Some foods of plant origin contain beta-carotene, an antioxidant that the body converts to vitamin A. Beta-carotene, or provitamin A, comes from fruits and vegetables. Carrots, pumpkin, , dark green leafy vegetables and apricots are rich sources of beta-carotene.
Requirement: Male 5,000 IU per day (1,000 µg retinol equivalent), female 4,000 IU per day (800 µg retinol equivalent), although 10,000 IU per day is normally used in supplementation. More of this vitamin is required when you consume alcohol, on a low-fat diet, or a diet high in polyunsaturated fatty acids, if you smoke or live in a polluted area. It may also be indicated if you suffer from diabetes or have an under-active thyroid gland. in pregnancy 4000 IU (800 Mg retinol equivalent), in lactating 6000 IU(1200 µg retinol equivalent).
Deficiency of this vitamin : 1- Night blindness presents when vit A status is marginal & with prolonged deficiency, changes to the cornea & conjunctiva occur. Theses changes collectively known as xerophthalmia, these changes consist of conjuctival xerosis, Bitot s spots, corneal xerosis, corneal ulceration & corneal scars. 2- very dry, rough skin may indicate a lack of vitamin A (follicular hyperkeratosis). 3- Immunity: vitamin A deficiency decrease resistance to infections, for ex: diarrhea,& respiratory infections. 4- vit A deficiency lead to nutritional deficiency anemia. 5-faulty tooth development, and slower bone growth. 6-Abscesses forming in the ear, sinusitis, frequent cold and respiratory infections as well as skin disorders, such as acne, boils and a bumpy skin, as well as weight loss might be indicative of the vitamin being in short supply. 7- Insomnia, fatigue and reproductive difficulties may also be indicative of the vitamin in short supply.
Prevension of vit A Deficiency: 1- promotion of breast feeding & for bottle fed baby, use of fortified formulas. 2- increase intake of vit A by at risk populations (pregnant & lactating females) & to include vit A rich sources in weaning food. 3- immunization, improve sanitation, food hygiene, combat against infections. 4- nutritional education of the public, & increase awareness of health personal. 5- early diagnosis & proper treatment. 6- in Iraq : national supplementation program had been implemented since 1995 in the following prophylactic doses & for the following groups:
*children at 9 months of age.: 50000 IU *children at 18 month of age: 100000 IU . *lactationg females (at 1st week after delivery):200000 IU. *children with measls or PEM in a dose of 100000 IU (< 1 year age), 200000 IU (older children) *children at 1st year in primary school: 200000 IU . 7- doing nutritional survey to find the prevalence of this problem (planning & evaluation).
Prevalence criteria for determining public health significance (according to WHO) are:
Signs Prevalence above (%)in children < 5 years
Night blindness 1
Bitot s spot 0.5
Corneal xerosis, ulceration, keratomalaci 0.01
Corneal scar 0.05
Plasma vit A < 10 µg/dl 5
toxic or excess levels of vitamin A are of more concern than deficiencies. Acute toxicity occurs when > 200 mg is consumed by adults or > 100 mg in children. It would be difficult to reach this level consuming food alone. But some multivitamin supplements contain high doses of vitamin A. If you take a multivitamin, check the label to be sure the majority of vitamin A provided is in the form of beta-carotene, which appears to be safe. The acute symptoms include vomiting, abdominal pain , anorxia, blurred vision , headache & irritability. Chronic toxicity can occur when 10 mg is consumed over periods of a month or more , symptoms include headache, muscle & bone pain, ataxia, skin disorders, alopecia, liver toxicity, & hyperlipidemia. Vit A is teratogenic & pregnancy intakes should not exceed 3mg/day. There is no risk of toxicity from carotenoids in foods although large intakes can lead to yellow discoloration of the skin. Vitamin A toxicity also can cause severe birth defects and may increase the risk for hip fractures.