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Fat Soluble Vitamins. Fat soluble vitamins include: A and carotenoids, E, K, D Associated with fat absorption Needed in small amounts Stored in fatty tissues Excess intake has toxic consequences. Retinol and caroteinoids Lipid-soluble red, orange, and yellow pigments produced by plants

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Fat soluble vitamins
Fat Soluble Vitamins

  • Fat soluble vitamins include: A and carotenoids, E, K, D

  • Associated with fat absorption

  • Needed in small amounts

  • Stored in fatty tissues

  • Excess intake has toxic consequences


  • Retinol and caroteinoids

  • Lipid-soluble red, orange, and yellow pigments produced by plants

  • Fewer than 10% have vitamin A activity

  • B carotene, a carotene, b cryptoxanthin

  • Others also have physiological importance

    • Lycopene

    • Canthaxanthin

    • Zeaxanthin

Fig. 10-1a, p. 327



70-90% vitamin A absorption if fat is present

<5% to 60% for carotenoids; vitamin E interferes

CRBPII = cellular retinol binding protein

LRAT = lecithin retinol acyl transferase

Specfic protein carrier- vitamin A

Passive diffusion - carotenoids

Fig. 10-2, p. 329


‘‘Outer limiting

membrane’’

Photoreceptor

(rod) cell

Müller cell

Outer segment

Inner

segment

Capillary

Outer of photoreceptor (rod) cell Segment

Pigment epithelium

Nucleus

  • Functions: Vitamin A

    • Vision

    • Cell differentiation, growth, reproduction

    • Bone development

    • Immune system

Fig. 10-7, p. 334



  • Functions: Vitamin A

    • Vision

    • Cell differentiation, growth, reproduction

    • Bone development

    • Immune system

Fig. 10-9, p. 335


  • Functions: Vitamin A

    • Vision

    • Cell differentiation, growth, reproduction

    • Bone development

    • Immune system


  • Functions: Vitamin A

    • Vision

    • Cell differentiation, growth, reproduction

    • Bone development

    • Immune system

  • Function: Carotenoids

  • Antioxidants for singlet oxygen;

  • Lycopene > vitamin E >  carotene > cryptoxanthin > zeaxanthin,  carotene > lutein

  • (also work better when used together)

  • Antioxidant for lipid peroxides (works with vitamin E)

  • Lower incidence of atherosclerosis through prevention of oxidation of LDLs


  • Interaction with other nutrients:

  • Vitamins E and K (inversely related; high A, low E and K)

  • Zinc and iron

  • Protein

  • Excretion: most in urine as oxoretinoic acid, small amounts in expired air, some in feces

Fig. 10-10, p. 339


  • Deficiency:

  • increased morbidity in children under age 5 with no evident clinical signs of deficiency

  • Signs, when present include xeropthalmia, anorexia, retarded growth, increased susceptibility to infections, enlargement of hair follicle, and keratinization of epithelial (mucous cells) of the skin.

  • Toxicity:

  • Hypervitaminosis A

    • Nausea, vomiting, double vision, headache, dizziness, and desquamation of the skin

  • Teratogen


Vitamin D (a seco-steroid)

plants

animals

Fig. 10-11, p. 344



  • Dietary Vitamin D is absorbed from a micelle, along with other fats.

  • About 50% of dietary D3 is absorbed. Most absorbed in distal small intestine.

  • Incorporated into chylomicrons

  • Cholecalciferol from the skin is bound to DBP and travels primarily to the liver, but can be picked up by other tissues as well (muscle and adipose)

  • Blood is the major storage site; half-life of 10-21 days

  • Hydroxylases generate the active form of the vitamin (25-OH cholecalciferol)

  • Release by the kidney of active forms; a half-life of 4-6 hours in the blood

Fig. 10-12, p. 346


  • Functions: other fats.

    • Acts as a steroid hormonein calcium homeostasis

      • Intestinal effects

      • Effects on the kidney

      • Effects on bone

Fig. 10-13, p. 347


Fig. 10-14, p. 348 other fats.


Fig. 10-15, p. 349 other fats.


Deficiency: other fats. rickets, osteomalacia

  • Interaction with other nutrients:

  • Calcium, phosphorus, vitamin K

  • Excretion:

  • Bile > feces > urine

  • Toxicity:

  • Not possible from excess exposure to sunlight

  • Few cases; calcification of soft tissues, hypertension, anorexia, renal dysfunction


Only form with biologic activity other fats.

Fig. 10-17, p. 353


  • Digestion and Transport: other fats.

  • Synthetic forms are de-esterified

  • Free alcohol forms are absorbed passively in micelles; non-saturable

  • 20-80% absorption; better with fats

  • Incorporated into chylomicrons in intestinal cell and sent out into lymph

  • Transfer between chylomicrons, HDLs and LDLs occurs in the blood. HDLs and LDLs contain highest concentration of the vitamin

  • Half-life of about 48 hrs.

  • Some stored in adipose, liver, lung, heart, muscle, adrenals

Table 10-3, p. 354


  • Functions: other fats.

  • Maintenance of membranes - prevents oxidation of unsaturated fatty acids contained in the phospholipids (includes membranes of mitochondria and ER)

    • Reduced LDL oxidation; decreased plaque formation

    • Reduction in cataract formation

    • Reduced oxidation in diabetics

  • Suppression of activity of HMGcoA reductase (cholesterol synthesis)

1

2

Fig. 10-18, p. 356


Regeneration other fats.

  • Nutrient Interactions:

  • Function closely linked to selenium (needed for GSH peroxidase), vitamin C, sulfur containing amino acids,

  • Inhibits carotene absorption and conversion to retinol; may impair vitamin K absorption; may cause vitamin -D dependent bone mineralization problems

  • Deficiency:

  • Rare except in populations with fat malabsorption (cystic fibrosis)

  • myopathy and weakness, croid pigment accumulation, and degenerative neurologic problems

  • Toxicity: one of the least toxic; bleeding problems

Fig. 10-19, p. 356


  • Vitamin K other fats.

    • Absorption: in micelles; incorporated into chylomicrons, then chylomicron remnants, then VLDLs, then HDLs and LDLs.

    • Found mainly in liver and heart. Turnover is once every 2.5 hrs.

Synthetic form

From green plants

Synthesized by bacteria

Fig. 10-20, p. 361


Table 10-4, p. 361 other fats.


Functions: other fats. blood clotting and bone mineralization

Fig. 10-21, p. 363


Vitamin K cycle other fats.

Needed for protein carboxylation

Vit. K usually only present in this form in the body

Osteocalcin or Bone Gla protein

Matrix Gla protein

Fig. 10-23, p. 364


Deficiency: other fats. rare in adults; newborns, chronic antibiotic administration, and malabsorption can result in deficiency

Bleeding episodes

Osteoporosis

Toxicity: none known


Table 10-1, p. 326 other fats.


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