Fat-Soluble Vitamins

Introduction

• Fat-soluble vitamins—Vitamins A, D, E, and K—are essential micronutrients that dissolve in fats and are stored in the body’s fatty tissues and liver.
• Fat-soluble vitamins and require carrier proteins for transport.
• Adequate uptake of these nutrients requires intact mechanisms for fat digestion and absorption.
• Unlike water-soluble vitamins, fat-soluble vitamins can accumulate in the body and do not need to be consumed daily in large concentrations.
• In this lecture, we will discuss vitamins A,E, and K.

Vitamin A (Retinol)

Significance

• Vitamin A is vital for vision, immune function, cell growth, and the development of skin and mucous membranes.
• It also plays an important role in maintaining healthy reproductive function.
• The daily requirement of vitamin A for an infant is 400-500 µg/day, which is higher than the amount needed for other age groups.

Sources

• Breast milk, infant formula.
• Animal products: liver, eggs, dairy products, and fortified foods.
• Plant-based sources (in the form of beta-carotene): carrots, sweet potatoes, spinach, and other dark leafy greens.

Deficiency

• Vitamin A deficiency can lead to:
  • Night Blindness (early symptom)
  • Bitot spots (keratinization of the cornea with an accumulation of squamous cells and keratin debris adjacent to the limbus.
  • Xerophthalmia (dry eyes)
  • Impaired immune function, increasing susceptibility to infections (mainly respiratory)
  • Growth retardation in infants.
  • In severe or prolonged cases, it can result in death.

Excess

• Vitamin A toxicity (hypervitaminosis A) can cause a variety of complications, including:
  • scaly skin, pseudotumor cerebri, bone and muscle pain, cortical hyperostosis, and hepatomegaly.
  • Chronic toxicity: bone fractures, and neurological problems.
  • In infants, excess vitamin A can cause bulging fontanelle.

Vitamin E (Tocopherol)

Importance

• Vitamin E (tocopherol) functions as a membrane-bound antioxidant by inhibiting free radical-catalyzed lipid peroxidation and terminating radical chain reactions.
• It serves to protect the body from biological processes that damage cellular and intracellular structures.
• The Daily Requirement of an infant 4-5 mg/day (as alpha-tocopherol)

Sources

• Breast milk, formula milk
• Plant-based oils (sunflower, safflower, olive oil), nuts, seeds
• Green leafy vegetables and fortified cereals

Deficiency

• Vitamin E deficiency is common in children with fat malabsorption and is particularly seen in children with pancreatic insufficiency (such as in cystic fibrosis) and liver disease.
• Vitamin E deficiency can occur in premature infants, because the transfer of vitamin E to the infant does not happen until the 3rd trimester.
• Can cause the following consequences:
  1. Hemolytic anemia, thrombocytosis, and edema.
  2. Muscle weakness or neurological dysfunction, including especially neuroaxonal degeneration and loss of reflexes.
  3. Vision problems and damage to the retina

Excess

• It can interfere with blood clotting and increase the risk of bleeding.
• Affect the immune system and impair wound healing.

Vitamin K (Phylloquinone and Menaquinone)

Importance

• Vitamin K is essential for coagulation factors synthesis ((prothrombin, VII, IX, and X), and helps prevent excessive bleeding.
• It also plays a role in bone metabolism by stimulating the osteoblast differentiation, increasing the level of some bone formation markers (e.g., alkaline phosphatase and insulin-like growth factor, and regulating the extracellular matrix mineralization.
• The Daily requirements of an infant is 2-2.5 µg/day (as retinol activity equivalents).
• Newborn babies don’t have sufficient levels of vitamin K, thus, it is routine to give vitamin K prophylaxis at birth (0.5-1.0 mg IM or 1-2 mg PO) to prevent hemorrhagic disease of the newborn.

Sources

• Dietary sources: Green leafy vegetables (spinach, kale), broccoli, and certain plant oils.
• Non-Dietary sources: The gut microbiota also synthesizes some vitamin K.

Deficiency

• Vitamin K deficiency is uncommon once the intestinal flora is established, except in children with malabsorption of fat soluble vitamins such as those with liver disease (no bile in intestine to emulsify fat) or pancreatic insufficiency (no lipase to break down fat so it can be absorbed).
• Generally, vitamin K deficiency is most common in these children or in newborns and infants who have not yet developed significant bacterial GI flora.
• Vitamin K deficiency can lead to:
  • Vitamin K Deficiency Bleeding (VKDB): a severe condition in newborns that can cause uncontrollable bleeding, especially in the brain or gastrointestinal tract.
  • Impaired blood clotting leading to easy bruising and excessive bleeding.

Excess

• Vitamin K toxicity is rare. However, vitamin K excess can cause:
  • Jaundice and hemolytic anemia in infants.
  • In extreme cases, liver damage

>Summary of Daily Requirements