Learning Outcome

• To understand the roles of vitamins and minerals important to human health

• To understand the impact on human health due to deficiency of important vitamins and minerals

Micronutrients

Macronutrients

• made up the bulk of the nutrition in food, i.e., carbohydrates, fats, and proteins

• supply calories and act as the building blocks for muscles and tissues

Micronutrients are….

• essential dietary components for the maintenance of health

  • deficiency can cause severe and life-threatening clinical disorders

• disproportionately common in low- and middle-income countries

• mostly preventable through

  • nutrient education

  • consumption of healthy diet

  • food fornication and supplementation

Fat-soluble vitamins

• Lipophilic, hydrophobic molecules

• incorporated into mixed micelles to be absorbed from intestine lume

• upon absorption, the fat soluble vitamins are incorporated into chylomicrons

  • transport via the lymph into peripheral blood circulation

    • stored in the liver and adipose tissues

• deficiencies occur with the malabsorption of fat

Vitamin A

• mainly consists of retinol and retinyl esters

• Two sources:

  • performed vitamin A (aka retinol and retinyl esters)

    • diary products, eggs, fish and liver

  • provitamin A carotenoids (beta-carotene)

    • green leafy vegetables, carrots and cantaloupe

• physiological roles:

  • vision

  • maintain healthy cell-mediated immunity

  • differentiation of certain tissues

  • morphogenesis in developing embryos

• deficiency

  • still common in developing countries due to poverty or traditional diets

  • night blindness, conjunctival keratosis, degeneration of cornea

  • abnormal lung development, respiratory diseases, anaemia and severe infection

• Excess

  • acute vitamin A toxicity (hypervitaminosis)

    • severe headache, blurred vision, nausea, dizziness, aching muscles, coordination problems

  • chronic hypervitaminosis

    • dry skin, painful muscles and joints, fatigue, depression

Vitamin D (calciferol)

• Two forms: vitamin D2, vitamin D3

• Sources:

  • naturally found in certain food, e.g., salmon, mackerel, sardines & mushrooms

  • fortified milk, fortified cereal and fortified juice, dietary supplement

  • produced endogenously in the skin when exposed to direct sunlight

• Activation of vitamin D

  • biologically inert and must undergo two hydrocylation steps for activation

    

• Physiological roles:

  • promote calcium absorption in the intestines

  • maintain normal bone mineralisation & prevent hypocalcemia

  • bone growth and bone remodelling

  • regulate genes involved in cell proliferation, differentiation and apoptosis

  • reduce inflammation

  • modulate cell growth, neuromuscular & immune function and glucose metabolism

• serum concentration of 25 (OH)D → assess the vitamin D status

Vitamin D deficiency

• Causes:

  • limited exposure to sunlight

  • low intake

  • failure of kidneys to convert 25(OH)D to its active form

  • inadequate vitamin D absorption

  • drugs

  • chronic diseases

• Clinical manifestations

  • rickets in children → soft bones & skeletal deformities

  • severe rickets cases → failur to thrive, developemtnal delay, hypocalcemic seizures, tetanic spasms, cardiomyopathy & dental abnormalities

  • osteomalacia in adolescents & adults

    • inadequate bone mineralisation during remodeling process

    • bone deformities, pain, hypocalcemic seizures, tetanic spasms & dental abnormalities

Vitamin E (alpha-tocopherol)

• exists in 8 naturally occurring plant rocopherols and tocotrienols

  • alpha-, beta-, gamma-, and delta-tocopherol

  • alpha-, beta-, gamma-, and delta-tocotrienol

• alpha-tocopherol is the only biologically active form in human

• sources:

  • plants oil, almonds, peanuts, leafy greens, poultry, eggs, dairy, fortified cereals, oral supplement in capsule or drops

• physiological roles:

  • important to vision, reproduction and the health of blood, brain and skin

  • as an antioxidant and free radicals scavenger

    • protect cells from damaging effects of free radicals

    • maintain integrity of all cell membranes

Vitamin E deficiency

• Rare; could be found in premature babies of very low birth rate

• oxidative destruction of membrane phospholipids, e.g.,

  • red blood cell fragility leading to haemolytic anemia

  • neuronal degeneration leading to peripheral neuropathies

• genetic abnormalities associated with vitamin E metabolism

1. abetalipoproteinemia

   1. poor absorption of dietary fat

      1. inadequate vitamin E delivery to tissues

      2. poor transmission of nerve impulses, muscle weakness, retinal degeneration

2. Friedreich type of spinocerebellar ataxia

   1. defects in hepatic alpha-tocopherol transferase

      1. develop nerve damage, lose the ability to walk

Vitamin K

• Vitamin K1; Vitamin K2

• Phylloquinone

  • present primarily in green leafy vegetables

  • main dietary form of vitamin L

• Menaquinones

  • predominantly bacterial origin

  • present in modest amount in animal-based or fermented foods

• Sources:

  • green leafy vegetables

  • vegetable oils

  • cereals

  • others such as meat, fish & dairy products

  • can be synthesised by Gram-positive bacteria in the jejunum & ileum

• Physiological roles

  • act as coenzyme for vitamin K-dependent carboxylase involved in the post-translational y-carboxylation of proteins

    • increase the capacity of proteins to bind to calcium

      • procoagulant proteins of the clotting cascade

      • anticoagulant proteins

      • bone matrix proteins

      • proteins of the renal epithelium

Deficiency of Vit K

• Clinical manifestation

  • bleeding and haemorrhage

  • reduce bone mineralisation → osteoporosis

• newborns are more susceptible due to

  • low placental transfer of vit k

  • lack of vit k in breast milk

  • bacterial flora not yet established

• adults limited to malabsorption disorder or drugs that interfere with vit k metabolism