Clinical Chem Vitamins & Minerals

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

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

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

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

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

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

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

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

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. poor absorption of dietary fat

1. inadequate vitamin E delivery to tissues 2. poor transmission of nerve impulses, muscle weakness, retinal degeneration

1. defects in hepatic alpha-tocopherol transferase

1. develop nerve damage, lose the ability to walk

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

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