Vitamins and Minerals: Needs, Functions, and Deficiency Symptoms

Posted on Sep 4, 2024 in Biology

Vitamins and Minerals in the Diet

Physiological Needs, Function in the Body, and Manifestation of Deficiency

Background:

Vitamins are essential organic substances required for growth and maintenance of the body. They cannot be synthesized in the human body and therefore must be included in the diet.

Note: The term “vitamin” is conditional upon the circumstances and the particular organism.

For example, ascorbic acid (vitamin C) is a vitamin for humans, but not for most other animal organisms.

Vitamin Deficiency:

Causes:

  • Inadequate intake
  • Impaired absorption
  • Insufficient utilization
  • Increased requirement
  • Increased excretion

Stages:

  • Subclinical (depletion of body stores)
  • Overt deficiency (accompanied by other malnutrition – e.g., proteins, etc.)

Vitamin Toxicity:

More common with fat-soluble vitamins since they are not easily excreted by the body; water-soluble vitamins are lost quite rapidly in urine.

Most common – vitamin A toxicity

Fat-Soluble Vitamins (A, D, E, K):

These are absorbed and transported in the bloodstream along with dietary fat to reach body cells; normal absorption is 40-90%.

Unabsorbed fat carries these vitamins into the large intestine where they are excreted in feces.

Stored in liver and fatty tissues

Vitamin A:

Source (as retinol or β-carotene): Liver, leafy vegetables, and some fruits

After absorption, there is esterification in mucosal cells; the ester is then transported in RBP (prealbumin) and taken up by cell membranes.

Function: Light-dark vision (and color vision to some extent), prevention of cardiovascular disease, and aid in immunity

Deficiency: Night blindness (→ keratinization of cornea → ulceration → blindness), GIT and RT infections…

Vitamin D:

Source: Precursor of vitamin D in skin, fatty fish, yogurt…

Function: Regulation of calcium and therefore bone metabolism

Deficiency: Impaired bone mineralization (pain, muscle weakness, tenderness, loss of weight)

  • Rickets (children): Delayed closure of fontanelles, bowing of long shafts, cupping of metaphyseal ends, enlarged epiphyseal growth plates
  • Osteomalacia (adults): Softening of bones

Vitamin E:

Source: Plant oils

Function: Antioxidant (mainly for LDL)

Protects against free radicals (electron-seeking compounds) which pull electrons from cell membranes and DNA, altering the DNA, causing cancer, etc.

Deficiency: Breakdown of cell membranes (e.g., hemolysis, nervous system…) – ataxia, dysarthria, loss of pain and sensation…

Vitamin K:

Sources: Liver, green leafy vegetables, and also synthesized by colonic bacteria

Function: Hepatic carboxylation of glutamate residues in blood clotting factors for their activation (II, VII, IX, X), activates proteins in kidneys, bones, and muscles

Deficiency: Bleeding diathesis, hematomas, hematuria, ecchymoses, bleeding from gums (intracranial hemorrhages in neonates)

Water-Soluble Vitamins (B, C):

B Vitamins:

B vitamins function as coenzymes (small molecules that interact with enzymes to enable their function).

After ingestion, B vitamins are first broken down from their coenzyme forms into free vitamins (in stomach + intestine).

Then the free vitamins are absorbed in the small intestine and once inside the cells the coenzyme forms are resynthesized.

Vitamin B1 = Thiamine:

Sources: Wheat germs, yeast, legumes, nuts

Transformed into its active form TPP (thiamin pyrophosphate) in the liver

Function: Helps release energy from carbohydrates in its derivative form of TPP

Deficiency: Polyneuropathy, beriberi heart disease (peripheral vasodilation, mural thrombi), Wernicke’s-Korsakoff syndrome (encephalopathy-psychosis)

Vitamin B2 = Riboflavin:

Sources: Milk and milk products

Function: The nucleotides of riboflavin are the prosthetic groups of many enzymes involved in electron transport

Deficiency: Ariboflavinosis (angular stomatitis, cheilosis, skin and eye lesions)

Vitamin B3 = Niacin = Nicotinamide = Nicotic Acid:

Sources: Poultry, tuna, beef, etc.

Niacin may also be endogenously synthesized from tryptophan

Function: Component of NAD (nicotinamide adenine dinucleotide) and NADP which are coenzymes of many dehydrogenases

Deficiency: Pellagra (3D’s – diarrhea, dermatitis, dementia)

Vitamin B6 = Pyridoxine:

Sources: Liver, cereals

Function: Prosthetic group of many enzymes (e.g., ALT, AST)

Vitamin B9 = Folic Acid:

Sources: Liver, kidney, and fresh vegetables

Function: Coenzyme for nucleic acid synthesis

Deficiency: Impaired cell division (e.g., megaloblastic anemia)

Vitamin B12 = Cyanocobalamine:

Sources: Animal (turkey, clams, beef, egg yolk, sardines, tuna fish) and fortified cereals

Deficiency: Megaloblastic anemia (pernicious anemia) and SC demyelination

Vitamin C = Ascorbic Acid:

Sources: Citrus, potatoes

Function: Hydroxylation of lysine during the synthesis of collagen, antioxidant

Minerals:

Chemical elements other than the four elements carbon, hydrogen, nitrogen, and oxygen present in common organic molecules.

In order of abundance in the human body include the seven major dietary elements: calcium, phosphorus, potassium, sulfur, sodium, chlorine, and magnesium.

Important “trace” or minor dietary elements, necessary for mammalian life, include iron, cobalt, copper, zinc, molybdenum, iodine, bromine, and selenium.

Iron (Fe):

RR: 70 mmol

Normal intake: 0.2-0.4 mmol/day (10-20 mg/day) – in fish, liver, meat

Rate of loss: 1 mg/day in males (higher in females) – iron released by Hb breakdown is conserved and reused

Transport, storage, utilization, and excretion:

Iron is taken up by intestinal mucosa and can follow 2 processes:

  • Incorporation into ferritin and retained by the mucosal cells. This iron is then lost from the body.
  • Transport across the mucosal cells into plasma where it is carried by transferrin.

Transferrin binding sites are usually 30-50% saturated. Total iron bound to transferrin is 50-70 μmol (3-4 mg).

Iron in plasma is taken up by cells and either:

  • Incorporated into haem
  • Stored as ferritin or hemosiderin

Iron excretion:

  • In the feces – exogenous iron (iron in diet that has not been absorbed)
  • Females lose more iron than men due to menstruation and pregnancy.

Deficiency: Decreased intake, increased requirements (e.g., pregnancy), increased losses (e.g., menorrhagia)

Overload: Hemochromatosis, hemosiderosis, increased intake, hemolytic anemia…

Copper (Cu):

  • Copper circulates bound to ceruloplasmin.
  • Function: Essential for enzyme function (e.g., cytochrome C oxidase, superoxide dismutase, tyrosinase, dopamine beta-hydroxylase, ascorbic acid oxidase…)
  • Excretion: In feces via bile
  • Decreased in Menke’s disease (hereditary copper malabsorption) – neurological disturbances, hypochromic microcytic anemia, neutropenia and hypopigmentation of hair and skin
  • Increased in Wilson’s disease (decreased ability to transport copper from liver into the bile and its incorporation in ceruloplasmin – deposition of copper in tissues (liver, basal ganglia…)

Zinc (Zn):

  • Function: Component of enzymes (e.g., carbonic anhydrase, ACE, ALP, etc.)
  • Deficiency: Acrodermatitis enteropatica (inherited disorder of zinc malabsorption) which leads to impaired formation of connective tissue and immunity, hair loss, night blindness, impaired smell and/or taste.

Selenium (Se):

  • Function: Component of glutathione peroxidase and deiodase (T4 → T3)
  • Deficiency presents as impaired antioxidative properties, increased susceptibility for tumors and hypothyroidism.

Chromium (Cr):

  • Active as Cr3+ which is poorly absorbed
  • Function: Component of chromodulin which amplifies cellular response to insulin
  • Deficiency causes impaired glucose metabolism leading to glycosuria, hyperglycemia, increased insulin levels…

Iodine (I):

  • RR: 20-30 mg – 75% in the thyroid gland
  • Absorbed in the form of iodide, circulates as free or protein-bound and is stored in the thyroid gland
  • Function: Synthesis of T3 and T4
  • Excretion: Iodine is usually conserved but if excretion is necessary it occurs via urine.
  • Excess leads to hyperthyroidism or hypothyroidism.

Cobalt (Co):

  • Function: Component of cyanocobalamin or vitamin B12

Fluoride (F):

  • Intake: 1-2 mg/day in fluoridated water
  • Excess causes fluorosis (> 3 mg/L of water) – infiltration into enamel of teeth

Manganese (Mn):

  • Function: Component of metalloenzymes and activation of other enzymes, synthesis of glycosaminoglycan, cholesterol and prothrombin.

Molybdenum (Mo):

  • Function: Component of xanthine oxidase (converts xanthine to uric acid)
  • Deficiency causes xanthinuria, decreased plasma urate and decreased uric acid in urine.