micronutrients


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mi·cro·nu·tri·ents

(mī'krō-nū'trē-ents),
Essential food factors required in only small quantities by the body; for example, vitamins, trace minerals.
Synonym(s): trace nutrient

mi·cro·nu·tri·ents

(mī'krō-nū'trē-ĕnts)
Essential food factors required in only small quantities by the body; e.g., vitamins, trace minerals.

micronutrients

Dietary substances necessary for health but required only in very small quantities. Vitamins and minerals.

Micronutrients

Essential dietary elements that are needed only in very small quantities. Micronutrients are also known as trace elements. They include copper, zinc, selenium, iodine, magnesium, iron, cobalt, and chromium.
Mentioned in: Malnutrition

micronutrients

nutrients needed by the body in relatively small amounts: the vitamins and minerals. With proper nutrition from a variety of food sources, the physically active person or competitive athlete need not consume vitamin and mineral supplements; such practices usually have no benefits and some micronutrients consumed in excess can adversely affect health and safety. See Table 1, Table 2.
Table 1: Micronutrients: vitamins
VitaminRNI (DoH 1991)SourcesAction/functionsDeficiencyExcessSpecial points
Water soluble
Vitamin B group
B1 Thiamin(e)0.4 mg/1000 kcalFortified breakfast cereals, yeast extract, vegetables, fruit, wholegrain cereals, milk, liver, eggs, porkCoenzyme for carbohydrate metabolismEncephalopathy can occur with alcohol excess and low food intake. Beri-beri where polished rice is stapleHeadache, insomnia, irritability, contact dermatitisRequirement related to carbohydrate intake
B2 Riboflavin
  • Female 1.1 mg/d
  • Male 1.3 mg/d
Milk, milk products, offal, yeast extract, fortified breakfast cerealsCoenzyme for the metabolism of carbohydrate, fat and proteinFissures at corners of mouth; tongue inflammation; corneal vascularizationNo toxic effects, since large quantities are not absorbedDestroyed by sunlight
B3 Niacin (nicotinic acid and nicotinamide)6.6 mg/1000 kcal as nicotinic acid equivalentsMeat, fish, yeast extract, pulses, wholegrains, fortified breakfast cerealsEnergy metabolism, as part of coenzymes NAD and NADP involved in oxidation and reduction reactionsPellagra: dermatitis, diarrhoea and dementiaLiver damage, skin irritationAlso synthesized from the amino acid tryptophan
B5 Pantothenic acidNone setWidespread in food, e.g. liver, eggs, yeast, vegetables, pulses, cerealsProtein, fat, carbohydrate and alcohol metabolismVomiting, insomniaNot reported
B6 Pyridoxine
  • Female 1.2 mg/d
  • Male 1.4 mg/d
Meat, fish, eggs, some vegetables, wholegrainsProduction of haemoglobin and of coenzymes involved in many metabolic processesRare. Metabolic and nervous system disordersPeripheral nerve damageRequirement is related to protein intake
BiotinNone setWidely distributed in many foods, e.g. offal, egg yolk, legumes, etc. Can be synthesized by intestinal bacteriaEssential in fat metabolismRare; dermatitis, hair loss, nausea, fatigue and anorexiaNone known
B12 Cobalamins15 μg/g of proteinAnimal products, meat, eggs, fish, dairy products, yeast extract
  • Essential for red blood cell formation and nerve myelination.
  • Needed for use of folate
Anaemia; irreversible spinal cord damageNot reported
  • Absorption requires 'intrinsic factor' produced by the stomach.
  • Only in foods of animal origin, so strict vegetarians and vegans require supplements
Folates (folic acid)200 μg/dGreen leaf vegetables, bread, fortified breakfast cereals, yeast extract, liverRed blood cell production; DNA synthesis
  • Anaemia; growth retardation. May contribute to Alzheimer's.
  • Fetal defects
Can mask the effects of B12 deficiencySupplements before and during pregnancy reduce the incidence of spinal cord defects
Vitamin C ascorbic acid40 mg/d
  • Citrus fruits, kiwi fruit, blackcurrants, strawberries; green peppers, green leaf vegetables, potatoes, tomatoes.
  • Content decreases with storage
Collagen synthesis, formation of bones, connective tissue, teeth. Iron absorption for red blood cell production. Acts as an antioxidantSore mouth and gums; capillary bleeding; scurvy; delayed wound healing, scar break downDiarrhoea; oxalate stones in kidneysDestroyed by cooking in the presence of air and by plant enzymes released when cutting and grating raw food
Fat soluble
Vitamin A retinol
  • Female 600 μg/d
  • Male 700 μg/d
As retinol in liver, kidney, oily fish, egg yolk, full-fat dairy produce. As the provitamin carotenes in green, yellow, orange and red fruit and vegetables, e.g. broccoli, carrots, apricots, mangoes, sweet potatoes and tomatoesVisual pigments in retina, aids night vision. Normal growth and development of tissues; essential for healthy skin and mucosae. Acts as an antioxidantPoor growth; rough dry skin and mucosae; xerophthalmia and eventual blindness; increased risk of infection; poor night visionIn pregnancy, high doses can cause fetal malformationsSynthesized in the body from carotenes present in the diet
Vitamin D cholecalciferol ergosterol10 μg/d if houseboundOily fish, egg yolk, butter, fortified margarine; action of ultraviolet rays (sunlight)Calcium and phosphorus homeostasisRickets (children); osteomalacia (adults)Rare; weight loss and diarrhoeaProduced in the body by action of sunlight on a provitamin in the skin: deficiency develops in those who are not exposed to sun
Vitamin E tocopherols tocotrienesNone setWheat germ, vegetable oils, nuts, seeds, egg yolk, cereals, dark green vegetables
  • Antioxidant.
  • Protects against cell membrane damage
Neurological abnormalities; anaemia: rare, from malnutrition or malabsorptionMuscle weakness, gastrointestinal disordersRequirement is increased with increased intake of polyunsaturated fatty acids
Vitamin K phylloquinones menaquinonesNone setGreen leafy vegetables, fruit and dairy productsNeeded for the production of prothrombin and other coagulation factorsImpaired clotting; liver damageNot so far observed from naturally occurring vitaminSynthesized by intestinal bacteria so deficiency unusual
Table 2: Micronutrients: minerals
Name and chemical symbolReference nutrient intake (adults, per day)SourcesFunctionsDeficiencyExcess
Calcium Ca700 mgMilk and milk products, green vegetables, soya beans, white bread, hard water
  • Crucial role in all cellular function, in neural transmission, muscle contraction, blood coagulation.
  • As phosphate in bones and teeth
  • Dietary deficiency not uncommon.
  • Rickets, osteomalacia from failure of Ca absorption in Vit D deficiency.
  • Low blood [Ca2+] causes tetany
Calcium deposits in soft tissue can occur, but probably not related to high intake
Chlorine Cl3.4 g (as chloride)Salt-containing foods
  • Major anion in ECF.
  • Role in maintaining electrical gradient across cell membranes
Unlikely with normal dietAs NaCl, risk factor for high blood pressure
Chromium Cr25 μgVegetables, cereals, meats, vegetable oils, whole grainsCo-factor for some enzymes involved in glucose and energy metabolism
  • Rare.
  • Impaired glucose metabolism
  • Inhibition of enzymes.
  • Occupational exposures can cause skin and kidney damage
Copper Cu900 μgMeat, drinking waterCo-factor for some enzymes; intermediate in electron transfer during oxidative phosphorylationLow activity of antioxidant enzymesVery high intake can cause liver damage
Iodine I140 μgSeafood, iodized salt, milk and milk products, meat and eggsSynthesis of thyroid hormonesThyroid swelling (goitre) with hypothyroidism: low BMR, lethargyRarely any effect; may exacerbate some skin diseases
Iron Fe
  • Women 14.8 mg
  • Men 8.7 mg
Liver, kidney, red meat, egg yolk, wholegrains, pulses, dark green vegetables, dried fruit, treacle, cocoa, molassesComponent of haemoglobin, myoglobin and many enzymes
  • Iron deficiency anaemia not uncommon.
  • In childhood, poor growth; impaired intellectual development
Can be toxic if very excessive. (from blood transfusions rather than from diet); gastrointestinal upset; may promote vascular disease
Fluoride F3-4 mgDrinking water, mostly as calcium fluoride; tea, seafoodMay be important in maintenance of bone structureIncreased risk of tooth decayUnlikely from dietary sources
Magnesium Mg
  • Women 270 mg
  • Men 300 mg
Cereals, milk, nuts, seeds, and green vegetablesCo-factor for enzymes essential in metabolism; role in calcium homeostasis; skeletal development; neuromuscular functionUncommon; can occur with malabsorption or in chronic renal failure, when it accompanies hypocalcaemiaUnlikely from dietary sources
Phosphorus-P550 mg (as phosphate)Milk, cheese, yogurt, meat, poultry, grains, fishAdenosine phosphate compounds vital in energy metabolism. With Ca in bones and teethOnly in severe malnutrition; muscle weakness, bone pain, rickets, anorexia, anaemiaIn treatment of osteoporosis or bone cancer with biphosphonates
Potassium K3.5 gFruit, vegetables, meat, wholegrains
  • Major intracellular cation; muscle contraction and nerve excitability.
  • Linked to acid-base regulation
  • Poor dietary intake rare. Can occur with prolonged use of diuretics and purgatives.
  • Muscular weakness; depression; confusion; cardiac arrhythmia
High ECF [K+] (hyperkalaemia) causes cardiac arrest
Selenium Se
  • Women 50 μg
  • Men 70 μg
Seafood, meat, grains, wheat flourKey component in the endogenous antioxidant, glutathione peroxidaseHealth implications of low intake in UK currently under DoH review. May cause abnormality of heart muscleExcessive supplements: hair loss, skin rash, neurological disorder
Sodium Na1.6 gMainly as salt: table salt, and in milk, meat, vegetables, sauces, pickles, processed foods, snacks, cheeseMajor extracellular cation; linked to ECF volume, hence to blood volume and blood pressure. Component of bone mineralLoss in sweat and diarrhoea; dilution in body fluids due to excess water intake. Weakness, cramp; faintness, confusionOedema, hypertension
Zinc Zn
  • Women 7.0 mg
  • Men 9.5 mg
Red meat, dairy products, eggs, wholegrains, peas, beans, nuts, lentils
  • Co-factor for many enzymes.
  • Synthesis of some proteins. Wound healing; immune system; physical and sexual development
  • Retarded skeletal growth; sexual immaturity.
  • Anorexia, fatigue
  • Nausea, vomiting, or anaemia with chronic excess.
  • Also decreases iron and copper bioavailability

micronutrients

essential food factors including trace elements and vitamins but which are required in only very small amounts by the body

micronutrients (mīˈ·krō·nōōˑ·trē·nts)),

n.pl substances such as vitamins and minerals needed in small amounts for normal body function.

mi·cro·nu·tri·ents

(mī'krō-nū'trē-ĕnts)
Essential food factors required in only small quantities by the body; e.g., vitamins, trace minerals.
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