Learn — Minerals

5 notes · 16 questions on the topic

Minerals — sources and deficiency

Minerals are the inorganic elements that the body needs from food, and they are grouped as macrominerals — calcium, phosphorus, magnesium, sodium, potassium, chloride and sulphur — required in more than about 100 mg a day, and trace elements such as iron, iodine, zinc, copper, selenium, fluoride, manganese and chromium required in milligram or microgram amounts. They matter clinically far beyond biochemistry, because iron, iodine, calcium and zinc deficiency are the four commonest nutritional problems in India, each has a national programme behind it, and each is corrected by advice and supplementation that a nurse gives.

Calcium: about 99 per cent is in bone as hydroxyapatite and the serum total calcium is roughly 8.5 to 10.5 mg/dL with about half of it ionised and active; parathyroid hormone raises calcium and lowers phosphate, calcitriol raises both and calcitonin lowers calcium, absorption requires vitamin D and is blocked by phytates and oxalates, and deficiency produces tetany with carpopedal spasm, positive Trousseau and Chvostek signs, laryngospasm and a prolonged QT interval, and over years osteoporosis.
Iron: the body holds about 3 to 4 g, haem iron from meat, fish and liver is absorbed far better than the non-haem iron of cereals and pulses, vitamin C and an acid stomach enhance absorption while tea and coffee tannins, phytates, calcium and antacids block it; deficiency gives a microcytic hypochromic anaemia in which serum ferritin falls first, serum iron falls and total iron-binding capacity rises, and it is treated with oral iron taken on an empty stomach with a citrus drink, with the patient warned about black stools, nausea and constipation.
Iodine: almost all of the body's small store is in the thyroid and it is needed to make thyroxine, so deficiency causes goitre and hypothyroidism in the adult and, in the fetus, cretinism with intellectual disability, deaf-mutism, short stature and spasticity, along with stillbirth and abortion; the adult daily requirement is about 150 micrograms, more in pregnancy, and prevention is universal salt iodisation, with iodised salt required to carry not less than 30 parts per million at production and 15 parts per million at the consumer end.
Zinc: it is the cofactor of more than 300 enzymes and is essential for growth, immunity, taste and wound healing, so deficiency causes growth retardation, delayed healing, hypogonadism, alopecia, persistent diarrhoea and the inherited absorptive defect acrodermatitis enteropathica; in childhood diarrhoea zinc is given with oral rehydration salts for 14 days — 20 mg daily in a child over six months and 10 mg daily below that — which shortens the episode and reduces recurrence for the next two to three months.
Magnesium: it is the cofactor for every ATP-dependent enzyme and for the sodium-potassium pump, and hypomagnesaemia causes tremor, tetany, arrhythmia including torsades de pointes, and — the point that is examined — a hypokalaemia and hypocalcaemia that refuse to correct until the magnesium is replaced first.
Copper: it is needed for ceruloplasmin, cytochrome c oxidase and lysyl oxidase which cross-links collagen; deficiency causes anaemia unresponsive to iron, neutropenia and bone changes, while the two named disorders are Menkes kinky hair disease (defective absorption) and Wilson's disease (accumulation in liver and brain with Kayser-Fleischer rings and a low serum ceruloplasmin).
Fluoride and selenium sit at the two ends of the trace-element story: fluoride at about 1 part per million in drinking water protects against dental caries, but above the permissible limit of 1.5 mg per litre it causes mottled dental fluorosis and, at higher intakes in endemic belts of India, crippling skeletal fluorosis, while selenium is the cofactor of glutathione peroxidase and its deficiency causes the cardiomyopathy of Keshan disease.
Phosphorus, sodium, potassium and chloride are covered by the electrolyte panel, but the nursing point is that phosphate is required for ATP and for 2,3-diphosphoglycerate in the red cell, and that a fall in phosphate, potassium and magnesium during the first days of refeeding a severely malnourished patient is the refeeding syndrome that kills.

Iron — dietary sources, absorption and daily requirements

Dietary iron is the trace element the body needs for haemoglobin, myoglobin and the cytochromes, taken from food in two chemically different forms — haem iron from meat, liver, fish and poultry, and non-haem iron from cereals, pulses, green leafy vegetables, jaggery and fortified foods. Because a cereal-based Indian diet supplies almost all of its iron as the poorly absorbed non-haem form, the practical questions are not how much iron a food contains but how much of it the gut can take up, what in the same meal helps or blocks that uptake, and how far the ICMR-NIN 2020 allowance sits above the amount actually absorbed.

Haem iron (meat, liver, fish, poultry) is absorbed at roughly 15 to 35 per cent and is little affected by the rest of the meal; non-haem iron (cereals, pulses, green leafy vegetables, jaggery, dates, fortified salt and rice) is absorbed at only about 2 to 10 per cent, so a mixed vegetarian Indian diet yields single-digit absorption and the allowance is set correspondingly high.
Absorption happens in the duodenum and upper jejunum in the ferrous (Fe2+) state, and is switched on and off by hepcidin according to body stores — stores are low in the growing child, the menstruating woman and pregnancy, which is why absorption rises when the body is short and why a deficient person absorbs more from the same food.
Enhancers to pair with a meal: vitamin C (lemon, amla, guava, orange, tomato), other organic acids, meat and fish (the meat factor), and germination and fermentation of cereals and pulses (sprouts, idli, dosa); the iron-folic acid tablet is best taken with water or a citrus drink an hour before food when tolerated.
Inhibitors to separate from a meal: tannins in tea and coffee, phytates in whole cereals and unsoaked pulses, oxalates (spinach), calcium and milk, and antacids or proton-pump inhibitors, which cut acid; the single most useful Indian counselling point is no tea or coffee with meals or with the iron tablet — keep them an hour apart, and keep calcium tablets two hours away from iron.
ICMR-NIN 2020 recommended allowances: adult man 19 mg a day, adult woman 29 mg (menstrual losses), pregnancy 27 mg, lactation 23 mg; adolescent girls need the most of any group, at about 30 mg a day, because the growth spurt and menstruation coincide.
Indian food sources worth naming: liver and meat; ragi and bajra among cereals; whole pulses and soya; amaranth, drumstick and other green leafy vegetables; jaggery, dates and sesame; and the fortified foods now in the public system — double-fortified salt (iodine plus iron) and fortified rice kernels blended into the rice of the public distribution system, ICDS and school meals, all carrying the +F logo.
Deficiency runs from depleted stores (low ferritin) through iron-deficient erythropoiesis (low transferrin saturation) to microcytic hypochromic anaemia, with fatigue, pallor, koilonychia, angular stomatitis, pica and poor work capacity; the anaemia itself, its haemoglobin bands and the test-and-treat programme are on the iron-deficiency anaemia and Anemia Mukt Bharat notes.
Side effects of oral iron — black stools, nausea, constipation or diarrhoea — are the usual reason tablets are stopped; take them after food if they are not tolerated on an empty stomach, alternate-day dosing is absorbed as well, and every iron bottle is kept out of a child's reach because a handful of adult tablets is a poisoning dose for a toddler.

Iodine — goitre, IDD control and salt iodisation

Iodine deficiency disorders (IDD) are the whole spectrum of harm caused by a diet short of iodine — goitre, hypothyroidism, cretinism, abortion, stillbirth, low birth weight and preventable loss of intellect — and they arise wherever the soil, and so the food grown on it, has been leached of iodine, classically the sub-Himalayan goitre belt but in fact every state of India. They matter because the damage to the developing brain is permanent while the prevention costs almost nothing: iodised salt, monitored at the kitchen table.

The requirement is about 150 micrograms a day for adults and rises in pregnancy and lactation, when WHO advises 250 micrograms a day; iodine is needed only to make thyroxine and triiodothyronine, so every consequence of deficiency is a consequence of too little thyroid hormone at the wrong age.
The spectrum by age: in the fetus abortion, stillbirth, congenital anomalies and cretinism; in the newborn goitre and neonatal hypothyroidism; in the child and adolescent goitre, impaired growth and mental function; in the adult goitre with its complications, hypothyroidism and reduced mental function — the iceberg is far larger than the visible goitre.
Endemic cretinism has a neurological form (deaf-mutism, squint, spastic diplegia, intellectual disability) from fetal deficiency and a myxoedematous form (dwarfism, hypothyroidism) from deficiency continuing after birth; both are prevented only if the mother has enough iodine before and during pregnancy.
India's programme began as the National Goitre Control Programme in 1962 and was renamed the National Iodine Deficiency Disorders Control Programme (NIDDCP) in 1992 on the strategy of universal salt iodisation; the sale of non-iodised salt for direct human consumption is banned under the food safety regulations.
The legal standard for iodised salt is not less than 30 parts per million of iodine at the manufacturing level and not less than 15 parts per million at the consumer level; the difference allows for the loss in transport, storage and cooking, and the consumer figure is the one the exam asks.
Monitoring runs on three measures: salt testing with the spot-testing kit by the ASHA, ANM and school teacher (a blue-violet colour means iodine is present), the median urinary iodine of school children (100 to 199 micrograms per litre is adequate, below 20 is severe deficiency), and goitre surveys in 6 to 12 year olds (a total goitre rate of 5 per cent or more marks a public-health problem).
Iodine is lost from salt by moisture, heat and sunlight, so the household advice is to buy packeted iodised salt, store it in a closed dry container away from the stove, and add salt towards the end of cooking rather than at the start; Global Iodine Deficiency Disorders Prevention Day is 21 October.

Calcium — sources, requirements and bone health

Dietary calcium is the mineral that builds and maintains the skeleton, where 99 per cent of the body's calcium sits as hydroxyapatite, while the remaining one per cent in blood and cells serves nerve conduction, muscle contraction, clotting and hormone release and is held in a narrow range whatever the diet does. The nursing questions are how much is needed at each stage of life under the ICMR-NIN 2020 tables, which Indian foods supply it, what helps and hinders its absorption, and why the intake of the teenage years and of pregnancy decides the bone of old age.

ICMR-NIN 2020 allowances: 1000 mg a day for adult men and women and for pregnancy, 1200 mg a day in lactation, and about 1000 mg through adolescence, when peak bone mass is being laid down; peak bone mass is reached by about 30 years, after which calcium can only slow loss, not add bone.
Sources: milk and its products are the best-absorbed (a 250 mL glass gives roughly 300 mg, and curd and paneer the same per equivalent), ragi is the richest cereal at about 350 mg per 100 g, sesame (til), small fish eaten with bones, soya, and green leafy vegetables such as amaranth and drumstick leaves; spinach is calcium-rich on paper but its oxalate makes most of it unavailable.
Absorption is about 30 per cent of intake and depends on vitamin D (calcitriol), an acid stomach and lactose; it is reduced by phytates, oxalates, excess phosphate (colas, processed foods), caffeine and a very high-fibre load, and is better from doses of 500 mg or less, so supplements are split across the day.
Supplement timing: calcium carbonate needs food and acid, calcium citrate does not; keep calcium two hours away from iron tablets and four hours away from levothyroxine, because it blocks the absorption of both; the antenatal programme gives 500 mg twice a day from 14 weeks of pregnancy to six months after delivery, at a different time from the iron.
Bone health is a triad — calcium, vitamin D (sunlight, fortified milk and oil, or supplements) and weight-bearing exercise — and the losers are the housebound elderly, post-menopausal women, patients on long-term steroids, and anyone with malabsorption or chronic kidney disease; osteoporosis is silent until the hip or vertebral fracture.
Low serum calcium presents as tingling around the mouth and fingertips, carpopedal spasm, Chvostek's and Trousseau's signs, tetany and, at worst, laryngospasm and seizures; the dietary deficiency itself shows as rickets in children and osteomalacia and osteoporosis in adults, which is why bone pain and proximal weakness in a veiled, indoor woman is a nutritional diagnosis.
Excess comes from supplements, not food: calcium with high-dose vitamin D can cause hypercalcaemia (thirst, polyuria, constipation, confusion, kidney stones), and calcium tablets taken with large amounts of milk and antacids produce the milk-alkali syndrome; the total from diet and tablets should stay below about 2000 mg a day.

Zinc, fluoride and trace elements — needs, excess and fluorosis

The trace elements are the minerals the body needs in milligram or microgram amounts — zinc, fluoride, selenium, copper, chromium, manganese and others — each essential as an enzyme cofactor or a structural component and each harmful in excess, so that the same element appears in the syllabus once as a deficiency disease and once as a toxicity. Zinc and fluoride carry most of the exam weight in India: zinc because it is a treatment given by every nurse in childhood diarrhoea, fluoride because the water of whole districts contains too much of it.

Zinc is the cofactor of more than 300 enzymes and is needed for growth, immunity, taste and wound healing; the ICMR-NIN 2020 allowance is about 17 mg a day for men and 13 mg for women, from meat, fish, eggs, nuts, pulses and whole grains, with the phytate of an all-cereal diet lowering its absorption.
Zinc deficiency shows as growth retardation and delayed puberty, hair loss, a scaly dermatitis around the mouth and anus, diarrhoea, loss of taste and poor wound healing; the inherited form, acrodermatitis enteropathica, is the textbook picture and responds dramatically to zinc.
Zinc in acute diarrhoea is a treatment, not a supplement: 20 mg of elemental zinc daily for 14 days for children from 6 months to 5 years and 10 mg daily for infants under 6 months, given with ORS and continued feeding, shortens the episode and lowers the risk of the next one for the following two to three months.
Fluoride at about 0.5 to 0.8 mg per litre of drinking water protects against dental caries, and the Indian standard for drinking water sets the acceptable limit at 1.0 mg per litre with a maximum of 1.5 mg per litre where no alternative source exists; above that, dental fluorosis appears as chalky white then brown mottling of the permanent teeth that erupt while the child drinks the water.
Skeletal fluorosis follows years of water at several milligrams per litre: stiff painful joints, a rigid spine, bony outgrowths and crippling deformity, with genu valgum in children; it is endemic in Rajasthan, Gujarat, Andhra Pradesh, Telangana, Karnataka, Tamil Nadu and Uttar Pradesh among other states, and the National Programme for Prevention and Control of Fluorosis maps and manages it.
Prevention of fluorosis is a water problem, not a diet problem: an alternative safe source, rainwater harvesting, or defluoridation by the Nalgonda technique (lime, alum and bleaching powder) or activated alumina filters; adequate calcium and vitamin C in the diet lessen the harm but do not prevent it.
Selenium is the antioxidant partner of vitamin E in glutathione peroxidase; deficiency gives Keshan disease, a cardiomyopathy, and excess gives selenosis with garlic breath and hair loss. Copper deficiency causes an anaemia that does not respond to iron and the kinky hair of Menkes disease, while copper excess is Wilson's disease with its Kayser-Fleischer rings; chromium improves glucose tolerance.

Free today: the 10-question daily quiz · the NORCET 11 recall paper · what ₹999 unlocks — once, no auto-renewal.