Abdullah Zuhair Alyouzbaki Gastroenterologist and hepatologist 2/11/2016
Physiology of nutritionNutrients in the diet can be classified into macronutrients and micronutrients: 1.macronutrients which are eaten in relatively large amounts to provide fuel for energy. 2.micronutrients (e.g. vitamins and minerals), which do not contribute to energy balance but are required in small amounts because they are not synthesised in the body.
Physiology of nutrition
Energy balance: energy intake = energy expenditure.Determinants of energy balance.
Physiology of nutritionPhysiology of nutrition
Energy intake is determined by the ‘macronutrient’ content of food. Carbohydrates, fat, protein and (alcohol) provide fuel for oxidation in the mitochondria to generate energy (as adenosine triphosphate (ATP). The energy provided by each of these elements differs: • carbohydrates (16 kJ/g) • fat (37 kJ/g) • protein (17 kJ/g) • alcohol (29 kJ/g).Regulation of energy balance
Macronutrients (energy-yielding nutrients)
CarbohydratesThe ‘available’ carbohydrates (starches and sugars) supply over half the energy in a normal, well-balanced diet. No individual carbohydrate is an essential nutrient, as carbohydrates can be synthesised from glycerol or protein. However, if the available carbohydrate intake is less than 100 g per day, increased lipolysis leads to ketosis.Macronutrients:Carbohydrates
Individuals who do not produce lactase (‘lactose-intolerant’) are advised to avoid or limit dairy products and foods with added lactose.Starches in cereal foods, root foods and legumes provide the largest proportion of energy in most diets around the world.Macronutrients:Carbohydrates
Glycaemic index of foods: This is the area under the curve of the rise in blood glucose concentration in the 2 hours following ingestion of 50 g carbohydrate, expressed as a percentage of the response to 50 g anhydrous glucose. There is emerging evidence linking high glycaemic index foods with obesity and type 2 diabetes.Glycaemic index
Macronutrients: Carbohydratessome starches are digested promptly by salivary and then pancreatic amylase, producing rapid delivery of glucose to the blood , other starches are digested more slowly. Sugar alcohols (e.g. sorbitol) that are used as replacement sweeteners can cause diarrhoea if eaten in large amounts.
Macronutrients : Carbohydrates
Dietary fiber:Dietary fiber is not digested by human enzymes in the gastrointestinal tract.Most dietary fiber is known as the ‘non-starch polysaccharides’ (NSP).Dietary fiber can be broken down by the resident bacteria in the colon to produce short-chain fatty acids.
Macronutrients : Carbohydrates
Dietary fiber: Some types of NSP, notably the hemicellulose of wheat, increase the water-holding capacity of colonic contents and the bulk of faeces. They relieve simple constipation, appear to prevent diverticulosis and may reduce the risk of cancer of the colon. Other viscous, indigestible polysaccharides like pectin slow gastric emptying, contribute to satiety, and reduce bile salt absorption and hence plasma cholesterol concentration.Macronutrients : Fats
Macronutrients : FatsFat has the highest energy density of the macronutrients (37 kJ/g) .The principal polyunsaturated fatty acid (PUFA) in plant seed oils is linoleic acid (18 : 2 ω6). This and alphalinolenic acid (18 : 3 ω3) are the ‘essential’ fatty acids, which humans cannot synthesise de novo. They undergo further desaturation and elongation, to produce, for example, γ-linolenic acid (18 : 3 ω6) and arachidonic acid (20 : 4 ω6). These are precursors of prostaglandins and eicosanoids, and form part of the structure of lipid membranes in all cells.
Macronutrients : Fats
Fish oils are rich in ω3 PUFA which promote the anti-inflammatory cascade of prostaglandin production . They inhibit thrombosis by competitively antagonising thromboxane A2 formation.Substituting saturated fat (i.e. from animal sources: butter) with PUFA in the diet can lower the concentration of circulating low-density lipoprotein (LDL) cholesterol and may help prevent coronary heart disease.Macronutrients : Fats
High intakes of trans fatty acids (TFA) reflect the use of oils that have been partially hydrogenated in the food industry and associated with cardiovascular disease. Cholesterol is also an important substrate for steroid and sterol synthesis, but not an important source of energy.Macronutrients :Proteins
Proteins are made up of some 20 different amino acids, of which nine are ‘essential’ i.e. they cannot be synthesised in humans but are required for synthesis of important proteins. Another group of five amino acids are termed ‘conditionally essential’, meaning that they can be synthesised from other amino acids, provided there is an adequate dietary supply.Macronutrients :Proteins
The nutritive or ‘biological’ value of different proteins depends on the relative proportions of essential amino acids they contain. Proteins of animal origin, particularly from eggs, milk and meat, are generally of higher biological value than proteins of vegetable origin, which are low in one or more of the essential amino acids.
Dietary recommendations for macronutrients
Anthropometric measurementsBody mass index (BMI) is useful for categorising underand over-nutrition. It is the weight in kilograms divided by the height in metres, squared. For example, an adult weighing 70 kg with a height of 1.75 m has a BMI of 70/1.752 = 22.9 kg/m2.
Anthropometric measurements
Anthropometric measurementsAnthropometric measurements
An indication of the degree of abdominal obesity is the waist circumference, measured at the level of the umbilicus. Hip circumference can be measured at the level of the greater trochanters. waist : hip ratios show whether the distribution of fat is android or gynoid . Skinfold measurementsAnthropometric measurements
Anthropometric measurements
DISORDERS OF ALTERED ENERGY BALANCEObesity:Obesity is widely regarded as a pandemic.Over one-quarter (25%) of adults in the UK were obese (i.e. BMI ≥ 30 kg/m2) in 2010, compared with 7% prevalence in 1980 and 16% in 1995. Moreover, almost two-thirds of the UK adult population are overweight (BMI ≥ 25 kg/m2).
Complications of obesity
Complications of obesityComplications of obesity
it is clear that the lowest mortality rates are seen in Europeans in the BMI range 18.5–24 kg/m2 (and at lower BMI in Asians). It is suggested that obesity at age 40 years can reduce life expectancy by up to 7 years for non-smokers and by 13 years for smokers. Coronary heart disease is the major cause of death but cancer rates are also increased in the overweight, especially colorectal cancer in males and cancer of the gallbladder, biliary tract, breast, endometrium and cervix in females.Complications of obesity
Epidemic obesity has been accompanied by an epidemic of type 2 diabetes and osteoarthritis particularly of the knee. Although an increased body size results in greater bone density through increased mechanical stress, it is not certain whether this translates to a lower incidence of osteoporotic fracturesComplications of obesity
Obesity may have profound psychological consequences, compounded by stigmatisation of the obese in many societies.Complications of obesity
Body fat distributionFor some complications of obesity, the distribution rather than the absolute amount of excess adipose tissue appears to be important. Increased intra-abdominal fat causes ‘central’ (‘abdominal’, ‘visceral’, ‘android’ or ‘apple-shaped’) obesity, which contrasts with subcutaneous fat accumulation causing ‘generalised’ (‘gynoid’ or ‘pear-shaped’) obesity; the former is more common in men and is more closely associated with type 2 diabetes, the metabolic syndrome and cardiovasculardisease.
Body fat distribution
The key difference between these depots of fat may lie in their vascular anatomy, with intra-abdominal fat draining into the portal vein and thence directly to the liver. Thus many factors that are released from adipose tissue (including free fatty acids; ‘adipokines’, such as tumour necrosis factor-α, adiponectin and resistin; and steroid hormones) may be at higher concentration in the liver and hence induce insulin resistance and promote type 2 diabetes.Body fat distribution
Recent research has also highlighted the importance of fat deposition within specific organs, especially the liver, as an important determinant of metabolic risk in the obese.Abdullah Zuhair Alyouzbaki Gastroenterologist and hepatologist 2/11/2016
Aetiology of ObesityAccumulation of fat results from a discrepancy between energy consumption and energy expenditure . A continuous small daily positive energy balance of only 0.2–0.8 MJ (50–200 kcal; < 10% of intake) would lead to weight gain of 2–20 kg over a period of 4–10 years.Given the cumulative effects of subtle energy excess, body fat content shows ‘tracking’ with age such that obese children usually become obese adults.
Aetiology
Obesity is correlated positively with the number of hours spent watching television, and inversely with levels of physical activity (e.g. stair climbing). It is suggested that minor activities such as chewing gum may contribute to energy expenditure and protect against obesity.Aetiology
Susceptibility to obesityIt is not true that obese subjects have a ‘slow metabolism’, since their BMR is higher than that of lean subjects. Twin and adoption studies confirm a genetic influence on obesity. The pattern of inheritance suggests a polygenic disorder.
Susceptibility to obesity
Some of these genes encode proteins known to be involved in the control of appetite or metabolism and some of which have unknown function. However, these genes account for less than 5% of the variation in body weight.Susceptibility to obesity
A few rare genetic conditions in which obesity is a feature include the Prader–Willi and Lawrence–Moon–Biedl syndromes.Reversible causes of obesity and weight gain
Clinical assessment and investigationsIn assessing an individual presenting with obesity, the aims are to:• quantify the problem• exclude an underlying cause• identify complications• reach a management plan.
Clinical assessment and investigations
Severity of obesity can be quantified using the BMI A waist circumference of > 102 cm in men or > 88 cm in women indicates that the risk of metabolic and cardiovascular complications of obesity is high.Clinical assessment and investigations
A dietary history may be helpful in guiding dietary advice. It is important to consider ‘pathological’ eating behaviour (such as binge eating, nocturnal eating or bulimia), which may be the most important issue to address in some patients. Alcohol is an important source of energy intake and should be considered in detail.The history of weight gain may help diagnose underlying causes.Clinical assessment and investigations
A patient who has recently gained substantial weight or has gained weight at a faster rate than previously, and is not taking relevant drugs is more likely to have an underlying disorder such as hypothyroidism or Cushing’s syndrome. All obese patients should have thyroid function tests performed on one occasion, and an overnight dexamethasone suppression test or 24-hour urine free cortisol if Cushing’s syndrome is suspected.Clinical assessment and investigations
Clinical assessment and investigationsAssessment of the diverse complications of obesity requires a thorough history, examination and screening investigations. The impact of obesity on the patient’s life and work is a major consideration.Assessment of other cardiovascular risk factors is important. Blood pressure should be measured with a large cuff, if required . Associated type 2 diabetes and dyslipidaemia are detected by measuring blood glucose or HbA1c and a serum lipid profile, ideally in a fasting morning sample. Elevated serum transaminases occur in patients with non-alcoholic fatty liver disease
Management
The health risks of obesity are largely reversible. Lifestyle advice that lowers body weight and increases physical exercise reduces the incidence of type 2 diabetes. Most patients seeking assistance with obesity are motivated to lose weight but have attempted to do so previously without long-term success.Management
These patients may hold misconceptions that they have an underlying disease, inaccurate perceptions of their energy intake and expenditure, and an unrealistic view of the target weight that they would regard as a ‘success’.Management
A reasonable goal for most patients is to lose 5–10% of body weight.The management plan will vary according to the severity of the obesity and the associated risk factors and complications. It will also be influenced by availability of resources.Management :
Management : Lifestyle advice
Behavioural modification to avoid ‘obesogenic’ environment is the cornerstone of long-term control of weight. Regular eating patterns and maximizing physical activity are advised.Where possible, this should be incorporated in the daily routine (e.g. walking rather than driving to work), since this is more likely to be sustained.Alternative exercise (e.g. swimming) may be considered if musculoskeletal complications prevent walking.Management : Lifestyle advice
Changes in eating behaviour (including food selection, portion size control, avoidance of snacking, regular meals to encourage satiety, and substitution of sugar with artificial sweeteners) should be discussed. Regular support from a dietitian or attendance at a weight loss group may be helpful.Management :Weight loss diets
In some patients, more rapid weight loss is required, e.g. in preparation for surgery. There is no role for starvation diets, which risk profound loss of muscle mass and the development of arrhythmias (and even sudden death) secondary to elevated free fatty acids, ketosis and deranged electrolytes.Management : Drugs
A huge investment has been made by the pharmaceutical industry in finding drugs for obesity. The side-effect profile has limited the use of many agents, with notable withdrawals from clinical use of sibutramine (increased cardiovascular events) , in recent years; only one drug, orlistat, is currently licensed for long-term use. There is no role for diuretics, or for thyroxine therapy without biochemical evidence of hypothyroidism.Management : Drugs
Orlistat inhibits pancreatic and gastric lipases andthereby decreases the hydrolysis of ingested triglycerides, reducing dietary fat absorption by approximately 30%. The drug is not absorbed and adverse side-effects relate to the effect of the resultant fat malabsorption on the gut: namely, loose stools, oily spotting, faecal urgency, flatus and the potential for malabsorption of fat-soluble vitamins. Orlistat is taken with each of the three main meals of the day and the dose can be adjusted (60–120 mg) to minimise side-effects.Surgery
‘Bariatric’ surgery is by far the most effective long-term treatment for obesity and is the only anti-obesity intervention that has been associated with reduced mortality. Bariatric surgery should be contemplated in motivated patients who have very high risks of complications of obesity , in whom extensive dietary and drug therapy has been insufficiently effective.
Surgery
It is usually reserved for those with severe obesity (BMI > 40 kg/m2), or those with a BMI > 35 kg/m2 and significant complications, such as type 2 diabetes or obstructive sleep apnea.Surgery
The mechanism of weight loss may not simply relate to limiting the stomach or absorptive capacity, but rather in disrupting the release of ghrelin from the stomach or promoting the release of other peptides from the small bowel, thereby enhancing satiety signalling in the hypothalamus.Endoscopic Interventions
Under-nutritionStarvation and famine: There remain regions of the world, particularly rural Africa, where under-nutrition due to famine is endemic, the prevalence of BMI < 18.5 kg/m2 in adults is as high as 20%, and growth retardation due to under nutrition affects 50% of children.
Under-nutrition
In adults, starvation is the result of chronic undernutrition, i.e. sustained negative energy (calorie) balance.Under-nutrition: Clinical assessment
The clinical features of severe under nutrition in adults include:• weight loss• thirst, craving for food, weakness and feeling cold• nocturia, amenorrhoea or impotence• lax, pale, dry skin with loss of turgor and, occasionally, pigmented patches ,cold and cyanosed extremities, pressure sores.
Under-nutrition: Clinical assessment
• hair thinning or loss (except in adolescents)• muscle-wasting, best demonstrated by the loss of the temporalis and peri scapular muscles and reduced mid-arm circumference• loss of subcutaneous fat, reflected in reduced skinfold thickness and mid-arm circumference• hypothermia, bradycardia, hypotension and smallheart•Under-nutrition: Clinical assessment
oedema, which may be present without hypoalbuminaemia (‘famine oedema’).• distended abdomen with diarrhea.• diminished tendon jerks.• apathy, loss of initiative, depression, introversion,aggression if food is nearby.• susceptibility to infections.Under-nutrition: Clinical assessment
Under-nutrition: Clinical assessmentUnder-nutrition often leads to vitamin deficiencies, especially of thiamin, folate and vitamin C. Diarrhoea can lead to depletion of sodium, potassium and magnesium. The high mortality rate in famine situations is often due to outbreaks of infection, e.g. typhus or cholera, but the usual signs of infection may not be apparent. In advanced starvation, patients become completely inactive and may assume a flexed, fetal position. In the last stage of starvation, death comes quietly and often quite suddenly.
Under-nutrition:Investigations
In a famine, laboratory investigations may be impractical, but will show that plasma free fatty acids are increased and there is ketosis and a mild metabolic acidosis. Plasma glucose is low but albumin concentration is often maintained because the liver still functions normally. Insulin secretion is diminished, glucagon and cortisol tend to increase, and reverse T3 replaces normal triiodothyronine.Under-nutrition:Investigations
The urine has a fixed specific gravity and creatinine excretion becomes low. There may be mild anemia, leucopenia and thrombocytopenia. The erythrocyte sedimentation rate is normal unless there is infection.Under-nutrition:Investigations
Tests of delayed skin hypersensitivity, e.g. to tuberculin, are falsely negative. The electrocardiogram shows sinus bradycardia and low voltage.
Under-nutrition:Management
People with mild starvation are in no danger; those with moderate starvation need extra feeding; those who are severely underweight need hospital care. In severe starvation, there is atrophy of the intestinal epithelium and of the exocrine pancreas, and the bile is dilute. When food becomes available, it should be given by mouth in small, frequent amounts at first, using a suitable formula preparation.Abdullah Zuhair Alyouzbaki Gastroenterologist and hepatologist 2/11/2016
Under-nutrition in hospitalmany patients lose weight due to factors such as poor appetite, poor dental health, concurrent illness and even being kept ‘nil by mouth’ for investigations.The elderly are particularly at risk.
Nutritional support of the hospital patient
Normal diet : As a first step, patients should be encouraged to eat a normal and adequate diet. In patients at risk of under-nutrition ,quantities eaten should be recorded on a food chart. Hospital staff must identify and overcome barriers to adequate food intake, such as unpalatability of food, cultural and religious factors .Dietary supplements
These are drinks with high energy and protein content. They should be prescribed, and administered by nursing staff, to ensure that they are taken regularly.Dietary supplements
During refeeding, a weight gain of 5% body weight per month indicates satisfactory progress. Other care is supportive, and includes attention to the skin, adequate hydration, treatment of infections, and careful monitoring of body temperature since thermoregulation may be impaired.Enteral tube feeding
Patients who are unable to swallow may require artificial nutritional support: for example, after acute stroke or throat surgery, or when there are long-term neurological problems such as motor neuron disease and multiple sclerosis. The enteral route should always be used if possible, since feeding via the gastrointestinal tract preserves the integrity of the mucosal barrier. This prevents bacteraemia and, in intensive care patients, reduces the risk of multi-organ failure.Enteral tube feeding
If the need for artificial nutritional support is thought to be short-term, then feeding is instituted using a finebore nasogastric tube or , in some instances , nasojejunal tube. If long-term artificial enteral feeding is needed, a percutaneous endoscopic gastrostomy (PEG) should be sited.Parenteral nutrition
Intravenous feeding should only be used when enteral feeding is impossible. Parenteral feeding is expensive and carries higher risks of complications. There is little benefit if parenteral feeding is required for less than 1 week.Parenteral nutrition
There are a number of possible routes for parenteralnutrition:• Peripheral venous cannula. • Peripherally inserted cannula (PIC). • Peripherally inserted central catheter (PICC).• Central line.Parenteral nutrition
The main energy source is provided by carbohydrate,usually as glucose. The solution also contains aminoacids, lipid emulsion, electrolytes, trace elements andvitamins.Relevant tests include:• daily: urea and electrolytes, glucose• twice weekly: liver function tests, calcium, phosphate, magnesium• weekly: full blood count, zinc, triglycerides• monthly: copper, selenium, manganese.Parenteral nutrition
Refeeding syndrome
When nutritional support is given to an under-nourished patient, there is a rapid conversion from a catabolic to an anabolic state. Administration of carbohydrates stimulates release of insulin, leading to cellular uptake of phosphate, potassium and magnesium, which may provoke significant falls in serum levels..Refeeding syndrome
The resulting electrolyte imbalance can have serious consequences, such as cardiac arrhythmias, so careful monitoring is essentialIn patients who are thiamin-deficient, Wernicke’sencephalopathy can be precipitated by refeedingwith carbohydrates ; this is prevented by administering thiamin before starting nutritional support.Refeeding syndrome
MICRONUTRIENTS, MINERALS AND THEIR DISEASESVitamins: Vitamins are organic substances with key roles in certain metabolic pathways, and are categorised into those that are fat-soluble (vitamins A, D, E and K) and those that are water-soluble (vitamins of the B complex group and vitamin C).
Fat-soluble vitamins
Vitamin A (retinol) Pre-formed retinol is found only in foods of animal origin. Vitamin A can also be derived from carotenes, which are present in green and coloured vegetables and some fruits. The most important consequence of vitamin A deficiency is irreversible blindness in young children.Vitamin A (retinol)
Early deficiency causes impaired adaptation to the dark (night blindness). Keratinisation of the cornea (xerophthalmia) gives rise to characteristic Bitot’s spots, and progresses to keratomalacia, with corneal ulceration, scarring and irreversible blindness.where xerophthalmia is commonly occurring , WHO recommend giving single prophylactic oral doses of retinyl palmitate to pre-school children. This also reduces mortality from gastroenteritis and respiratory infections.
Vitamin A (retinol)
Vitamin A (retinol)Repeated moderate or high doses of retinol can cause liver damage, hyperostosis and teratogenicity. Acute overdose leads to nausea and headache, increased intracranial pressure and skin desquamation. Excessive intake of carotene can cause pigmentation of the skin (hypercarotenosis); this gradually fades when intake is reduced.
Vitamin D
Vitamin DThe effects of vitamin D deficiency is calcium deficiency,rickets and osteomalacia. Excessive doses of cholecalciferol, ergocalciferol or the hydroxylated metabolites cause hyper calcaemia. There is increasing evidence that vitamin D is important for immune and muscle function, and may reduce falls in the elderly.
Vitamin E
The most important dietary form is α-tocopherol. Human deficiency is rare and has only been described in premature infants and in malabsorption. It can cause a mild haemolytic anaemia, ataxia and visual scotomas. Diets rich in vitamin E are consumed in countries with lower rates of coronary heart disease.Vitamin K
Vitamin K2 is also synthesised by bacteria in the colon. Vitamin K is a co-factor for carboxylation reactions of some clotting factors. Vitamin K deficiency leads to delayed coagulation and bleeding.Vitamin K
In obstructive jaundice, dietary vitamin K is not absorbed and it is essential to administer the vitamin in parenteral form before surgery. Warfarin and related anticoagulants act by antagonising vitamin K. Vitamin K is given routinely to newborn babies to prevent haemorrhagic disease.
Water-soluble vitamins
Thiamin (vitamin B1 )Thiamin is widely distributed in foods of both vegetable and animal origin. Thiamin pyrophosphate (TPP) is a co-factor for enzyme reactions involved in the metabolism of macronutrients (carbohydrate, fat and alcohol)
Thiamin (vitamin B1 )
In thiamin deficiency, cells cannot metabolise glucose aerobically to generate energy as ATP. Neuronal cells are most vulnerable, since they depend almost exclusively on glucose for energy requirements. Impaired glucose oxidation also causes an accumulation of pyruvic and lactic acids, which produce vasodilatation and increased cardiac output.Thiamin (vitamin B1 ) Deficiency – beri-beri In the developed world, thiamin deficiency is mainly encountered in chronic alcoholics. Poor diet, impaired absorption, storage and phosphorylation of thiamin in the liver, and the increased requirements for thiamin to metabolise ethanol all contribute. In the developing world, deficiency usually arises as a consequence of a diet based on polished rice.
Thiamin (vitamin B1 ) Deficiency – beri-beri The body has very limited stores of thiamin, so deficiency is manifest after only 1 month on a thiamin-free diet. There are two forms of the:1.Dry (or neurological) beri-beri manifests with chronicperipheral neuropathy and with wrist and/or footdrop, and may cause Korsakoff’s psychosis andWernicke’s encephalopathy .2. Wet (or cardiac) beri-beri causes generalised oedemadue to biventricular heart failure with pulmonarycongestion.
Thiamin (vitamin B1 ) Deficiency – beri-beri In dry beri-beri, response to thiamin administration is not uniformly good. However, multivitamin therapy seems to produce some improvement, suggesting that other vitamin deficiencies may be involved.Wernicke’s encephalopathy and wet beri-beri should be treated without delay with intravenous vitamin Band C mixture . Korsakoff’s psychosis is irreversible and does not respond to thiamin treatment.
Riboflavin (vitamin B2 )
It mainly affects the tongue and lips and manifests as glossitis, angular stomatitis and cheilosis. The genitals may be affected, as well as the skin areas rich in sebaceous glands, causing nasolabial or facial dyssebacea. Rapid recovery usually follows administration of riboflavin 10 mg daily by mouth.Niacin (vitamin B3 )
Niacin include nicotinic acid and nicotinamide. Niacin can be synthesised in the body in limited amounts from the amino acid tryptophan.Niacin deficiency: Pellagra
Pellagra was formerly endemic among poor people who depend chiefly on maize, which contains niacytin, a form of niacin that the body is unable to utilise. Pellagra can develop in only 8 weeks in individuals eating diets that are very deficient in niacin and tryptophan. It remains a problem in parts of Africa, and is occasionally seen in alcoholics and in patients with chronic small intestinal disease in developed countries.Niacin deficiency: Pellagra
Pellagra can occur in Hartnup’s disease, a genetic disorder characterised by impaired absorption of several amino acids, including tryptophan. It is also seen occasionally in carcinoid syndrome when tryptophan is consumed in the excessive production of 5-hydroxytryptamine (5-HT).Niacin deficiency: Pellagra
Pellagra has been called the disease of thethree Ds: • Dermatitis. • Diarrhoea. • Dementia.Niacin deficiency: Pellagra
Treatment is with nicotinamide, given in a dose orally or parenterally. The response is usually rapid. Within 24 hours, the erythema diminishes, the diarrhoea ceases and a striking improvement occurs in the patient’s mental state. Nicotinic acid is a lipid-lowering agent.Pyridoxine (vitamin B6 )
Pyridoxine, pyridoxal and pyridoxamine are different forms of vitamin B6 that undergo phosphorylation to produce pyridoxal 5-phosphate (PLP). PLP is the co-factor for a large number of enzymes involved in the metabolism of amino acids. Deficiency is rare, although certain drugs, such as isoniazid and penicillamine, act as chemical antagonists to pyridoxine.Pyridoxine (vitamin B6 )
Pyridoxine administration is effective in isoniazid-induced peripheral neuropathy and some cases of sideroblastic anaemia. Large doses of vitamin B6 have an antiemetic effect in radiotherapy-induced nausea. Although vitamin B6 supplements have become popular in the treatment of nausea in pregnancy, carpal tunnel syndrome and premenstrual syndrome, there is no convincing evidence of benefit. polyneuropathy.Biotin
Deficiency results from consuming very large quantities of raw egg whites and It may also be seen after long periods of total parenteral nutrition. The clinical features of deficiency include scaly dermatitis, alopecia and paraesthesia.Folate (Folic acid)
Folates exist in many forms. The main circulating form is 5-methyltetrahydrofolate. Folic acid is the stable synthetic form. Folate works as a methyl donor for cellular methylation and protein synthesis. It is directly involved in DNA and RNA synthesis, and requirements increase during embryonic development.
Folate (Folic acid)
Folate (folic acid)Folate deficiency may cause three major birth defects (spina bifida, anencephaly and encephalocele). All women planning a pregnancy are advised to include good sources of folate in their diet, and to take folate supplements throughout the first trimester. Folate deficiency has also been associated with heart disease, dementia and cancer.
Hydroxycobolamin(vitamin B12)
Vitamin B12 is a co-factor in folate co-enzyme recycling and nerve myelination. Vitamin B12 and folate are particularly important in DNA synthesis in red blood cells. The hematological disorders (macrocytic or megaloblastic anemia) due to their deficiency . Vitamin B12, but not folate, is needed for the integrity of myelin, so that vitamin B12 deficiency is also associated with neurological diseaseNeurological consequences of vitamin B12 deficiency
In older people and chronic alcoholics, vitamin B12 deficiency arises from insufficient intake and/or from malabsorption. Several drugs, including neomycin, can render vitamin B12 inactive. In severe deficiency there is insidious, diffuse and uneven demyelination.Neurological consequences of vitamin B12 deficiency
It may be clinically manifest as peripheral neuropathy or spinal cord degeneration affecting both posterior and lateralcolumns (‘subacute combined degeneration of the spinalcord), or there may be cerebral manifestations (resembling dementia) or optic atrophy. Vitamin B12 therapy improves symptoms in most cases.
Vitamin C (ascorbic acid)
Deficiency – scurvyVitamin C deficiency causes defective formation of collagen with impaired healing of wounds, capillary haemorrhage and reduced platelet adhesiveness (normal platelets are rich in ascorbate). A dose of 250 mg vitamin C 3 times daily by mouth should saturate the tissues quickly. Daily intakes of more than 1 g/day have been reported to cause diarrhoea and the formation of renal oxalate stones.Vitamin C (ascorbic acid)
Vitamin C (ascorbic acid)Inorganic micronutrients
Calcium and phosphorusCalcium is the most abundant cation in the body and there are powerful homeostatic mechanisms control circulating ionised calcium levels. Between 20 and 30% of calcium in the diet is absorbed, depending on vitamin D status and food source.
Calcium and phosphorus
Calcium deficiency causes impaired bone mineralisation and can lead to osteomalacia in adults. Too much calcium can lead to constipation and toxicity has been observed in ‘milk-alkali syndrome.Calcium and phosphorus
Dietary deficiency of phosphorus is rare (except in older people with limited diets) since it is present in nearly all foods and phosphates are added to a number of processed foods. Deficiency causes hypo phosphataemia and muscle weakness secondary to ATP deficiency.
Iron
Iron is involved in the synthesis of haemoglobin, and is required for the transport of electrons within cells and in a number of enzyme reactions. Non-haem iron in cereals and vegetables is poorly absorbed but makes the greater contribution to overall intake, compared to the well-absorbed haem iron from animal products. Fruits and vegetables containing vitamin C enhance iron absorption, while the tannins in tea reduce it.Iron
Dietary calcium reduces iron uptake from the same meal which may precipitate iron deficiency in those with borderline iron stores. There is no physiological mechanism for excretion of iron, so homeostasis depends on the regulation of iron absorption.Iron
A regular loss of only 2 mL of blood per day doubles the iron requirement. On average, an additional 20 mg of iron is lost during menstruation, so pre-menopausal women require about twice as much iron as men.Iron
The major consequence of iron deficiency is anaemia. Dietary iron overload is occasionally observed and results in iron accumulation in the liver and, rarely, cirrhosis. Haemochromatosis results from an inherited increase in iron absorptionIodine
Iodine is required for synthesis of thyroid hormones. It is present in sea fish, sea weed and most plant foods grown near the sea. Iodine is lacking in the highest mountainous areas of the world and in the soil of frequently flooded plains .Iodine
In those areas where most women have endemic goitre, 1% or more of babies are born with cretinism (characterised by mental and physical retardation). There is a higher than usual prevalence of deafness, slowed reflexes and poor learning in the remaining population.
Zinc
Zinc is present in most foods of vegetable and animal origin. Acute zinc deficiency has been reported in patients receiving prolonged zinc-free parenteral nutrition and causes diarrhea, mental apathy, a moist, eczematoid dermatitis, especially around the mouth, and loss of hair.Zinc
Chronic zinc deficiency occurs in dietary deficiency, malabsorption syndromes, alcoholism and its associated hepatic cirrhosis. It causes the clinical features seen in the very rare congenital disorder known as acrodermatitis enteropathica (growth retardation, hairloss and chronic diarrhoea).acrodermatitis enteropathica
ZincIn the Middle East, chronic deficiency has been associated with dwarfism and hypogonadism. zinc supplements may accelerate the healing of skin lesions, promote general wellbeing, improve appetite and reduce the morbidity associated with the under-nourished state, and lower the mortality associated with diarrhoea and pneumonia in children.