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Nutritional and metabolic diseases By Dr.Dlair Maroof MB.CH.B , D.I.M , F.I.C.M NUTRIENT AND ENERGY REQIUREMENTS Macronutrients ENERGY-YIELDING NUTRIENTS • Carbohydrates, Lipids, Proteins • Functions: – Energy – Structure – Function Three dietary components can provide fuel for oxidation in the mitochondria to generate energy as (ATP). These have different energy densities: carbohydrates (4 kcal/g), lipids (9 kcal/g) and protein (4 kcal/g). Carbohydrates • Free sugars monosaccharide glucose , fructose disaccharides sucrose , maltose and lactose • Short chain CHO oligosaccharides maltodextrins Carb. Form Example Monosaccharide Glucose Fructose • Starch Galactose • Non starch polysaccharide fibrous cellulose Disaccharide Sucrose Lactose Maltose viscous pectins Polysaccharide Starch Cellulose Glycogen Sugars Classified into intrinsic (part of the cellular structure of fruit ,milk …etc ) more acceptable nutritionally and less harmful metabolically because of association with other natural nutrients Extrinsic( concentrated or refined ) goals Reduce intake to minimum as possible refined sugar is the major factor for dental carries Sugars also lead to hyperinsulinemia which associates with hyperlipidemia ,atherosclerosis and tumors like colon cancer Starches • In cereals(wheat, rice );in root foods (potato) and in legumes • Provides the largest proportion of calories • Some digested by salivary amylase others by pancreatic amylase , absorbed to increase blood sugar • A small % escape digestion to pass to colon to be fermented there by resident bacteria thus ,behaves like dietary fibers • Glycemic index :is the incremental area under the 2 hr glucose curve after eating the amount of food that contains 50 gm carbohydrates Non starch polysaccharide= dietary fibers They are parts of food not digested by human GIT enzymes Classficaton Fibrous NSP :cellulose ,hemicelluloses and lignin .increase the water holding capacity colonic contents and bulk of feces Relieve simple constipation , reduces incidence of diverticulosis and colon cancer Viscous NSP :pectins and gums more effective in upper intestine Slow gastric emptying ,contribute to satiety , flatten GTT curve and reduce plasma cholesterol Proteins • • • Dietary protein consists of both essential and other amino acids that are required for protein synthesis. Are main structural components of human body cells, adequate intake is essential for life as their constituents of essential amino acids(9 of 20 that can not be synthesized in the body) The nine essential amino acids are histidine, isoleucine, leucine, lysine, methionine/cystine, phenylalanine/tyrosine, threonine, tryptophan, and valine. • All amino acids can be used for energy, and certain amino acids (e.g., alanine) can also be used for gluconeogenesis. • When energy intake is inadequate, protein intake must be increased, since ingested amino acids are diverted into pathways of glucose synthesis and oxidation. In extreme energy deprivation, proteincalorie malnutrition may ensue • Current recommendations for a healthy diet call for at least 10–14% of calories from protein. • Biologic value tends to be highest for animal proteins, followed by proteins from legumes (beans), cereals (rice, wheat, corn), and roots. • Combinations of plant proteins that complement one another in biologic value or combinations of animal and plant proteins can increase biologic value and lower total protein requirements. • Protein needs increase during growth, pregnancy, lactation, and rehabilitation after malnutrition Fats • High energy density (9kcal /gm) contributes to obesity in sedentary people Classification Saturated :increases LDL and total cholesterol Monounsaturated (oleic acid ) Poyunsaturated w6 /lenolenic ,lenoleic [essential fatty acids ,precursor of prostogandins and leukotriens& arachidonic acids . w4/docosahexanoic acid[in fish oil are antagonists of thromboxane A2 & inhibitors of thrombosis]) Recommendations depending on individual’s risk for CHD , obesity &cancer Vs energy requirements