Organic Nutrients
Including: Proteins Charbohydrates Fats & lipids VitaminsObjectives:
By the end of this lecture you should be able: To know; definitions, classifications, food levels of cholesterol, To memorize; food prot. ,prot. Complementarities, factors affecting nitrogen balance, recommended intakes,(health effects of high protein, sugar &lipid intake), functions of prot., importance of dietary fibers, CHO, lipids,& E.F.A., def. of E.F.A. To calculate the daily requirement of prot., CHO, &Fat."Proteins"
* Is the 1st substance recognized to be vital (primary component) to the human tissues. *It is a complex of nitrogenous compound made up of 20 different amino acids in peptide linkage.Functions of proteins:
Dietary protein involves in; 1-Anabolic processes; growth & maintenance, to build up &maintain body tissues (keep up &replace). 2-Energy source: when decrease in CHO & fat (expensive). 3-Structural role: formation of Hb., enzymes, hormones &various body secretions. 4-Function of immune system: Ab. 5-Transportation: of TG., cholesterol, phospholipids ,fat sol. vit.& drugs.6- Hemeostasis: maintain normal osmotic pr. (decr. prot. Edema).7- Maintenance of appropriate PH (buffer).8-Detoxification (in the liver) for food toxins or drugs.9-Blood clotting : fibrin, collagen.10-Stored as fat if consumed in excess.11-Vision – opsin.
Amino Acids Classifications:
1-Essential a.a.= indispensable (IDAA): the body synthesis is inadequate to meet the metabolic needs (should be supplied from diet). There deficiency lead to negative nitrogen balance, wt. loss. 2-Non-essential a.a.= dispensable (DAA): can be synthesized in the body from essential a.a.Complementarity of food prot.: A diet high in animal prot. will provide adequate (E.A.A.) for efficient prot. synthesis. When eat a meal with a mixture of food (in sufficient quantity, the various prot. tend to complement each other.
High biological value protein (H.B.V.): Is that prot. containing all the E.A.A. in right amount for building tissues.
Eating large amount of cereal prot. which lack of one ess. a.a. lysine ( such as rice or wheat) in addition to legumes which lack in methionine (beans, chick peas &lentils), make the complementarity. Also can add small amount of meat to cereal diet will complement the inadequate protein.
Protein in food :
1-Complete prot. food: contain all 9 E.A.A. in sufficient quantities & ratio for the body needs e.g. milk, egg, meat- -(animal sources of prot.). 2- Incomplete prot. food: food that deficient in one or more of E.A.A. e.g. cereals, legumes& seeds (when take alone but when they are combined together they form a complete prot. food).Nitrogen Balance:
Because prot. are the only nutrients that contain nitrogen; there has been a strong relationship between nitrogen input (protein intake) & the outcome in the organism : "Nitrogen intake = Nitrogen output" (in urine, feces& sweat) " N.B. = I – ( U+ F+ S) " There difference may be +ve , –ve or zero =(N. equilibrium).In normal adult is in nitrogen equilibrium with losses just balanced by intake. Positive N.B. is seen during infancy, childhood, pregnancy & those during convalescence period(if adequately nourished). Negative N.B. can result following injuries, major trauma, fever or illness because of increased catabolism of the body protein stores.
Factors affecting N.B.:
1-Growth (+ve in children, -ve in elderly). 2-Age; (like growth) +ve in children&-ve in elderly 3-Hormones; growth H., insulin, male sex H.(+ve N.B.) 4-Injury& stress; operation, infection(-ve N.B.). 5-Psychological stress; -ve N.B. 6-physical exercise; ordinary exercise not affect N.B., but in athletic individual prolong exercise lead to gain in wt. due to muscular hypertrophy. 7-Diet;- in malnutrition -ve N.B. - in over intake +ve N.B. 8- Diseases; tissues break down -ve N.B.Recommended protein intake (RDA) : 1- An average of 15-20% of total energy intake for adult male &female in form of essential a.a. (0.8 gm/kg IBW). 2-For infants require 35% of total energy requirement in form of essential a.a. (2.2 gm/kg) for <0.6 m age.
Calculating your daily requirement of protein: Ideal Body wt.( kg) x 0.8gm/kg= gm of protein (RDA) e.g. 63.5 kg x 0.8gm/kg = 50.8 gm prot. RDA RDA=recommended daily allowance
Health effects of High protein diet: It should be not more than twice the RDA. It increase deamination by the liver which increase keto acids& ketosis.If more than twice it produce rapid wt. loss by stimulating fluid loss from the body.High protein diets may INCREASE the risk of cancer of the digestive tract, because they discourage eating carbohydrate (starchy) foods which reduce mutagenic 'pre-cancerous’ activity.
Consumption of high protein diet (esp.animal proteins.)associated with faster decline in kidney function esp. in patients with mild impairment of kidney function. Increased the risk of having microalbuminuria in people with both high blood pressure and diabetes. Increased calcium loss and increased incidence of Osteoporosis. Increased incidence of kidney stone formation (esp. animal proteins) due to increase blood & urine acidity.
"Carbohydrates (CHO)"
Carbohydrates: are organic compound consist of carbon, hydrogen &oxygen. CHO; consist of starches & sugars, they are rich food in their natural state are low in calories & high in fibers. Starches; are the least expensive (cheapest source of energy), the most easily obtained & the most readily digested form of fuel, also they considered as the major source of food for the people of the world (staple food).The main source of CHO; Cereals; breads, pastas, rice ----. Grains: legumes: lentils, chick peas, beans, favabeans,-- Fruits& vegetables Sugars( candy, sweats, sodas, ----).
Classification of CHO:
1-Monosaccharides = Simple sugars; (great sources of quick energy), include: Glucose =grape sugar= dextrose; the simplest form, in fruits, vegetables &honey. Fructose= fruit sugar; in fruits, veg., sugar beet, sugar cane & honey. Galactose& mannose = milk sugar : in milk (not occur in free form in the food).Sorbitol; in fruits (apple, peach), vegetables & dietetic diet, have the same sweeting power of glucose with very slow absorption rate. It less likely to cause dental caries than sucrose. Mannitol; in pineapples, olives, carrots& dietetic diet (50% of it absorbed from intestine, useful in obesity). Xylitole: it is absorbed 1/5 rate of glucose. It is used in sugarless chewing gum.
2-Disaccharides: Sucrose= table sugar (glucose+ fructose); in cane, beet sugar &molasses. Lactose= milk sugar (glucose+ galactose); in milk &dairy products (not occur in plant food). Maltose= malt sugar (glucose +glucose): in malt produces. Latulose: synthetic product not occur free in food, not digested= used as laxative. Trehalose (glucose): in mushrooms &yeast.
3-Polysaccharides = complex CHO; (take longer time to be digested &release glucose to the blood), include: A-Digestible form: *Starches: in cereals; bread, rice, oatmeal &whole grains, (the end product is glucose). *Glycogen= animal starch( stored in the muscles & liver): in meat products& sea food (glucose). B- Partially digestible: *Inulin: onion, garlic& mushrooms (fructose). *Galactogens: snails (galactose). *Mannosans: legumes (mannose). *Raffinose: sugar beets, kidney beans, lentils (glucose,fructose, galactose). *Stachyose: beans. *Pentosans: fruits& gums. The digestion is incomplete, needs further splitting by bacteria in large bowel which leads to production of flatus.
C- Indigestible= dietary fibers (in plant food): These substances have affinity for water, form bulk& slow gastric emptying time& may bind to bile acids. They are not digested by G.I. enzymes, may divide into; -Soluble form: pectin, &gum. -Insoluble forms: cellulose & hemi cellulose. (Bran cereals; are the most concentrated fiber sources, providing 6-13 gm fibers/ serving). *Cellulose: in leaves of veg., outer covering of seeds. *Hemi cellulose: in leaves of veg., outer covering of seeds, it used as laxatives & feeling of satiety. *Pectin: fruits, jams &jellies (absorb water to form jells). *Gums: plant secretion & seeds.
Importance of Dietary Fibers:
1-Prevent constipation: by normalizing the intestinal transit time, increase the fecal bulk which decreases colon intra luminal pressure, act as substrate for colonic fermentation& gas production to move fecal material through the colon. Without sufficient water it leads to dry stool & hemorrhoids. Transit time: is the time of contact of food particles to the wall of the colon.2-Role in CVS: By reducing cholesterol by 3 mechanisms (when give large amount of soluble fiber); *Binding to the bile salts& cholesterol & prevent reabsorption. *Increasing the fecal bulk which reduce the exposure of bile salt to mucosal cells. *Bacteria in the colon reduce soluble fibers to short chain fatty acids which block cholesterol synthesis in the liver.
3-Role in diabetic patients: The water soluble fibers play a hypoglycemic role by; *Affecting the glycemic index of food. *Delay gastric emptying time. *Slow starch hydrolysis& decrease glucose absorption. *Shortening intestinal transit time & reduce glucose absorption. 4-Protective role against Ca colon, by: *Decrease concentration of carcinogen. *Reduce the transit time. *Affect production of bile acids.
5-Stimulate chewing, saliva flow& gastric juice ( beneficial effect on digestion). 6-Benifitial role in management of obesity by; *Filling the stomach & providing a sense of satiety. *Delay gastric emptying& slows the rate of digestion & absorption of nutrients. 7-Prevention of diverticulae. Notes: -Excessive fibers intake may interfere with the absorption of Ca, Fe,& Zn esp. in children& elderly.
Importance of CHO:
1-Major & cheapest source of energy. 2-Protein sparing action. 3-Anti-ketogenic action; when decr. CHO intake leads to lipolysis which incr. fat& keton bodies +Na acidosis& dehydration. 4-Role in the activity of nervous tissues &they are the only source of energy for brain (glucose). 5-Importance of dietary fibers.6-Lactose affects growth of bact. in the colon laxative effect &synthesis of v.k. in large intestine incr. absorption of Ca &P. 7-Glucouronic acid (metabolites of glucose) act in the liver to combine with chemical &bacterial toxins to form substances that can be excreted outside. 8-CHO &their derivatives serve as a precursors for production of nucleic acid, conn. tissue matrix &galactosides of nervous tissues.
Recommended intake of CHO: 1-Total CHO intake 50-60% of total energy intake. Refined sugar limited to 5-10%. 2- Minimum intake 50-100gm/day is needed to meet glucose needs &prevent ketosis. 3-Recommended dietary fiber intake to 25-35gm/d. -Fibers intake should consist of equal amount of sol. & insol. Fibers (5 serving of veg. &fruits + 6 serving of whole grain, cereals& legumes).
How to calculate your daily requirement of CHO?
Health Effects of Sugars over intake:The sugars should be consumed in moderate amount but the over consumption of sugars lead to: 1-Nutrient displacement; which the major health problem because of losing important nutrients replaced by empty energy foods. 2-Dental caries. 3-Obesity: high calories intake stored as fat. 4-Risk of development of D.M. type II. 5-Hyperactivity &/ or attention deficient disorders (ADD): in children whose increase sugars intake, these foods possibly cause altered behaviors due to nutrients deficiency.
"Lipids"
Include; fats, oils, phospholipid (lecithin),& sterols (cholesterol), waxes& related compounds in the foods & body, they are insoluble in water , soluble in organic solvent (chloroform ðer). Fatty acids: basic units of fats composed of chains of carbon atoms with an acid group at one end and hydrogen atoms attached all along their length.Chemical properties of fatty acids:
1-Length of f. a. chain: the longer the chain more solid the fat. 2-Degree of saturation; a-Saturated f. a.: e.g. steanic acid (in butter & eggs), solid at room temp.(fat). b-Unsaturated f. a.: liquid at room temp.(oil). I-mono-unsaturated e.g. linolenic acid (olive oil, almond oil& peanuts oil). II-poly-unsaturated e.g. linoleic acid (corn oil& sunflower oil).Notes: T.G.: the major class of dietary lipids form >90% of lipids in the body& food . Polyunsaturated & monounsaturated fat has the same numbers of calories as saturated fat. T.G. in most foods of animal origins are saturated. T.G. in most food of plant origins are unsaturated except palm oil &coconut oil are saturated. Fresh water fish & sea foods contain predominant unsaturated f. a. Cholesterol is present only in foods of animal origin esp. organs (liver, kidney, brain--)&absent in plant foods. Cholesterol is imp. for the synthesis of folic acid, some hormones & brain growth in children.
Importance of the lipids:
1-Major source of energy (in storage form). 2-Protein sparing action for tissue synthesis. 3-Adepose tissues help to hold body organs& nerves in position (padding). 4-The subcutaneous layer of fat insulates the body & maintain body temp. 5-Transport & absorption of fat sol. vit.,& Ca. 6-They depress gastric sec. &slow emptying time= satiety. 7-Add palatability to food.
Problems caused by lipids:
1-Insoluble &floating over water leads to decrease their excretion outside the body &when there is increase intake leads to obesity. 2-Over intake of fat sol. vit. leads to hypervitaminosis & toxicity (A&D). 3-In a mixed meal containing CHO, prot. &fat, the fat float over them (delayed emptying from the stomach causing indigestion). 4-The incr. in fat & chol. Intake leads to CVD (Saturated Fats increases total cholesterol& LDL). 5-The oxidation of lipid leading to turbidity. 6- Reuse of lipids in frying cause health problems .Essential f.a.:
There are 2 groups of essential F.A.1-Omega 6 =lenoleic acid( in corn oil, soybeans, nuts, seeds). Its advantages: – Decreases total cholesterol – Decreases LDL-cholesterol But it decreases HDL-cholesterol 2-Omega 3 =alpha-linolenic acid (in olive oil, peanuts & fish). Its advantages: – Decreases total cholesterol – Decreases LDL-cholesterol – Increases HDL-cholesterol – Decreases serum triglyceridesImportance of Essential Fatty Acids:
1-Important activity in formation of cholesterol esters, plasma phospholipids &mitochondrial lipoproteins. 2-Integrity of capillary wall& cell membrane. 3-Helps to lower s. cholesterol. 4-Helps in prolongation of blood clotting time & incr. fibrinolytic activity. 5-Important for growth, skin integrity, fertility &maintenance of RBC structure. 6-Important in formation & function of cell membrane in retina &CNS. 7-Help in regulating blood pressure& immune function.Deficiency of E.F.A
1-Scaly dry skin & eczema in neonate (fed on canned milk which is def. in linoleic acid). 2-Liver impairment. 3-Poor wound healing. 4-Growth failure. 5-Vission impairment. 6-Thrombocytopenia 7-Increased susceptibility to infections.Cholesterol:
Present only in animal foods, it is essential component of structural membrane of all cells especially brain & nervous tissues. Recommended daily value for cholesterol = 300 mg/day. Sources: Exogenous cholesterol (from food). Endogenous cholesterol (synthesis in liver &intestinal cells &stored in the liver).Food sources of cholesterol; Liver 400mg/3 oz serving. Lamb& beef 80-85mg/3oz serving. Egg 252mg (1 large). Poultry 74mg/3 oz serving (skinless). Fish45-60mg/3 oz = Whole milk 34mg/cup Ice cream 54-98mg/cup Cheese 28mg/oz serving.
Dietary facts of lipids:
1-Each gm. Supply 9Kcal. 2-High intake of dietary chol. increase s. chol. level by few mg/100ml. 3-Dietary intake containing only sat. f.a. it incr. s. chol. level by 40-50 mg/100ml. 4-Dietary intake of PUFA (corn oil) &mono- unsaturated f.a. (olive oil) they decr. s. chol. 5-Dietary fibers decrease s. chol. by binding to bile acids & preventing their reabsorption. 6-Strees increase s.chol.How Much Fat Do you Need?
No more than 30% of total calories daily intake should come from fat, in equal ratio1:1:1 8-10% from saturated fat 10% from polyunsaturated fat 10% from monounsaturated fatHow to calculate your daily requirement of fat? 1-Determine your appropriate energy needs Kcal /day . Multiply it by 0.3 for 30% fat intake. 2- Divide that no. by 9 Kcal/gm fat. eg. If you consume 1800Kcal/day 1800x 0.3=540 divide by 9Kcal=60gm fat/day