general physiology - nutrition

NUTRITION Prepared by Dr. Iyad Sunna

Energy intake & output are balanced Intake of different food provide energy that can be used to perform body

function or stored for later use. Stability of body weight over a period of time requires that the person’s

energy intake be balanced with the energy consumed.

Example: • When energy intake is more than the energy consumed that will result in

weight increase.• When energy intake is less than the energy consumed that will result in weight

loss.

BODY ENERGETICS

Energy liberated from each gram of Carbohydrates is 4.1 calories, energy liberated from each gram of Fat is 9.3 calories and energy liberated from each gram of Protein is 4.3 calories.All these substances vary in the average percentage that are absorbed in the Gastrointestinal tract about 98% of Carbohydrates, 95% of Fat and 92% of Protein are absorbed. Therefore the average energy in each gram of these substances in diet is as follows: Carbohydrates 4 calorieFat 9 calorieProtein 4 calorie

ENERGY AVAILBALE IN FOOD

In this table we can see that the composition of selected food specially with high proportions of fat and protein in animal products. And the food with high proportion of carbohydrates is in vegetables and grain products.

Daily requirements of protein is from 30 to 50 grams, person usually use from 20 to 30 grams of the body protein to produce body chemicals on daily basis. So the cells will be able to form new protein to compensate those who were destroyed depending on the person’s protein diet ( some proteins don’t have good quantities of some essential amino acids and therefor cannot be used to replace the destroyed protein, these proteins are called partial proteins).

In general proteins derived from animal product are better than proteins that are derived from vegetables and grains and this is the reason why some individuals in poor countries who depend on their protein intake from vegetable and grain products develop a protein deficiency syndrome called “Kwashiorkor”

AVERAGE DAILY REQUIRMENTS OF PROTEIN

KWASHIORKOR

Characteristics: • Retarded growth• Fatty liver • Severe Edema • Anemia • Malabsorbtion due to atrophy of the

small intestinal villi.• Depigmented bands in the hair or

skin.• Loss of muscle with preservation of

subcutaneous fat

MARASMUS SYNDROME

Is caused by wide spread deficiency of almost all nutrients, notably proteins.

Characteristics:

• Retarded growth• Loss of muscle with loss of subcutaneous fat • Prominent bones • Loose skin

• Sensation of hunger associated with several objective sensations such as contraction of stomach and restlessness and that’s cause the person to search for food.

• The person’s appetite is the desire for certain type of food, if the food selection was successfully done, the feeling of satisfaction occurs.

• Each of there feelings( Hunger, appetite and satisfaction) influenced by environmental and cultural factors as well as specific centers in the brain (Hypothalamus).

• Stimulation of the lateral nuclei of Hypothalamus (act as a feeding center) will result in hyperphagia, conversely destruction on lateral nuclei of Hypothalamus will result in lack of desire of food, muscle weakness, weight loss and decrease in metabolism

REGULATION OF FOOD INTAKE

• Stimulation of the ventro medial nuclei of Hypothalamus (act as a satisfaction center) will give complete feeling od satisfaction even in the presence of food and the person refuses to eat (Aphagia)

• Conversely destruction of this region will result in too much and continuous eating.

• The Paraventricular and dorsomedial nuclei of Hypothalamus also involved in regulation of food intake. Example: lesions of paraventricular nuclei cause excessive eating and lesion of the dorsomedial nuclei depress eating.

• Also these nuclei of Hypothalamus affect the secretion of several hormones which is important in regulation energy balance and metabolism including those from Thyroid and Adrenal glad and pancreatic cells.


• Also Hypothalamus receives neural signals from gastro intestinal tract about stomach filling and chemical signals from nutrients in blood (glucose, amino acids and fatty acids) and other signals from the gastro intestinal tract hormones and cerebral cortex (sight, smell and taste) that influence feeding behavior.

• Hypothalamic feeding and satisfaction centers have high density of receptors for neurotransmitters and hormones that control feeding behavior.

Decreases Feeding Increase FeedingSerotonin,

NorepinephrineLeptinInsulin

Corticotropin- releasing hormone

Neuropeptide YMelanin concentrating hormone

GalaninCortisol


• Other aspects of feeding is the mechanical action of the feeding process( salivation, licking the lip, chewing and swallowing) so if we sectioned the brain below Hypothalamus and above mesencephalon the person can still do the mechanical features of feeding, therefore the actual mechanics of feeding controlled by centers in the brain stems.

• We have centrals higher than Hypothalamus which is important in controlling feeding specially appetite. These centers are Amygdala and Prefrontal Cortex.

• Destruction of Amygdala on both sides of the brain will lead to psychic blindness in choice of food, in other words the human loses the appetite and loses control of type and quality of food.


• Factors regulating quantity of food intake are divided into : a. Short Term Regulations b. Intermediate and Long Term Regulations

FACTORS REGULATING QUANTITY OF FOOD INTAKE

Short Term Regulations: Which concerns with preventing over eating at the time of each meal. We have several of feedback signals as:

1. Gastro intestinal filling inhibition factor When the gastro intestinal tract become full specially stomach and duodenum, stretching inhibition signals is transmitted to suppress feeding centers .

2. Hormonal factorsCholecystokinin a gastro intestinal hormone released when fat inters the duodenum has an effect on suppressing feeding centers. Also presence of food in stomach and duodenum cause the pancreas to secrete glucagon and insulin which have effect on suppressing feeding centers .

3. Oral receptors meters food intakeOral factors related to feeding (salivation, chewing, tasting and swallowing) meters the food as it pass through the mouth and after certain amount it suppresses the feeding centers


Intermediate and Long Term Regulations Which concerns with maintaining normal quantities of energy stored in the body.

1. Glucostatic, aminostatic and lipostatic theoriesDecrease in the blood contents of glucose or amino acids or lipids(Fatty acids) will cause hunger ( stimulating of feeding centers).

2. Relation between body temperature and food intake.When a person is exposed to cold, he over eats and when a person is exposed to heat he under eat. This is due to the interaction in the hypothalamus between temperature regulating system and food regulating system. Example: increase food intake in the cold person leads to an increase in the metabolic rate and an increase in the fat insulation. Both tend to correct the cold state


Intermediate and Long Term Regulations 3. Feedback signals from adipose tissue regulate food intake

Most of stored energy consist of fat, so the relation between the fat and the energy storing (food intake) is as follows: recent studies suggest that hypothalamus senses the energy stored by peptide hormones called leptin.When adipose tissue increase there will be an increase in the production of leptin in the blood to reach the leptin receptors in the hypothalamus, stimulating of these receptors will cause: a. Decrease production of appetite stimulatorsb. Increase production of hormones which decreases food intake as Corticotropin- releasing hormonec. Increase in metabolic rate.d. Decrease in insulin secretion which decrease the energy storage.


VITAMINS

Its an organic compound needed in small amount for normal body metabolism. Vitamins are divided into Water soluble and Fat soluble.

Water Soluble Fat Soluble Vitamin B1Vitamin B2Vitamin B3

Vitamin B6 Vitamin B12Vitamin C Folic Acid

Vitamin A Vitamin D Vitamin E Vitamin K

Water soluble vitamins are not stored in the body, so regular intake of these vitamins is important except for Vitamin B12 because it is stored in the liver in large quantities which can last for months or even a year.

Toxicity from excessive intake is rare because excess amount will go out with the urine

VITAMINS- Water Soluble Vitamins

The co-enzyme Thiamine pyrophosphate plays an important role in carbohydrates and amino acids metabolism

Deficiency in this vitamin will cause: Wet Beriberi Dry Beriberi Infantile Beriberi Wernicke-korsakoff Syndrome.


Vitamin B1 (Thiamine)

Wet Beriberi

Wet beriberi affects the heart and circulatory system. It is sometimes fatal, as it causes a combination of heart failure and weakening of the capillary walls, which causes the peripheral tissues to become edematous. Wet beriberi is characterized by:

• Increased heart rate• Vasodilation leading to decreased systemic vascular resistance, and high output cardiac failure• Elevated jugular venous pressure• Dyspnea (shortness of breath) on exercise.• Peripheral oedema (swelling of lower legs)



Dry BeriberiDry beriberi causes wasting and partial paralysis resulting from damaged peripheral nerves. It is characterized by:

• Difficulty in walking• Tingling or loss of sensation (numbness) in hands and feet• Loss of tendon reflexes• Loss of muscle function or paralysis of the lower legs• Mental confusion/speech difficulties• Pain• Involuntary eye movements • Vomiting.



Infantile Beriberi Infantile beriberi usually occurs between two and six months of age in children whose mothers have inadequate thiamine intake. In the acute form, the baby develops dyspnea and cyanosis and soon dies of heart failure. Infantile Beriberi is characterized by: :

• Hoarseness, where the child makes moves to moan with no sound • Weight loss, Vomiting, Diarrhea• Pale skin• Edema• Ill temper• Alterations of the cardiovascular system, especially tachycardia (rapid heart rate)



Wernicke-korsakoff Syndrome. also called wet brain or Korsakoff's psychosis, is the combined presence of Wernicke's encephalopathy and Korsakoff's syndrome due to the close relationship between these two disorders. WKS is usually secondary to alcohol abuse. It is characterized by:

• Ocular disturbances • Changes in mental state • Unsteady walking and stand (ataxia)



Vitamin B2 is a component of two important coenzymes ( Flavin mononucletoide FMN and Flavin adenine dinucleotide FAD) which are hydrogen carrier of the oxidative system of mitocondria.

The deficiency in vitamin B2 causes:• Cheilosis • Corneal Vascularization• Glossitis • Dermaitis


Vitamin B2 (Riboflavin)

Vitamin B3 act as a coenzymes in the form of Nicotinamide Adenine Dinucleotide (NAD) or Nicotinamide Adenine Dinucleotide Phosphate NADP which are essential to glycolysis and they are hydrogen acceptors they combine with hydrogen atoms .

The deficiency in vitamin B3 causes Pellagra :

Pellagra: A disease due to deficiency of niacin, a B-complex vitamin.

Pellagra is the "disease of the four D's" -- Diarrhea; Dermatitis: A scaly rash on skin exposed to light or trauma; Dementia: Mental disorientation, delusions and depression; and Death.


Vitamin B3 (Niacin, Nicotinic Acid)

http://www.medicinenet.com/rash/article.htm

http://www.medicinenet.com/depression/article.htm

Vitamin B6 is necessary in synthesis of Niacin from Tryptophan.

The deficiency in vitamin B6 causes:• Cheilosis • Glossitis • Anemia • Nuerologic dysfunction


Vitamin B6 (Pyridoxine)

Vitamin B12 is necessary in folate synthesis and in DNA synthesis and the major fuction of B12 is the promotion of growth and promotion of red blood cells formation and maturation .

The deficiency in vitamin B12 causes:• Pernicious Anemia • Megablastic Anemia • Neurologic Dysfunction (Demyelination of the large nerve fibers of the spinal

cord)


Vitamin B12 (Cobalamin)

Folic Acid Act as hydroxymythyl and formyl groups. The most important use in the body is in the syntheses of

purines, and thymine, which are required for formation of DNA, therefore, Folic acid like Vitamin B12 is required for replication of the cellular genes, thus its essential to promote growth.

Folic acid is more potent growth promoter than vitamin B12, and like vitamin B12 in the importance of RBC maturation.

Deficiency of Folic acid result in megaloblastic anemia, and it does not cause neurologic changes as in Vitamin B12 deficiency.

Vitamin C is essential in collagen synthesis and hydroxylation of dopeamin in synthesis of norepinephrine.


Vitamin C (Ascorbic Acid)

The deficiency in vitamin C causes:

• Weakness in collagen fibers• Defective wound healing • Scurvy: is a disease resulting from a deficiency

of vitamin C. Scurvy often presents initially with fatigue, followed by formation of spots on the skin, spongy gums, and bleeding from the mucous membranes.

Scurvy

Fat soluble vitamins are stored in the body, either in the cells or in the liver so regular intake is not that important ( Person can stay from 5-10 months without Vitamin A intake and from 2-4 months without Vitamin D intake.

VITAMINS- Fat Soluble Vitamins

Vitamin A is a term for a group of compounds (Retinoids) . Vitamin A is important in the maintenance of mucus secretion epithelium. Also Retanol is a Vitamin A derivative and its component of visual pigment Rhodopsin.

The deficiency in vitamin A causes:• Night blidness due to insufficiant retinal rhodopsin • Squmous metaplasia of tracia, bronchi and renal pelvis

Hypervitaminosis can cause alopecia, hepatoceluar damage and bone changes.


Vitamin A

Synthesized in the skin by ultra violate light. It is important in Calcium and Phosphorus intestinal absorption.

The deficiency in vitamin D causes:• Rickets in children • Osteomalasia in adults due to improper calcium absorption.

Hypervitaminosis can cause growth retardation in children and hyper calciurea and renal calculi in adults.


Vitamin D

Its an antioxidant.

The deficiency in vitamin E is rare but if it happens it can cause neurologic dysfunction


Vitamin E

It is essential in the formation of clotting factor ( II, VII, IX and X).

The deficiency in vitamin K will cause a bleeding problem marked by prolonged prothrombin and activated partial thrombopastin time


Vitamin K

MINERALSThe importance, function and deficiency of some essential minerals in the body

Magnesium act as a catalyst for many reactions specially those related to carbohydrates metabolism.

The extracellular fluid magnesium concentration is slight only 1.8 to 2.5 mEq/l Increased extracellular of magnesium depressed activity in the nervous system as

well as skeletal muscle contraction. Low magnesium concentration causes irritability of the nervous system, peripheral

vasodilation and arrhythmias.

MINERALSMagnesium (Mg)

Present in the body in the form of Calcium Phosphate in the bone. Excess Calcium concentration in the extracellular fluid can cause the heart to stop in

systole and it can act as a mental depressant. Low level of Calcium concentration can cause spontaneous discharge of nerve fibers

resulting in Tetany.

MINERALSCalcium (Ca)

Phosphorus have the ability to combine reversibly with many coenzymes systems with multiple other compound that are necessary in metabolic process

MINERALSPhosphorus (P)

Trace elements are few elements present in the body in small quantities, yet without any one of them deficiency syndromes will develop.

TRACE ELEMENTS

Iodine is very important in the formation and function of thyroid hormones which are essential for maintaining normal metabolic rate in all the cells

TRACE ELEMENTS Iodine (I)

Fluorine (F) Presence of Fluorine in small amount during a certain

period of time when the teeth are being developed is important for protecting against caries.

Excess intake of fluorine causes Fluorosis which affect teeth and they become mottled and in sever cases it causes bone enlargement.

Fluorosis

Is an integral part of many enzymes specially carbonic anhydrase which present in high concentration in the red blood cells.

This enzyme is responsible for rapid combination of CO2 with water in the red blood cells of the peripheral capillary and rapid release of CO2 from the pulmonary capillaries into the alveoli.

This enzyme is also found in the gastrointestinal mucosa, in the tubules of the kidney and in the epithelial cells of many glands. Therefore Zinc in small amount is important for many reactions related to CO2 metabolism.

Zinc is also a component of lactic dehydrogenase and therefore it is important for the interconversion between Pyruvic acid and lactic acid.

Finally zinc is a component of peptidases, therefore it is important in protein digestion

TRACE ELEMENTS Zinc (Zn)

The main function of iron is formation of Hemoglobin. Two thirds of Iron in the body is in the form of Hemoglobin, and the rest is found in

other forms in the liver and bone marrow. Electron carriers containing Iron ( specially in the cytochromes) are present in the

mitochondria and there fore iron is essential for transport of oxygen and for operation oxidative system within the tissue.

Without Iron life can come to an end in seconds.

MINERALSIron (Fe)

Dietary Sources B Complex Vitamins, except

Vitamin B12 Wholegrain cereal Green leafy vegetables Fish Meat Dairy Products Vitamin B12 Food of animal origins only Vitamin C Fruits, Specially Citrus fruits and Tomatoes Vegetables Meat Millk

Dietary Sources Folic Acid Green Leafy Vegetables Citrus Fruits Dried Beans and Peas Vitamin A Sweet Potato Carrot Butter Liver of Turkey, Beef, Fish, and Chicken Vitamin D Sunlight

Vitamin E Sunflower Oil Almond Oil Nuts Oil Butter and Egg yolk Vitamin K Green Leafy Vegetables Tomatoes Olive Oil Green Apples

THANK YOU!

general physiology - nutrition

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