PHYSIOLOGY OF NUTRITION PHYSIOLOGY OF NUTRITION AND VITAMINSAND VITAMINS

MUDr. Romana Šlamberová, Ph.D.

NutritionNutrition Food is any substance that can be consumed.

Food is the main source of energy and of nutrition, and is usually of animal or plant origin.

Food is a source of substances that are not energy and nutrient supply, but are esencial for our life (vitamins, salts, trace elements).

Metabolism (change) = is the biochemical modification of chemical compounds in living organisms and cells. This includes the biosynthesis of complex organic

molecules (anabolism) and their breakdown (catabolism).

CalorieCalorie A calorie is a unit of measurement for energy.

The small calorie or gram calorie approximates the energy needed to increase the temperature of 1 g of water by 1 °C. This is about 4.185 J.

The large calorie or kilogram calorie approximate the energy needed to increase the temperature of 1 kg of water by 1 °C. This is about 4.185 kJ, and exactly 1000 small calories.

The amount of food energy in a particular food could be measured by calorimetry.

Recommended daily energy intake values for young adults are: 2500 kcal/d (10 MJ/d, 120 W) for men and 2000 kcal/d (8 MJ/d, 100 W) for women. Children, sedentary and older people require less energy, physically active people more.

CalorimetryCalorimetry

Calorimetry is the science of measuring the heat of chemical reactions or physical changes.

Energy moving from one place to another is called heat and calorimetry uses the measurement of temperature changes to track the movement of heat. Direct calorimetry = oxidation of substances in calorimeter or

change of water temperature induced by a body Indirect calorimetry = measuring products of biological

oxidations (CO2, H2O, final products of protein catabolism) or

consumption of O2 (4,82 kcal freed energy / 1 litre of O2).

Indirect calorimetryIndirect calorimetry The Respiratory Quotient is used in BMR calculations (basal

metabolic rate) and is a form of indirect calorimetry. RQ = CO2produced / O2consumed

RQ carbohydrates = 1 RQ lipids = 0,7 RQ proteins = 0,8

Basal metabolic rate (BMR), is the rate of metabolism that occurs when an individual is at rest in a warm environment and is in the post absorptive state, and has not eaten for at least 12 hours. BMR = 2000 kcal/day (during sleep even lower)

The release of energy in this state is only sufficient for the vital organs.

BMR decreases with age and with the loss of body mass. Regular cardiovascular exercise can increase BMR. Other factors can also affect BMR, such as illness, previous food, environmental temperature, and stress levels.

Body Mass IndexBody Mass Index Energy balance = balance between intake and dispensation of

energy Negative = consumption of inner supplies Positive = storage to inner supplies

  BMI = body mass index = weight (kg) / height squared (m)2

< 20 underweight 20 - 25 normal weight 25 - 30 overweight – 1st degree (light) obesity 30 - 40 2nd degree (significant) obesity > 40 3rd degree (malignant) obesity

Intake controlIntake control Two areas in the hypothalamus:

Centre of fullness (ventromedial nucleus) = if it is activated, no need of food intake

Centre of hunger (lateral nucleus) = if it is activated, need of food intake

Hormones: Leptin is protein hormone that plays a key role in regulating

energy intake. Leptin is released by fat cells in amounts body fat stores. Thus, circulating leptin levels give the brain (hypothalamic centers) information about energy storage for the purposes of regulating appetite and metabolism.

Orexin (hypocretin) is hormone that was suggested to be primarily involved in the stimulation of food intake. Now it is know that it is also responsible for sleep (its dysregulation causes narcolepsy).

Disorders = obesity or cachexia

Factors affecting food intakeFactors affecting food intake Activation or inhibition of hypothalamic food intake centers

Information from the stomach = few hours after emptying stomach spontaneous “hungry” contractions appear

Surrounding temperature = cold stimulates feeling of hunger, warm inhibits it

Body temperature = after meal body temperature increases and decreases appetite and induce feeling of fullness.

Glycostatic cells in the hypothalamus = register level of glycemia. Decrease of glycemia stimulates centre of hunger, increase of glycemia inhibits it.

Other regions of the CNS = cortex – conditioned reflex (perception of aroma, form), tradition, time schedule

Total energy situation of organism = decrease of supplies and increase of appetite after sport, hard work

ObesityObesity Obesity is a condition where the natural energy reserve,

stored in the fatty tissue is increased to a point where it is thought to be a significant risk factor for certain health conditions as well as increased mortality.

Excessive body weight has been shown to correlate with various important diseases, particularly cardiovascular disease, Diabetes mellitus type 2, sleep apnea and osteoarthritis.

Not only percentage of fat in the body but also the WHR = waist hip ratio is important Abdominal (men’s) type of obesity (like apple) = high risk for most of the

diseases WHR men > 0.95 WHR women > 0.85

Gynoid (women’s) type of obesity (like pear) = lower risk

BMI > 30BMI > 30

AnorexiaAnorexia Anorexia nervosa is an eating disorder characterized by

voluntary starvation involving psychological and sociological components.

Symptoms: Refusal to maintain body weight at or above a minimally

normal weight for age and height (less than 85% of that expected, BMI < 17.5).

Intense fear of gaining weight or becoming fat. Amenorrhea (the absence of at least three consecutive

menstrual cycles). Treatment: hospitalization, psychotherapy, collaboration

with family

BulimiaBulimia Bulimia nervosa is an eating disorder. It is a

psychological condition in which the subject engages in recurrent binge eating followed by the following activities in order to compensate for the food intake and prevent weight gain: vomiting inappropriate use of laxatives, enemas, diuretics or

other medication excessive exercising fasting

Water intake controlWater intake control Centers in the hypothalamus near to the

paraventricular nucleus Centre of thirst

Regulation: osmoreceptors = activated based on the osmotic changes in the body hypertonic environment induces feeling of

thirst hypotonic the opposite

Role of ADH, Aldosterone and others

Monitoring of food intakeMonitoring of food intake Quantitative point of view = energy from food intake

should be the same as energy consumption Qualitative point of view = ratio of food components has

to correspond to demand of the body (with respect of the age, work, climatic conditions, etc.) Carbohydrates - 50 – 80 % Lipids - 20-30 % Proteins - 10-15 %

During starvation 70-80% of glucose needed for the brain, the rest erythrocytes. Muscles use fatty acids.

CarbohydratesCarbohydrates

Function: important storage and transport form of energy.

Low carbohydrates intake: Very low carbohydrate diets can slow down brain and neural function (the nervous system especially relies on glucose).

High carbohydrates intake: Diabetes mellitus

LipidsLipids Function:

Cell membrane structure Energy storage Important for some vitamins (absorption and metabolism of vitamins soluble

in fat; butter important source of vitamin A) Essential lipids: Arachidonic acid, Linoleic acid and Linolenic acid (mostly

in vegetal oils = include important fosfolipids) Low lipid intake:

missing essential lipids hypovitaminosis

High lipid intake: Hyperlipidemia – risk of cardiovascular diseases Normal: cholesterol < 5.2 mmol/l

triacylglycerols < 1.7 mmol/l LDL < 3.9 mm/l

HDL > 0.9 mmol/l

Proteins (1)Proteins (1) Function: proteins are involved in functions controling

almost all the molecular processes of the body (enzymes, hormones, structural proteins, antibodies etc.). Essential aminoacids: leucine, isoleucine, valine, methionine,

phenylalanine, lysine, threonine, tryptophan. Semiessential aminoacis: histidine, arginine (during growing),

tyrosine (during kidney failure – not formation from phenylalanine).

Nitrogen balance: protein intake and excretion Positive nitrogen balance: Higher intake (kidney load) Optimal protein intake: 0.8 g / kg (in children and pregnant

women 1.3-2.0 g/kg)

Proteins (2)Proteins (2) Low protein intake:

Marasmus = insufficient amount of food with balanced composition Extremely decreased lipid storage in the body, muscle atrophy

("autocannibalism") and body weight less than 80% of normal Kwashiorkor = type of childhood malnutrition caused by

inadequate protein intake in the presence of fairly good total calorie intake. Low oncotic pressure – ascites

Secundar hypoproteinemia: Insufficient carbohydrate intake (gluconeogenesis), cirrhosis (albumin insufficiency), kidney failure (lost of proteins), malabsorption (absorption disorder)

High protein intake: (more than 1.5 – 2.0 g/kg/day) Kidney overload, increased blood pressure (salty sausages)

Vitamins Vitamins ((11)) The word vitamine was coined by the Polish

biochemist Casimir Funk in 1912. Vita in Latin is life and the -amine suffix is for

amine; at the time it was thought that all vitamins were amines.

A vitamin is an organic molecule required by a living organism in small amounts for proper health.

An organism deprived of all sources of a particular vitamin will eventually suffer from disease symptoms specific to that vitamin – Avitaminosis.

Vitamins Vitamins ((22))

Avitaminosis is any disease caused by chronic or long-term vitamin deficiency or caused by a defect in metabolic conversion.

Hypervitaminosis is the syndrome of symptoms caused by over-retention (mostly of fat-soluble vitamins) in the body, which can lead to toxic symptoms.

In humans, there are thirteen vitamins, divided into two groups, the four fat soluble vitamins (A, D, E and K) and the nine water soluble vitamins (eight B vitamins and vitamin C).

Water soluble vitaminsWater soluble vitamins Vitamin C - Ascorbic acid Vitamins B

Vitamin B-1 (Thiamine) Vitamin B-2, also Vitamin G (Riboflavin) Vitamin B-3, also Vitamin P or Vitamin PP (Niacin) Vitamin B-5 (Pantothenic acid) Vitamin B-6 (Pyridoxine and Pyridoxamine) Vitamin B-7, also Vitamin H and Vitamin B-w (Biotin) Vitamin B-9, also Vitamin M and Vitamin B-c (Folic acid) -

important for pregnancies Vitamin B-12 (Cyanocobalamin)

Fat soluble vitaminsFat soluble vitamins Vitamin A – Retinol Vitamin D

Vitamin D2 - Ergocalciferol Vitamin D3 - Cholecalciferol

Vitamin E - Tocopherol Vitamin K

Attention!

Risk of hypervitaminosis!

Vitamin AVitamin A Chemical Name: Retinol Solubility: Fat Daily dose: 620μg Source:

Plants: green vegetable, darkly colored fruits Animals: milk, liver, eggs, fish oil

Function: Antioxidant. Production of rhodopsin (visual pigment), essential for the correct functioning of epithelial cells, glycoprotein synthesis, involved in maintaining healthy lymphocytes and T-cells, needed for normal haemopoiesis, production of human growth hormone.

Deficiency disease:Night blindness, blindness by making the cornea very dry and damaging the retina, immunodeficiency, abnormalities in iron metabolism.

Hypervitaminosis: 7.5 mg or higher dose. High levels of carotene are not toxic.

Vitamin A toxicityVitamin A toxicity Livers of certain animals, especially those adapted

to polar environments (polar bears) contain toxic dose of vitamin A.

Xavier Mertz, a Swiss scientist who died in January 1913 on an Antarctic expedition that had lost its food supplies and fell to eating its sled dogs.

Vitamin A supply: Osteoporosis Lung cancer Teratological effects

Vitamin EVitamin E Chemical Name: Tocopherol Solubility: Fat Daily dose: 12 mg Source:

Plants: Vegetable oils, nuts, green leafy vegetables Animals: milk, eggs, meat

Function: Antioxidant. Vitamin E is often used in skin creams and lotions because it is believed to play a role in encouraging skin healing and reducing scarring after injuries such as burns.

Deficiency disease: Persons who cannot absorb dietary fat, has been found in premature, very low birth

weight infants Individuals who cannot absorb fat may require a vitamin E supplement because some

dietary fat is needed for the absorption of vitamin E from the gastrointestinal tract. Muscle dystrophy, sterility.

Hypervitaminosis: 4,000 mg or higher dose, not clear yet. May have anticoagulant effect and increase the risk of bleeding problems?

Vitamin DVitamin D Chemical Name: D3 = cholecalciferol Solubility: Fat Daily dose: 2 µg for all Vitamin D Source: fish oil, fish liver

It is made in the skin when cholesterol reacts with ultraviolet light in the skin. Function: The most active form of the vitamin is calcitriol, a potent

steroid hormone. Calcitriol is synthesized from calcidiol in the kidneys to perform its endocrine function of maintaining the calcium metabolism.

Deficiency disease: Rickets (kids) = bone pain, slowed growth, dental problems, muscle loss and

increased risk of fractures. Osteomalacia (adults) = lack of calcium results in bone fragility In certain parts of the world, particularly at higher latitudes, total vitamin D

input is usually not sufficient, especially in the winter (milk with D2 or D3) Hypervitaminosis: 1,250 mg or higher dose, hypercalcemia,

atherosclerosis

Vitamin KVitamin K Chemical Name: Naphthoquinone Solubility: Fat Daily dose: 75 µg Source: vegetables Function:

Involved in the carboxylation of certain glutamate residues in proteins to form gamma-carboxyglutamate residues.

blood coagulation (prothrombin-factor II, factors VII, IX, X) bone metabolism vascular biology

Deficiency disease: Bleeding. Normally it is produced by bacteria in the intestines, and dietary deficiency is

extremely rare unless the intestines are heavily damaged. Vitamin K-deficiency may occur by disturbed intestinal uptake (such as

would occur in a bile duct obstruction), by therapeutic or accidental intake of vitamin K-antagonists

Hypervitaminosis: GIT disorders, increased coagulation - anemia

Vitamin CVitamin C (1)(1) Chemical Name: Ascorbic acid Solubility: Water Daily dose: 75 mg Source:

Plants: Citrus fruits (orange, lemon, grapefruit, lime), tomatoes, potatoes, cabbage, wild roses

Function: Participation in hydroxylation, vitamin C is needed for the production of

collagen in the connective tissue. Strong antioxidant. Required for synthesis of dopamine, noradrenaline and adrenaline in the

nervous system or in the adrenal glands. Vitamin C is also needed to synthesize carnitine, important in the transfer of

energy to the cell mitochondria.

Vitamin CVitamin C (2)(2) Deficiency disease: Scurvy

loose teeth superficial bleeding fragility of blood vessels poor healing compromised immunity mild anemia

Hypervitaminosis: Not known

Vitamin B-1Vitamin B-1 Chemical Name: Thiamine or thiamin Solubility: Water Daily dose: 1 mg Source:

Plants: yeast, pulse, cereal Animals: liver

Function: Cofactor in decarboxylation processes. Deficiency disease: Beri-beri, GIT disorders (anorexia, nausea,

vomiting), tiredness, weakness, PNS disorders (paresthesia, coordination disorders), psychic disorders (depression, irritation, disorders in memory and coordination).

Hypervitaminosis: Not known.

Beri-BeriBeri-Beri In people whose staple diet consists mainly of polished

white rice, which contains little or no thiamine. Disease of nervous system Symptoms

weight loss, emotional disturbances, impaired sensory perception (Wernicke's encephalopathy), weakness and pain in the limbs, and periods of irregular heartbeat.

Swelling of bodily tissues (edema) is common. may cause heart failure and death.

Vitamin B-2Vitamin B-2 (1) (1) Chemical Name: Riboflavin or Vitamin G Solubility: Water Daily dose: 1.1 mg Source:

Plants: leafy green vegetables, yeast, almonds, soybeans Animals: milk, cheese, liver

Function: supports energy production by aiding in the metabolising of fats,

carbohydrates, and proteins. required for red blood cell formation and respiration, antibody production,

and for regulating human growth and reproduction. essential for healthy skin, nails, hair growth and general good health,

including regulating thyroid activity. helps in the prevention or treatment of many types of eye disorders, including

some cases of cataracts.

Vitamin B-2Vitamin B-2 (2) (2)

Deficiency disease: leasion of GIT mucous (glossitis, stomatitis, corner of

mouth, cheilitis) skin diseases (dermatitis)

Hypervitaminosis: Not known

Vitamin B-3Vitamin B-3 Chemical Name: Niacin or Vitamin P, resp.PP or nicotinic acid Solubility: Water Daily dose: 12mg Source:

Plants: yeast, corn Animals: eggs, liver

Function: its derivatives such as NADH play essential role in energy metabolism in cell and DNA repair.

Deficiency disease: mild deficiency slows down the metabolism, which in turn decreases cold

tolerance and is a potential contributing factor towards obesity. Pelagra: caused by dietary lack of niacin and protein, especially the essential

amino acid tryptophan. Symptoms: red skin lesions, diarrhea, dermatitis, weakness, mental confusion, and eventually dementia.

Hypervitaminosis: 2,500 mg or higher dose. Symptoms: High blood pressure, low blood cholesterol levels

Vitamin B-5Vitamin B-5 Chemical Name: Pantothenic acid Solubility: Water Daily dose: 10 mg Source:

Plants: yeast, whole grain cereals Animals: eggs, liver

Function:Part of CoA. Necessary for breaking down carbohydrates, proteins, and fats.

Deficiency disease: allergies (e.g. stuffed or runny nose), adrenal insuffiency (Addison's disease) and rheumatoid arthritis. Dermatitis, enteritis, alopecia.

Hypervitaminosis: Not known

Vitamin B-6Vitamin B-6 Chemical Name: Pyridoxine Solubility: Water Daily dose: 1.1 mg Source:

Plants: yeast, whole grain cereals Animals: liver

Function: Balancing of Na+ and K+, promoting red blood cell production. It is linked to cancer immunity and helps fight the formation of homocysteine. Helps children with learning difficulties, may prevent dandruff, eczema, and psoriasis. Helps balance hormonal changes in women.

Deficiency disease: Anemia, nerve damage, seizures, skin problems, and sores in the mouth. Pyroluria.

Hypervitaminosis: 400 mg or higher dose. Causes temporary deadening of certain nerves (proprioceptory nerves) and feeling of disembodiment common with the loss of proprioception.

Vitamin B-7Vitamin B-7 Chemical Name: Biotin or Vitamin H Solubility: Water Daily dose: 30 µg Source:

Plants: yeast Animals: seafood, liver, kidneys, milk, eggs

Function: Important in the catalysis of essential metabolic reactions to synthesize fatty acids, in gluconeogenesis, and to metabolize leucine.

Deficiency disease: Hair loss which progresses in loss of eye lashes and eye brows. Dry skin, seborrheic dermatitis, fungal infections. Changes in mental status, depression, generalized muscular pains (myalgias), hyperesthesias and paresthesias

Hypervitaminosis: Not known

Vitamin B-9Vitamin B-9 Chemical Name: Folic acid or Vitamin M Solubility: Water Daily dose: 320 μg Source: Green vegetable, fruits, cereals Function: Production and maintenance of new cells (especially

during infancy and pregnancy), necessary for replicating DNA and synthesizing RNA. Both adults and children need folate to make normal red blood cells and prevent anemia.

Deficiency disease: Diarrhea, loss of appetite, weight loss, weakness, sore tongue, headaches,

heart palpitations, irritability, and behavioral disorders. Hypervitaminosis: 1,000 µg or higher dose. Low risk - may shade

the B12 deficiency.

Vitamin B-12Vitamin B-12 Chemical Name: Cyanocobalamin Solubility: Water Daily dose: 2 µg Source:

Plants: breakfast cereals (only source for vegetarians) Animals: Liver, shellfish, eggs, milk

Function: coenzyme in metabolism of aminoacids, stimulates erytropoesis

Deficiency disease: Megaloblastic anemia = inadequate intake of B12 Pernicious anemia = autoimmune anemia (antibodies are directed against

intrinsic factor). Intrinsic factor is required for vitamin B12 absorption, so impaired absorption of vitamin B12 can result. The term pernicious anemia is sometimes used more loosely to include non-autoimmune causes of vitamin B12 deficiency.

Malabsorption in terminal ileum, demyelination of periferal nerves. Hypervitaminosis: Now known