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The Nutritional Connection
Chapter 11 Sport Books Publisher
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The Digestive System Sport Books Publisher
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The Digestive System Role:
To produce energy from food ingested To transfer energy-rich nutrients, water, and electrolytes into your body’s internal environment Composed of numerous structures and organs that work together The digestive tract forms a continuous route from mouth to anus The contents of the digestive tract are actually part of the external environment until absorbed through the intestinal wall Sport Books Publisher
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The Gastrointestinal (GI) Tract
Digestive Tract Mouth Pharynx Esophagus Stomach Small intestine Large intestine (colon) Rectum Anus Glandular Organs Salivary glands Liver Gall bladder Pancreas Sport Books Publisher
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Basic Processes of the Digestive System
Digestion Secretion Absorption Motility Sport Books Publisher
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Digestion Processes that dissolve and break down foods into molecules that can be absorbed by the body Sport Books Publisher
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Secretion The release of substances from exocrine glands
Works closely with the digestion process Includes many secretions, some of which are: Saliva by salivary glands Hydrochloric acid by the stomach Bile by the liver Sport Books Publisher
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Absorption Uptake of digested molecules across a layer of epithelial cells lining the gastrointestinal wall Molecules enter the blood or lymph to be distributed to body cells Sport Books Publisher
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Motility The muscular contractions that mix and move the contents of the digestive tract forward Propels the contents of the digestive tract forward Mixes food with digestive juices that promote digestion Sport Books Publisher
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The Digestive System The digestive system aims to absorb maximally
Waste material excreted via the gastrointestinal tract is called ‘feces’ Feces consist mainly of bacteria and undigested material (including fibre) Sport Books Publisher
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Functional Overview of the Gastrointestinal Organs
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Functional Overview of GI Organs: The Salivary Glands
Digestion begins in the mouth The mechanical breakdown of food is achieved by chewing Saliva produced by the salivary glands Three salivary glands in the head Sport Books Publisher
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Functional Overview of GI Organs: The Salivary Glands
Saliva contains mucus that moistens and lubricates food Saliva also contains ‘amylase’ Amylase is an enzyme that catalyzes the breakdown of carbohydrates Sport Books Publisher
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Functional Overview of GI Organs: The Mouth and Throat
Voluntary swallowing is initiated in the oropharynx (posterior mouth) The bolus of food moves to the pharynx Involuntary swallowing occurs in the esophagus ‘Peristalsis’ is the involuntary contraction of muscles and is involved in moving food to the stomach Sport Books Publisher
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Functional Overview of GI Organs: The Stomach
A sac-like organ Serves as a storage site Dissolves and partially digests food Prepares food for optimal digestion and absorption in the small intestine Little absorption occurs across the stomach wall Sport Books Publisher
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Functional Overview of GI Organs: The Stomach
Glands in the stomach secrete hydrochloric acid (HCl) HCl dissolves particulate matter in food (except fat) HCl also kills some bacteria that is ingested with food The precursor ‘pepsinogen’ forms the enzyme ‘pepsin’ Pepsin begins protein digestion Amylase (from the salivary glands) continues to break down carbohydrates Sport Books Publisher
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Functional Overview of GI Organs: The Small Intestine
Site of completion of digestion Site where most absorption occurs Approximately nine feet in length Three segments: Duodenum Jejunum Ileum Most absorption occurs in the duodenum and jejunum (vitamins, minerals, water) Sport Books Publisher
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Hydrolytic Enzymes Monosaccharides Carbohydrates AMYLASE Amino Acids
Proteins PEPSIN Fatty Acids Fats LIPASE Sport Books Publisher
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Functional Overview of GI Organs: The Pancreas
Secretes digestive enzymes Secretes an alkaline fluid mainly of bicarbonate ions The alkaline fluid counteracts the acidity of the contents of the stomach to protect the small intestine Alkaline substance also maintains an optimal pH range for enzymatic functions Sport Books Publisher
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Functional Overview of GI Organs: The Liver
Secretes ‘bile’ Bile contains cholesterol, bicarbonate ions, and bile salts Bile salts are essential for fat digestion and absorption Bile is stored in the gall bladder Sport Books Publisher
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Absorption in the Small Intestine
Absorption within the small intestine occurs via: DIFFUSION (Fatty Acids) OSMOSIS (Water) ACTIVE TRANSPORT (Mineral Ions) CARRIER-MEDIATED TRANSPORT (Monosaccharides and Amino Acids) Sport Books Publisher
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Functional Overview of GI Organs: The Large Intestine
Upon reaching the large intestine, very little water remains, and salts and undigested material are left Here, the material is further concentrated by further reabsorption of salt and water When reabsorption is complete, the feces move to the rectum as a result of involuntary contractions (peristalsis) The coordinated relaxation of sphincter muscles results in defecation Sport Books Publisher
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Nutritional Requirements: Types and Sources of Nutrients
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Nutrition The science of food and how the body uses it in health and disease Sport Books Publisher
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Essential Nutrients Proteins Fats Carbohydrates Vitamins Minerals
Water In this context, ‘essential’ refers to nutrients that the body is unable to manufacture (or not in sufficient quantities) They must be obtained from the diet Sport Books Publisher
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Essential Nutrients Necessary for energy
Needed for the building and maintenance of tissues Relied upon for the regulation of body functions Sport Books Publisher
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Energy-Providing Nutrients
Three nutrients provide the body with energy: Proteins Fats Carbohydrates Sport Books Publisher
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Energy Measurements Energy is expressed in ‘kilocalories’
1 kilocalorie = 1000 calories Kilocalorie = Calorie (note capital ‘C’) 1 kilocalorie = heat required to raise the temperature of 1kg of water 1°C An average person requires approximately 2000 kilocalories per day Sport Books Publisher
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FATS ALCOHOL CARBOHYDRATES PROTEINS
Calorie Densities of Various Energy Sources FATS 9 Cal/g ALCOHOL 7 Cal/g CARBOHYDRATES 4 Cal/g PROTEINS Sport Books Publisher
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Proteins Found in every living cell Act as structural components for:
Muscles Bones Blood Enzymes Some hormones Cell membranes Sport Books Publisher
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Proteins Composed of chains of amino acids
20 commonly recognized amino acids Nine essential (can not be synthesized) amino acids Methionine Phenylalanine Threonine Tryptophan Valine Histidine Isoleucine Leucine Lysine Sport Books Publisher
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Protein Individual sources of protein are ‘complete’ if they supply all nine essential amino acids Complete protein sources include animal products such as meat, cheese, fish, eggs, poultry and milk Sport Books Publisher
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Protein ‘Incomplete’ protein sources include those foods that do not contain all nine essential amino acids Usually from plant sources such as grains, beans, peas, and nuts Still good sources of amino acids Foods must be combined to get all amino acids (rice and beans for example) Sport Books Publisher
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Protein Protein should comprise 10-15% of total caloric intake
Protein consumed in excess of needs is stored as fat Inadequate protein consumption can lead to muscle wasting Sport Books Publisher
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Fats Also known as lipids Concentrated source of energy Fat serves to
Provide a source of energy Insulate the body Cushion organs Aid the absorption of fat-soluble vitamins Add flavour and texture to foods Sport Books Publisher
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Fats Fats in food are mostly triglycerides
Include a glycerol (an alcohol) Three fatty acid molecules Sport Books Publisher
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Fats Fats can be classified as
Saturated Monounsaturated Polyunsaturated Based on the degree of saturation or number of double bonds that exist between carbon atoms No double bonds = saturated One double bond = monounsaturated Two or more double bonds = polyunsaturated Sport Books Publisher
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Saturated Fat Monounsaturated Fat Polyunsaturated Fat
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Saturated Fats Food usually contains more than one type of fat
The dominant fat determines the characteristics of the fat Saturated fats are solid at room temperature Saturated fat is found predominantly in animal products Saturated fat has also been linked to cardiovascular disease Sport Books Publisher
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Unsaturated Fats Monounsaturated and polyunsaturated fats usually come from plant sources Unsaturated fat is liquid at room temperature (oil) More desirable, not linked to cardiovascular disease Unsaturated fats appear to lower blood cholesterol Also shown to reduce the risk of heart disease Sport Books Publisher
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Hydrogenation Processed plant oils can be high in saturated fat
Tropical oils (such as palm oil and coconut oil) used in processed foods are high in saturated fats Hydrogenated fats and oils are created from unsaturated fats are used to prevent spoiling and to add texture Sport Books Publisher
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Cholesterol Elevated intake of saturated fats may increase blood cholesterol levels Hydrogenation produces trans fatty acids that may increase blood cholesterol Increased blood cholesterol and triglyceride levels have been implicated with the development of heart disease Sport Books Publisher
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Carbohydrates Primary source of energy (60% of daily Calories)
Three groups based on the number of saccharides Monosaccharides and disaccharides are considered sugars Polysaccharides are considered starches Sport Books Publisher
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Monosaccharides Simplest sugar Include glucose, fructose, galactose
Glucose makes up the blood sugar (the brain, nervous system are fueled by glucose exclusively) Glucose found in vegetables, fruit, honey Fructose found in fruits and berries Sport Books Publisher
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Disaccharides Two monosaccharides
One monosaccharide is always glucose, e.g., lactose = glucose + galactose Many ‘hidden’ sugars in food Primary concern related to sugar consumption is dental cavities Sport Books Publisher
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Polysaccharides Found in vegetables, fruit, grains
Complex carbohydrates composed of chains of many sugars Starches often contain many vitamins, minerals, water, protein Dietary fibre is an important complex carbohydrate Sport Books Publisher
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Carbohydrates Liver and muscles use glucose for carbohydrate storage in the form of glycogen Carbohydrates consumed in excess of storage capacity as glycogen are stored as fat An important component of the diet for athletes competing in events of long duration Sport Books Publisher
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Vitamins Serve as coenzymes in chemical reactions
‘Organic’ because they contain carbon atoms Required in small amounts Necessary for Growth Reproduction Health Maintenance Sport Books Publisher
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Vitamins Two classifications, Water-soluble vitamins; and
Fat-soluble vitamins Based on the ability to dissolve in either water or fat tissue, respectively Sport Books Publisher
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Water-soluble Vitamins
Not stored Excess eliminated in the urine Include vitamin C and B-complex vitamins Dissolve quickly in water, so overcooking fruits and vegetables in water will result in the vitamins being lost to the water Sport Books Publisher
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Fat-soluble Vitamins Includes vitamins A, D, E, K
When taken in excess, these vitamins are stored in fat tissue Over-consumption of these vitamins (especially A and D) can result in toxicity Sport Books Publisher
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Antioxidants Formed from vitamins Aid in preserving healthy cells
When the body breaks down fats, or uses oxygen, free radicals are formed Free radicals can damage cell membranes and mutate genes Antioxidants react with free radicals to decrease their negative effects Include vitamins E, C, beta carotene (from vitamin A) Sport Books Publisher
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Minerals Numerous functions in the body
‘Inorganic’ because they do not contain carbon atoms Necessary for Structural elements (teeth, hormones, muscles) Regulation of body functions (muscle contractions, blood clotting, heart function) Aid in the growth and maintenance of body tissues Catalytic action in energy release Sport Books Publisher
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Minerals Approximately 17-21 identified essential minerals
Macronutrients (major minerals) are found in relatively large amounts in the body Calcium Phosphorus Magnesium Sulfur Sodium Potassium Micronutrients (trace elements) are needed in small amounts Zinc Iron Copper Fluoride Iodine Selenium Sport Books Publisher
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Vitamins and Minerals Needed in small amounts
Essential component to good health Consumption of too little or too much can have detrimental effects To ensure adequate intake, eat a balanced diet with variety Sport Books Publisher
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Water Large component of our bodies and food Important for:
Nutrient transport Waste transport Digestion & absorption Regulation of body temperature Lubrication Chemical reactions Sport Books Publisher
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Water Body water is lost through: Urine Feces Sweat
Evaporation in lungs Excessive water loss through: Illness Exercise Hot environment Consumption of coffee, tea, alcohol Sport Books Publisher
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Water Need to consume approx. 1mL of water for every Calorie burned
About 8 cups of fluid per day More if you are active or live in a warm climate Weakness or fatigue can be a sign of dehydration Sport Books Publisher
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Fibre Fibre includes plant substances that cannot be digested by the body Adds bulk to feces to facilitate elimination A large intake of fibre can lead to intestinal gas Sport Books Publisher
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Fibre Rich sources include: Fruit Legumes Oats Barley
Other sources include: Wheat Grains Vegetables Whole grain foods Sport Books Publisher
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Fibre Soluble fibre Lowers blood cholesterol
Slows absorption of glucose Insoluble fibre Facilitates feces elimination Can prevent constipation, lower intestinal tract cancer Sport Books Publisher
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