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NUTRIENTS, CHAPTER 23
Protein, carbohydrates, protein, fats and nucleic acids
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Nutrition
• Major nutrients
1. Carbohydrates
2. lipids
3. proteins
• Minor nutrients:
• vitamins
• minerals
• water
Copyright © 2011 Pearson Education, Inc. Figure 23.1b
Red meat, butter:use sparingly
Vegetables inabundance
Whole-grainfoods atmost meals
Daily excercise and weight control
(b) Healthy eating pyramid
Dairy or calcium supplement: 1–2 servings
White rice, white bread,potatoes, pasta, sweets:
use sparingly
Fish, poultry, eggs:0–2 servings
Nuts, legumes:1–3 servings
Fruits:2–3 servings
Plant oilsat most
meals
Revised Food Pyramid
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NUTRIENT SOURCE AND FUNCTION
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Carbohydrates
• Preferred energy source
• Used to make ATP
• Used by neurons and RBCs
• Excess stored as fat or glycogen
• Minimum 100g/day
• Found in:
• Complex carbohydrates (starches, grains and vegetables)
• Sugars (fruits, sugarcane, sugar beets, honey and milk)
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Lipids
• Triglycerides
• Saturated fats:
• meat, dairy foods, and tropical oils
• Unsaturated fats
• seeds, nuts, olive oil, and vegetable oils
• Cholesterol, found in animal products
• Less than 300 mg/day
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Lipid Function
• Functions of fatty deposits (adipose tissue)
• Protective cushions around body organs
• Insulating layer beneath skin
• Concentrated source of energy
• Cholesterol:
• Stabilizes membranes
• Precursor of bile salts and steroid hormones
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Proteins
• Dietary sources:
• Eggs, milk, fish, and meat (animal products)
• Legumes, nuts, and cereals contain incomplete proteins
• Recommend: 0.8g/kg body weight
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Proteins
• Uses
• Structural materials:
• Keratin
• Collagen
• Muscle proteins
• Functional molecules, enzymes
• Used for energy only when carbohydrates and fats are gone.
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Vitamins
1. Water-soluble vitamins
• B complex and C
• absorbed with water
2. Fat-soluble vitamins
• A, D, E, and K
• absorbed with lipids
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Minerals
• Important for body function
• Examples
• Calcium, phosphorus, and magnesium salts harden bone
• Iron is essential for oxygen binding to hemoglobin
• Iodine is necessary for thyroid hormone synthesis
• Sodium and chloride are major electrolytes in the blood
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ABSORPTION OF NUTRIENTS
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Absorption
• There are four main classes of nutrients
1.Carbohydrates (sugars)
2.Protein
3.Fats
4.Nucleic acids (DNA/RNA) / minerals
• water
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Absorption of Carbohydrates
• Digestive enzymes – break sugars into absorbable pieces
• Salivary amylase (salivary glands)
• Pancreatic amylase (pancreas)
• Border enzymes (small intestine)
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Absorption of Proteins
• Pepsin (stomach)
• Trypsin (pancreatic proteases)
• Peptidases (brush border enzymes)
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Absorption of Lipids
• Bile salts (liver)
• Pancreatic lipases (pancreas)
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Absorption of Nucleic Acids
• Digested by pancreatic enzymes
• Absorbed by active transport
• Used for DNA and RNA synthesis
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Vitamins and Electrolyte Absorption
• Absorbed by small intestine
• Based on solubility
• Fat-soluble vitamins (A, D, E, and K) absorbed similar to fats
• Water-soluble vitamins (vitamin C and B vitamins) are absorbed by diffusion
• Ca2+ absorption is regulated by vitamin D
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Water Absorption
• 95% by small intestine via osmosis
• Rest reclaimed by large intestine
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CHOLESTEROL LEVELS
HDL vs LDL
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Lipids and Cholesterol
• Cholesterol is a type of lipid
• Low-density lipoproteins (LDL) “bad cholesterol”
• Transport lipids to adipose tissue
• High-density lipoproteins (HDL) “good cholesterol”
• Uses lipids for hormone production
• Lowered by: stress, cigarette smoking, and coffee
• Increased by: Aerobic exercise
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Cholesterol
• Made by the liver
• Saturated fatty acids
• Stimulate synthesis of cholesterol
• Unsaturated fatty acids
• Enhance excretion of cholesterol
• Trans fats
• Reduce HDLs and raise LDLs
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Cholesterol
• Body shape
• “Apple”: Fat carried on upper body is correlated with high cholesterol and LDL levels
• “Pear”: Fat carried on hips and thighs is correlated with lower cholesterol and LDL levels
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FOOD INTAKE REGULATION
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Regulation of Food Intake
• Leptin
• Hormone secreted by fat cells (adipose tissue)
• Suppresses appetite in response to increased body fat mass
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Regulation of Food Intake
• Additional factors
• Temperature
• Stress
• Psychological factors
• Adenovirus infections
• Sleep deprivation
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Obesity
• Body mass index (BMI) = wt (lb) 705/ht (inches)2
• Considered overweight if BMI is 25 to 30
• Considered obese if BMI is greater than 30
• Higher incidence of atherosclerosis, diabetes mellitus, hypertension, heart disease, and osteoarthritis
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DISORDERS OF THE DIGESTIVE SYSTEM
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Malabsorption of Nutrients
• Celiac Disease - gluten-sensitive enteropathy
• Gluten causes an allergic reaction that damages the intestinal villi
• Symptoms: diarrhea, fatigue, weight loss
• Treatment: gluten free diet
• all grains but rice and corn
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Diarrhea
•Watery stool
• Caused by any condition that rushes food through the large intestine before water has been reabsorbed.
• Cholera – diarrhea cause by bacterium Vibrio cholerae
• Found in feces
• Massive dehydration
• Can lead to death if not treated
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Jaundice
• Yellowing of the skin and sclera
• Caused by build of up bilirubin (liver enzyme)
• Results from liver damage or blood disorder
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Cancer
• Alimentary cancers rarely have early signs
• Polyps
• Metastasized colon cancers frequently cause secondary liver cancer
• Prevention
• Regular dental and medical examination
• Colonoscopies after age 40