Introduction to Human Nutrition

1. Introduction to Human Nutrition the science of foods and the nutrients they contain

2. The food choices you make daily have a cumulative impact on your health. Poor food choices lead to chronic disease. Diet:the food one consumes

3. What is Food? • Foodcontain nutrients and are derived from plant or animal sources • Nutrients are used by the body to provide energy and to support growth, maintenance and repair of body tissues

4. Functional Foods • Functional foods contain substances that provide health benefits beyond those of their nutrients • May be a natural functional food or as a result of additives • Tomatoes – contain lycopene • Orange juice with calcium

5. 1. Carbohydrates 2. Lipids (fats) 3. Proteins 4. Vitamins 5. Minerals 6. Water The 6 Classes of Nutrients

6. Body Composition

7. Classification of Nutrients • Organic or inorganic • Essential or nonessential • Macronutrient or micronutrient • Energy yielding or not

8. Essential Nutrients • Nutrients the body either cannot make or cannot make enough of to meet its needs • Must be obtained from foods • Examples: • Vitamins • Calcium, iron, and other minerals • Some of the amino acids

9. NonessentailNutrients • Body can make from other nutrients ingested • Examples: • Cholesterol • Some amino acids

10. Classifying Nutrients by Composition • Organic nutrients - contain carbon • Carbohydrates • Lipids • Proteins • Vitamins • Inorganic nutrients - do not contain carbon • Minerals • Water

11. Quantity Needed • Macronutrients: need in relatively large amounts • Carbohydrates, lipids, proteins • Micronutrients: need in relatively small amounts • All other nutrients

12. 3 Energy Yielding Nutrients • Carbohydrates • Fats (lipids) • Proteins • Where does the energy come from?

13. A little more on energy • Measure energy in kilocalories in U.S. • What most think of as a “calorie” is really a kilocalorie • Kcal = amount of energy needed to raise the temperature of 1 kg of water by 10C • Measure energy in kilojoules (kJ) in most other countries

14. Energy-Yielding Nutrients

15. Carbohydrates • C H O • 4 kcal/gram • Body’s primary source of energy • Use as glucose • Brain’s only source of energy • Stores are limited ~12-24 hours (in liver and muscle)

16. Carbohydrates • Energy Metabolism • Glucose is the fuel used by cells to make ATP • Neurons and RBCs rely almost entirely upon glucose • Excess glucose is converted to glycogen or fat and stored

17. Carbohydrates • Dietary sources • Starch (complex carbohydrates) in grains and vegetables • Sugars in fruits, sugarcane, sugar beets, honey and milk • Insoluble fiber: cellulose in vegetables; provides roughage • Soluble fiber: pectin in apples and citrus fruits; reduces blood cholesterol levels

18. Carbohydrates • Dietary requirements • Minimum 100 g/day to maintain adequate blood glucose levels • Recommended minimum 130 g/day • Recommended intake: 45–65% of total calorie intake; mostly complex carbohydrates

19. Carbohydrates • Dietary Fiber • water-insoluble fiber adds bulk to fecal matter facilitating its passage through and elimination from the digestive system • water-soluble fiber may absorb dietary cholesterol, reducing its absorption by the digestion tract

20. Wheat Seed

21. Lipids • C H O (P) • 9 kcal/gram • Body’s alternate source of energy • Use fat along with glucose as an energy source most of the time • Stores are unlimited

22. Lipids • Dietary sources • Triglycerides • Saturated fats in meat, dairy foods, and tropical oils • Unsaturated fats in seeds, nuts, olive oil, and most vegetable oils • Cholesterol in egg yolk, meats, organ meats, shellfish, and milk products

23. Lipids • Essential fatty acids • Linoleic and linolenic acid, found in most vegetable oils • Must be ingested

24. Lipids • Essential uses of lipids in the body • Help absorb fat-soluble vitamins • Major fuel of hepatocytes and skeletal muscle • Phospholipids are essential in myelin sheaths and all cell membranes

25. Lipids • Functions of fatty deposits (adipose tissue) • Protective cushions around body organs • Insulating layer beneath the skin • Concentrated source of energy

26. Lipids • Regulatory functions of prostaglandins • Smooth muscle contraction • Control of blood pressure • Inflammation • Functions of cholesterol • Stabilizes membranes • Precursor of bile salts and steroid hormones

27. Lipids • Dietary requirements suggested by the American Heart Association • Fats should represent 30% or less of total caloric intake • Saturated fats should be limited to 10% or less of total fat intake • Daily cholesterol intake should be no more than 300 mg

28. Pathways of Lipid Metabolism

29. Atherosclerosis diseased normal

30. Your Cholesterol Level • Cholesterol: <175 mg/dl • Triglycerides: blood fats, 30-175 mg/dl • HDL: Good cholesterol, > 35 mg/dl • LDL: Bad Cholesterol, <130 mg/dl • Chol/HDL ratio: < 4.5 indicates heart disease

31. Protein • C H O N • 4 kcal/gram • Body’s least desirable source of energy • WHY? • Protein is used for energy only when there isn’t any carbohydrate available as an energy source.

32. Proteins • Enzymes • Structural proteins (shape and form of cells and tissues) • Hormones • Immunoglobulins (antibodies)

33. Essential Amino Acids • Tryptophan • Methionine • Valine • Threonine • Phenylalanine • Leucine • Isoleucine • Lysine • Arginine • Histidine • (infants)

34. Proteins • Dietary sources • Eggs, milk, fish, and most meats contain complete proteins • Legumes, nuts, and cereals contain incomplete proteins (lack some essential amino acids) • Legumes and cereals together contain all essential amino acids

35. Proteins • Uses • Structural materials: keratin, collagen, elastin, muscle proteins • Most functional molecules: enzymes, some hormones

36. Proteins • Use of amino acids in the body • All-or-none rule • All amino acids needed must be present for protein synthesis to occur • Adequacy of caloric intake • Protein will be used as fuel if there is insufficient carbohydrate or fat available

37. Proteins • Nitrogen balance • State where the rate of protein synthesis equals the rate of breakdown and loss • Positive if synthesis exceeds breakdown (normal in children and tissue repair) • Negative if breakdown exceeds synthesis (e.g., stress, burns, infection, or injury)

38. Proteins • Hormonal controls • Anabolic hormones (GH, sex hormones) accelerate protein synthesis

39. Vegetarian diet may result in protein deficiency • Need essential amino acids • beans  lysine & isoleucine • corn  tryptophan & methionine

40. Transamination

41. Energy-Yielding Non-nutrient • Alcohol – 7 kcal/gram • Non-nutrient because it interferes with growth, maintenance and repair of the body • Alcohol’s metabolites are harmful

42. Energy Density • Measure of the kcal per gram of food • Fat has the highest energy density of the 3 energy-yielding nutrients. • Foods with a high energy density provide more kcal per gram than low density foods.

43. Energy Density

44. Vitamins • Essential • Organic, micronutrient • Not energy-yielding • Fairly easily destroyed/damaged • Can be water-soluble or fat-soluble

45. Vitamins Organic compounds needed by the body in small, but essential amounts Cannot be synthesized by the body in sufficient amounts Function in a variety of ways in metabolic reactions Thirteen known vitamins

46. Water-Soluble Vitamins C (ascorbic acid) B1 (thiamin) B2 (riboflavin) Niacin B6 (pyridoxine) Pantothenic acid Biotin B12 (cyanocobalamin) Folic acid

47. Water-Insoluble Vitamins A (retinol) D E K

48. Minerals • Essential • Inorganic, micronutrient • Not energy-yielding • Indestructible

49. Minerals • Essential inorganic elements • Involved in a variety of metabolic processes • Major minerals versus trace minerals

50. Major Minerals Calcium Phosphorus Magnesium Sodium Potassium Chlorine