INTRODUCTION TO HUMAN NUTRITION 1219

1. INTRODUCTION TO HUMAN NUTRITION1219 Steven C Seideman Extension Food Processing Specialist Cooperative Extension Service University of Arkansas

2. OBESITY RANKED #2 HEALTH ISSUE • Obesity has recently been ranked the #2 health problem in the U.S. behind cigarette smoking. • Obesity in itself is not a problem but causes several secondary problems including diabetes, hypertension (high blood pressure), and others. • Obesity is a result of excessive caloric intake and the lack of physical exercise.

4. Human Nutrition • Human nutrition is the study of how food effects the health and survival of the human body. • We need food to supply the human body for functions such as growth, maintenance and reproduction. • Nutrients are classified as carbohydrates, proteins, fats, vitamins, minerals and water.

5. DIGESTION

6. Overview of the Digestive Process • All foods contain nutrients, and nutrients are released from food through the process called “digestion”. • Let’s go through the steps of the digestive process.

7. DIGESTION • The first steps of digestion occur when we put food in our mouth. • Chewing is a mechanical action that breaks food down to smaller particles. • The saliva in our mouths contains enzymes (proteins that break down foods) that chemically reduce the food to smaller particles.

8. DIGESTION • After food is chewed, it goes to the stomach. • Acids and enzymes in the stomach break the food down into even smaller particles. • Food then goes through the intestines and is moved along by muscle contractions. • Nutrients are absorbed from the inside of the small intestine into the bloodstream and carried to the sites in the body where they are needed.

9. DIGESTION • The parts of the food that are not absorbed continue to move down the intestinal tract and are eliminated from the body as feces.

10. COMPONENTS OF FOOD

11. COMPONENTS OF FOODS • Foods are essentially made up of water, carbohydrates, proteins, fats, vitamins and minerals. • The most abundant component of food is water, often as high as 75- 95%. • Vitamins and minerals make up the least abundant components of food, often in the range of 1-4%.

12. COMPONENTS OF FOODS • Carbohydrates – These are short and long branches of glucose molecules. Shorter molecules such as sugars and starches are readily digested and utilized. Longer and branched chain molecules, called hemicellulose and cellulose, often referred to as “fiber” are not useable as a nutrient source.

13. COMPONENTS OF FOOD • Proteins- Proteins are made up of long chains of amino acids. Some proteins are highly digestible while others are not. The action of acids and enzymes in the stomach break down most proteins into amino acids that can be adsorbed in the intestinal wall.

14. COMPONENTS OF FOOD • Fats – Fats and oils are very similar in structure, however, oils contain more double bonds and are often referred to as unsaturated or polyunsaturated. Fats/oils are chemically altered (esterified) in the stomach by bile which makes them more readily absorbable in the small intestine.

15. TYPES OF FOODS Foods are generally high in some components and low in others. • Milk – Very high in water, 3.5% protein, 3.5% fat • Cheeses- High in protein and fat • Cereals (Bread, crackers, etc.)- High in carbohydrates • Beverages- very high in water • Meats- High in protein and fat • Fruits and Vegetables- High in water and carbohydrates

16. COMPONENT Milk Beef Chicken Fish Cheese Cereal grains Potatoes Carrots Lettuce Apple Melon % Water %Carbohydrates %Protein % Fat % Min/Vit 87.3 5.0 3.5 3.5 0.7 60.0 0 17..5 22.0 0.9 66.0 0 20.2 12.6 1.0 81.8 0 16.4 0.5 1..3 37.0 2.0 25.0 31.0 5.0 10-14 58-72 8-13 2-5 0.5-3.0 78.0 18.9 2.0 0.1 1.0 88.6 9.1 1.1 0.2 1.0 94.8 2.8 1.3 0.2 0.9 84.0 15.0 0.3 0.4 0.3 92.8 6.0 0.6 0.2 0.4 COMPOSITION OF FOODS

17. CALORIES

18. CALORIES • Food components can be classified by their energy value or “calorie content”. • A “calorie” is the amount of energy or heat required to raise the temperature of one gram of water one degree Celsius. • The kilocalorie (1,000 calories) is the unit commonly used in expressing energy values of foods.

19. CALORIES • The total energy of foods is determined by burning the food in a steel bomb calorimeter. • Food is burned in the bomb calorimeter, and the rise in water temperature is measured, which is the total potential energy value of the food.

20. CALORIES • The total potential energy of a food as determined by a bomb calorimeter may not be equal to the energy that may be derived from it by a human. If a food is not totally digestible, acidified in the stomach or absorbed by the small intestine, or it is not totally oxidized within the body, then its caloric value will be less than its theoretical total energy content.

21. CALORIES • On average, the following components of food yield the following potential energy values; • Carbohydrates = 4.0 kcal/gram • Proteins = 4.0 kcal/gram • Fats = 9.5 kcal / gram • These figures permit approximate calculations of the energy values of foods.

22. CALORIES • The previous values were determined by a bomb calorimeter which is not exactly the same as human digestion and utilization; • For example, carbohydrates- The values hold true for sugars and starches, but cellulose is potential energy is not utilizable by humans. • Similar situations also hold true for proteins and fats.

23. CALORIES • The body needs calories for production of heat, synthesis of body tissues and performance of work. • Even the heart that beats all day and night uses energy. • In a broad sense, nutrients are needed for maintenance (body heat, heart beat,etc.), growth (we are constantly rebuilding body tissues) and reproduction.

24. CALORIES • The amount of energy /calories you require varies greatly depending upon such factors as; • Physical Activity- Someone that physically labors all day will require far more calories than an office worker. • Climatic Condition- cold temperatures require more energy to keep the body warm. • Weight – more weight equals more work to move. • Age- calorie utilization decreases as we increase in age • Sex- females may require additional energy if pregnant • Individual metabolic differences – efficient feed converters.

25. CALORIES • Daily requirements typically 2,000 kcal per day except real young and real old. • Fats are the most concentrated source of food calories; carbohydrates are the cheapest source, and proteins are the most expensive. • In much of the world, people go hungry, but in the US and certain other countries, obesity from excess caloric intake is a major nutritional disease.

26. BIOLOGICAL PRIORITIZATION

27. BIOLOGICAL PRIORITIZATION • Nature has a way of prioritizing the order in which we use energy. • If we take the total supply of energy digested and utilized by the body, it goes to various tissues and locations in a way to preserve life.

28. Body Functions Body Tissues Body Locations Fat Depots Total Supply of Energy =

29. Biological Prioritization • Body Functions 1) Maintenance- heat, heartbeat, digestion, physical activity 2) Growth 3) Reproduction Once these activities are all satisfied, excess energy goes to fat.

30. Biological Prioritization • Body Tissues- those most needed for life 1)Nervous tissues 2)Skeletal tissues 3)Muscle 4)Fat

31. Biological Prioritization • Body Locations- most needed to sustain life 1) Head 2) Neck and shoulder 3) Hind limb 4) Mid section (back)

32. Biological Prioritization • Fat Depots 1) Kidney 2) Intermuscular 3) Subcutaneous 4) Intramuscular

33. Biological Prioritization • Energy sources are used in this order; • CARBOHYDRATES 1) Blood Glucose 2) Muscle Glycogen • FATS • PROTEINS

34. METABOLISM

35. METABOLISM • Once food is digested, absorbed through the small intestine and carried throughout the body via the bloodstream, it now needs to be utilized by the ultimate tissue such as muscle or skin cells. • Once a nutrient is inside a tissue, whether it be muscle or skin cells, the basic metabolism is all very similar. • Almost all tissues carry out the same functions such as glycolysis and the Kreb’s Cycle. Carbohydrates, Proteins and Fats are all inter-convertible inside tissues.

38. METABOLISM • It is important to mention again that all carbohydrates, protein and fats are interrelated and inter-convertible to energy. • This means that you can eat a diet high in protein and still have excess calories beyond your needs to store as fat. Excess carbohydrates are also stored as fat. • This also means that cells have the ability to inter-convert carbohydrates to fat and fat to protein, etc.

39. METABOLISM • The fact that carbohydrates, fats and proteins are inter-convertible shows the amazing ability of the body to live through periods of malnourishment; it is not recommended as a practice. • The body has need of certain amino acids (building blocks of protein) and some fatty acids (fats) that cannot be made in the body and must be supplied by certain foods. • Some vitamins such as A, D, E and K are fat soluble and are to be found associated with the fatty fractions of natural foods.

40. VITAMINS

41. Vitamins • Vitamins are organic chemicals that must be supplied to the body in small amounts to maintain health. • Vitamins function in enzyme systems which facilitate the metabolism of proteins, carbohydrates and fats. • Vitamins are characterized as either fat soluble (A,D, E and K) or water soluble.

42. FAT SOLUBLE VITAMINS(Vitamins A,D, E and K)

43. FAT SOLUBLE VITAMINS • Vitamin A- occurs only in animal materials such as meat, milk, eggs, etc. Plant material contains no vitamin A but has its precursor, B-carotene that can be converted in the cell to vitamin A. • Vitamin A deficiency can lead to blindness, poor bone and tooth development, and can decrease the body’s resistance to disease.

44. FAT SOLUBLE VITAMINS • Vitamin D – is formed in the skin of humans by activation of sterols (cholesterol and ergosterol) and by ultraviolet light from the sun. • Shortage of vitamin D results in bone defects, the principle one being rickets. • Most milk is now fortified with ergosterol from yeasts as a source of vitamin D.

45. VITAMIN E • Vitamin E is also known as alpha-tocopherol. • Although claimed to do a lot of things from preventing diseases, prolonging youth and increasing sexual potency, there is little scientific data to support these claims. • Vitamin E is a strong antioxidant and plays a role in iron absorption. Since deficiencies of vitamin E are rare, it is hard to study its importance to nutrition.

46. VITAMIN K • Vitamin K is essential for normal blood clotting. • Vitamin K deficiency generally parallels liver disease where fat absorption is abnormal.

47. THE WATER SOLUBLE VITAMINSVitamins C, Thiamin B1, Riboflavin B2, Niacin, B6, Pantothenic Acid, B12,and Folic acid

48. Vitamin C • Vitamin C, also known as ascorbic acid, prevents scurvy – a disease sailors (limies) used to get from not having fruit for long periods of time. • Vitamin C deficiency causes fragile capillary walls (easy bruising), easy bleeding of gums, loosening of teeth and bone joint diseases. • Vitamin C is readily found in citrus fruit, tomatoes, cabbage and green peppers.

49. VITAMINS OF THE B COMPLEX GROUP • All members of the vitamin B complex generally are found in the same principle food sources, such as liver, yeast and the bran of cereal grains. All are required for essential metabolic activities, and several function as parts of active enzymes. Absence of a particular B vitamin results in a specific deficiency disease.

50. THIAMIN ( Vitamin B1) • A deficiency of vitamin B1 results in “beriberi”. • The deficiency is common where polished rice (bran has been removed) is a major dietary item. • Most wheat breads are now fortified with thiamin.