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Presentation on theme: "INTRODUCTION TO HUMAN NUTRITION 1219"— Presentation transcript:

Steven C Seideman Extension Food Processing Specialist Cooperative Extension Service University of Arkansas

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.


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.


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 %. 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 COMPOSITION OF FOODS % Water %Carbohydrates %Protein % Fat % Min/Vit
COMPONENT Milk Beef Chicken Fish Cheese Cereal grains Potatoes Carrots Lettuce Apple Melon % Water %Carbohydrates %Protein % Fat % Min/Vit


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.


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


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.

36 This is glycolysis, the Krebs cycle and oxidative phosphorylation
This is glycolysis, the Krebs cycle and oxidative phosphorylation. It is the basis of all living cells.

37 This is a basic summary of the Krebs cycle. Go through the slide.

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.


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 VITAMINS Vitamins 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.

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.

51 RIBOFLAVIN (Vitamin B2)
Riboflavin functions in the oxidative processes of living cells and is essential for cellular growth and tissue maintenance. Deficiency in humans generally results in skin conditions such as cracking at the corners of the mouth. Milk, liver and eggs are excellent sources.

52 NIACIN (Nicotinic acid)
Niacin should not be confused with nicotine in tobacco products. Deficiency of niacin adversely affects tissue respiration and oxidation of glucose and results in a disease known as pellagra or black tongue, once common in Southeastern U.S. Deficiency is characterized by skin and mucous membrane disorders as well as depression and confusion. Most breads are now fortified with niacin.

53 Vitamin B6 Vitamin B6 is essential in the human diet for specific enzyme systems and normal metabolism. A deficiency of this vitamin does not cause a well-recognized disease. Vitamin B6 is widely distributed in foods.

54 PANTOTHENIC ACID Because pantothenic acid is widespread in foods, there appears to be no deficiency problems in humans.

55 VITAMIN B12 Vitamin B12 is important in nucleic acid formation and in fat and carbohydrate metabolism. It is often referred to as the anti-pernicious anemia factor. Strict vegetarians may not get enough B12 in their diet, since it is virtually absent in plant tissue, and they may suffer from pernicious anemia. Good sources include liver, meat and seafoods. Vitamin B12 has recently been implicated in memory function especially in the elderly where meat is restricted.

56 FOLACIN Folacin and folate are names of chemicals exhibiting the vitamin activity of folic acid. Folic acid, like B12, prevents certain kinds of anemias and is involved in the synthesis of nucleic acids.


58 MINERALS Minerals, like vitamins, are needed for normal metabolism. They are generally required in very small amounts, but the lack of certain ones can lead to severe consequences.

59 ESSENTIAL MINERALS Calcium Phosphorus Magnesium Iron Copper Cobalt
Zinc Sodium Chloride Potassium Iodine Fluorine Manganese Chromium Molybdenum

60 Dietary Guidelines

61 Dietary Guidelines Avoidance of overweight
Consumption of a variety of foods Reduction of total fat to less than 30% of calories Reduction in the amount of saturated fats and cholesterol consumed. Moderation in the consumption of salt and alcohol. Increased consumption of fresh fruits and vegetables and other fiber-containing foods.


63 NUTRITION Eat from all food groups each day.
Obesity in the U.S. is caused primarily by overeating. Understand what portion size is. Fat, carbohydrates and protein are all interconvertable via Krebs cycle. Atwater Factor; Carbohydrates=4.5, Proteins=4.5; Fat =9.0. Calories per gram. Nutritionally better off today. Few cases of goiter, rickets, pellagra, kwashiorkor, scurvy. Read the slide

64 Caloric Intake Current Calories in the U.S. diet come from carbohydrates ( 46%), fat (42%) and protein (12%). It is recommended that the caloric intake should be from carbohydrates (45-65%), fat ( 20-35%) and protein (12%). This means we should increase our percentage of calories from carbohydrates and reduce the percentage of calories from fat.

65 Diets There are lots of diet plans, and all may work to some extent. The bottom line to losing weight is decreased caloric intake and increased physical activity.

66 Dr Adkins High Protein Diet
The Adkins high protein diet stresses the reduction in calories from carbohydrates and increased consumption of protein. This diet plan has worked for millions of Americans, however, there are concerns within the scientific community of its consequences over an extended period of time.

67 Dr Phil McGraw’s Plan Dr Phil McGraw’s The Ultimate Weight Solution is a 7 point plan to lose weight. The plan focuses on several lifestyle changes and ways we behave and think about food. Focus on portion size, eating water-rich foods, intentional exercise, eat slower and not being distracted- know when you are full.

68 Exercise Americans need more exercise.
The heart is a muscle and becomes stronger with exercise. In addition to the role of exercise in calorie burning, it also reduces stress and creates a feeling of inner peace. Children don’t play outside as much and play more non physical games (computers etc). Really need at least 20 minutes of physical exercise 3-4 time per week. Walking is great exercise.


70 The Diet and Disease In recent times, we have seen a shift in the the U.S. and other developed countries from the lack of nutrition (such as kwashiorkor- lack of protein) or lack of certain vitamins or minerals (goiter, rickets, beriberi, etc.) to nutritional diseases from over abundance of certain nutrients (calories).

71 ATHEROSCLEROSIS Defined as a number of pathological processes leading to coronary heart disease, stroke and diseases of the peripheral circulatory system. Cholesterol buildup in arteries- hard on the heart and circulation. First noted in the Korean war. Causes include diet, obesity, hypertension, diabetes, sedentary living, cigarette smoking and high blood cholesterol levels.

72 Courtesy of USDA

73 HYPERTENSION High blood pressure
Problem with cardiovascular diseases and other organs like the kidney. It has a genetic component but is further complicated by obesity, lack of physical activity, emotional stress, cigarette smoking and diet. Sodium intake has been shown to increase blood pressure while calcium has been shown to reduce it.

74 CANCER One third of all cancers are related to diet.
Stomach and colon cancers related to diets high in fat and low in fresh fruits and vegetables. Excessive consumption of cured and smoked meats has been associated with an increase in esophagus and stomach cancers. Increased consumption of foods rich in antioxidants may prevent some cancers.

75 Recommendations Eat a variety of foods for a balanced diet. You MUST reduce caloric intake in some way that works for you. Learn the different food groups and learn what portion size is. Get plenty of physical exercise- it burns excess calories and creates a peaceful feeling. Eat to live- learn to eat slowly knowing when to quit; don’t resolve anxiety issues with eating.

76 Need More Information? In Arkansas, contact your local county agent or Nutrition Specialists at the Cooperative Extension State Office in Little Rock; / USDA Website;



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