Protein Chapter 3 and Vitamins Chapter 5

1. Protein Chapter 3and Vitamins Chapter 5

2. Protein Chapter 3

3. Protein • A component of every living cell • Accounts for 20% of adult weight • Immune to the controversy over optimal intake

4. Protein—(cont.) • Amino acids • Basic building blocks of protein • Composed of carbon, hydrogen, oxygen, and nitrogen atoms • Twenty common amino acids • Nine are considered essential in the dietbecause the body cannot make them—indispensable; they must be consumed through food. • Eleven are considered nonessential in the dietbecause they can be made by the body—dispensable. However… • Conditionally essential amino acids-situation arises when insufficient substrate(s) levels for synthesis of non-essential amino acids and/or a problem with the metabolic machinery to make non-essential amino acids occurs

5. Essential Amino Acids • Histidine • Isoleucine • Leucine • Lysine • Methionine • Phenylalanine • Threonine • Tryptophan • Valine

6. Nonessential Amino Acids • Alanine • Arginine • Asparagine • Aspartic acid • Cystine (cysteine) • Glutamic acid • Glutamine • Glycine • Proline • Serine • Tyrosine

7. Protein—(cont.) • Protein structure • Most contain several dozen to several hundred amino acids. • Shape (i.e. structure) determines function.

8. Protein—(cont.) • Functions of protein • Major structural and functional component of every living cell • Body structure and framework • Enzymes • Other body secretions and fluids • Acid–base balance • Transport molecules

9. Protein—(cont.) • Functions of protein—(cont.) • Other compounds • Some amino acids have specific functions within the body. • Fueling the body

10. Protein—(cont.) • How the body handles protein • Digestion • Begins in the stomach • Hydrochloric acid converts pepsinogen to the active enzyme pepsin. • Small intestine is the principal site of protein digestion. • Enzymes located on the surface of the cells that line the small intestine complete the digestion.

12. Protein—(cont.) • How the body handles protein—(cont.) • Absorption • Amino acids, and sometimes a few dipeptides or larger peptides, are absorbed through the mucosa of the small intestine. • Metabolism • Liver acts as a clearinghouse. • Retains amino acids to make liver cells, nonessential amino acids, and plasma proteins such as heparin, prothrombin, and albumin • Regulates the release of amino acids into the bloodstream

13. Protein—(cont.) • How the body handles protein—(cont.) • Metabolism—(cont.) • Liver acts as a clearinghouse.—(cont.) • Removes the nitrogen from amino acids • Converts amino acids to fatty acids which form triglycerides for storage in adipose tissue • Forms urea from the nitrogenous wastes of protein

14. Protein—(cont.) • Protein synthesis • Complicated but efficient process that quickly assembles amino acids into proteins the body needs • Part of what makes every individual unique is the minute differences in body proteins. • Important concepts • Protein turnover, metabolic pool, and nitrogen balance

15. Important Concepts Protein turnover Metabolic pool Contains supply of each amino acid Consists of recycled amino acids from body proteins that have broken down and also amino acids from food In a constant state of flux • Continuous process • Body proteins vary in their rate of turnover.

16. Important Concepts—(cont.) • Nitrogen balance • Reflects the state of balance between protein breakdown and protein synthesis • Determined by comparing the amount of nitrogen consumed (intake) with the amount of nitrogen excreted (output) • Healthy adults are in neutral nitrogen balance.

17. Important Concepts—(cont.) • Nitrogen balance—(cont.) • Positive nitrogen balance: when protein synthesis exceeds protein breakdown (e.g. growth, pregnancy) • Negative nitrogen balance: an undesirable state that occurs when protein breakdown exceeds protein synthesis (e.g. illness, insufficient dietary protein)

19. Protein—(cont.) • Protein catabolism for energy • Counterproductive-proteins (enzymes) are required to get energy from carbohydrates and lipids • Over time, loss of lean body tissue occurs. • Loss of 30% of body protein causes • Impaired breathing • Altered immune function • Altered organ function • Ultimately death

20. Sources of Protein • Protein quality • Differs based on content of essential amino acids and digestibility of the protein • Quality can become a crucial concern.

21. Sources of Protein—(cont.) • Complete and incomplete proteins • Complete proteins • High biologic value • Provide adequate amounts and proportions of all essential amino acids needed for protein synthesis necessary to support tissue growth and repair • Animal proteins, soy, quinoa protein are complete proteins- but with quinoa have digestibility of protein issue- explain

22. Sources of Protein—(cont.) • Complete and incomplete proteins—(cont.) • Incomplete proteins • Lack adequate amounts of one or more essential amino acids • Except for soy and quinoa protein, all plants are sources of incomplete proteins. • Gelatin is also an incomplete protein. • Complementary proteins • Two proteins that when combined provide adequate amounts and proportions of all essential amino acids needed to support protein synthesis

23. Examples of Complementary Plant Proteins • Black beans and rice • Bean tacos • Pea soup with toast • Lentil and rice curry • Falafel sandwich (ground chickpeas on pita) • Peanut butter sandwich • Pasta e fagioli (pasta with white beans)

24. Examples of a Plant Protein Complemented by a Small Amount of an Animal Protein to Form a Complete Protein • Bread pudding • Rice pudding • Corn pudding • Cereal and milk • Macaroni and cheese • Cheese fondue • French toast • Cheese sandwich • Vegetable quiche

25. Dietary Reference Intakes • RDAs • For healthy adults is 0.8 g/kg • Acceptable Macronutrient Distribution Range for protein for adults is 10% to 35% of total calories. • RDA for healthy adults does not apply to others than healthy adults

26. Dietary Reference Intakes—(cont.) • Protein deficiency • Protein–energy malnutrition (PEM) • Kwashiorkor • Results mainly from acute critical illnesses • Enough energy but not enough protein • Get swollen abdomen • Aggressive nutritional support is used to restore metabolic balance as quickly as possible. • Marasmus • Occurs secondary to chronic diseases • Not enough energy or protein • Skin and bones appearance • Nutritional therapy is started slowly and advanced gradually.

27. Dietary Reference Intakes—(cont.) • Protein excess • No proven risks from eating an excess of protein • Conflicting data as to whether high-protein diets increase the risk of: • Osteoporosis • Renal stones • Renal disease

28. Protein in Health Promotion • Vegetarian diets • Pure vegetarians or vegans • Eat no animal products. • Eat only plants. • They form the smallest group of vegetarians • Must eat a wide variety of plant foods to get sufficient of all essential amino acids • Vitamin B12 usually comes from plant foods with vitamin B12 added to food prior to purchase or if that fails via vitamin B12 in tablet form.

29. Protein in Health Promotion—(cont.) • Vegetarian diets—(cont.) • Most vegetarians are • Lacto-vegetarians, whose diets include milk products • Lacto-ovo vegetarians, whose diets include milk products and eggs • Nutrients of concern • Most vegetarian diets meet or exceed the RDA for protein and are nutritionally adequate across the life cycle. • Iron, zinc, calcium, vitamin D, omega-3 fatty acid, and iodine are nutrients of concern.

30. Protein in Health Promotion—(cont.) • Is vegetarianism for everyone? • A personal choice, subject to personal interpretation • Proper planning means paying close attention to the nutrients of concern and using a vegetarian food guide for planning.

32. VitaminsChapter 5

33. Vitamins • In 1913, thiamin was discovered as the first vitamin, the “vital amine” necessary to prevent the deficiency disease beriberi. • Today, 13 vitamins have been identified as important for human nutrition.

34. Understanding Vitamins • Organic compounds made of carbon, hydrogen, oxygen, and sometimes nitrogen or other elements • Some vitamins facilitate biochemical reactions within cells • Essential to life • Individual molecules • Do not provide energy (calories), but some are needed for metabolism of energy • Needed in microgram or milligram quantities • Too little of a food source(s) of a vitamin leads to deficiencies of that vitamin lead to loss of function (role) of vitamins • Too much of a food source(s) or supplement of a vitamin leads to toxicities lead to impairment of some bodily functions-fat soluble vitamins are particularly a problem here but some water soluble vitamins can also be affected • A complete listing of the effects of various vitamin deficiencies and toxicities is available online

35. Understanding Vitamins—(cont.) • Vitamins may exist in more than one form • Different forms perform different functions in the body. • Provitamins • Vitamins are essential • With few exceptions, the human body cannot make vitamins. Humans can for example make vitamin D • Some vitamins are coenzymes • Many enzymes cannot function without a coenzyme, and many coenzymes are vitamins.

36. Understanding Vitamins—(cont.) • Some vitamins are antioxidants • Free radicals are produced continuously in cells as they burn oxygen during normal metabolism. • Oxidize body cells and DNA in their quest to gain an electron and become stable • Antioxidants protect body cells from being oxidized (destroyed) by free radicals. • Major antioxidants are vitamin C, vitamin E, and beta-carotene.

37. Understanding Vitamins—(cont.) • Some vitamins are used as food additives • Some foods have vitamins added to them simply to boost their nutritional content. • Vitamins as drugs • In megadoses, vitamins function like drugs, not nutrients. e.g. vitamin E can lower ability to clot

38. Vitamin Classifications Based on Solubility • Fat-soluble vitamins • Characteristics • Sources are the fat and oil portion of foods. • Absorption: fat encased in chylomicrons that enter the lymphatic system before circulating in the bloodstream • Transportation through the blood occurs by attaching to protein carriers because fat is not soluble in watery blood. • When consumed in excess, stored primarily in liver and adipose tissue

39. Vitamin Classifications Based on Solubility—(cont.) • Fat-soluble vitamins • Characteristics—(cont.) • Can be toxic if consuming high intakes through supplements –why? • Generally do not have to be consumed daily because the body can retrieve them from storage as needed

40. Vitamin Classifications Based on Solubility—(cont.) • Vitamins A,D,E,K are fat soluble • B vitamins, non-B vitamins and vitamin C are water soluble.

41. Vitamin Classifications Based on Solubility—(cont.) • Vitamin A • Preformed vitamin A is found only in animal sources. • Also includes provitamin A carotenoids • Natural plant pigments found in deep yellow and orange fruits and vegetables and most dark-green leafy vegetables • Beta-carotene, lutein, and lycopene are among the most commonly known carotenoids.

42. Vitamin Classifications Based on Solubility—(cont.) • Vitamin A—(cont.) • Best known for its roles in normal vision, reproduction, growth, and immune system functioning • Body can store up to a year’s supply of vitamin A. • Only preformed vitamin A is toxic in high doses. • Beta carotene is nontoxic. • Hypercarotenemia –orange-coloured skin in Caucasians

43. Vitamin Classifications Based On Solubility—(cont.) • Vitamin D • Unique in that the body has the potential to make all of the vitamin D it needs if exposure to sunlight is optimal and liver and kidney function are normal • Another distinctive feature of vitamin D is that it acts like a hormone because it is synthesized in one part of the body (skin) and stimulates functional activity elsewhere.

44. Vitamin Classifications Based on Solubility—(cont.) • Vitamin D—(cont.) • Primary function of vitamin D is to maintain normal blood concentrations of calcium and phosphorus. • Calcium and phosphorous are used for bone and teeth development and maintenance • Vitamin D is important for immune function. • It is possible to fulfill the vitamin D requirement by taking a daily 15-minute walk in the sun under optimal conditions. • Winter, living in northern latitudes, and being of black race and older age are associated with low vitamin D synthesis.

45. Vitamin Classifications Based on Solubility—(cont.) • Vitamin D—(cont.) • Dietary source is considered essential because few people meet optimal conditions. • Vitamin D occurs naturally in only a few foods. • Many experts believe the AI for vitamin D is set too low. • Overt deficiency of vitamin D causes poor calcium absorption. • Rickets and osteomalacia • Current upper limit for vitamin D is set at 100 µg/day (4000 IU/day) for ages 9 years and older.

46. Vitamin Classifications Based on Solubility—(cont.) • Vitamin E • Generic term that describes a group of at least eight naturally occurring compounds • Alpha-tocopherol is considered the most biologically active form of vitamin E. • Functions as the primary fat-soluble antioxidant in the body • Protects polyunsaturated fatty acids (PUFAs) and other lipid molecules, such as LDL cholesterol, from oxidative damage

47. Vitamin Classifications Based on Solubility—(cont.) • Vitamin E—(cont.) • Need increases as the intake of PUFA increases. • Megadoses may help protect against atherosclerosis, some types of cancer, cataracts, age-related macular degeneration, Parkinson’s disease, and Alzheimer’s disease. • Deficiency can occur in very specific instances. • Premature infants • May occur secondary to a genetic abnormality or malabsorption syndromes such as cystic fibrosis and short bowel syndrome

48. Vitamin Classifications Based on Solubility—(cont.) • Vitamin E—(cont.) • Signs and symptoms of deficiency include peripheral neuropathy, ataxia, and ultimately death. • Vitamin K • Occurs naturally in two forms • Phylloquinone, found in plants • Menaquinones, which are synthesized in the intestinal tract by bacteria

49. Vitamin Classifications Based on Solubility—(cont.) • Vitamin K—(cont.) • Coenzyme essential for the synthesis of prothrombin • Clinically significant vitamin K deficiency is defined as vitamin K–responsive hypoprothrombinemia. • Characterized by an increase in prothrombin time • Deficiency does not occur from inadequate intake but may occur secondary to malabsorption syndromes or the use of certain medications that interfere with vitamin K metabolism or synthesis, such as anticoagulants and antibiotics.

50. Vitamin Classifications Based on Solubility—(cont.) • Water-soluble vitamins • Thiamin • Coenzyme in the metabolism of carbohydrates and branched-chain amino acids • Deficiency Beriberi (what is beriberi?) • Beriberi has been virtually eliminated. • Deficiency is usually seen only in alcoholics. • No adverse effects have been noted from high intakes of thiamin.