Part I:(Due on 7th) max 200-250 wordsThere are two water soluble vitamins that can be synthesized by some animals but not by others, including humans: They areVitamin C (AscorbicAcid) and Vitamin B12 (Cobalamin). Therefore these vitamins would not be essential nutrients for all species. For your main post, choose one of the these to begin your thread. Don't use up a lot of space re-stating all the functions we learned in class, but expand upon them instead. Do you feel you might be at risk for deficiency for the vitamin you choose to start with? What are the consequences of deficiency? Include food sources and how certain dietary choices affect the vitamin's status in the body. Is it better to obtain the vitamins from food or supplements? Are there toxicity issues with the vitamin of your choice? Feel free to include your own personal experiences, if applicable. Include at least one credible reference (Text book is OK if you also include an additional reference).
Part II: 20-50 words for each reply.Then, reply to two of the following posts in short. (Due on 9th)One of your replies must be on the vitamin that you did not choose. Your own words please! ( I'll post it once you finish the other parts.
PowerPoint Presentation 1 Bio 125 Distance Learning Lecture 5 Janine Grant Vitamins Learning Objectives To be able to discuss the following about vitamins: Definition Classification: Essential, micronutrients, fat vs. water soluble Vitamin enrichment. Vitamins that are conditionally essential. Most important basic functions for each of the water soluble vitamins. (Fat soluble vitamins will be addressed in Lecture 6.) Food sources. Deficiency diseases and deficiency symptoms. Toxicity. 2 Vitamin Enrichment of Refined Grains The following water soluble vitamins are removed during the refinement of grains. They are replaced with a synthetic version. Look at “enriched white bread” Thiamin Riboflavin Niacin Enriched white flours are also now fortified with Folic Acid White flour is also fortified with iron. Remember that Enrichment differs from Fortification Enrichment replaces nutrients lost, fortification adds nutrients that are not normally present For example, Vitamin D is added to milk Salt is available fortified with iodide (mineral covered in lecture 9) 3 Definition: Vitamins are organic compounds that are required in the diet in small amounts to regulate body functions. To be classified as a vitamin, a lack of any of these organic compounds must produce deficiency symptoms that would be alleviated by replacement in the diet. There are 13 known vitamins in human nutrition. Four are lipid soluble and 9 are water soluble. Choline, an essential water soluble nutrient, is not classified as a vitamin at this time, but dietary recommendations have been made Vitamins are essential nutrients, i.e. they can’t be synthesized in adequate amounts in the body, if at all, so they must be obtained from the diet. (The exception is Vitamin D, which is more like a hormone than a vitamin and can be synthesized from cholesterol following exposure to sunlight.) Vitamins differ from the macronutrients in their structure and function. Vitamins are required in tiny amounts, they are not broken down to yield energy, nor are they assembled into body structure. Many vitamins are catalysts for chemical reactions. For example, the B-Vitamins function as coenzymes. (Coenzymes are organic non-protein molecules that bind to enzymes and activate them.) Some vitamins function as antioxidants or as hormones. Most vitamins are absorbed in the small intestine. Vitamin content in food can be affected by cooking, storage, exposure to light and oxygen, and by processing. Processed foods that are stripped of their vitamins (and other nutrients) are often “enriched”, such as white flour. Not all of the vitamins, minerals, and other nutrients stripped during processing are replaced. Some foods are also “fortified”, whereby some vitamins or minerals that were not originally present are added. For example, milk is fortified with Vitamin D. 4 Requirements Recommended vitamin intakes for healthy people in the U.S. and Canada are based on the DRIs (Dietary Reference Intakes – see outline 1), which provide an RDA value, or an AI (Adequate Intake) value which is an estimation used when not enough data is available to determine the RDA. The DRIs also incorporate the UL (Tolerable Upper Intake Level) as some vitamins are toxic in high doses. A limitation of the RDAs is that they are based on studies that determine the requirement to prevent known deficiency symptoms; however many vitamins have multiple functions in the body and actual needs may differ from the RDAs. 5 The Water Soluble Vitamins Vitamin C (Ascorbic Acid) and the 8 “B” Vitamins, Thiamine, Riboflavin, Niacin, Pyridoxine (B6), Biotin, Pantothenic Acid, Folate, B12. Excess intake is excreted by the kidneys, except B12 which is stored. Therefore, they have to be regularly consumed in the diet. However, there can still be toxicity issues, particularly with niacin and B6. The Fat Soluble Vitamins Vitamins A, D, E, and K Found together with fats and oils in foods. Absorbed along with dietary fat – requiring emulsification into micelles and incorporation into chylomicrons. (refer to outline 3). They tend to be stored in the liver and adipose tissue. Therefore it generally takes at least a few days to develop deficiency symptoms. On the other hand, deficiencies of fat soluble vitamins can occur with very low dietary fat intake, or with fat malabsorption. 6 6 7 THE WATER SOLUBLE VITAMINS The “B” Vitamins and Vitamin C The “B Vitamins The 8 “B” Vitamins participate in numerous metabolic pathways. Many of them are found together in foods. Deficiencies often occur in combination. Some of the deficiency symptoms overlap. Excess intake is eliminated by the kidneys, but toxicity is possible, for example with niacin and B-6 (from supplements). The “B” Vitamins function as coenzymes in many metabolic reactions. Basically: Thiamin, riboflavin, niacin, biotin, pantothenic acid, and B-6 participate in the metabolism of energy yielding nutrients (among other functions). Folate and B-12 participate in DNA synthesis (and for B12 – maintaining the nervous system). 8 THIAMIN (Vitamin B1) The first compound to be recognized as a vitamin. The deficiency disease beri-beri (“I can’t, I can’t) was originally found in populations in which polished white rice was a dietary staple because the vitamin is found in the bran and germ of the rice. It mainly functions in carbohydrate metabolism and nervous system function. Can be destroyed by high cooking temperatures. Absorption and Metabolism Thiamin is absorbed in the duodenum (small intestine) and phosphorylated intracellularly to its biologically active coenzyme form, thiamin pyrophosphate (TPP) which contains two phosphates. TPP is the coenzyme for reactions involving the removal of a carbon, such as the transformation of pyruvate to acetyl-CoA. Functions Production of energy (ATP) from carbohydrates (glucose). The formation of Acetyl-CoA from pyruvate formed from glycolysis Also participates in the Citric Acid Cycle Nervous System Function Production of neurotransmitter acetylcholine 9 RDAs for Adults 1.2 mg/day for men, 1.1 mg/day for women. Thiamin requirements go up with increased kilocalorie intake, especially from sugar, and with pregnancy and lactation. Deficiency Beri- Beri, which affects the cardiovascular, muscular, nervous, and gastrointestinal systems. Early symptoms are depression and weakness and occur after about 10 days on a thiamin-free diet. There are 3 types: “Dry beri-beri (neuritic) – degeneration of the nervous system, tingling in the extremities, confusion, poor coordination of the arms and legs, irritability, weakness. “Wet beri-beri (cardiovascular) – enlarged heart, edema, heart failure Wernicke-Korsakoff Syndrome – found in people with alcoholism. Signs/symptoms are nystagmus (involuntary movement of eye muscle), staggering, mental confusion, psychosis. Toxicity None known 10 Good Food Sources Brewer’s yeast, wheat germ, whole grains, beans, seeds, pork. Refined, enriched grains and cereals are sprayed with synthetic thiamin. Some foods contain enzymes known as thiaminases which antagonize thiamin. These anti-thiamin factors are found in raw shellfish, and other raw fishes, and are destroyed by cooking. Other anti-thiamin factors are found in tea, coffee, betel nuts (not commonly consumed in the West), blueberries, and red cabbage. Alcoholic beverages also deplete thiamin. Chronic heavy drinking (not moderate social drinking) can result in Wernicke-Korsakoff syndrome. 11 RIBOFLAVIN (Vitamin B2) A fluorescent yellow-green compound, stable to heat and acid. Discovered after thiamin (B1). As coenzymes (FAD and FMN) participates in glucose and fatty acid metabolism. Destroyed by exposure to light. Absorption and Metabolism Absorbed in the small intestine Functions Riboflavin forms the active co-enzymes flavin adenine dinucleotide (FAD) and flavin mononucleotide (FMN). FAD and FMN participate in the Citric Acid (Kreb’s) Cycle in macronutriet metabolism (electron transport chain accepting and releasing electrons, forming ATP. FAD participates in the beta-oxidation of fatty acids (where they break down to acetyl-CoAs for entry into the Citric Acid (Kreb’s) Cycle. Riboflavin is involve in the conversion of other vitamins into their active forms, such as folate, niacin, B-6 and Vitamin K. 12 RDAs for Adults 1.3 mg/day for men; 1.1 mg/day for women Deficiency Ariboflavinosis: Not very common. Can occur after about 2 months on a riboflavin free diet. Symptoms include cracks at the corners of the mouth (cheilosis), inflammation of the tongue (glossitis), hypersensitivity to light, itchy eyes, seborrheic dermatitis (greasy, scaly skin eruptions), and confusion. Riboflavin helps to convert other vitamins to their active forms, plus it occurs in foods together with other vitamins, therefore riboflavin deficiency rarely occurs alone. Toxicity None known Good Food Sources Dairy products, liver, meat, fish, poultry, green vegetables, brewer’s yeast, almonds, enriched grains and cereals. Because riboflavin is affected by exposure to light, milk is sold in opaque containers. 13 NIACIN (Vitamin B3) Niacin deficiency (pellagra) was first seen in regions where corn was used as a dietary staple. In the early 1900’s, many people were institutionalized with a dementia cause by pellagra. This led to the discovery that pellagra was a nutritional deficiency disease rather than an infectious disease as previously thought. The disease has historically been a problem among very poor people, especially those who relied primarily on corn in their diet. The niacin in corn is not bioavailable. Absorption and Metabolism Easily absorbed in the small intestine. Niacin is different than the other B vitamins because some can be synthesized from the amino acid tryptophan. Niacin exists in two forms: nicotinic acid and nicotinamide. Both forms can be converted to the active coenzymes NAD and NADP. Niacin is stable to light, heat, acid, alkali and oxidation. 14 Functions Carbohydrate and lipid metabolism, health of the skin, nervous system, and digestive system. Similar to the coenzyme forms of riboflavin, niacin participates in glucose metabolism. Glycolysis, Citric Acid (Krebs) Cycle, Electron Transport Chain where NAD accepts and releases electrons, forming ATP. Formation of lactic acid from pyruvate during anaerobic conditions. Alcohol metabolism as NAD and NADP. Fatty acid and cholesterol synthesis as NADP. RDAs for Adults 16 mg/day for men, 14 mg/day for women. 1 mg = 1 NE (niacin equivalent) or 60 mg of tryptophan. Deficiency Pellagra. The first symptoms of fatigue. Then, the 4 Ds: dermatitis, diarrhea, dementia, and eventually death. The dermatitis is worsened by sun exposure and resembles sunburn. The dementia is preceded by irritability, loss of appetite, confusion and dizziness. High intake of corn that is not treated with the mineral lime (calcium