Vitamins: Exam 5 Study Guide

• Exam 5 will be held March 27-28.
• The exam consists of 40 questions and will cover all vitamins (Ch. 12 & 13).
• The exam reviews metabolism, proteins, and amino acid structures.
• A late fee of $5 starts at 2pm on Friday, March 28.
• Scratch paper is allowed for the exam.

Vitamins

• Recognize the chemical structure of each vitamin.
• Outline the absorption process of each vitamin.
• The exam will cover the function and major metabolic pathways for each vitamin.
• Deficiency diseases, including symptoms, should be memorized for each vitamin.
• Know the best food sources, including provitamins for each vitamin.
• It is important to know the basis for the RDA/AI of each vitamin.
• Discuss the toxicity of each vitamin.
• Know the basis of the UL, if applicable, for each vitamin.
• Fat-soluble vitamins (KADE) and water-soluble vitamins (B-vitamins & vitamin-C) must be differentiated for the exam.
• Vitamins are essential organic substances needed in small amounts in the diet.
• The body cannot synthesize vitamins.
• A vitamin deficiency must be associated with a decrease in health which can be corrected by consuming the vitamin.
• Vitamins were initially named alphabetically in the order of discovery.
• B vitamins were initially classified together because of their similar chemical structures, however that was discovered to be wrong.
• Fat-soluble vitamins enter the lymphatic system and then the blood stream in chylomicrons.
• Carrier proteins and lipoproteins transport fat-soluble vitamins.
• Fat-soluble vitamins are not easily excreted, with the exception of vitamin K.
• Fat-soluble vitamins are stored in adipose tissue or the liver.
• Water-soluble vitamins directly enter the blood stream.
• The body excretes water-soluble vitamins rapidly, except for B-6 and B-12.
• Water-soluble vitamins limit toxicity.
• Antioxidants protect cell membranes from oxidation.
• Antioxidants stop chain reactions caused by free radicals.
• The body uses free radicals to destroy pathogens, and antioxidants control these reactions.
• Vitamins K, E, A, C, and Riboflavin (synthesis) are antioxidants.
• Vitamins are cofactors that bind to apoenzymes and make holoenzymes.

Vitamin K (Fat-Soluble KADE)

• Vitamin K functions as a coagulation cascade and it converts preprothrombin to prothrombin for blood clotting.
• Bacteria in the colon synthesize vitamin K.
• Infants are a vulnerable population, but deficiencies are rare after infancy.
• Bleeding disorders are a sign of deficiency, common at birth because the bacteria have not colonized the gut.
• Treatment involves vitamin K injections.
• High doses of vitamins E and A can interfere with vitamin K absorption.
• No UL (Tolerable Upper Intake Level) is set for vitamin K.

Vitamin A (Fat-Soluble KADE)

• Growth and development are key functions.
• Vitamin A is critical for the development of eyes, limbs, nervous and cardiovascular systems.
• A lack of vitamin A leads to birth defects.
• Cell differentiation is another of vitamin A's functions.
• Retinoids bind to retinoid receptors (RXR and RAR).
• Vitamin A regulates gene (DNA) expression.
• Another key function is immune function.
• An increase in infection is an early indication of vitamin A deficiency.
• Vision is contingent on vitamin A.
• Vitamin A converts light into neurological signals in the retina.
• Being an antioxidant, vitamin A prevents damage from free radicals.
• Night blindness is indicative of vitamin A deficiency; rhodopsin is recycled more slowly.
• Vitamin A deficiencies are prevalent in developing countries.
• Polar bear liver toxicity can result from polar bear liver consumption.
• UL: 3000 ug/day, which is 100 times the RDA.
• Toxicities include headache, blurred vision, and poor muscle coordination.
• High consumption that occurs during pregnancy can cause birth defects.

Vitamin D (Fat-Soluble KADE)

• Main function is to maintain serum calcium and phosphorus levels and absorption.
• Vitamin D is responsible for hormone secretion, regulating gene expression and immune function.
• The body synthesizes Vitamin D when exposed to sunlight.
• Fatty fish and fortified milk are dietary sources.
• People with fat malabsorption, bedridden people or those with limited sun exposure are vulnerable populations.
• Deficiency leads to Rickets/Osteomalacia, causing brittle/weak bones.
• Vitamin D toxicity causes too much calcium to be absorbed, which can be fatal.
• UL is 1000-3000 IU/day (0-8 years), and 4000 IU/day (8+ years).
• Excess calcium deposits can occur in the kidney, heart and lung.
• Overexposure from the sun does not result in toxicity.

Vitamin E (Fat-Soluble KADE)

• Key functions are antioxidant and peroxidation.
• It halts peroxidation chain reactions via free radical stabilization but must be regenerated by reducing agents.
• Free radical reactions break apart fatty acids.
• Preterm infants are a vulnerable population.
• Deficiency is rare in humans, but can lead to hemolytic anemia associated with fat malabsorption.
• Synthetic forms of vitamin E are not as effective as naturally occurring forms.
• May interfere with vitamin K absorption, which could inhibit blood clotting and cause hemorrhaging.
• Particular concern for individuals taking blood thinners.
• The UL is 1000 mg/day.

B-vitamins & vitamin-C

• All 8 B-vitamins participate in energy metabolism.
• Whole grains are a source of these vitamins.

Thiamin

• The body requires it for carbohydrate metabolism.
• Those who have had its source removed from bran in milling, developing countries, and those with eating disorders are vulnerable.
• Deficiency causes Beriberi, leading to peripheral neuropathy, weakness, muscle weakness, tenderness, enlargement of the heart, difficulty breathing, edema, anorexia, weight loss, and/or confusion.
• Alcoholics, and those who have low thiamin diets may develop Wernicke-Korsakoff Syndrome.
• Alcoholics will experience decreased absorption and increased excretion.
• There is no UL for thiamin.

Riboflavin

• The vitamin promotes REDOX reactions (FAD+ / FADH2), energy metabolism, activation of other B-vitamins and antioxidant synthesis.
• Alcoholics, persons with malabsorption disorders, and individuals with poor diets are vulnerable.
• Aribinoflavinosis, which causes inflammation of the mouth and tongue, is a disease of riboflavin deficiency.
• There is no UL.

Niacin

• The vitamin is required for REDOX reactions (NAD+ / NADH).
• Hispanic populations and corn eaters are vulnerable.
• Pellagra, defined by Italian "pelle" or "skin" and "agra" or rough, is a deficiency of niacin.
• Joseph Goldberger’s “Filth parties” proved Pellagra was a dietary disease and not infectious.
• The deficiency is identified by the three D's: dermatitis, diarrhea, and dementia.
• Niacin Flush can result due to toxicity.

Pantothenic Acid

• The creation of acetyl-CoA (Coenzyme A) requires pantothenic acid in the body.
• This acetyl-CoA stems from pyruvate, beta-oxidation, amino acids, and alcohol.
• N/A represents the population at risk for deficiency.
• There is no UL.
• Deficiencies are very rare because it is abundant in foods (Greek pantothen = everywhere).

Biotin

• Carboxylation reactions require biotin.
• Biotin helps with pyruvate to oxaloacetate, fatty acid synthesis, and catabolism of amino acids.
• Those with genetic mutations are vulnerable to deficiency.
• Deficiency is due to a rare genetic disease which lacks biotinidase.
• There is no UL.

Vitamin B-6

• It functions as a coenzyme or synthesizer.
• Essential to amino acid transamination, and folate metabolism.
• Blacks, smokers, alcoholics, and those taking oral contraceptives are vulnerable to deficiency.
• Deficiency leads to microcytic anemia, convulsions, depressions, and confusion.
• 100mg is toxic and causes serious nerve damage, weakness, paralysis, neuropathy, and sensory loss.
• Vitamin B-6 can limit symptoms of Carpal Tunnel Syndrome, Premenstrual Syndrome, and Nausea.

Folate

• Folate enables absorption, DNA synthesis, amino acid regulation, and neurotransmitter activity.
• Critical to neural tube development.
• Pregnant women are a vulnerable population and may experience neural tube defects.
• Deficiency symptoms of Megaloblastic or macrocytic anemia.
• A toxicity of over 1mg can mask vitamin B12 deficiencies.

Vitamin B-12

• Metabolism of fatty acids with an odd number of carbons and methyl donors are functions of the vitamin.
• Only animal products have it because it is produced by bacteria from grazing animals.
• Absorbed in the ileum, HCl helps break it down in the stomach, binds to intrinsic factors and R-proteins which are secreted in the stomach.
• Elderly adults, vegetarians, and vegans are vulnerable to deficiency due to absorption and decreased supply.
• Deficiency can include Macrocytic anemia and neurological changes.
• There is no UL for cobalamin.

Vitamin C

• Vitamin C is an electron donor that aids iron absorption, and immune function and helps recycle vitamin-E.
• Collagen synthesis requires vitamin C as a coenzyme for proline and lysine hydroxylation.
• Most animals also synthesize their own vitamin C, but humans do not.
• People in poverty or those with poor diets are vulnerable to vitamin C deficiency.
• Scurvy, prevents collagen synthesis, bleeding gums are clinical signs of deficiency.
• 2g/day is toxic based on GI distress.

Vitamin-like molecules

• Needs are met from animal foods and biosynthesis in liver.
• Carnitine functions to transport fatty acids from cytosol to mitochondria, aids mitochondria in removing excess organic aids and helps remove toxic amounts of built up compounds in those with inborn errors of metabolism.
• Taurine is synthesized in the body and found in foods of animal origin & energy drinks, such as, meat and seafood Redbull®, and Rock Star drinks.
• Taurine is involved in many vital functions in the body.
• Taurine deficiencies are rare.

Metabolism Review

• Understanding of alcohol metabolism, fat metabolism, and protein metabolism will be needed for this exam.
• No digestion or transport is required for alcohol to enter the blood stream and 20% of it is absorbed in the stomach.
• The body prioritizes metabolizing alcohol because it cannot be stored.