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49 Cards in this Set
- Front
- Back
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3 Classes of B vits
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* Those influencing energy release
* Those affecting blood formation * Those affecting other metabolic actions |
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B Vits influencing energy release are?
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Thiamine (vit B1); riboflavin (vit B2), niacin (vit B3), pantothenic acid
(vit B5), biotin, pyridoxine (vit B6) |
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B Vits affecting blood formation?
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Folic acid, cobalamin (vit B12), vitamin B6, pantothenic acid ( vit B5)
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2 groups of compounds have vitamin A activity
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– Retinol, retinaldehyde and retinoic acid (preformed vitamin A)
– A variety of carotenes (carotenoids) (provitamin or previtamin A) |
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Vit A daily amount required
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circa 700ug in retinol equivqlent
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Vit A sources
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Beef Liver 100g - 4968
Tuna 100g - 655 1 medium egg 100g - 140 Butter 1 tbsp - 97 Carrots 100g - 835 Butternut s 100g - 532 Spinach 100g - 469 Mango - 100g - 38 |
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Vit A needs a what nutrient to work
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Zinc required to make retinol binding protein (RBP)
• RBP moves vitamin A from liver storage to tissues for utilisation • People displaying vitamin A deficiency signs & symptoms may have sufficient levels of vitamin A but inadequate zinc levels to move the vitamin A to where it is required! |
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Absorption rate of Retinol and things to watch for
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• Retinol is absorbed from the small intestine dissolved
in lipid • About 70‐90% of dietary retinol is absorbed, even at high levels it falls only slightly • This is one of the reasons that animal food sources of vitamin A can lead to vitamin A toxicity • In people with very low‐fat diets (< 7% of total energy) absorption of retinol is impaired |
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Metabolic function Vit a - RED
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• R – REPRODUCTION
• E – EYES • D – DIFFERENTIATION (of cells) |
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Vit A specific therapeutics
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• Taking vitamin A orally is effective for preventing and
improving symptoms of xerophthalmia and night blindness – Doses are very high, therefore strictly under medical supervision • Breast cancer: epidemiological evidence shows an association between high dietary intake of vitamin A in the form of carotenoids and a reduced risk of breast cancer – However, it's not known if supplemental vitamin A or carotenoids have a similar benefit |
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sign Vit A def
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• Worldwide vitamin A deficiency is a major public health
problem in developing countries – the most preventable cause of blindness! • The earliest signs of deficiency are linked with vision – Initially there is a loss of sensitivity to green light, followed by impairment of the ability to adapt to dim light, and then inability to see in dim light: night blindness • More prolonged deficiency leads to xerophthalmia: irreversible damage to the eye causing blindness Other signs and symptoms: • Hyperkeratosis of skin of upper arms (blockage of hair follicles with keratin “goose flesh”) • Cysts especially on endocrine glands • Lowered immunity ‐ decreased neutrophil & NK cell function, decreased Th2 antibody response, allergies • Decreased corticosteroid production • Reduced skin integrity – rough dry skin, acne, eczema, inflammation, poor wound healing • Poor bone growth, growth retardation • Poor sense of taste and smell • Dry hair |
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Factors that might affect Vit A individual requirments
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• Gastrointestinal conditions affecting fat absorption can lead
to insufficiency – Diabetes mellitus (due to reduced ability to convert carotene to retinol) – Alcoholism (alcohol accelerates the breakdown of retinol) – Hyperthyroidism – Liver disease – Cystic fibrosis |
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Signs of Vit A toxicity
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• Chronic toxicity of vitamin A can follow regular intake of 7.5‐9mg
retinol/day by adults (significantly less by children) Signs and symptoms: – Headaches, nausea, anorexia, inability to move – Enlarged liver and hyperlipidaemia – Joint pains, thickening of long bones, soft tissue calcification – Excessive dryness, scaling of the skin; hair loss |
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Vit A Drug interaction
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– Hepatotoxic Drugs: excessive doses of vitamin A can cause
hepatotoxicity; taking high doses of vitamin A in combination with other potentially hepatotoxic drugs might increase the risk of liver disease – Warfarin: vitamin A toxicity is associated with haemorrhage; high doses of vitamin A could increase the risk of bleeding with warfarin. Advise patients taking warfarin to avoid doses of vitamin A above the Tolerable Upper Intake Level of 3000 μg/day |
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Carotenes
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•Found in green, yellow, and red fruits and vegetables
•In addition to being precursors of vitamin A, carotenoids have an antioxidant action •Fat is required for optimum absorption of both vitamin A and carotenes •No toxicity risk from excessive consumption – however smokers are advised not to take high doses of supplemental beta-carotene |
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Carotene Conversion
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•Recent studies indicate approximately 50% of Caucasian woman lack the correct form of the gene needed to convert beta carotene into vitamin A (Leung et al. 2009)
•In addition thyroid problems an diabetes can also interfere reduce a persons ability to convert carotenes into vitamin A •(Bender 2002; Bender 2005; Liska et al 2004) |
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Vitamin D
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•Vitamin D is not strictly a vitamin since it can be synthesized in the skin when we are exposed to sunlight
•Dietary sources are only required when sunlight exposure is inadequate •There are 2 types of vitamin D: –Vitamin D2 (plant source) –Vitamin D3 (animal source) •D3 is approximately 87% more potent in raising and maintaining serum 25(OH)D concentrations and produces 2- to 3-fold greater storage of vitamin D than does equimolar D2 (Heaney et al 2011) |
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Vitamin A & Vitamin D
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•Vitamins A and D are distinct from other vitamins in that their biological metabolites (retinoic acid and 1,25-dihydroxyvitamin D3) have hormone–like properties
•More than 532 genes are regulated by retinoic acid and over 220 by vitamin D •Retinoic acid and 1,25(OH)2D3 compete for the same nuclear receptor partners •Both the retinoic acid receptor and the vitamin D receptor must form heterodimers with retinoic X receptors to be able to bind to response elements and intitate transcription •For this reason, the two vitamins moderate each others uncontrolled effects - a balanced intake is vital |
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Vitamin E
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•Family of compounds consisting of eight different vitamers – four tocopherols, four tocotrienols
•Alpha tocopherol is considered the most bioactive •Natural D-forms are generally preferred in clinical practice, ideally in combination with other tocopherols/ tocotrienols •Functions: –The primary function of vitamin E is to prevent peroxidation of unsaturated fatty acids that form the structural component of phospholipid membranes, especially RBC, neurons, lung cells and phagocytes –More recently, it’s also been identified that vitamin E plays an important role in repairing plasma membrane, especially in muscle cells (Howard et al. 2011) |
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Vitamin K
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•There are two naturally-occurring forms of vitamin K:
–K1 (phylloquinone) is the dietary form of vitamin K found in green leafy vegetables. –K2 (menaquinone) is found in fermented dairy and soy products and in small amounts in animal foods. It is also synthesised by intestinal bacteria |
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Vit K Mechanism of Action
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•Vitamin K is essential for the activation of vitamin-K-dependent proteins, which are involved in blood coagulation, bone metabolism and the inhibition of arterial calcification
•In humans, vitamin K is primarily a cofactor in the enzymatic reaction that converts glutamate residues into gamma-carboxyglutamate residues in vitamin K-dependent proteins •In the absence of vitamin K, the these proteins are not carboxylated and are therefore biologically inactive |
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Thiamin - B1
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Thiamin - B1
•Thiamin is involved in the transfer of aldehyde groups. •Functions: –Participates in enzymatic reactions central to energy production, including decarboxylation and transketolation (also vital to make nucleic acids) –Modulates chloride ion channels in the central nervous system. –Provides energy for the respiratory burst of phagocytes during inflammation. –Vitally important in neuronal and neurocognitive –Synthesis and release of acetylcholine (ACh) at the synaptic junction 173 |
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Riboflavin - B2
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•The major function of riboflavin is to serve as a precursor for the coenzymes FAD and FMN
•Important roles of riboflavin include: –Energy metabolism as FAD –Drug or xenobiotic metabolism via cytochrome P450 enzymes –Lipid metabolism –Antioxidant protection by virtue of its role as cofactor in the regeneration of glutathione via glutathione reductase –Riboflavin is also involved in the metabolism of folic acid, pyridoxine, vitamin K, and niacin |
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B2 – Increased Requirement
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•Riboflavin is required for the generation of the active form of folate in the body
•It is also required as a cofactor for the MTHFR enzyme needed for homocysteine metabolism •In people with the MTHFR 667C=>T variant, MTHFR is functionally defective, partly because it has difficultly staying attached to its riboflavin cofactor •As a consequence, optimising B2 status in this population has been shown to reduce blood pressure even where traditional antihypertensives have been ineffective (Horigan G. 2010) |
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Niacin – B3
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•Niacin is used to form the active cofactors NAD and NADP, important in many oxidation-reduction and dehydrogenation reactions in the body
•Main functions include: –Cofactor for energy production –Cofactor for fatty acid and steroid synthesis –Cofactor for poly-ADP-ribose polymerase – important for DNA repair and cell differentiation –Formation of glucose tolerance factor |
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Pantothenic Acid – B5
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•Primary biological function of pantothenic acid is to serve as part of the coenzyme A (CoA) molecule.
•CoA has numerous functions in the body including: –Synthesis of several amino acids, steroid hormones, vitamin D, fatty acids and the porphyrins. –Oxidation of fatty –Acetylation of choline –Metabolism of proteins and carbohydrates –Vitamin B5 also works with carnitine and CoQ10 in fatty acid transport and use |
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Vitamin B6
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•Three primary forms exist: pyridoxine, pyridoxal and pyridoxamine
•The active coenzyme forms of vitamin B6 are pyridoxamine 5’ phosphate and pyridoxal 5’ phosphate •This nutrient is involved in roughly 100 enzymatic reactions •Zinc, riboflavin and magnesium are required for adequate PLP at target sites |
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B6 Key Functions
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•Removal of sulfur groups from amino acids, helping to transfer amine groups from one amino acid to another
•Methylation and homocysteine metabolism •Decarboxylation reactions, important in the conversion of tryptophan to serotonin •Conversion of tryptophan to niacin •Gluconeogenesis •Modulation of steroid hormone activity by binding to steroid receptors (It may also attach to the DNA receptor for these endocrine messengers and alter the action of the hormone) |
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Folate
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•Family of compounds including folic acid and folacin
•Methyl-tetrahydrofolate is the most abundant folate in the circulation and it functions with vitamin B12 to transfer a methyl group to homocysteine to produce methionine |
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Folate Other Functions
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•Methylation of brain myelin
•Synthesis of nucleic acids – Folate is vital for all rapidly dividing cells, including blood cells, cells of the gastrointestinal tract, and germinal cells. •Synthesis of cysteine from methionine - Since formation of glutathione depends upon the presence of adequate cysteine, glutathione formation is indirectly dependent upon adequate folate |
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Vitamin B12
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•Vitamin B12 is synthesized by bacteria and exists in all animal foods.
•It is freed through the process of proteolysis in the stomach. •The stomach secretes intrinsic factor (IF), which is necessary for the absorption of B12 in the ileum •Calcium is also needed for this process •Cyanocobalamin, hydroxycobalamin, adenosylcobalamin and methylcobalamin are the forms of B12 available for supplementation •In the body coenzyme activity is carried out by methylcobalamin and 5’-deoxyadenoxyl cobalamin |
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Functions of B12
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•Regeneration of folic acid – important for methylation, DNA synthesis and haemopoeisis
•Vital for nervous system function –Protecting glial cells from homocysteine accumulation –Synthesis of choline - a lack of which could lead to impaired fatty acid synthesis and nervous system dysfunction –Myelination –Production of some neurotransmitters |
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B12 & Veganism
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•The best food sources of B12 are animal products
•Plants do not contain bioactive forms of B12 unless they are contaminated by microorganisms (e.g. marmite!) •Sea vegetables such as wakame or nori contain vitamin B12 analogues, but these do not appear to be metabolically active •Individuals who have had vegan dietary habits for a number of years should always be asked about vitamin B12 supplementation. •Vitamin B12 stores in the liver may mean that up to five years may pass before problems of B12 shortage are evident. •B12 may also be low in individuals with health conditions that impact intrinsic factor production |
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Vitamin C
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•Unlike most other mammals, humans are unable to synthesize vitamin C from glucose because of their lack of one vital enzyme
•As well as being an important antioxidant vitamin C also functions as a cofactor for: –Collagen synthesis - helps form hydroxyproline from proline, important for forming strong connective tissue, repairing wounds, improving gum health, and reducing bruising –Catecholamine synthesis and tyrosine metabolism –Peptide amidation - many peptide hormones, neurotransmitters and growth factors require an amide group at one end to be biologically active |
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Calcium
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•Functions
–Bone and teeth mineralisation –Blood clotting – activation of prothrombin, conversion of fibrin to fibrinogen –Muscle contraction –Neurotransmitter release at the synapse •Active calcium absorption in the intestines requires calcitriol (active form of vitamin D) |
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Phosphorus Functions
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•Key inorganic component of bone and teeth
•Contributes to critical life-maintaining compounds, including: Phospholipids, nucleic acids, ATP, 2,3-disphosphoglycerate (regulates oxygen release from hemoglobin) •Phosphorylation – a vital process in many cellular functions and enzymatic reactions •Regulate a number of enzymes •Participates in buffer systems within the body •Development and repair of body tissue •Lipid metabolism |
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Magnesium
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•Needed for over 300 enzymatic reactions including those involved in:
–Energy metabolism –Protein synthesis –Fat synthesis –EFA metabolism (cofactor for delta-6-desaturase) –Urea cycle •One of the enzymes in which magnesium plays an important role is sodium/potassium ATPase, which activates and regulates: –Cellular energy metabolism –Transport across membranes –Vascular tone •Magnesium is necessary for glucose transportation between membranes, glucose oxidation, all reactions involving phosphorylation and energy exchange and it is essential for insulin action, since it is a cofactor of the tyrosine kinase insulin receptor |
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Sodium, Potassium & Chloride
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•The major solutes in the extra cellular fluid are sodium and chloride, while potassium is the major component of the intracellular fluid
•This balance in vital for: –Nerve transmission –Muscle contraction –Maintenance of cellular integrity •In addition, potassium plays a role in glycogen and glucose metabolism •Sodium is important for transport of carbon dioxide and amino acids •Chloride is needed to make stomach acid •Note: magnesium deficiency will contribute to potassium loss; this same deficiency also makes it difficult for the cells to regain potassium stores |
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Chromium
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•Chromium is the major component in glucose tolerance factor, along with niacin (vitamin B3) and the amino acids glycine, glutamic acid, and cysteine
•It also increases GLUT4 expression on cell plasma membranes resulting in improved glucose trafficking in response to insulin •As a result is has a strong insulin-enhancing activity •This is thought to be mediated by the fact that chromium increases membrane fluidity by reducing plasma membrane cholesterol levels •It may also activate p38 MAPK, an enzyme thought to play a role in insulin-stimulated glucose uptake •Chromium is particularly useful when insulin resistance is present, especially if accompanied by an abnormal lipid profile, as chromium has also been shown to raise HDL in some studies •The immune response may also benefit from chromium, as it may decrease serum cortisol and increase immunoglobulins |
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Zinc
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•Functions
–Cofactor in a number of enzymatic reactions –Assists in many hormone activities (thymic hormones, growth hormones, and insulin). –Important for protein and DNA synthesis –Wound healing and immune function –Needed to make superoxide dismutase - antioxidant –Bone structure –Skin oil gland function –Important for healthy prostate tissue •Iron and calcium may interfere with zinc absorption •It’s also important that zinc intake is balanced with copper to avoid copper deficient anaemia developing •Zinc has been shown to be deficient in individuals with AIDS •Smokers also have lower zinc levels •If the patient has a history of recurrent infections, skin conditions, slow wound healing, or disrupted inflammatory response, zinc status should be assessed. |
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Copper
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•Functions
–Important in a number of enzyme systems, including the antioxidant superoxide dismutase –Haemoglobin synthesis –Electron transport chain –Cofactor for lysyl oxidase – needed to cross link collagen and elastin –Catecholamine metabolism –Melanin synthesis |
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Iodine
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•Functions
–Production of thyroid hormones such as thyroxine - Since thyroid hormones are needed to increase cellular reactions, including oxygen consumption and basal metabolic rate, and to influence growth and differentiation, iodine obviously plays a major role in these activities. –Immune function - iodine works with neutrophil peroxidases in bactericidal activity |
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Iron
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•Functions
–Part of the haemoglobin and myoglobin –Cofactor for Kreb cycle enzymes and electron transport chain –Helps to maintain normal immune function –Aids normal collagen synthesis –Cofactor for thyroperoxidase enzymes in the thyroid |
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Iron Absorption
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•Haem iron is found in animal tissue and is absorbed better than other iron forms
•Iron absorption may be inhibited by phytic acid, tannins, calcium, oxalates and partially digested proteins. •Ascorbic acid and cysteine aid iron uptake •Low stomach acid may also impair iron absorption •NB Low iron may indicate occult blood loss and should be investigated! •NB Excess iron is stored rather than excreted – iron is therefore toxic in large amounts |
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Manganese
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•Manganese aids:
–Carbohydrate metabolism - cofactor in a number of enzymes important in energy production –Bone development –Prothrombin synthesis –Protein digestion –Collagen formation –Fatty acid synthesis –Protein synthesis –Antioxidant defence – cofactor for superoxide dismutase |
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Selenium
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•Functions
–Cofactor of glutathione peroxidise - works with vitamin E in the vital antioxidant systems of the body, including aiding DNA repair –Reduces heavy metal toxicity –Important in sulfur amino acid metabolism –Needed in the deiodinase enzyme to convert T4 to T3 in the liver - A selenium deficiency can cause thyroid enlargement. •While selenium is also found in vegetables and grains, the soil content will determine the content of these food sources |
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Lignans
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•The lignans are a group of chemical compounds found in plants.
•Lignans are one of the major classes of phytoestrogens and also act as antioxidants •Lignans are acted upon by colonic bacteria to produce the two major mammalian lignans, enterodiol and enterolactone •Both enterodiol and enterolactone are structurally similar to oestrogen and produce weak estrogenic and anti-oestrogenic activities •One of the best dietary sources of lignans are flaxseeds |
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Diversion - Phytoestrogens
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•Phytoestrogens are plant compounds that have the capacity to bind to oestrogen receptors (ER) and appear to have both oestrogenic and anti-oestrogenic effects, depending on the expression of ER sub-types in target cells and on the level of endogenous oestrogen present
•Lignans and isoflavones are both types of phytoestrogen The main actions through which they have a beneficial effect on oestrogen metabolism are: –They have a similar structure to oestradiol and can bind to the ER –They increase plasma SHBG levels –They decrease aromatase activity –They shift oestrogen metabolism away from the 16-α-OHE pathway to the 2-OHE pathway (Hall D, 2001) |
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Flax & Kidney Health
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•Flax seeds have also demonstrated reno-protective effects in diabetes models by reducing the levels of oxidative stress and increasing the antioxidant defence systems
•In a two-year cross-over study, use of 30g per day of ground flax was found to reduce serum creatinine from a mean of 0.97 mg/dl to a mean of 0.94 mg/dl in a group of lupus nephritis sufferers. •A decline in leakage of albumin into the urine micro-albumin was also observed (Velasquez et al. 2003) (Haliga et al. 2009) (Makni et al. 2010) (Clark et al 2001) |
