Vitamins, Minerals and Nutrition Flashcards
DRVs =
Dietary Reference Values
= estimates of the energy and nutrients needed by different groups of healthy people in the UK
Estimated Average Requirement (EAR) =
The level of a nutrient required to satisfy about 50% of the population
Reference Nutrient Intake (RNI)
Set 2 standard deviations above the mean (EAR) and will meet the individual requirements of 97.5% of the population
GDAs
Guideline Daily Amounts
Intended as guidance for consumers in their understanding of their recommended daily consumption of energy (calories), fat and saturates and a base against which the content of individual foods can be compared
Currently no GDAs for children
BMR (Basal Metabolic Rate)
Approx 60% of energy obtain by food oxidation used to maintain body function = basal metabolic rate
e.g. heart beat, inflating lungs, maintaining ion gradients, synthesising bio-molecules e.g. proteins, hormones, DNA, RNA, fat etc.
Small Intestine
- Duodenum (proximal)
o First part of small intestine
o Receives secretions from pancreas (enzymes for protein digestion) and bile from gallbladder to aid digestion - Jejunum (middle)
- Ileum (distal)
o Inner surface highly folded into villi – increases SA for absorption
Attached to body wall by mesentery
Function: Nutrient Absorption
Large Intestine
- Constitutes o Caecum o Ascending colon o Transverse colon o Descending colon o Sigmoid colon o Rectum o Anal canal
- Function
o Water absorption
o Formation of faecal mass
o Secretion of mucus
Accessory Organs of GI tract
Pancreas – enzyme secretion into duodenum
Liver
- Bile production
- Detox – drugs, alcohol
- Albumin production – protein that maintains osmotic pressure
- Production of clotting factor precursors
- Storage of glycogen
Gallbladder – stores and secretes bile into duodenum; emulsifies lipids
Omentum
- Covers GI tract
- Consists of greater and lesser omenta
- Greater omentum hangs from greater curvature of stomach like a curtain, also contains extra-peritoneal tissue; lymph nodes, lymph vessels, small blood vessels, variable amounts of fat. Has irregular lacy appearance.
Peritoneum
= membranes of the abdomino-pelvic cavity
Visceral peritoneum: covers external surfaces of most digestive organs
Parietal peritoneum: lines body wall
Peritoneal cavity = potential space between the two
Peritoneal fluid = normal lubricating fluid found in peritoneal cavity
digestion of carbohydrate in the oral cavity
Oral cavity → Mechanical (mastication exposes terminals to enzymatic action) + Chemical (enzymatic – salivary amylase secreted from serous cells in salivary glands)
Salivary amylase
- Secreted by serous acini of parotid and submandibular salivary glands
- Optimal pH= 6.7
- Action begins in oral cavity, assisted by mechanical breaking up of polysaccharides during mastication
- Mode of action = hydrolysis of α-1-4 linkage in polysaccharides → mixture of oligosaccharides (di/tri-saccharides)
- Works for 1/2hrs in stomach before being deactivated by gastric acids
digestion of carbohydrate in GIT
GIT → Chemical (enzymatic)
Pancreatic amylase
- Secreted from pancreatic exocrine acini into duodenum through the pancreatic duct – along with bicarbonates raises pH to optimum for amylase to work
- Optimum pH=6.7-7.0
- Mode of action = hydrolysis of α-1-4 linkage
- Responsible for digestion of more complex carbohydrate, take longer to break down to disaccharides (maltose) or oligosaccharides (dextrins)
NB: salivary & pancreatic amylases cant completely digest carbohydrates
- *Brush border enzymes: Maltase, Sucrase, Lactase **
- Found on membrane surface of micro-villi (brush border) of epithelial cells lining small intestines
- Optimal pH=7-8
- Mode of action = hydrolysisng disaccharides → monosaccharides
absorption of glucose from the small intestine at the cellular level
Villi & Microvilli (brush border) -> Increase SA, facilitates absorption
Monosaccharides = absorbable form of carbs
Glucose & Galactose
- Enter epithelial cells of intestine through the apical border via active transport (against concentration gradient) using sodium dependant co-transporters (Na-K pump requires energy)
- Leave the cells through the Basolateral side using facilitated diffusion and glucose co-transporter- 2 (GLUT-2) into the circulation (no energy required)
Fructose
- Enters (GLUT-5) and leaves (GLUT-2) the epithelial cells using facilitated diffusion (no energy required)
Factors affecting carbohydrate absorption
- Faster through intact mucosa; absorption decreased if inflammation or injury to the mucosa.
- Thyroid hormones ↑ the rate of absorption of glucose.
- Mineralocorticoid: e.g. Aldosterone ↑ the rate of absorption.
- Na+ concentration: high concentration ↑ the rate of absorption
role of insulin in glucose homeostasis
Insulin = hormone secreted by ß-cells in islets of Langerhans in pancreas (endocrine glands)
Responsible for regulating levels of glucose in blood by stimulating body cells to take up glucose – all body cells sensitive to insulin except: brain, liver and muscles during exercise
Structure of Insulin:
2 polypeptide chains A & B linked by a disulphide bond
Glucagon
= hormone secreted by α- cells in islets of Langerhans in pancreas
Responsible for converting glycogen stored in liver -> glucose and releasing it in blood when blood glucose levels low
Also stimulates gluconeogenesis from untraditional mechanisms (fat/protein sources) – used in case of starvation
➢ Clinical significance of insulin deficiency
Insulin deficiency (Type 1 – autoimmune disease) Insulin resistance (Type 2 – unresponsive cells)
–> leads to hyperglycaemia (causes the symptoms and complications of diabetes) and diabetes mellitus.
➢ Symptoms and complications of diabetes and its relevance to oral health and dental management
impaired wound healing
dry mouth
nausea
yeast infections
Diabetes -> damage to blood vessels -> more susceptible to collecting cholesterol -> blockage of blood vessels: macrovascular, microvascular
Dental Complications:
- Dry mouth
- Periodontal disease
- Loss of teeth
- Impaired/delayed healing
- Infections
Dental management of diabetic patients
• Regular visits to dentist and dental hygienist
• Maintenance of oral hygiene
• Regular periodontal check and management
• Antibiotic coverage for surgeries (surgical extraction, implants)
• Controlled blood sugar levels before any surgical intervention
• Mouth wash
• Artificial saliva if required
Nutrition and Caries
proteins - can adsorb to enamel surface and prevent remineralisation
dehydration -> reduced salivary flow
Caesin (milk protein) promotes natural remineralisation
fluoride insufficient -> caries prone
fluoride excess -> fluorosis
Vit D deficiency -> decreased Ca -> poorly mineralised enamel, enamel hyperplasia, rickets
Vit E def (rare) -> disturbed enamel formation
Vit A def -> enamel hyperplasia and malformed dentine
fermentable dietary components (carbohydrate)
pyruvate -> lactic acid/acetic acid
sucrose = worst carb
- bacteria can use to produce extracellular polymer
sucrose = glucose + fructose
Glucan (polymer of glucose) + Fructan (polymer of fructose) -> plaque
sugar substitutes = non-fermentable
Nutrition and Periodontal disease
nutrition modulates immune response .’. poor nutrition -> poor wound healing
vit A -> essential in maturation of epithelial tissues
vit D -> maintains blood Ca levels and metabolism of osseous (bony) tissues - may be associated with periodontal disease
vit C *(humans can’t make it C = essential vit) -> required for collagen maturation
deficiency -> tissue bleeding, marked gingivitis, increased risk of period disease
vit B complex -> can increase periodontal wound healing
dairy - inverse relationship between intake and period
alcohol - may be associated with increased severity of CAL
fish oils -> anti-inflammatory actions
Fat soluble vitamins
A
D
E
K
fat must be present in diet to adsorb these vitamins
can accumulate in adipose and can reach toxic levels
Water Soluble vitamins
C B6 B12 Biotin Folate Niacin Rriboflavin (B2) Thiamin (B1)
Excess water soluble vitamins excreted in urine .’. generally less toxic
Vitamin C (Ascorbic Acid)
RNI = 40 mg/day
Sources = Fruiit, veg, liver
Functions =
- Antioxidant
- Required for iron (Fe) adsorption
- Required in synthesis of many biomolecules (esp. collagen)
Deficiency -> Scurvey --> loose teeth superficial bleeding fragile blood vessels poor healing compromised immunity mild anaemia (due to decreased Fe adsorption)
Vitamin D
Most toxic of all vitamins; in high doses -> nausea and muscle weakness. V high doses -> increased Ca adsorption & bone resorption, resulting increased Ca levels in body fluids can lead to calcification of arteries and organs.
T-Dehydrocholesterol (from liver) = inactive
+ UV –>
Cholecalciferol (Vitamin D - also from diet) = inactive
–> Activated by hydroxylation
Controls serum Ca & phosphate levels - critical for correct development of bones and teeth
Folate (Folic Acid)
- one of B group vitamins
RNI = 200ug/day
Sources = green leafy veg, liver (where stored), nuts, cereals
Functions =
Carrier of 1 carbon units
*very important in many biosynthetic reactions
Deficiency:
occurs 2-3 months ->
- megaloblastic anaemia
- fatigue
- hair loss
- birth defects -> neural tube defects e.g. spina bifida, anencephaly
- glossitis, mouth ulceration, angular chelosis = general symptoms of B group vitamin deficiency
Activation:
Folic Acid not active form of vitamin, needs to be reduced to tetrahydrofolate
- occurs via: dihydrofolate reductase = enzyme targeted by anti-cancer drugs
*Coenzyme in many reactions involving transfer of 1C atom to other compounds. Single C groups can be carried in N5, N10 or bridged between both these Nitrogens. E.g. in synthesis of dTMP (t base in DNA) - v.important in rapidly dividing cells e.g. bone marrow cells (->RBCs), hair follicles, mucosal cels, cancer cells - explains why chemotherapy causes hair loss. Methotrexate inhibits dTMP production.
Vitamin B12
cobalamin
RNI = 1.5ug/day (NB: a healthy adult will have enough B12 stored in their liver to last years)
Sources = only produced by microorganisms - naturally we obtain by eating animals, eggs and dairy products
Functions =
1. B12 required in folate metabolism –> FOLATE TRAP in deficiency - Impacts DNA synthesis, important in rapidly dividing cells
- Required by methylmalonyl CoA mutase (B oxidation of odd chain fatty acids)
Deficiency ->
- megaloblastic (pernicious) anaemia; due to impact on folate metabolism
- Neurological disorders; due to impact on odd carbon FA metabolism)
NB: dietary deficiency found only in strict vegans/vegetarians. Deficiency due to adsorption problems more common.
B12 binds a glycoprotein (intrinsic factor; secreted by parietal cells) in stomach
vitamin-intrinsic factor complex recognise and absorbed
Vitamin K
=> Blood Clotting and formation of mineralised tissues
Sources =
1 - Made by gut bacteria (70%)
2 - Diet; green veg, liver, egg yolk (30%)
Functions =
ESSENTIAL in formation of CARBOXYGLUTAMATE
Deficiency Causes:
- Dietary deficiency
- Long term antibiotic use -> decreasing levels of gut bacteria
- Anticoagulant drugs e.g. Warfarin (= vit K antagonists) - inhibit clotting by preventing gamma carboxylation
NB: Newborns have sterile guts .’. can’t make bit K in first week of life
Vitamin A
RNI =
Sources =
Functions =
Deficiency ->
Thiamin (Vitamin B1)
RNI =
Sources =
Functions =
Deficiency ->
Beriberi disease
Pyridoxine (Vitamin B6)
RNI =
Sources =
Functions =
Deficiency ->
Tocopherol (Vitamin E)
RNI =
Sources =
Functions =
Deficiency ->
Rriboflavin (Vitamin B2)
RNI =
Sources =
Functions =
Deficiency ->
Niacin (Vitamin B3)
RNI =
Sources =
Functions =
Deficiency ->
Pantothenic acid
RNI =
Sources =
Functions =
Deficiency ->
Biotin
RNI =
Sources =
Functions =
Deficiency ->
Which vitamin is a coenzyme for methylmalonyl CoA mutase in B oxidation of odd C FAs
B12
In absence of B12 L-Methylamlonyl CoA accumulates; causing demyelination of nerve cells because disrupts FA synthesis (get branched FAs) –> Irreversible, neurological damage
A primary deficiency in which vitamin causes a secondary folate deficiency?
B12
Even if folate in diet -> deficiency due to FOLATE TRAP
N5-Methyl tetrahydrofolate + Hemcysteine —-> Methionine + Tetrahydrofolate
Reaction occurs via methionine synthase with vitamin B12 as a coenzyme.
(Tetrahydrofolate accepts methyl group in different reactions and is converted back to Nf-Methyl tetrahydrofolate)
- ONLY reaction that can utilise N5-Methyl tetrahydrofolate
- If B12 deficient methionine synthase reaction stops and eventually all folate trapped as Nf-Methyl tetrahydrofolate which can’t be used for anything
Which vitamin required in formation of Carboxyglutamate? What is the significance of Carboxyglutamate?
[Carboxyglutamate = amino acid glutamate with extra carboxyl group added to gamma carbon end of it’s side chain]
Glutamate —–> γ-carboxyglutamate
(carboxylation rxn: Enzyme + vit K)
when vit K deficient or antagonised by drug can’t synthesise γ-carboxyglutamate & protein function impaired - extra carboxyl group allows binding of Ca ions necessary for functions
Blood Clotting: Factors II, VII, IX, X contain γ-carboxyglutamate
Bone Mineralisation: Osteocalcin = protein involved in bone mineralisation
Calcium (Ca)
Absorption greatly increased by parathyroid hormone and active Vitamin D!
Functions: – Structural in skeleton – Intracellular second messenger (like cAMP) – In transmission at synapses – Muscle contraction – Blood clotting
Deficiency: due to Ca deficient diet, secondary vitamin D deficiency or Malabsorption → Ostemalacia (rickets in children) – usually caused by secondary deficiency in vit D, not aided by Ca poor diet → Oral problems – Incomplete mineralisation of teeth – Increased caries risk – Tooth malformation – Increased risk of perio problems – People aged 20-30 consuming
Phosphorus
RNI = 550mg/day – higher during growth, pregnancy, lactation, post menopause.
Sources: Most foods – dietary deficiency unknown
Adsorption: 50-70% in diet absorbed (enhanced by vitamin D)
Functions:
– With Ca in mineralised tissues
– Biological buffer
– Required for many biomolecules and processes e.g. phosphorylated proteins, ATP, DNA, RNA etc.
Deficiency: usually due to kidney malfunction, aluminium in antacids, total starvation. If severe will affect functioning of all cells. Impact on bone metabolism could → rickets and Ostemalacia (softening of bones). Oral problems similar to Ca deficiency.
Excess: Disturbance of Ca balance, increased porosity of skeleton.
Iron (trace element)
RNI = 8.7mg/day men ; 14.8mg/day – higher RNI than biological requirement to compensate for inefficient absorption
Sources: Dietary iron has 2 forms
- Haem iron : liver, meat – from haemoglobin/myoglobin = rapidly absorbed
- Non haem iron : green veg, cereals = slowly absorbed (aided by meat proteins, vit C, alcohol)
Adsorption: Tannins (found in tea), Ca, polyphenols, phytates (found in legumes and whole grains), oxalate (green leafy veg) can decrease absorption of non-haem iron. Some proteins in soybeans also inhibit non-haem iron absorption.
Functions:
– In many proteins and enzymes; oxygen transport proteins, electron transport proteins etc.
Deficiency: due to -
Inadequate dietary intake
Blood loss (menstruation, ulcers etc.)
→ Anaemia
Excess: Fe = toxic, deposited in tissues which distrupts function (free radical damage)
Transported in blood bound to Transferrin – stored bound to ferritin in bone marrow & spleen, haemosiderin in liver.
Iodine (trace element)
THYROID
Functions:
– Synthesis of thyroid hormones by thyroid glands
– Control of metabolic rate
– Essential for brain development in early life
Deficiency → reduced synthesis of thyroid hormones – goitre (abnormal swelling of the thyroid gland that causes a lump to form in the neck) in children and adults and mental retardation in neonates
Na (cationic electrolyte)
Functions: – Main cation in extracellular fluid – Controls extracellular fluid volume – Na gradient used in transport of molecules e.g. glucose pump – Neuromuscular transmission
Deficiency:
Due to: vomiting, diarrhoea, diuretics, Addison’s disease, renal problems
Causes: water loss, decreased plasma volume → circulatory failure and collapse
Excess: role in hypertension in sensitive individuals – weak relationship
K (cationic electrolyte)
.
Chloride (anionic electrolyte)
RNI = m2.5g/day – higher during
Source: meat, sea food, eggs, salt
Functions:
– Major anion in body
Deficiency: rare – usually associated wit Na loss
Copper (trace element)
.
Magnesium
.
Zinc (trace element)
.
Chromium (trace element)
INSULIN
Functions:
– Improves insulin function by increasing insulin binding to cells, insulin receptor number and phosphorylation of the insulin receptor → increased insulin sensitivity
Deficiency: only likely in those only eating refined/processed foods or those on intravenous nutrition. Exercise appears to increase excretion of chromium.
Diets high in simple sugars increase urinary chromium excretion in adults.
Selenium (trace element)
.
