Lecture 16 Flashcards
What factors affect bioavailability?
- Efficiency of digestion/transit time
- Previous nutrient intake and nutritional status
- Other foods consumed simultaneously
- Food preparation method
- Source of nutrient - synthetic or natural
- Health status
What does fat malabsorption limit?
Ability to absorb fat-soluble vitamins
What food preparation methods should we avoid?
Cooking to high temperatures and cooking in water
Out of natural and supplement folate, which is more bioavailable?
Folate in supplement (monoglutmate) is more bioavailable than natural sources (polyglutamate).
When does most of the nervous system develop?
Within 4-8 weeks of pregnancy
What are the MoH guidelines for folic acid in pregnancy?
- 800 micrograms per day 4 weeks prior to 12 weeks
- 5000 micrograms per day previous history
Who needs vitamin and mineral supplements?
People who have:
- poor nutrient intake (elderly, dieters, adolescents)
- Increased nutrient requirements (children, pregnancy, lactation)
- Increased metabolic demands (surgery, trauma, fracture)
- Maldigestion or malabsorption (liver disease, GI, diarrhoea)
- Drug-nutrient interactions (prednisone/vitamin D, diuretics/K,Mg)
- Medical treatment interactions (chemo/radiation)
What causes deficiency of folate?
- Low dietary intake
- less intestinal absorption
- Anticonvulsant drug and some lipid lowering drugs
- Folate antagonists - methotrexate
- High alcohol intake - leading to decreased absorption, increased catabolism, often accompanied by poor diet
- Pregnancy
What are vitamins?
Organic molecules that function in a wide variety of capacities within the body.
What is the most prominent function of vitamins?
As cofactors for enzymatic reactions
What are the properties of the water-soluble vitamins?
- Absorbed directly into the blood
- Travel freely
- Circulate freely in water-filled parts of the body
- Kidneys detect and remove excess in urine
- Possible to reach toxic amounts when consumed from supplements
- Needed in frequent doses (1-3 days)
List the water-soluble vitamins
- Vitamin C
- B vitamins
What are the alternative names for vitamin B1, 2, 3, 5, 6, 7, 9, 12
B1: Thiamine B2: Riboflavin B3: Niacin B5: Pantothenic acid B6: Pyroxidine B7: Biotin B9: Folate B12: Cobalamin
What is the active form of vitamin C?
Ascorbic acid
What are the major functions of vitamin C?
Connective tissue synthesis
Hormone synthesis
Neurotransmitter synthesis
Anti-oxidant
What is the primary deficiency of vitamin C? Describe its symptoms
Scurvy: poor wound healing, bleeding gums, haemorrhages
What are the common food sources of vitamin C?
Citrus fruits, strawberries, dark green vegetables, tomatoes, potatoes, tropical fruits
What is the active form of thiamine?
Thiamine pyrophosphate
What is the major function of thiamine?
Coenzyme of carb metabolism.
- Oxidative decarboxylations
- Transketolases (Pentose Phosphate Pathway)
What are the primary deficiencies of thiamine?
Wet and dry Beriberi
Wernicke’s encephalopathy
Describe wet beriberi
Oedema, lung congestion, increased heart rate, congestive heart failure
Describe dry beriberi
Wasting, neuropathy (tingling or loss of sensation), pain, brain damage
What is the main cause of thiamine deficiency in the Western World?
Alcoholism
What is Wernicke’s encephalopathy related to? What are the symptoms?
Related to thiamine deficiency. Alcohol related brain damage. Language problems, walking difficulty, unusual eye movemnt
What is Korsakoff syndrome related to? What are the symptoms?
Related to thiamine deficiency. Anaemia, inability to learn, confabulation
Where are thiamine deficiencies seen in elevated levels?
In countries with heavy reliance on refined grains
What are the common food sources of thiamine?
Whole grain cereals, fortified cereals, pork, sunflower seeds, legumes
What is the active form of riboflavin?
FMN FAD
What is the major function of riboflavin?
- Coenzyme of carb metabolism
What are the primary deficiencies of riboflavin?
- Inflammation of mouth and tongue - ariboflavinosis, cracks at corner of mouth, eye disorders
What are the common food sources of riboflavin?
Milk products, fortified cereals, liver, mushrooms
What is the active form of Niacin?
NAD+ NADP+
What are the major functions of niacin?
- Coenzyme of energy metabolism
- Coenzyme of fat synthesis
- Coenzyme of fat breakdown
What is the primary deficiency of niacin?
Pellagra: diarrhoea, dermatitis, dementia, death
What are the common food sources of niacin?
Milk, eggs, meat, poultry, tuna, salmon, fortified cereals
What is the active form of pyridoxine?
Pyridoxal phosphate
What are the major functions of pyridoxine?
- Coenzyme of protein metabolism
- Phosphorylase modification
- Neurotransmitter synthesis
- Haemoglobin synthesis
What are the primary deficiencies of pyridoxine?
- Scaly dermatitis
- Microcytic anaemia
- Headache
- Convulsions
- Nausea
- Vomiting
- Sore tongue
What are the common food sources of pyridoxine?
Meat, fish, poultry, potatoes, legumes, non-citrus fruits, salmon, seeds, spinach
What is the active form of biotin?
Amide link to lysine
What are the major functions of biotin?
- Coenzyme of glucose production
- Coenzyme of fat production
- Carboxylations (ATP dependent)
What are the primary deficiencies of biotin?
Depression, lethargy, dermatitis, anaemia
What are the common food sources of biotin?
Cheese, organ meats, egg yolks, soybeans, fish, wholegrain cereals, GI bacteria
What is the active form of folate?
Tetrahydrofolate
What are the major functions of folate?
Coenzyme involved in DNA synthesis (one carbon transfers)
Methylation cycle
What are the primary deficiencies of folate?
- Macrocytic (megaloblastic) anaemia
- Homocysteinuria
- Poor growth
- Inflammation
- Neural tube defects during fetal development (spina bifida)
- Increased risk of cancer, heart disease, and mental abnormalities
What are the common food sources of folate?
Leafy green vegetables, legumes, seeds, liver, fortified cereals
What is the active form of cobalamin?
Cobalamin (methyl- or 5’deoxyadenosyl-)
What are the major functions?
- Coenzyme of folate metabolism
Methylmalonyl CoA -> Succinyl CoA -> Homocysteine -> Methionine (THF dependent)
What are the primary deficiencies of cobalamin?
- Macrocytic anaemia
What are the common food sources of cobalamin?
Animal products (meat, fish, poultry, milk, cheese, eggs), fortified cereals
What are the properties of fat-soluble vitamins?
- Absorption first into lymph then blood
- Many require protein carriers
- Stored in the cells associated with fat
- Less readily excreted and tends to remain in fat-storage sites
- Likely to reach toxic levels when consumed from supplements
- Needed in periodic doses (weeks or months)
List the fat-soluble vitamins
A, D, E, K
What is the active form of vitamin A?
11-cis retinal - amide link to lysine in rhodopsin
All-trans retinol and retinoic acid
What are the functions of vitamin A?
- Photoreception, promote vision especially night colour
- Health of cornea
- Promote growth
- Prevent drying of skin and eyes
- Promote resistance to bacterial infection and overall -immune
- Protein synthesis and cell differentiation
What are the deficiencies associated with Vitamin A?
Night-blindness as part of Xerothalmia
Keratomalacia
Developmental defects
Keratinisation (chicken skin): topical treatments with vitamin A
What are the ways in which vitamin A toxicity can occur?
Beta carotene: - Inefficient conversion - Overconsumption from food Retinol: - Overconsumption from supplements
What are the common sources of vitamin A?
Milk, cheese, eggs, liver, some acne treatments
What are the common food sources of beta carotene?
Dark green leafy vegetables, deep orange fruit and vegetables
What is the animal version of vitamin D?
Vitamin D3/Cholecalciferol
What is the plant version of vitamin D?
Vitamin D2/Ergocalciferol
What is the active form of vitamin D?
1,25 dihydroxycholecalciferol/Calcitriol (Steroid-like hormone)
What is another name for Vitamin D?
Calciferol
What are the funcitons of vitamin D?
Increases absorption of calcium and phosphorus
Maintains optimal blood calcium and calcification of bone
Regulates BP, insulin production, cell growth and division, immune function
What are the deficiencies associated with vitamin D?
Rickets in children: long bones poorly formed resulting in bowed legs
Osteomalacia in adults: poor formation of bones and unable to weight bear
What are the common sources of Vitamin D?
Sunlight
Liver, fatty fish, cod liver oil, milk (fortified), sardines in oil, mushrooms (raw), egg
What is the role that sunlight plays in vitamin D absorption?
Causes reaction under skin that converts cholesterol to 1,25 dihydroxyvitamin D3 (active form)
What is the active form of vitamin E?
Alpha-tocopherol
What is the function of vitamin E?
General cell antioxidant (regenerated by interaction with vitamin C)
What is the deficiency associated with Vitamin E?
Haemolysis of RBC’s
What are the common food sources of Vitamin E?
Polyunsaturated oil, leafy green vegetables, liver, egg yolks, nuts, seeds
What is the active form of Vitamin K?
Hydroquinone form of vitamin
What are the functions of Vitamin K?
- Activation of blood clotting factors
- Carboxylation of glutamate to gamma-carboxyglutamate
- Activation of proteins involved in bone metabolism
What are the deficiencies associated with vitamin K?
Clotting defects
Foetal Warfarin syndrom
Fractures
What are the common food sources of vitamin K?
GI bacteria, liver, leafy green vegetable, cabbage type vegetables