Vitamins Flashcards
Bioavailability
The amount of the nutrient that has an active affect within our bodied.
Factors of bioavailability
- efficiency of digestion in the GIT
- other foods consumes at the same time
- method of preparation
- source of nutrient- synthetic, fortified or naturally occurring
Water soluble vitamins
Vitamins B and C.
Found in the watery components of foods.
They can enter straight into the blood stream and can travel freely.
The kidneys can detect small excesses of water-soluble vitamins and excrete they through urine (toxicity is rare).
Are required more frequently because they are not stored.
Fat soluble vitamins
Vitamins A, D, E & K
Occur in the fats and oils of foods.
Enter the lymph, then blood.
many require protein carriers for transport.
Can be help in fatty tissues and the liver until needed (chances of toxicity are higher).
B group vitamins
- vitamins help use the energy from fats, proteins and carbohydrates
- Thiamin, riboflavin, niacin, pantothenic acids and biotin- coenzymes that assist enzymes to release energy
- other B group vitamins play a role in metabolism (vitamin B6 assist metabolise amino acids; Vitamin B12 help cells to multiply by making new DNA)
Thiamin functions
- Vitamin B1
- part of the coenzyme thiamin pyrosphosphate (TTP) which assists in energy metabolism of cells (e.g. glycolysis).
- production of fuel for working muscles
Thiamin deficiency and toxicity
Dry Beri Beri- peripheral neuropathy, loss of sensation and function to the legs
Wet Beri Beri- cardiomyopathy, fluid build up puts pressure on heart
Wernicke-Korsakoff syndrome- generally occurs in alcohols, affects brain and CNS- disorientation, confusion, reduced consciousness, paralysis
Thiamin food sources
many different foods contribute some thiamine, several servings of nutritious rich foods will help meet thiamin needs.
main sources is grains and cereals.
mandatory fortification of thiamine in bread.
- pork, lamb, beef
- wholemeal bread
Thiamin losses in preperation
- prolonged cooking
- leaches into water when foods are boiled
suggested: cooking methods that require little or no water (steaming or microwave heating)
Riboflavin functions
- vitamin B2
- coenzyme in energy metabolism
- coenzyme forms of riboflavin are FMN (flavin mononucleotide) and FAD (flavin adenine dinucleotide)
- involved in metabolic pathways that generate energy from carbohydrates and fat
- involved in protein and uric acid metabolism
- supports antioxidants
Riboflavin deficiency and toxicity
- often accompanies other nutrient deficiencies
- lack of can cause inflammation to the membranes of the mouth, skin, eyes and GIT
- if intake is low for several months may lead to Ariboflavinosis
- excess riboflavin appear to cause no harm
Riboflavin food sources
- mainly from milk and dairy products
- fortified breads and cereals
- wholegrains
- egg
Riboflavin losses in preparation
- UV light and irradiation (milk should be in opaque plastics/cartons)
- stable to heat- cooking does not destroy it
Niacin functions
- Vitamin B3
- Niacin equivalents:
Nicotinic acid (converted into NAD)
NAD- Nicotinamide (coenzyme)
Tryptophan (amino acid that is converted to niacin) *body can make it - not in high enough quantities - participate in numerous metabolic reactions
Niacin deficiency and toxicity
Pellagra- (4 Ds)
Diarrhoea (effect on GIT)
Dermatitis (rough skin)
Dementia (effects on CNS)
Death
- occurred in populations where corn was staple
- naturally occurring niacin causes no harm
