Vitamins, minerals and trace elements Flashcards
How are vitamins absorbed?
Fat soluble vitamins (K, A, D and E) are solubilised into micelles and absorbed in small intestine
Water soluble vitamins are absorbed by diffusion or mediated transport, mainly in the jejunum
Vitamin B12 and intrinsic factor complex absorbed in terminal ileum
MUST - Malnutrition Universal Screening Tool. 5 steps.
1 - Measure height and weight to get a BMI score
2 - Note percentage unplanned weight loss
3 - Establish acute disease effect and score.
4 -Add scores from steps 1, 2 and 3 together to obtain overall risk of malnutrition.
5 - Use management guidelines and/or local policy to develop care plan.
BMI
BMI is a person’s weight in kilograms (kg) divided by his or her height in meters squared. The National Institutes of Health (NIH) now defines normal weight, overweight, and obesity according to BMI.
Digestion and absorption of lipids
- Lipase breaks bonds forming a monoglyceride and 2 fatty acids (colipase from pancreas binds lipase to cell surface)
- Large droplets are broken down by mechanical disruption of GI tract and emulsified by bile salts
- They form micelles (which act as holding stations, this maintains the diffusion gradient)
- Uptake into epithelial cell of intestine, smooth endoplasmic reticulum contains enzymes for triglyceride synthesis
- Vesicles containing fat molecule pinch off cell membrane
forming chylomicrons which are taken up by lymphatics and blood system - Lipoprotein lipase is activated in the capillary and converts triglycerides to fatty acids and glycerol
- fatty acid are taken into cell and either reesterfied for storage or oxidised for use as fuel
Digestion and absorption of proteins
Pepsin in the stomach
Pancreatic endopeptidases and exopeptidases in the small intestine
Free amino acids are absorbed in the small intestine by active transport coupled to sodium
Digestion and absorption of carbohydrates
- Digestion starts in the mouth with amylase
- Gastric acid in stomach, deactivates amylase
- Pancreatic enzymes in the small intestine (95% amylase- converts into disaacharides, maltose and mix of short branched changes of glucose molecules)
- BB enzymes break down into monosaccharides
- Absorbed into enterocyte through villi (Na+/glucose, galactose cotransporter) (fructose via GLUT5 carrier)
- Absorbed into blood stream via GLUT2 protein (fructose, glucose and galactose)
Complex polysaccharides are partially digested in the large intestine by bacteria
What is the vitamin B complex
Vitamin B is composed of 8 substances
- essential for the working of certain enzymes in the body
- not chemically related
- generally found together in the same foods.
- They include thiamine ( vitamin B1 ), riboflavin ( vitamin B2 ), pyridoxine ( vitamin B6 ), and cyanocobalamin ( vitamin B12 ).
What can vitamins be classed into? give some examples
- Water-soluble (form coenzymes, NAD, FAD, coenzymeA)
- fat soluble (K, A, D, E, ) -poorly excreted
What does Vit A do?
- forms light-sensitive pigment in eye
- can lead to night time blindness
What is malabsorption?
-When foods are not absorbed properly
eg, if there is interference with bile salt production or action in small intestine fat soluble vitamins and fats will not be absorbed properly
eg 2. celiac’s disease/gluten-senstive enteropathy/non-tropical sprue = autoimmune mediated loss of intestinal SA due to sensitivity to gluten. Loss of BB = decreased absorption of many nutrients = vitamin D = decreased calcium ion absorption in GI tract
How are most water-soluble vitamins absorbed?
Via diffusion or mediated transport
How is B12 absorbed?
-Large charged molecule
-Terminal ileum
-binds to intrinsic factor in stomach (secreted by parietal cells in stomach/)
-bound B12 then binds to specific sites on epithelial cells in terminal ileum
-absorbed via endocytosis
B12= erythrocyte production so deficiencies = pernicious anemia (can be due to stomach removal or when intrinsic factor is not secreted properly, or terminal ileum removal)
treatment = B12 injections
What is hemochromatosis?
Large ingestion of iron, increased iron deposition in tissues, changes in skin pigmentation, diabetes mellitus, liver and heart failure, decreased testicular function
- can be genetic when ingestion is normal
- frequent blood transfusions
What is vit C needed for, name some sources
Ascorbic acid (vitamin C)
Antioxidant; part of an enzyme needed for protein metabolism; important for immune system health; aids in iron absorption
Found only in fruits and vegetables, especially citrus fruits, vegetables in the cabbage family, cantaloupe, strawberries, peppers, tomatoes, potatoes, lettuce, papayas, mangoes, kiwifrui
What is vit B12 needed for, name some sources
Cobalamin (vitamin B12)
Part of an enzyme needed for making new cells; important to nerve function
Meat, poultry, fish, seafood, eggs, milk and milk products; not found in plant foods
What is folic acid needed for, name some sources
Folic acid
Part of an enzyme needed for making DNA and new cells, especially red blood cells
Leafy green vegetables and legumes, seeds, orange juice, and liver; now added to most refined grains
What is vit A needed for, name some sources
Vitamin A (and its precursor*, beta-carotene)
- FAT SOLUBLE
- A precursor is converted by the body to the vitamin.
Needed for vision, healthy skin and mucous membranes, bone and tooth growth, immune system health
Vitamin A from animal sources (retinol): fortified milk, cheese, cream, butter, fortified margarine, eggs, liver
Beta-carotene (from plant sources): Leafy, dark green vegetables; dark orange fruits (apricots, cantaloupe) and vegetables (carrots, winter squash, sweet potatoes, pumpkin)