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Agenda. Calendar Research project presentation Finish up Lipids Lecture 9: Vitamins Lecture outline Vitamin Background Fat soluble vitamins. Lipid Wrap up. Last time Lipid Digestion and three main types of lipids Lipoproteins – Vehicles for fat Chylomicrons – carry exogenous fat - PowerPoint PPT PresentationTRANSCRIPT
Agenda
• Calendar• Research project presentation• Finish up Lipids• Lecture 9: Vitamins• Lecture outline– Vitamin Background– Fat soluble vitamins
Lipid Wrap up
• Last time– Lipid Digestion and three main types of lipids– Lipoproteins – Vehicles for fat
• Chylomicrons – carry exogenous fat• VLDL – Carry endogenous fat• LDL – transport cholesterol made by liver• HDL – pick up fat and cholesterol and take it back to liver for
recyleing– Functions for the various types of lipids– Discussed Cardiovascular disease
• Finish up with how to minimize CV disease risk
Risk Factors for Heart Disease
• Total blood cholesterol >200mg/dL of blood– Especially high when over 240 mg/dL and LDL exceeds
130 mg/dL • Smoking– Increases risk of CV event by 20%
• Hypertension – Systolic pressure over 139 ml of mercury and diastolic pressure over 89.
• Diabetes – pretty much guarantees a CV event– Remember insulin ↑ cholesterol synthesis in the liver,
thus elevating LDL
How to mitigate risk• QUIT SMOKING• Overhaul diet and lifestyle
– Switch to low-fat diet– Increase exercise
• Medications for more aggressive treatment– Statins – reduce liver production of cholesterol
• ~$1600 annual– Bile binders/inhibitors – block the emulsifying effects of bile reducing
the cholesterol consumed– Triglyceride production inhibitors – aim to reduce triglyceride
production in the liver• Overall goal of therapy is to get blood LDL < 70mg/dL
Lecture 9 - Vitamins
Will Brown2/7/2012
Vitamins Background
• Name derived from the words “Vital Amines”– Later shortened to vitamins
• Two categories– Fat soluble – A, D, E, and K– Water Soluble – B vitamins and C
• Considered “essential” because we are unable or have limited ability to synthesize them
• Named as they were found: A, B, C, D, etc– Some turned out to be a collection of compounds
• The B vitamins
• Others found to not be “essential” and were dropped
Vitamins Background• All have disease associated with them when not enough in
diet– Scurvy – vitamin C
• Both plant and animal sources of vitamins• Supplements
– If you are eating a well balanced diet, there is no need for supplements
– There are toxic levels of vitamins; “little is good so more is better” mentality does not apply
– Synthetic varieties have varying degrees of petency• Natural Vitamin E more potent• Synthetic folic acid (vitamin B9) more potent
Vitamins Background
• Generally believed all essential vitamins are known
• Vitamin storage – most do not stick around to long; they are used fairly quickly– Most fat soluble vitamins are longer lived in the
body; not excreted in urine• Exception is vitamin K
– Most water soluble vitamins are lost rapidly• Exceptions vitamins b-6 and B-12
Vitamins Background• Toxicity
– All vitamins have toxic levels although very hard to achieve toxic levels with some• For a 160 lb man, need to eat ~2 kg of vitamin C
– Fat soluble vitamins have lower toxic limits• Vitamin A begins at 2X RDA values
• Preservation– Because they are organic compounds, vitamins breakdown
• Heat, light, air, time from harvest– The fresher the better– Store in cool dry places– Freezing also protects and preserves vitamins
Fat soluble Vitamins
• There are 4 fat soluble vitamins – A, D, E, and K
• Absorbed in dietary fat– Pharmaceuticals that intervene in fat absorption
also inhibit uptake of these vitamins• Carried in the bloodstream along with the fat• Stored in liver and to some degree in adipose
tissue
Vitamin A• Narrow therapeutic range for vitamin A
– Too little and you develop blindness• 1 in 3 children in developing countries
– Too much you get liver damage• Especially with high levels of alcohol consumption
• Comes in multiple forms – Retinoids – preformed vitamin A found in fish and organ meat– Carotenoids – provitamins that are converted to vitamin A– Only 3 (of the over 600) carotenoids can be used by people
• Beta-carotene• Lutein• Zeaxanthin
• Mainly found in dark green or yellow-orange fruits and veggies
RAELife stage group
Adequate intakes (AI*)μg/day
Upper limitμg/day
Infants 0–6 months7–12 months 400*
500*600600
Children 1–3 years4–8 years 300
400600900
Males 9–13 years14–18 years19 – >70 years
600900900
170028003000
Females 9–13 years14–18 years19 – >70 years
600700700
170028003000
Pregnancy <19 years19 – >50 years 750
77028003000
Lactation <19 years19 – >50 years 1200
130028003000
REA=Retinal activity equivalents, takes into account preformed and provitamin forms.
Functions of Vitamin A
• Vision– Critical for component of rhodopsin in eye-retinal– Night blindness is first sign of vitamin A deficiency– Also helps with mucus layer that protects the eye– Second leading cause of blindness world wide
• Epithelium requires vitamin A for mucous production– Lower levels of protective mucous in lungs and
intestines increases risk of infection
Functions of Vitamin A
• Retinoic acid form is critical in gene transcription– Specialized nuclear receptors specifically for retinoic acid
• Act as antioxidants– May help prevent cardiovascular disease– Lycopene (vitamin A form found in tomatoes) shown to
reduce prostate cancer risk• Used in acne medication– Retin-A is topical form– Accutane is oral form but has restricted use because it is
teratogenic
Vitamin D• Made of a cholesterol based substance 7-dehydrocholesterol • Unique in that it can be produced in the skin due to sun
exposure (UVB)– Most common vitamin deficiency in northern climates during winter– Only need about 10 minutes of exposure for fair skinned individuals;
the higher the melanin the more exposure is needed• Acts as a prohormone which is converted to active form in
kidneys and liver• Toxicity of vitamin D only associated with supplements because
the body regulates amount made in skin– Same symptoms as calcium toxicity: weakness, loss of appetite,
diarrhea, vomiting, confusion, increased urine output, Ca+ deposits in kidney
Functions of Vitamin D• Primary function is to help regulate calcium• Nuclear receptor (VDR) activation leads to increased gene
expression of calcium transport molecules in the intestine• VDR activation increases bone remodeling
– Indicates why calcium supplements are not enough in osteoporosis patients
• Rickets and osteomalacia caused/cured by vitamin D– Vitamin D production decreases with age
• VDR activation also plays a role in neurons and in immune cells
Vitamin D Recommendations
• RDA– 1–70 years of age: 600
IU/day (15 μg/day)– 71+ years of age: 800
IU/day (20 μg/day)– Pregnant/lactating: 600
IU/day (15 μg/day)
• Upper intake levels– 0–6 months of age: 1,000
IU– 6–12 months of age:
1,500 IU– 1–3 years of age: 2,500 IU– 4–8 years of age: 3,000 IU– 9-71+ years of age: 4,000
IU– Pregnant/lactating: 4,000
IU
Vitamin E• Acts as a fat-soluble antioxidant • Helps to protect cell membranes from breaking down due
to oxidization of the fatty acid chains in the phopholipids– One example is hemolysis of red blood cells is reduced with
vitamin E• Despite many trials, no known benefit in supplementing
vitamin E• Family of 8 molecules; 4 tocopherols and 4 tocotrienols
– The book only mentions the tocopherols – they are a, b, g, d
Sources and Recommendations for Vitamin E
• Primarily come from plant oils – gamma is the most common in plants
• Other sources include nuts, seeds and eggs• RDA: 15 mg/day of a-tocopherol; the most
common form in human body• Upper limit is 1000 mg/day due to the ability
to interfere with vitamin K which leads to hemorrhage
Vitamin K
• Consists of two primary forms K1 and K2
– No known toxicity for natural forms however synthetic form K3 does have toxicity
– K1 is primary form from plant sources
– K2 is produced by bacteria in the gut; ~10% of total vitamin K
• The K comes from the Danish spelling of coagulation– Discovered by a Danish guy named Henrik Dam
Functions of Vitamin K
• Involved in the carboxylation of glutamate residues which then can bind Ca+ ions
• Found in 3 biological roles– Blood coagulation – all of the major clotting
factors contain the glutamate residues– Bone metabolism – many of the proteins involved
in calcium binding have the glutamate residues– Vascular biology – certain growth arrest proteins
contain the glutamate residues
Water Soluble Vitamins• Soluble in water• Consist of the B family (and a related nutrient choline) and
vitamin C• Rapidly excreted if taken in excess• Most are lost during food processing• Most B vitamins occur together so a lack of one indicates a
lack of the others• B vitamins act as coemzymes – that is the act so that
enzymes can function– Play key roles in metabolism of carbs, fats and amino acids– Needs increase as energy needs increase