Vitamins - Essential organic compounds required in small amounts for normal metabolism and good health - not a source of energy Water soluble - C and Bs - must be replenished everyday - Difficult to overdose Fat soluble - A, D, E, K -does not need to be replenished everyday -can cause toxicity
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Vitamins-Essential organic compounds required in small amounts for normal metabolism and good health- not a source of energy
Water soluble - C and Bs-must be replenished everyday-Difficult to overdose
Fat soluble - A, D, E, K-does not need to be replenished everyday-can cause toxicity
Names and RolesVitamins
A retinol phototransduction
D cholecalciferol bone remodelingE tocopherols antioxidant
• All absorption takes place in the small intestine
• Fat-soluble vitamins – Are absorbed in the duodenum– Storage
• Vitamin A is mainly stored in the liver • Vitamins K and E are partially stored in the liver• Vitamin D is mainly stored in the fat and muscle tissue• Can build up in body to point of toxicity
Vitamin Absorption and Storage
• Water-soluble vitamins– Absorbed with water and enter directly into the
blood stream– Most absorbed in the duodenum and jejunum– Most are not stored in the body– Excess intake excreted through the urine– Important to consume adequate amounts daily– Dietary excesses can be harmful
Digesting and Absorbing Water-Soluble Vitamins
Figure 10.1
Water-Soluble Vitamins
Fat-SolubleVitamins
Absorbed in the Small Intestine Small IntestineHydrophobic or
Hydrophilic Hydrophilic Hydrophobic
Absorbed into the Blood Lymph
Stored in the body Not Generally Yes
Can build up and become toxic Not Generally Yes
Need to consume daily Yes No
Bioavailability
• Varies based on– Amount in food– Preparation– Efficiency of digestion and absorption of food– Individual nutritional status– Natural or synthetic
• Fat-soluble vitamins are generally less bioavailable than water-soluble vitamins
• Vitamins from animal foods are generally more bioavailable than those in plant foods
Fat Soluble Vitamins
- Many have precursors- Less vulnerable to cooking losses- Can cause toxicity- Transported like fat in chylomicrons, VLDL, LDL
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vitamin A
• aka: retinol• Converted to active form• Regulates response of rod and cone cells in the retina to light • Regulates gene expression of development of epithelial tissue• Used to treat severe acne, wrinkled skin
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vitamin D• A prohormone synthesized
from cholesterol
• Vitamin D3 = cholecalciferol
• Found in animal products
• Vitamin D2 = egocalciferol
• Found in plants and fortified foods
Vitamin D3 and D2
• Time spent outdoors
• Amount of skin exposed
• Skin color
• Clothing
• Body fat
• Latitude
• Season and time of day
What affects your vitamin D level?
Vitamin D Synthesis and LatitudeVitamin D Synthesis and Latitude
Childhood rickets
• Epidemic with industrialization in 19-20th centuries
• With discovery of vitamin D and fortification, rickets was almost entirely eliminated
• Until now…
London 1889
Idaho 1989
• 40-90% of US community dwelling elderly• 50% of premenopausal women• 50% of Hispanic and black adolescents• 48% of French preteens• 30-50 % of adults in Saudi Arabia and UAE• 73 % of pregnant women taking prenatal
vitamins …are DEFICIENT
How to get vitamin D...
• 100 IU/d raises level by about 1 ng/mL
• Sunlight 3000 IU/10 minutes• Oily fish 300 IU/3 oz
Endocrine, paracrine and intracrine functions of Vitamin D
• Role in Cancer Prevention– Low intake of vitamin D and calcium has been associated
with an increased risk of non-Hodgkin lymphomas, colon, ovarian, breast, prostate, and other cancers.
– The anti-cancer activity of vitamin D is thought to
result from its role as a nuclear transcription factor that regulates cell growth, differentiation, apoptosis and a wide range of cellular mechanisms central to the development of cancer. These effects may be mediated through vitamin D receptors expressed in cancer cells.
– Vitamin D is not currently recommended for reducing cancer risk
• Role in Cardiovascular Diseases– Vitamin D deficiency activates the renin-
angiotensin-aldosterone system and can predispose to hypertension and left ventricular hypertrophy.
– Additionally, vitamin D deficiency causes an increase in parathyroid hormone, which increases insulin resistance secondary to down regulation of insulin receptors and is associated with diabetes, hypertension, inflammation, and increased cardiovascular risk.
Updated Recommendations In Process
• Studies suggest that the daily vitamin D intakes should be much higher than 400 IU/d.
• Daily intakes in the range of 800 to 1000 IU/d should be strongly considered.
• Although there are concerns regarding vitamin D toxicity, side effects at intakes exceeding the current upper limit of 2000 IU/d have not been reported to date.
• Assessment of vitamin D status with serum measurements of 25(OH) vitamin D levels for a broader range of patients should be encouraged.
Key clinical recommendation
• Daily vitamin D supplementation of 800 to 1,000 IU is a reasonable dose for adults. Levels of 25-OH vitamin D should be maintained > 32 ng per mL (80 nmol per L) to maximize bone health.
• In patients with severe vitamin D deficiency, 50,000 IU of vitamin D should be given daily for one to three weeks, followed by weekly doses of 50,000 IU.
Vitamin E
• There are four different tocopherol compounds, but only the alpha-tocopherol has vitamin E activity in human beings.
• Vitamin E as an Antioxidant– Stops the chain reaction of free radicals
– Protection of polyunsaturated fatty acids and vitamin A
– Protects the oxidation of LDLs
Vitamin E• Easily destroyed by heat and
oxygen• Deficiency symptoms
–Red blood cell breakage–Nerve damage
• Toxicity symptoms–Augments the effects of
anticlotting medication
Vitamin E Deficiency
– Primary deficiency due to inadequate intake is rare
– Erythrocyte hemolysis• Occurs in premature infants• Hemolytic anemia can be treated with vitamin E.
Vitamin E Toxicity
– Rare and the least toxic of the fat-soluble vitamins– Upper level for adults: 1000 mg/day– May augment the effects of anticlotting
medication
Vitamin E• Other name: alpha-tocopherol• 2000 RDA
– Adults: 15 mg/day
• Upper level for adults:1000 mg/day
• Chief function in the body– Antioxidant (stabilization of cell
membranes, regulation of oxidation reactions, protection of polyunsaturated fatty acids and vitamin A)