58 terms

Ch. 8 Vitamins

vitamin: definition (3)
1. An essential noncaloric, organic nutrient needed in tiny amounts in the diet.
2. not a mineral
3. The role of vitamins is to help make possible the processes by which other nutrients are digested, absorbed, and metabolized or built into body structures. didn't do any of these things but assisted enzymes
vitamin: basic concepts (3)
What is a vitamin?
1. A complex organic compound that:
- Is not made by the body — or made in amounts that are enough to maintain good health;
2. Occurs naturally in common foods;
3. Causes a deficiency disorder when it is missing from the diet & only vitamins can cure it
- Restores good health, if the deficiency disorder is treated early by supplying the missing substance.
4. are micronutrients
classifying vitamins (2)
1. Fat soluble — A, D, E, & K
- Associated with lipids in foods and the body
- Do not dissolve in water or urine
- stored in the body (liver & body fat) and may (easier)
be toxic
2. Water soluble — B vitamins & C
- Dissolve in watery components of foods and the body
- Excreted in urine
- Most are not stored to a major extent
- Generally non toxic
- Choline is generally referred to as "vitamin like."
vitamin: introduction history & disease (2)
1. Vitamins were discovered at the beginning of the twentieth century.
- Certain diseases (now known to de deficiencies in specific vitamins) could be prevented or readily cured with the addition of certain foods to the diet
2. The only disease a vitamin can cure is the one caused by a of that vitamin.
vitamin: general, types & number (6)
1. 13 organic micronutrient molecules that the body cannot make "from scratch", but are required for various metabolic purposes.
2. Generally required in the milligram range or less
3. Some need certain minerals to function
4. Some act as coenzymes
• organic, non-protein, cofactor molecules needed for enzyme function
5. 4 are fat soluble
6. 9 are water soluble soluble
do vitamins provide any calories?
Vitamins do not supply energy, but many participate in the chemical reactions that release the energy stored in macronutrients.
vitamins: enzymes - coenzymes (7)
1. Vitamins - small organic molecules needed to make coenzymes
2. Often part of the coenzyme's molecular structure
3. Are required only in trace amount
4. Cannot be made by our cells
5. Without the vitamin, the coenzyme is not made
6. Without the coenzyme, the enzyme won't function
7. The cell will lack certain products it needs
vitamin precursors (2)
1. The body cannot make vitamins, but can convert certain food molecules into vitamins
2. Some vitamins exist as precursors, or provitamins
- Compounds that can be converted into active vitamins
1. substance that gives up electrons to radicals to protect cells
- Oxidation reactions can form radicals (or "free radicals"), substances with an unpaired electron.
• Oxidation = loss of electrons
• Reduction = gain of electrons
radical (3)
• substance with an unpaired electron
• Most free radicals are highly (unstable)
- Because they have an unpaired electron
• A free radical can remove an electron from a more stable molecule, such as DNA, a protein, or a polyunsaturated fatty acid.
fat soluble vitamins (6)
A, D, E, K
1. - Found in fats and oils of foods
2. - Require bile for absorption
3. - Stored in liver and fatty tissues until needed
4.- Not needed in the diet daily
• Long term (weeks) adequate average is sufficient
5. Can reach toxic levels if too much is consumed
• Not readily excreted in the urine
6. Deficiencies can occur when people eat diets that are extraordinarily low in fat or in any disease causing fat malabsorption
water soluble vitamins (3)
Vitamin C and the B vitamins
1. Cooking and washing cut foods with water can leach out these vitamins out of the food.
2. Absorbed easily and easily excreted in urine.
• "The most expensive urine in town"
3. Foods never deliver a toxic dose of them
• but large doses concentrated in some vitamin supplements can reach toxic levels.
Vitamin A (2)
1. Beta-carotene = plant derived precursor
- strongly-colored red-orange pigment abundant in plants and fruits
2. Retinol active form stored in the liver
- Converted by cells into its other two active forms, retinal and retinoic acid, as needed
Vitamin A: functions (8)
• Jack of all trades
• Gene expression
• Maintenance of body linings and skin
• Immune defenses
• Growth of bones and of the body
• Normal development of cells
• Reproduction
Vitamin A: regulation of gene expression
Vitamin A exerts influence on body functions through its regulation of genes.
- Hundreds of genes are regulated by the retinoic acid form of vitamin A.
Vitamin A: Eyesight (2 Roles)
Vitamin A plays two roles:
1. Process of light perception at the retina
2. Maintenance of a healthy cornea
Night blindness: definition (2)
1. • The inability to see in dim light
2. • Early sign of vitamin A deficiency
- The retina, the light-sensitive area inside each eye, contains rods and cones that are specialized nerve cells essential for vision.
• Rods and cones need vitamin A to function properly.
Vitamin A: eyesight how functions (3)
1. Vitamin A is part of the rhodopsin molecule, a pigment within the cells of the retina.
- When light falls on the eye, it bleaches rhodopsin, which breaks off the vitamin A, initiating a signal that conveys the sensation of sight to the optic center of the brain.
2. The vitamin then reunites with the pigment, but a little vitamin A is destroyed each time this reaction takes place, and fresh vitamin A must replenish the supply.
3. If the vitamin A supply runs low, night blindness
can result - a lag before the eye can see again after a flash of bright light at night.
Vitamin A: eyesight problems
1. A more serious deficiency of vitamin A occurs when the protein keratin accumulates and clouds the eye's outer vitamin A-dependent part, the cornea.
- Keratinization of the cornea can lead to xerosis (drying) and then progress to thickening and permanent blindness, xerophthalmia.
- 500,000 of the world's vitamin A-deprived children become blind each year due to xerophthalmia.
xerophthalmia (2)
1. Keratinization of the cornea can lead to xerosis (drying) and then progress to thickening and permanent blindness, xerophthalmia.
2. If untreated, vitamin A deficiency eventually leads to blindness
Vitamin A: skin & body linings (2)
1. Vitamin A is needed by all epithelial tissue which includes the protective linings of the lungs, intestines, vagina, urinary tract, and bladder.
- If vitamin A is deficient, cells fail to make mucus and secrete keratin, the same protein found in hair and nails.
2. Keratinization makes the tissues dry, hard and cracked which makes them more susceptible to infection.
makes the tissues dry, hard and cracked which makes them more susceptible to infection.
Vitamin A: Immunity
Vitamin A has a reputation as an "anti- infective" vitamin.
- Body's defenses depend on an adequate supply.
- Part of the reason why AIDS is such a problem in areas of the world where deficiency is common (b/c lacking the vitamin or precursor_
Vitamin A: Growth
Vitamin A assists in growth of bone (and teeth).
- In children, failure to grow is one of the first signs of poor vitamin A status.
Vitamin A: deficiencies around the world
1. Between 3 and 10 million of the world's children suffer from a severe vitamin A deficiency including
- Xerophthalmia - Diarrhea
- Appetite loss
- Reduced food intake
2. 275 million more children have impaired immunity, leaving them open to infections
Vitamin A: Toxicity (3)
1. Can occur when excess vitamin A is taken as supplements or fortified foods
2. Chronic/LT use of vitamin supplements providing three to four times the recommended dose for pregnancy has caused birth defects
3. With the exception of liver, it is not easy to ingest toxic amounts of vitamin A.
- 1 oz of beef liver contains 3 times the DRI.
Vitamin A: adequacy & deficiency (2)
1. Dietary Adequacy = RDA: 700 - 900 mcg RAE
2. Vitamin A Deficiency
- Certain epithelial cells produce too much keratin
• Keratin - tough protein found in hair, nails, and outermost layers of skin
- Excess keratin:
• Skin becomes rough and bumpy
• Inner eyelid cells that normally secrete mucus to
protect cornea become keratinized.
- Can result in xeropthalmia ("dryeye")
Vitamin A: recommendations, intakes & UL (5)
1. Vitamin A is not needed every day. Why? = you can store, you can convert betacarotene
2. DRI for man is 900 micrograms
3. DRI for woman is 700 micrograms
4. Tolerable Upper Intake Level is 3,000 micrograms
5. Adjust intake based on weight
Vitamin A: Food sources
1. Beta-carotene is found in vegetables and fruits
- Orange or muddy green colored
2. Active vitamin A is found in foods of animal origin
- Liver, fish oil, milk, fortified cereals, eggs, butter
Beta-carotene & carotenoids (2)
1. In plants, vitamin A only exists in its precursor form.
2. Beta-carotene, the most abundant of these carotenoid precursors, has the highest vitamin A activity.
- 12 micrograms of beta carotene from food supplies the equivalent of 1 microgram of retinol in the body.
- Beta-carotene in foods is measured in Retinol activity equivalents (RAE)
- Beta-carotene from food is not converted to retinol efficiently enough to cause vitamin A toxicity. Excess beta-carotene is stored in the fat under the skin, imparting a yellow cast.
- Excess beta-carotene (carotenemia)
Excess beta-carotene
Vitamin A: carrots promote good vision?
Yes, eating carrots and other rich sources of beta-carotene promotes good vision.
- Dark green vegetables = Spinach, broccoli, collard greens
- Orange fruits and vegetables = Carrots, sweet potatoes, pumpkins, mango, cantaloupe, apricots
carotenoids & diseases
1. People with low intakes of beta-carotene have a high incidence of macular degeneration.
2. Beta-carotene is an antioxidant along with vitamin E, vitamin C, selenium, and many phytochemicals.
Vitamin D: general (2)
1. Can be self-synthesized with the help of sunlight "sunshine vitamin"
- Body can make all it needs if adequate exposure to sunlight
- Ultraviolet B light acts on a cholesterol-derived molecule
2. Whether made with the help of sunlight or obtained from food, vitamin D undergoes chemical transformations in the liver and kidneys to activate it.
Vitamin D: Roles/functions (3)
Vitamin D functions as a hormone to:
1. Regulate blood calcium and phosphorus levels, thereby maintaining bone integrity
2. To replenish blood calcium, vitamin D acts at three body locations to raise blood calcium levels:
• Skeleton
• Digestive tract
• Kidneys
3. Vitamin D stimulates maturation of cells, including immune cells that defend against disease
- Vitamin D acts on genes, affecting how cells grow, multiply, and specialize
Vitamin D: Why necessary (2)
Is needed for:
1. Metabolism of calcium & phosphorus
2. Production & maintenance of healthy bones
vitamin d: parathyroid hormone (2)
aka PTH
1. Released when blood calcium levels drop
2. Stimulates kidneys to increase active vitamin D production & decrease urinary calcium excretion
vitamin D: deficiencies (5)
• High blood pressure
• Some common cancers
• Rheumatoid arthritis
• Multiple sclerosis
• Psoriasis
Vitamin D: Rickets (2)
1. leads to bowed legs to unmineralized bone and also beaded ribs as calcium is deposited on the ribs, rather than in the ribs.
2. vitamin D deficiency in children
- Results in soft bones that do not grow properly and become deformed
Vitamin D: osteomalacia
In adults, the poor mineralization of bone results in osteomalacia.
- Brittle, soft, and deformed bones
Vitamin D: Toxicity
1. Vitamin D is the most potentially toxic of all vitamins
2. More likely if supplements are taken
- Toxic to bones, kidneys, brain, nerves, heart, and arteries
Vitamin D: sunlight (7)
1.When ultraviolet light from the sun shines on a
compound in human skin, the compound is transformed into a vitamin D precursor and is absorbed directly into the blood.
2. Over the next day, the liver and kidneys finish converting the precursor to active vitamin D.
3. Sunlight presents no risk of vitamin D toxicity; sun breaks down excess vitamin D in the skin
4. At the end of winter, many otherwise healthy northern U.S. adults, even those drinking milk fortified with vitamin D, may test low for blood vitamin D.
5. Dark-skinned people need up to 3 hours of direct sun for several days to make enough vitamin D.
6. Light-skinned people need much less time -10 or 15 minutes.
7. People who live south of the 37th parallel and are outdoors when sunlight is most intense are most likely synthesizing adequate pro hormone D.
Vitamin D: sources
sunlight, fish liver oils, fatty fish (salmon, herring & catfish), fortified foods such as milk, cereal, OJ, margarine
Vitamin D: intakes & UL
1. 5 micrograms/day for adults 19 to 50 years
2. UL 50 micrograms/day (2,000 IU on supplement labels)
Vitamin E: Name
Vitamin E: functions (3)
1. Major fat-soluble antioxidant found in cell
• Protects polyunsaturated fatty acids
2. Improves vitamin A absorption
3. Maintains nervous system and immune system function
Vitamin E: extraordinary bodyguard
1. Vitamin E is an antioxidant.
- Vitamin E, a.k.a. tocopherol
2. Oxidative damage occurs when highly unstable molecules known as free radicals, formed normally during cell metabolism, run amok and disrupt cellular structures.
- Vitamin E protects cell membranes from oxidation by reacting with lipid radicals
Antioxidants: how do they work? & examples
• By giving up an electron to a free radical, an antioxidant protects other molecules.
- Action stabilizes the free radical
• Beta-carotene and vitamins E & C function as antioxidants.
Vitamin E: deficiency (3)
1. Deficiencies are almost never seen in healthy humans.
2. A classic vitamin E deficiency occurs in premature babies born before the transfer of the vitamin from mother to the infant, which takes place in the last weeks of pregnancy.
- Infant's RBC lyse and infant becomes anemic
3. Hemolysis (breaking apart) of RBC
• Due to oxidation of polyunsaturated fatty acids in cell membrane
Chronic diseases & Vitamin E intakes (2)
1. Heart disease and cancer may arise in part
through tissue oxidation and inflammation.
2. People with low blood vitamin E concentrations die more often from these and other causes than do people with higher blood levels.
Vitamin E: toxicity & UL
1. Upper Limit (UL) 1000 mg/day
2. Excess may interfere with vitamin K's** role in blood clotting
3. No adverse effects arise from consuming foods that naturally provide vitamin E.
4. Vitamin E supplements appear safe at lower doses.
- An increase in brain hemorrhages, a form of stroke, among smokers taking just 50 mg of vitamin E per day has also been noted.
- Supplements may also increase the effects of a
Vitamin E: intakes
1. 15 milligrams/day for adults 19 to 50 years (RDA)
2. UL 1000 milligrams/day (1,500 IU on supplement labels)
3. on average, US intakes of Vitamin E fall substantially below the recommendation
Vitamin E: sources
Raw vegetable oils contain substantial vitamin E, but high temperatures destroy it, whole grains, fatty nuts
vitamin K: Functions (3)
1. Main function of vitamin K is to help synthesize proteins that help blood clot.
2. Also necessary for the synthesis of key proteins.
3. increase RBC, WBC, Platelets (have chemicals & enzymes=Vitamin K & calcium)
Vitamin K: sources (3)
1. Vitamin K can be made by intestinal bacteria.
- produced by bacteria in the large intestine, and dietary deficiency is extremely rare unless the intestines are heavily damaged, are unable to absorb the molecule, or are subject to decreased production by normal flora, as seen in broad spectrum antibiotic use
2. Vitamin K is found chiefly in leafy green vegetables
- spinach, swiss chard, and Brassica (e.g. cabbage, kale, cauliflower, broccoli, and brussels sprouts); some fruits such as avocado and kiwifruit are also high in vitamin K. By way of reference, two tablespoons of parsley contain 153% of the recommended daily amount of vitamin K. Some vegetable oils, notably soybean, contain vitamin K, but at levels that would require relatively large caloric consumption to meet the USDA recommended levels
3. Newborns are given a dose of vitamin K at birth.
- They lack the mature gut bacterial flora • No bacteria to make vitamin k
Vitamin K: Toxicity (2)
1. Toxicity is rare and there is no UL.
2.Toxicity causes jaundice and may occur if supplements of a synthetic version are given too enthusiastically.
- Excess vitamin K causes jaundice - symptom: yellow colored skin
• breaks RBCs -they release their pigment - colors skin
• Liver also releases blood cell pigment (bilirubin) into the blood instead of excreting it into bile
Vitamin K: Intakes
1. Men: 120 micrograms per day
2. Women: 90 micrograms per day
Vitamin K: deficiency
May occur in newborns or people with impaired liver function or absorption, on long term antibiotic therapy