Chapter 9 and 10: Vitamins Flashcards
vitamins are essential nutrients
called micronutrients
fat soluble vitamins
- absorbed with dietary fat and can be stored in the body
- easily stored in fat upon absorption
- should be taken with food to absorb them
- ADEK
water soluble vitamins
- absorbed with water and enter the bloodstream directly
- not stored in the body, but excesses can still be harmful
- excreted through the urine
- similar to how we absorb carbs/proteins
- B vitamins and vitamin C
vitamin absorption
- similar to how we absorb macronutrients
- vitamins bound to proteins are released in the stomach
- in the SI, the fat soluble vitamins are transported into the intestinal cells as part of micelles
- once inside the intestinal cells, fat soluble vitamins are packaged with fat and other lipids into a chylomicron
- the chylomicrons travel through the lymph system to the main circulation
- water soluble vitamins are absorbed directly into the portal vein from the SI through diffusion
vitamins as antioxidants
- some vitamins function as antioxidants, which counteract oxidation by neutralizing substances called free radicals
- vitamins A, E, C, and beta-carotene
free radicals
unstable oxygen containing molecules that can damage the cells of the body and possibly contribute to increased risk of chronic diseases
vitamins can be damaged by water, heat, and air
- air exposure can destroy both water and fat soluble vitamins
- store in airtight containers
- a little water is enough for cooking veggies
- steaming and microwaving results in the least amount of nutrient loss
- heat will destroy water soluble vitamins (especially vitamin C)
- reduce cooking times
bioavailability
the degree to which a nutrient is absorbed from foods and used in the body
bioavailability of vitamins
- vitamins differ
- vitamins can be destroyed by air, water, and heat
- provitamins can be converted to vitamins by the body
- if deficient in one vitamin, can absorb higher levels of it to counteract
provitamins
- provitamins are substances found in foods that are not in a form directly usable by the body, but that can be converted into an active form once they are absorbed
- think of these as precursors to the active form of the vitamin
- biologically inactive compounds
preformed vitamins
are vitamins found in foods that are already in the active form and do not undergo conversion in the body
vitamin A
- fat soluble vitamin
- same plants contain provitamin A compounds which are converted to retinol in the body
- preformed vitamin A found primarily in animal food
provitamin A
beta carotene and carotenoids
preformed vitamin A
retinyl ester
food sources of provitamin A
- plant sources
- carrots, kale, spinach, apricots, broccoli, pumpkin
food sources of preformed vitamin A
- animal sources
- eggs, fish, liver
primary functions of vitamin A
- vision
- protein synthesis and cell differentiation
- reproduction
- bone healthy
- immune system
- may help fight cancer as carotenoids are antioxidants
vitamin A toxicity
- excess amounts of preformed vitamin A can be toxic
- occurs via supplements not food intake
- hypervitaminosis A: liver damage and death
- during pregnancy can conception, can cause birth defects in the face, skull, and CNS
- can potentially increase the risk for osteoporosis and bone fractures in adults
vitamin A deficiency
- chronic deficiency can cause night blindness
- prolonged can lead to xerophthalmia (disease that causes dry eyes)
- leading cause of blindness in children in most developing countries
- can lead to keratinization of the epithelial tissues
vitamin D functions
- promotes calcium absorption
- needed for proper bone growth
- reduces inflammation
- modulates cell growth
- regulates immune and neuromuscular function and glucose metabolism
- reduces the risk of heart disease (by reducing cholesterol and lowering blood pressure)
- helps the body regulate blood sugar in type 2 diabetes
RDA for vitamin D
600 IU
vitamin D food sources
fatty fish, fish liver oils, fortified foods (milk, yogurt, orange juice, cereal), egg yolks, cheese, mushrooms
environmental sources of vitamin D
- the human body can synthesize vitamin D
- requires exposure to sunlight
- UV radiation reacts with a form of cholesterol in the skin to produce vitamin D3
- D3 can then undergo hydroxylation by the liver and kidney and eventually form active vitamin D
- season, time of day, length of day, cloud cover, smog, skin melanin content, and sunscreen are some factors that affect UV radiation exposure and vitamin D synthesis
location on earth effect on vitamin D
- the closer to the equator you live, the easier it is for your body to synthesize vitamin D
- latitudes above 37 degrees N and below 37 degrees S the equator don’t get enough UV radiation energy from the sun (only during the summer)
vitamin D toxicity
- very rare
- usually caused by excessive intake of supplements
- very difficult to reach toxic levels through sun exposure and diet alone
- can cause high levels of calcium in the blood (hypercalcemia) which lead to mild symptoms like nausea, vomiting, and muscle weakness
- severe symptoms include renal failure, calcification of tissues, cardia arrhythmias, and death
vitamin D deficiency
- more likely to develop this if intake is under the RDA, there is little sun exposure, or there is insufficient absorption of vitamin D
- leads to weak bones, osteomalacia in adults, rickets in children, pain, hypocalcemic seizures, tetanic spasms, and dental deformity
osteomalacia
softening of the bones in adults
rickets
softening and weakening of the bones in children (bowed legs)
vitamin E functions
- antioxidant: protects against free radicals
- keeps immune system strong
- helps form red blood cells
- protects against clotting
- helps the body use vitamin K
- cells use it to interact with each other
vitamin E food sources
vegetable oils, nuts, seeds, green leafy veggies, fortified cereals, juices, spreads, and margarine
vitamin E toxicity
- could increase risk of prostate cancer
- high doses are more dangerous after a heart attack or stroke
- oral use can cause diarrhea, nausea, intestinal cramps, fatigue, headaches, blurred vision, and increased creatine in the urine
- generally safe
vitamin E deficiency
- very rare
- linked to diseases like Crohn’s disease, cystic fibrosis, and rare genetic diseases
- needs fat to be absorbed
- can cause nerve and muscle damage, loss of body movement control, muscle weakness and vision problems
- weakened immune system
vitamin K functions
- known as the clotting vitamin
- needed to make certain proteins in the liver that cause blood to clot
- reduces risk of bleeding in liver disease
- body needs vitamin K to use calcium to build bones
- higher levels of vitamin K = greater bone density
- improves bone health and reduces risk of fractures
vitamin K food sources
- green leady veggies (spinach, kale, broccoli)
- meat and dairy (cheese, chicken, eggs)
- fruits (blueberries and grapes)
- vegetable oils
- soybeans
- fortified meal replacement shakes
vitamin K toxicity
- extremely rare
- most common in formula fed infants
- formula is fortified with significantly higher levels of vitamin K compared to breast milk
- can cause hemolytic anemia and jaundice
vitamin K deficiency
- uncommon in healthy adults because vitamin K is widespread in foods, the vitamin K cycle conserves it, and bacteria in the large intestine synthesizes vitamin K
- adults at risk include those taking vitamin K antagonists, people with significant liver damage or disease, and people with fat malabsorption disorders (inflammatory bowel disease and cystic fibrosis)
- newborn infants have low vitamin K status because vitamin K transport across the placental barrier is limited, liver storage of vitamin K is very low, vitamin K cycle may not be full functioning yet, and they have immature gut flora
- deficiency in adults can result in impaired blood clotting (easy bruising or bleeding, increased risk of nosebleeds or bleeding gums, blood in the urine or stool, heavy menstrual bleeding) and weakened bones or increased risk of fractures
- deficiency in infants can result in vitamin K deficiency bleeding (VKDB) and an intracranial hemorrhage