nutrisci

Lipid Soluble Vitamins

1. What are the deficiency diseases associated with each vitamin? Forms and symptoms?

• Vitamin E - generally result of insufficient fat absorption, generally rare

  • symptoms - retinopathy, peripheral neuropathy, ataxia, lower immune function 

• Vitamin A - mostly a concern in developing countries

  • night blindness - can’t adapt to darkness

    • diminished ability to generate rhodopsin

  • xerophthalmia - excessive dryness of eye caused by lack of mucus production

    • leads to corneal and conjunctival scarring, blindness 

• Vitamin K - primary deficiency rare 

  • secondary deficiency - malabsorption and anticoagulant drugs 

• Vitamin D - 

  • osteomalacia - soft bones

    • occurs in adults 

  • rickets - occurs in children; bowed legs, enlarged heads and rib cage; deformed pelvis 

2. What are the conversions of the different forms of Vitamin A? Are all conversions

reversible?

• retinol and retinal can be converted back and forth 

• retinoic acid is active form 

• pre-formed - animal products, dairy, fish

• pro vitamin 

  • carotenoids - plant pigments found in many fruits and veggies 

  • conversion of beta carotene requires BCO1

    • converts carotene to retinal

    • abundant in small intestine

3. What factors are involved in the physiological response to low blood calcium?

• parathyroid hormone is released from gland

• PTH activates hormones in kidneys that convert inactive Vitamin D into calcitriol 

• PTH and calcitriol stimulate production of osteoclasts

  • demineralize bone to release Ca²⁺ and phosphorus into blood 

  • calcitriol increases calcium absorption from intestine and reabsortpion from kidneys 

4. How long do deficiency symptoms take to develop for fat soluble vitamins? Why?

• They take longer because they are primarily stored in adipose tissue and liver for prolonged storage and use later on 

5. How is vitamin D processed to its active form, and what does this indicate about

potential vitamin D treatment in the context of organ failure?

• two step activation

  • liver: 25-Ohase

  • kidney: 1 alpha-Ohase

• Final product: 1,25-(OH)₂D3 [calcitriol] - active Vitamin D

• regulates its own breakdown (negative feedback

• in case of organ failure the final step is inhibited 

6. What does the nomenclature Retinol Activity Equivalents account for?

• The RAE system was developed to account for the varying bioavailability and efficiency of conversion among different forms of vitamin A. Retinol from animal sources is highly bioavailable, whereas provitamin A carotenoids, such as beta-carotene from plant sources, require enzymatic conversion in the intestine

  • basically means plant sources are insufficient compared to meat 

7. What forms of which vitamins have potent effects on gene expression?

• retinoic acid is active form of Vitamin A

  • produced in small amounts locally in small tissues 

  • regulates cell differentiation, growth, embryonic development, reproduction, immunity

• 1,25-dihydroxyvitamin D binds to the vitamin D receptor (VDR), which interacts with DNA to modulate the expression of genes involved in calcium homeostasis and immune function

8. How is sufficiency status of each vitamin assessed (for the ones where this was talked

about)?

9. What are the best food sources for each vitamin?

• Vitamin E: vegetable oils 

• Vitamin A: animal products, sweet potatoes

• Vitamin K: green leafy vegetables, 

• Vitamin D: liver, beef, veal, eggs, fish, sun, fortified foods 

10. Where is the body’s preference specifically for alpha-tocopherol realized?

• several forms but alpha-tocopherol most relevant responsible for antioxidant functions

• absorption - absorbed with fats, incorporated into chylomicrons for circulation

  • processed in liver

Water Soluble Vitamins

1. What are the deficiency diseases associated with each vitamin? Forms and symptoms?

• Niacin (B3) pellagra - diarrhea, dementia, dermatitis, death 

• Thiamin (B1) beriberi - wet - Cardiovascular system; dry - nervous system 

• Riboflavin (B2) - ariboflavinosis - cracked lips, inflamed mouth, light sensitivity

• microcytic hypochromic anemia (B6) - small, pale RBCs due to impaired hemoglobin synthesis 

  • seborrheic dermatitis

  • depression, confusion, convulsions

  • impaired immune function

  • drug interactions

    • L-Dopa (parkinsons)

    • Isoniazid (TB)

• pernicious anemia (B12) - identical to folate deficiency 

  • symptoms - peripheral neuropathy, gait ataxia, memory loss, myelin sheath damage 

• megaloblastic anemia (B9 - folate) - 

  • decreased DNA synthesis in bone marrow

  • protein synthesis continues but cell division slows making cells larger

  • neural tube defects - folate necessary for closing neural tube 

2. Are there particular things (environmental, chemical, etc) that might affect vitamin

content in food? Are there specific techniques that are particularly bad for preserving

vitamin content?

• sensitive to heat, light, and O2

3. What is the relationship between THF, homocysteine/cysteine/methionine metabolism,

and folate, cobalamin, and pyridoxal?

• THF converts homocysteine to methionine

• B6 (pyridoxal) converts homocysteine to cysteine

4. What is the neural tube and how does it relate to folate requirements during pregnancy?

• it eventually develops into the brain and spinal cord 

• inadequate folate intake could lead to.. 

  • anencephaly

    • no brain develops

    • depending on severity may see paralysis, incontinence, hydrocephalus (water), learning disabilities 

6. How are THF and vitamins B6, B9, and B12 related to anemia?

• Anemia resulting from vitamin deficiencies depends on the type of vitamin affected. Vitamin B6 deficiency leads to microcytic anemia due to its role in hemoglobin synthesis. Folate and B12 deficiencies cause megaloblastic anemia, characterized by large, immature red blood cells due to impaired DNA synthesis. B12 deficiency also has neurological consequences due to its role in myelin formation.

7. What are the best food sources for each vitamin?

• thiamin (B1) - rich in whole grains, pork, legumes

• riboflavin (B2) - dairy products 

• niacin (B3) - meats, poultry, seafood

• pyridoxal (B6) - poultry, bananas, potatoes

• Pantoic acid (B5) - beef liver great source 

• biotin (B7) - eggs, liver, yeast 

• Folate (B9) - green leafy veggies 

• (B12) - animal origin or fortified foods 

8. What is involved in absorption of the water-soluble vitamins? Any specific vitamins have

special factors involved in absorption (there are more than 1)?

• Some water-soluble vitamins require specialized absorption mechanisms. Vitamin B12 requires an intrinsic factor, a glycoprotein secreted in the stomach, for proper absorption in the ileum. Folate absorption involves a reduction step before being taken up by intestinal cells. Vitamin C enhances iron absorption by reducing ferric iron (Fe3+) to ferrous iron (Fe2+), which is more bioavailable

9. What does it mean to say that folate can mask B-12 deficiency?

• high folate can correct the anemia associated with B12 deficiency without fixing the neurological problems like lack of myelin formation 

10. What cofactor is involved in many, many enzymatic reactions?

• Many enzymatic reactions require cofactors, and B vitamins serve as some of the most common. Notably, NAD+ and NADP+ (derived from niacin) are involved in redox reactions, FAD (from riboflavin) is important in the electron transport chain, and pyridoxal phosphate (from B6) is essential in amino acid metabolism

11. How is sufficiency status of each vitamin assessed (for the ones where this was talked

about)?

• Vitamin sufficiency is assessed using biomarkers such as serum levels. Folate and B12 are commonly measured in the blood, while functional tests like homocysteine levels can indicate deficiencies. Vitamin C status is assessed via plasma ascorbic acid levels

12. What drug-vitamin interactions were described?

• riboflavin nutrient drug interaction

  • phenobarbital - sedative 

    • metabolism of this drug causes dramatically increased utilization of riboflavin

    • often provided a riboflavin supplement for those individuals that are prescribed phenobarbital

• pantoic acid (B5) 

  • nutrient drug interaction: estrogen-containing oral contraceptives may increase requirements 

13. Which vitamins have upper intake limits that are only a couple of fold higher than the

RDA?

• Niacin and vitamin B6 have upper intake limits only a few times higher than the RDA, as excessive intake can cause flushing (niacin) or neurological toxicity (B6)

Water and Electrolytes

1. How does the renin-angiotensin system work? Does it function in particular locations in

the body?

• Renin

  • enzymes released from kidneys in response to decreased blood pressure

  • acts in blood on angiotensinogen to produce angiotensin 1

  • angiotensinogen made in liver

    • angiotensin 1 - converted to angiotensin 2 in lungs

      • angiotensin 2

        • most powerful vasoconstrictor in body

        • constricts blood vessels to increase blood pressure

        • increases vasopressin production

        • also causes release of the hormone aldosterone from adrenal glands 

      • ACE inhibitors - angiotensin-converting-enzyme inhibitors

        • treat high blood pressure

        • inhibit ACE enzymes that convert angiotensin 1 to angiotensin 2

        • inhibit hydrolysis of bradykinin, which is a vasodilator

        • net effect: lower blood pressure

        • side effects: cough and angioedema

2. What are the physiological steps that occur during prolonged sweating?

• During prolonged sweating, the body loses water and electrolytes, leading to dehydration and electrolyte imbalances. This triggers increased thirst, reduced urine output, and activation of the RAS to conserve fluid

3. What are the fluid compartments of the body, and how much water (by weight and

volume) do they each account for?

• ECF - ⅓ of body water

  • 20% of body weight

  • interstitial is 75% 

  • plasma is other 25%

• ICF - ⅔ of body water

  • 40% of body weight

4. What is isotonic saline?

• Isotonic saline (0.9% NaCl) has the same osmolarity as blood plasma and is used to maintain hydration without causing fluid shifts between compartments

5. What is osmolarity, and how does it vary by whether you are inside or outside of the cell

(including what the osmolytes are)?

7. How does dehydration affect urine production?

• Dehydration triggers antidiuretic hormone (ADH) release, increasing water reabsorption in the kidneys and reducing urine output

8. What is involved in regulating body pH?

• The body maintains pH via buffer systems, respiratory control (CO2 exhalation), and renal mechanisms (bicarbonate excretion or reabsorption

9. What drugs were discussed related to the renin-angiotensin system?

10. What is the structure of the kidneys, including functions of each part?

• kidneys

  • regulate body fluid osmolarity and volume and electrolyte balance

  • regulate acid/base balance

  • excrete metabolic waste products 

  • produce and secrete hormones 

  • principles of the nephron - functional unit of kidney

    • filtration

      • initial removal of solutes and water from blood

      • doesn’t include large proteins or blood cells

      • solutes in filtrate include some vitamins, minerals, and nutrients

    • reabsorption

      • selective removal of water and solutes from the glomerular filtrate back into blood 

      • regulated by hormones (Ca²⁺ and PTH)

        • PTH induces kidney to activate more Vitamin D

        • increases Calcium reabsorption and lowers excretion

    • secretion

      • selective removal of certain solutes from the plasma into the tubules 

      • occurs after blood has passed through the glomerulus

    • excretion

      • removal or final urine to bladder

    • tubular system involved in urine production

    • glomerulus - part of nephron

      • rich in capillaries and site of plasma filtration into the renal tubes 

    • tubules - site of processing of the plasma filtrate to create urine