Nutrition exam 4 final

1. Key features of mineral nutrients:
   
   

   • Inorganic elements required in small amounts.
     
     

   • Essential for physiological functions (e.g., enzyme activity, bone health, fluid balance).
     
     

   • Cannot be synthesized by the body.
     
     

   • Stability during cooking and storage.
     
     

2. Macrominerals and trace elements:
   
   

   • Macrominerals (needed in >100 mg/day): Calcium, phosphorus, magnesium, sodium, potassium, chloride, sulfur.
     
     

   • Trace elements (needed in <100 mg/day): Iron, zinc, copper, selenium, iodine, manganese, fluoride, molybdenum, chromium.
     
     

3. Major functions of calcium:
   
   

   • Bone and teeth formation.
     
     

   • Muscle contraction.
     
     

   • Nerve transmission.
     
     

   • Blood clotting.
     
     

   • Enzyme activation.
     
     

4. Blood calcium regulation:
   
   

   • Regulated by parathyroid hormone (PTH), vitamin D (calcitriol), and calcitonin.
     
     

   • Low calcium triggers PTH → increases bone resorption, kidney reabsorption, and activates vitamin D → increases intestinal absorption.
     
     

   • High calcium triggers calcitonin → inhibits bone resorption.
     
     

5. Osteoblasts and osteoclasts:
   
   

   • Osteoblasts: Cells that build bone by depositing calcium.
     
     

   • Osteoclasts: Cells that break down bone and release calcium into blood.
     
     

6. Bioavailability:
   
   

   • The proportion of a nutrient that is absorbed and utilized by the body.
     
     

7. Factors modulating calcium bioavailability:
   
   

   • Enhancers: Vitamin D, acidic pH, lactose, certain amino acids.
     
     

   • Inhibitors: Phytates (grains), oxalates (spinach), excessive fiber, high sodium or protein diets.
     
     

8. Good dietary calcium sources:
   
   

   • Dairy products, fortified plant milks, leafy greens (low oxalate), almonds, tofu (calcium-set), canned fish with bones.
     
     

9. Main functions of iron:
   
   

   • Oxygen transport (hemoglobin, myoglobin).
     
     

   • Enzyme cofactor in redox reactions.
     
     

   • Energy metabolism.
     
     

   • DNA synthesis.
     
     

10. Factors modulating iron bioavailability:
    
    

• Enhancers: Vitamin C, meat/fish/poultry (MFP factor).
  
  

• Inhibitors: Phytates, polyphenols (tea/coffee), calcium, oxalates.
  
  

11. Iron transport and storage proteins:
    
    

• Divalent Metal Transporter 1 (DMT1): Imports Fe²⁺ into enterocytes.
  
  

• Ferritin: Intracellular iron storage.
  
  

• Ferroportin: Exports iron from cells to blood.
  
  

• Ferroxidase (hephaestin/ceruloplasmin): Converts Fe²⁺ to Fe³⁺.
  
  

• Transferrin: Transports Fe³⁺ in blood.
  
  

• Transferrin Receptor: Imports iron into cells.
  
  

• Hepcidin: Liver hormone that degrades ferroportin to reduce iron absorption.
  
  

12. Heme vs. non-heme iron:
    
    

• Heme iron: Found in animal sources (meat), better absorbed (~25%).
  
  

• Non-heme iron: Found in plant sources, less efficiently absorbed (~10%).
  
  

13. Systemic iron homeostasis regulation:
    
    

• Hepcidin is the main regulator—when iron stores are high, hepcidin increases to block iron absorption and release from stores.
  
  

14. Cellular iron homeostasis regulation:
    
    

• Controlled by iron regulatory proteins (IRPs) that bind to iron response elements (IREs) on mRNAs for ferritin and transferrin receptors, adjusting synthesis based on iron levels.
  
  

15. Indicators of iron status:
    
    

• Serum ferritin, transferrin saturation, serum iron, total iron-binding capacity (TIBC), hemoglobin, hematocrit.
  
  

16. Hemochromatosis:
    
    

• Genetic disorder causing excessive iron absorption and accumulation, leading to organ damage (commonly liver).
  
  

17. Conditions increasing iron requirements:
    
    

• Pregnancy, menstruation, growth (infants, adolescents), blood loss, endurance athletes.
  
  

18. Zinc homeostasis regulation:
    
    

• Through zinc transporters (ZIPs and ZnTs), metallothionein binding, and intestinal absorption/excretion regulation.
  
  

19. Metallothionein's role in zinc and copper metabolism:
    
    

• Binds excess zinc and copper in the intestines, modulating absorption and protecting against toxicity.
  
  

20. Genetic copper metabolism diseases:
    
    

• Menkes disease: Copper deficiency due to transport defect (ATP7A mutation).
  
  

• Wilson’s disease: Copper toxicity due to impaired excretion (ATP7B mutation).
  
  

21. Iodine function, sources, deficiency:
    
    

• Function: Thyroid hormone synthesis (T3, T4).
  
  

• Sources: Iodized salt, seafood, dairy.
  
  

• Deficiencies: Goiter, cretinism, hypothyroidism.
  
  

22. Key features of selenium:
    
    

• Component of selenoproteins (e.g., glutathione peroxidase).
  
  

• Antioxidant function, thyroid hormone metabolism.
  
  

• Found in Brazil nuts, seafood, grains.
  
  

• Both deficiency (Keshan disease) and excess (selenosis) are harmful.
  
  

23. Examples of nutrient-nutrient and nutrient-gene interactions:
    
    

• Nutrient-nutrient: Vitamin C enhances non-heme iron absorption; calcium competes with magnesium.
  
  

• Nutrient-gene: MTHFR gene affects folate metabolism; APOE genotype affects lipid response to diet.
  
  

24. Personalized vs. precision nutrition:
    
    

• Personalized: Tailored to individual’s preferences, lifestyle, and biology.
  
  

• Precision: Uses genetic, metabolic, microbiome data to optimize health outcomes.
  
  

25. Definitions:
    
    

• Nutritional genomics: Broad field studying how genes and nutrients interact.
  
  

• Nutrigenetics: How genetic variation affects nutrient response.
  
  

• Nutrigenomics: How nutrients affect gene expression.
  
  

• Epigenetics: Heritable changes in gene expression without DNA sequence change (e.g., via diet).
  
  

• Microbiota: Community of microorganisms in the body (e.g., gut).
  
  

• Microbiome: The collective genomes of the microbiota.
  
  

• Prebiotics: Non-digestible compounds that promote growth of beneficial bacteria.
  
  

• Probiotics: Live beneficial bacteria taken via diet/supplement.
  
  

• Symbiotics: Combination of prebiotics and probiotics.
  
  

• Metagenomics: Study of genetic material from environmental samples (e.g., gut microbiota).

MINERALS

• functions

  • electrolyte, structure, signal transduction, cofactor role, 

• bioavailability of minerals - the rate and extent to which a nutrient is absorbed and used 

  • nutrient-nutrient interactions - other foods consumed at the same time 

  • nutritional status of the mineral in the individual

• minerals are not expended/destroyed during biological processes

• required in diets due to variable efficiency in recycling 

• transition metals like iron can be reactive and/or toxic if not bound to specialized proteins 

• calcium

  • most abundant mineral in body 

  • functions

    • structural role: crucial for bone health

      • part of bone structure

      • calcium reserve

      • hydroxyapatite in bone 

      • osteoclasts build new bone

      • osteoclasts dissolve bone 

    • catalytic role, such as blood clotting

    • signal transduction and second messenger 

Factors that enhance calcium absorption:

• Vitamin D: Increases calcium absorption in the intestines.

• Stomach acid: Helps dissolve calcium salts, making them more absorbable

• Lactose: Especially in infants, lactose can enhance calcium absorption

• Optimal calcium intake: Moderate calcium intake is absorbed better than very high doses

Factors that inhibit calcium absorption:

• Phytates (found in whole grains, legumes): Bind calcium and reduce its absorption

• Oxalates (found in spinach, rhubarb): Also bind calcium and prevent absorption

• Excess phosphorus: Competes with calcium for absorption

• High sodium intake: Increases calcium excretion in urine

• Caffeine and alcohol: Can decrease calcium absorption and increase loss.

• bioavailability of calcium from foods

  • > 50% absorbed - cauliflower, cabbage, brussel sprouts, kale, broccoli

  • =  30% absorbed - milk, calcium-fortified soy milk, cheese, yogurt, 

  • = 20% absorbed - almonds, sesame seeds, pinto beans, sweet potatoes 

  • < 5% absorbed - spinach, rhubarb, swiss chard 

parathyroid hormone and calcitonin

• rising blood calcium signals the thyroid gland to secrete calcitonin

1. calcitonin inhibits the activation of Vitamin D

2. calcitonin prevents calcium reabsorption in the kidneys

3. calcitonin limits calcium absorption in the intestines

4. calcitonin inhibits osteoclast cells from breaking down bone, preventing the release of calcium

• all these actions lower blood calcium levels, which inhibits calcitonin secretion 

• falling blood calcium signals the parathyroid glands to secrete PTH

1. parathyroid hormone stimulates the activation of Vitamin D

2. Vitamin D and parathyroid hormone stimulate calcium reabsorption in the kidneys 

3. Vitamin D enhances absorption in the intestines

4. Vitamin D and PTH stimulate osteoclast cells to break down bone, releasing calcium into the blood 

• all these actions raise blood calcium levels, which inhibits PTH secretion

• bones in maintaining blood calcium

  • with adequate intake, blood calcium is normal

    • and bones deposit calcium, result is strong dense bones 

  • with a dietary deficiency, blood calcium still remains normal

    • bones give up calcium to the blood, the result is weak, osteoprotic bones 

• osteoporosis

  • silent disease - no symptoms until it’s too late

  • risk increases with age, leading cause of fractures in the elderly

    • most common in non-hispanic white women and asian women 

  • working against gravity = higher risk of osteoporosis (astronauts)

    • cycling and swimming doesn’t count

  • resistance exercise

    • increase the mechanical force that osteoblasts increase and osteoclasts decrease 

    • delay or slow down the rate of bone density drop 

• phosphorus

  • second most abundant mineral in body

    • hydroxyapatite crystals of bone and teeth

  • functions

    • part of major buffer system

    • part of DNA and RNA

    • assists in energy metabolism

    • helps transports lipids in the blood 

    • structural component of cell membranes 

• magnesium

  • maintains bone health

  • part of protein making machinery

  • necessary for energy metabolism

  • participates in enzyme systems

  • muscle contraction and blood clotting

  • supports normal function of immune system

  • stabilizes ATP
    
    

TRACE ELEMENTS

• Iron - transports oxygen

  • most common nutrient deficiency

  • cofactor of enzymes

    • enzymes in TCA

    • cytochromes in ETC

    • production of neurotransmitters

    • redox active - can promote production of free radicals 

  • gene expression

    • packing/unpacking DNA

    • transcription

    • mRNA processing/transport/degradation

    • translation

    • protein processing and degradation

  • protein in interacting with iron: Ferrous (Fe²⁺) vs Ferric (Fe³⁺) iron

    • proteins requiring iron to function

      • hemoglobin, myoglobin, and iron-containing enzymes

    • iron transport proteins 

      • transferrin, ferroportin

    • iron storage proteins

      • ferritin

  • food sources: heme vs non-heme

    • iron from animals is heme and non-heme

    • inorganic iron mostly from plants (non-heme)

    • heme: accounts for 10% of the average daily iron intake but is well absorbed 

    • non-heme: accounts for remaining 90% but is less well absorbed 

  • mucosal cells in intestine store excess iron in mucosal ferritin

    • mucosal ferritin release iron to mucosal transferrin, which hands off iron to another transferrin that travels through the blood to the rest of the body

  • ferroportin 1: transports ferrous iron out of enterocyte and liver

  • ferroxidase: oxidize ferrous iron to ferric iron so it can attach to transferrin 

  • transferrin: transport ferric iron to different body cells 

  • transferrin receptor: on cell membrane 

  • ferritin: can be in blood and different cells

  • iron homeostasis:

    • systemic: iron regulates the expression of hepcidin, a hormone that regulates how much iron is released from cells, including hepatocytes, macrophages, and enterocytes 

      • determines how much iron is absorbed from diet

    • cellular: iron regulates expression of several proteins important for iron metabolism, including transferrin receptor and ferritin to maintain cellular iron homeostasis

  • iron overload and toxicity:

    • UL: 45 mg

    • accidental iron overdose is leading cause of accidental poisoning in children

    • high-risk population

      • excessive supplementation

      • frequent blood transfusions

      • hemochromatosis

        • body fails to sense how much iron is present 

        • higher risk of developing T1D

• zinc

  • found in all cells, required for important biological functions

  • zinc doesn’t accept or donate electrons 

  • essential structure or catalytic cofactor

    • DNA-binding proteins

    • metalloenzymes

  • homeostasis maintained by absorption and excretion

  • zinc finger

    • small protein structural motif that has one or more zinc ions

    • helps stabilizing structure of DNA

    • organizing chromatin and gene regulations 

    • transcription factors contain zinc finger domains 

  • zinc absorption

    • metallothionein

      • small proteins

      • bind to many metals as well as free radicals

      • level tightly regulated by metal availability

      • reservoir for Zn and Cu

  • zinc deficiency

    • dietary components that inhibit zinc absorption

    • growth retardation

    • impaired immune response 

    • delayed sexual development

    • damage to central nervous system 

    • acrodermatitis enteropathica

  • zinc toxicity

    • interference with copper metabolism

    • supplementation: treatment of childhood infections

• copper

  • transition metal

  • essential cofactor for many enzymes

    • metalloenzymes in redox reaction 

  • homeostasis maintained by absorption and excretion

  • copper absorption

  • genetic disease of Cu metabolism

    • CTR1 is the Cu uptake transporter 

    • Menkes and Wilson are Cu efflux transporters 

• iodine

  • present in body as iodide

  • integral part of thyroid hormones

  • homeostasis maintained by excretion

  • function

    • in thyroid, enzymatically added to tyrosine residues in thyroglobulin, which condense to form thyroxine (T4) and transported to other tissues 

      • T4 is converted to active thyroid hormone (T3) by Se-dependent deiodinases 

  • deficiency - cretinism and goiter

• selenium

  • component of at least 25 enzymes and proteins 

  • antioxidant defense, spares Vitamin E for use in other antioxidant functions 

  • thyroid metabolism; iodothyronine deiodinase converts T4 to T3

• fluoride

  • supports deposition of calcium and phosphorus in teeth and bones 

  • protection against dental caries

    • people who grew up with fluoridated water have 40-60% less dental caries 

  • may also strengthen bone by reducing bone resorption/mineralization 

PERSONALIZED NUTRITION

• personalized nutrition - consider personal and lifestyle information 

  • approach - holistic, integrates multiple factors

  • level of specificity - tailored to individuals preferences and circumstances

  • examples - adjusting diet for cultural preferences, food intolerances, and lifestyle 

• precise nutrition - focus on biological factors 

  • approach - scientific, focuses on biological mechanisms

  • level of specificity - tailored to individual biological responses and genetic makeup

  • examples - designing diets based on genetic variants or metabolic responses

• prebiotics - diet modulates gut microbiome

  • non-digestible food components that stimulate the growth and/or activity of bacteria in the digestive system in ways beneficial to health 

• probiotics - gut microbiota modulate dietary responses

  • live microorganisms which when administered in adequate amounts confer a health benefit of the host 

• nutrigenetics

  • single-gene (monogenic) disorders

    • mutations of a single gene resulting in altered traits like lactose intolerance, phenylketonuria, genetic hemochromatosis

  • multi gene disorders - obesity, diabetes 

• nutrigenomics

1. nutrients and phytochemicals can interact directly with genetic signals that turn them on or off

   1. activating/silencing leads to increase/decrease of protein synthesis

      1. affects person’s health

• roles of gut microbiota

  • biosynthesis

    • vitamins, steroids, neurotransmitters

• metabolism 

  • branch-chain amino acids 

  • bile salts

  • drugs/xenobiotics 

  • dietary fibers 

• modulation of host physiological processes

  • immune maturation and homeostasis

  • intestinal endocrine functions

  • energy metabolism

  • intestinal barrier, reducing pathogen burden

• modulates energy balance

  • satiety, release of hormones, storage of fat, energy utilization, systemic inflammation