Exam 2: Nutrition Flashcards

Question

Energy Measurement

Answer 1

**1 Calorie = 1,000 calories** Often labeled as **kcal**. Becoming common to replace kcal with **kilojoules** **1 Cal = 4.184 kJ**

Answer 2

The **rate per hour that we expend calories by merely subsisting** i.e. just sleeping. Expenditure proportionally higher if awake and active.

Answer 3

RQ = 63/77 = 0.82 **Protein oxidation** is not evaluated with RQ but rather through **measurement of urea excretion**. Test called **urinary urea nitrogen** or UUN.

Answer 4

**The total of all calories expended over the course of a 24-hour day.** ~ 60% of TEE is due to basal metabolism aka **basal energy expenditure (BEE).**

Answer 5

**Basal metabolic rate (BMR)** refers to a very specific set of conditions ⇒ at rest, fasted, not subject to stimuli, etc. Not always practical to measure. **Resting metabolic rate (RMR)** measured under more realistic conditions and regarded as "close enough" to BMR.

Answer 6

Metabolic rates can be estimated based on **crude estimates** or using **emperical equations**. Estimated **BMR for a man is 1 kcal/kg/hr** and that of a **woman is slightly less**. * **Empirical equations** are based on population averages. * Harris-Benedict equations most common * Uses **height, weight, age, and set of constants**. * Different equations used for men and women. * Can be determined by **measuring the oxygen consumed or carbon dioxide produced**. * Factors exist that relate liters of gas respired to Calories expended * Normalized to Cal/hr or Cal/kg-hr

Answer 7

Amount of **O₂ consumed and CO₂ produced** used to estimate the number of **kcal expended** over time. Used to **estimate RMR or BMR**.

Answer 8

**Ratio of CO₂/O₂****** **Determines what proportion of calories used comes from fats vs carbs.** **RQ ≈ 0.85 in a typical american diet.** Typically get 50% of non-protein-derived energy from carbs and 50% from fats. Patients with severe dyspnea/hypercapnia may benefit from burning fats d/t lower RQ.

Answer 9

* **Carbohydrates** * Max 4.1 Cal/g possible * 98% efficiency of digestion/absorption * **Corrects to 4 Cal/g** * **Fats** * Max 9.4 Cal/g * 95% absorbed * **Corrects to 9 Cal/g** * **Proteins** * Max 5.6 Cal/g * Only 92% absorbed * Only 75% of absorbed protein catabolized to CO₂ * **Corrects to 4 Cal/g**

Answer 10

1 lb of body weight translates to a deficit of ~ 3,500 Cal

Answer 11

_PAR divided into 3 activity levels:_ Light (1-1.8) Moderate (2-4) Heavy (\>4) Each activity level then multiplied by BMR to calculate the energy expended performing that activity.

Answer 12

Similar to PAR. Also refers to the increase in energy expenditure relative to basal.

Answer 13

In healthy individuals: * Requires * **BMR/RMR** * **energy expenditure** due to physical activity * **thermic effect** * amount of energy above BMR used for processing of food for use and storage * estimated as additional 10% added to energy expenditure

Answer 14

Sick or injured patients enter a **hypercatabolic state**. **Counterregulatory hormones** **rise**. (glucocorticoids, epi, norepi) Results in increased protein breakdown, gluconeogenesis, and glycogenolysis. Increased catabolism termed the "**injury factor**"

Answer 15

Requires: * **BMR** * **Injury factor** * **Physical activity factor (PAR)** * simplified to 1.20 if bed riden * simplified to 1.30 if allowed out of bed * **Thermic effect** * if they are digesting and absorbing food

Answer 16

1. **Inadequate Intake** 2. **Inadequate Absorption** 3. **Decreased Utilization** 4. **Increased Losses** 5. **Increased Requirements** * due to various **stresses** such as fever, burns, trauma, etc * **hypercatabolic state** caused by elevated counterregulatory hormones * **increased need** for calories, proteins, and some vitamins

Answer 17

**The physical measures of weight or body dimensions.** * **_For children:_** * most commonly involve **height and weight** * **mid-arm circumference** common in developing countries * **comparison to growth charts** * **_For adults:_** * **BMI** most common criterion * **waist size measurement** also used * **skin-fold thickness** provides a measure of sub-Q fat

Answer 18

Most common method for calculating ideal body weight. Comparison of ideal weight & weight at which people have the greatest longevity found them in close agreement.

Answer 19

Proxy for body fat percentage. Used to classify individuals as obese or non-obese in order to evaluate for potential risk factors.

Answer 20

BMI ranges associated with weight classifications.

Answer 21

An involuntary weight loss of 10% or more over a 6-month period.

Answer 22

1. **_Serum albumin_** * most common visceral protein evaluated as part of nutrition assessment * useful for free-living populations or upon hospital admission * gives an integrated picture of **nutritional intake over a period of several weeks** 2. **_Serum prealbumin_** (aka transthyretin) * half-life of 2-3 days * measure of choice for monitoring progress of hospitalized patients * gives information about **short-term changes in nutritional status** 3. **_Transferrin_** * intermediate half-life of **8-9 days** * useful in establishing cumulative nutrition status over an **intermediate time interval** 4. **_Hemoglobin and hematocrit_** * likely the first detected sign of severe protein malnutrition 5. **_Creatine-height index (CHI)_** * sometimes used to estimate skeletal muscle mass

Answer 23

1. **_Twenty-four hour recall_** * all food & beverages consumed over the past 24 hours * usually starts with meal immediately preceding interview and working backwards 2. **_Food frequency questionnaire_** * retrospective review of intake frequency * how much of each category consumed per day, week, or month 3. **_Typical day history_** * patient orally reports all foods and beverages consumed on a typical day 4. **_Food diary_** * only prospective approach * patient records specific types and exact amounts of food & beverages eaten as soon as possible after consumption

Answer 24

Typically used with the elderly. Evaluates areas such as: * **anthropomorphic measures** * **dietary measures** * **"global assessment"** * mobility * lifestyle * medications * etc * **subjective measures** * self-perception of health and nutritional status

Answer 25

* **Cancer** development through _oxidative DNA damage_ leading to mutagenesis * **Atherosclerosis** due to _oxidation of LDL_ and _uptake by macrophages_ ⇒ **foam cells** * **Alzheimer's disease** due to _neuronal death_ from _elevated NO_ and/or _mitochondrial dysfunction_ * **Aging** attributed to progressive _decline in mitochondrial function_

Answer 26

Routes for feeding of a patient incapable of taking food by mouth: 1. **_Enteral_** * liquid diet fed directly into stomach or intestine via tube * **preferred method** * preserves gut integrity * less expense 2. **_Parenteral (IV)_** aka hyperalimentation or "hyperal" nutrition * formulas require glucose, AAs, vitamins, minerals, and triglyceride emulsions * components in the form normally encountered in blood * no fiber * must be sterile

Answer 27

**ROS are by-products of oxygen metabolism.** Typically generated in the mitochondria. * Add 1 e^- ⇒ **superoxide** (O₂^-) * Add 2 e^- ⇒ **hydrogen peroxide** (H₂O₂) * Add 3 e^- ⇒ _extremely reactive_ **hydroxyl radical** (OH・) * Concerted addition of 4 electrons generates the desired H₂O product **Nitric oxide** (NO・) is another physiological free radical.

Answer 28

* _In membranes and lipoproteins_, **hydroxyl radical** acts on **unsaturated fatty acid groups** to form **lipid carbon-centered radicals** * Can initiate a _chain reaction_ * Lipid carbon-centered radicals _seen as foreign_ * **Oxidative stress** occurs when production of ROS faster than antioxidant defenses can consume them * Ex. **respiratory burst** * Can lead to cell damage and death * With **ischemia-reperfusion injury,** most tissue damage occurs on re-exposure to oxygen * Tissue undergoes necrosis and death

Answer 29

Lipophilic Antioxidant * **Synthesized in plants** * High levels in **grains** and **vegetable oils** * wheat germ, whole grain bread and cereals, egg yoke, nuts and sunflower seeds * Absorbed in intestines and transported to liver in **chylomicrons** * May include a variety of **tocopherols** (saturated side-chains) and **tocotrienols** (3 double bonds in side-chain) * **_𝛼-tocopherol_** with highest activity ⇒ "natural" vitamin E * RDA is 15 mg/day * TUL is 1,000 mg/day * Vit E supplementation at high doses can compete with Vit K

Answer 30

Lipophilic Antioxidant * Can function as a **chain-breaking antioxidant** * **Prevents propagation of lipid carbon-centered radicals** of FA residues of membranes * Able to **cross BBB and protect lipids in CNS** from oxidative damage * Deficiency can result in neurological sx * Important at **blocking formation of atherogenic lipoprotein species** * Concomitant reduction in CAD not yet adequately demonstrated * **Antioxidant supplements are not currently recommended**

Answer 31

Celiac's results in **autoimmune damage of intestinal villous**. **Prevents absorption of lipid-containing mixed micelles** which would normally deliver fat-soluble vitamins to enterocytes. Results in **malabsorption of many nutrients** including iron, calcium, Vit D, and less frequently Vit E. Causes **progressive systemic degeneration of large-caliber myelinated sensory axons** in spinal cord and peripheral nerves. Presenting symptoms: Neuromyopathy, Sensory neuropathy, Optic atrophy, Cerebellar syndrome Hemolytic anemia, myopathy, weakness, ataxia, impaired reflexes, ophthalmoplegia, retinopathy, damage to nervous tissue Treatment includes Vit E replacement with 𝛼-tocopherol.

Answer 32

**Major hydrophilic antioxidant vitamin.** Many important physiological roles: 1. **Returns Vit E back to reduced state** * Indirectly impacts oxidation of membrane components 2. **Important for collagen synthesis** * Coenzyme for several hydroxylases * **Vit C deficiency results in** **scurvy** * loose teeth, bleeding gums, ecchymoses, slow wound healing 3. Dietary Vit C **reduces ferric iron to ferrous iron** (absorbed form) * Results in improved absorption of dietary iron Beneficial effects of ascorbate seen in **lowered markers of DNA oxidation** (_8-oxoguanine_) and **lowered markers for membrane oxidation** (_malondialdehyde_)

Answer 33

ROS are enzymatically inactivated. * ***Superoxide dismutase*** * **superoxide → hydrogen peroxide** * mammals with at least 2 isozymes * ***Catalase*** * **hydrogen peroxide → water and oxygen** * heme protein * located in peroxisomes * ***Glutathione peroxidases*** * Catalyzes reduction of H₂O₂ by glutathione (GSH) * Oxidized GSSG returned to GSH by ***glutathione reductase*** utilizing **NADPH** * Found in cytosol * **Selenium** is an important prosthetic group in these enzymes and is therefore essential.

Answer 34

**Plant-derived hydrophilic antioxidants.** Found in **blueberries, green tea, red wine, and cocoa**. Possible role in reduction of CAD and cancer.

Answer 35

Have also been suggested to act as antioxidants. Ex. beta-carotene

Answer 36

Studies unable to prove health benefits of antioxidant supplements. **Balanced diet rather than supplementation is the most consistent health recommendation.** Many antioxidants advertised without significant scientific validation e.g. lipoic acid, CoQ, grape seed extract.

Answer 37

Thiamine = Vit B₁ Riboflavin = Vit B₂ Niacin = Vit B₃ Pantothenic Acid = Vit B₅ Pyridoxine = Vit B₆ Biotin = Vit B₇ Folic acid = Vit B₉ Cobalamin = Vit B₁₂

Answer 38

**_Vitamin B_****₁** * **_Sources:_** * **Lean pork, whole-grain cereals,** legumes, and yeast * **Chronic ethanol ingestion** strongly favors thiamine deficiency * Absorbed primarily in the **jejunum** * **_Functions:_** * Phosphorylated form ⇒ **thiamine pyrophosphate (TPP)** * Cofactor for **formation or degradation of 𝛼-ketols** by *transketolase* * Cofactor in **oxidative decarboxylation of 𝛼-keto acids** * conversion of **pyruvate to acetyl-CoA** by *pyruvate dehydrogenase* * **Important for * **carbohydrate catabolism** * **proper heart and brain function** * structural component of nervous system membranes

Answer 39

Caused by **weak TPP binding**. Becomes **manifested if thiamine intake is compromised** ⇒ _alcoholism, poor diet, malabsorption_. Similar _symptoms to beri-beri_ but also **memory problems, disorientation, confabulation,** **and coma**.

Answer 40

**Caused by a thiamine (Vit B₁) deficiency.** _Two forms:_ "**wet**" (edematous) and "**dry**" (non-edematous). * **_Causes:_** * Most commonly seen with **alcoholic patients** * ****due to interference by alcohol on B vitamin absorption * Associated with **bariatric surgery** when Vit B supplementation inadequate * absorbed primarily in the jejunum * restrictive reconstruction results in mild malabsorptive state * B₁ level can be depleted after PO or IV carb intake * Sx can occur within 6 months of surgery in adolescent cases * **Considered a medical emergency** * can progress to _cardiac failure_ * can result in _permanent neurological deficits_ * **_Symptoms include:_** * muscle weakness * ataxia * foot drop * ophthalmoplegia * nystagmus * neuropathy * cardiac abnormalities * GI manifestations

Answer 41

**_Vitamin B₃_** * **_Substituted pyridine derivatives_** * **Niacin** (nicotinic acid) * **Niacinamide** (nicotinamide) * **_Sources:_** * **Dietary:** * Mostly as physiologically active forms: **NAD⁺ or NADP⁺** * **Legumes, cereals, lean meat, poultry, and fish** * Absorption **impeded by alcohol** * **Synthesized from tryptophan** * Requires sufficient dietary tryptophan and **pyridoxal (Vit B₆) cofactor** * B₆ deficiency or inadequate tryptophan absorption can result in _pellagra-like symptoms_

Answer 42

* **_Pyridine nucleotide functions:_** * Essential co-substrates/co-enzymes for **most dehydrogenase reactions** * Substrates for **ADP-ribosylation reactions** * Precursors of **cyclic ADP-ribose** * Role in _intracellular Ca_²⁺ _handling_ * Important for: * **cellular repair** * **DNA repair**

Answer 43

Niacin (but not nicotinamide) used at high doses for **treatment of hypercholesterolemia**. High doses of niacin only in excess of 1 g/day causes **acute flushing**. Chronic intake at these levels can cause **biochemical abnormalities**. Abnormal liver function, hyperglycemia, increased plasma uric acid, vasodilation.

Answer 44

**Caused by a niacin deficiency.** * Clinical signs are the **three Ds**: * **Diarrhea** * **Dementia** * **Dermatitis** * glossitis * angular cheilitis * _characteristic Casal's necklace_ * Can result in death if untreated * Serious disease in Africa, Europe, and Southeastern US * _Diet consisting mainly of corn_ which is low in niacin and tryptophan

Answer 45

Pellagra due to frank malnutrition rare in the US. Pellagra-like symptoms can result from: 1. **_Bariatric surgery_** * can result in vitamin malabsorption * ↓ plasma pyridoxine and niacin levels can be seen * treat with supplements of pyridoxine, nicotinamide, zinc sulfate, and riboflavin 2. **_Drug-nutrient interaction_** * ****Ex. **isoniazid** (commonly prescribed anti-Tb drug) * mimics niacin deficiency * **competetively inhibits conversion of nicotinamide acid to NAD⁺ and NADP⁺** * coenzyme deficiency inhibits repair of cell damage * affects tissues of high turnover i.e. skin and GI tract * Other agents known to cause pellagra-like sx * 6-mercaptopurine, 5-fluorouracil, and chloramphenicol 3. **_Abnormalities of tryptophan metabolism_** 1. Carcinoid syndrome 2. Hartnup's disease

Answer 46

**_Vitamin B₉_** * **_Sources:_** * Derived from **leafy green vegetables, legumes, and some fruits** * **Grains fortified with folate** * Most dietary folate with **chain of glutamate residues** * **Folate masks a B₁₂ deficiency** * TUL is set at 1 mg/day * **_Absorption and transport:_** * Involves specific enzyme systems: * Dietary folate taken up by a **saturable transport system** * Absorbed mostly in **jejunum** * _Reduced_ and some _methylated_ to **5-methyl-THF** before entering blood * **_Functions:_** * **One-carbon donor** in many biochemical reactions * **Tetrahydrofolate (THF)** ⇒ reduced coenzyme form of folate * Role in **biosynthesis of purines, TMP, and methionine**

Answer 47

Reversion of **5-methyl-THF → THF** requires **Vit B₁₂**. **B₁₂ deficiency "traps" folate** in the 5-methyl-THF form preventing re-entry into the folate pool.

Answer 48

**Common**, particularly among the poor. * Forms of folate required for _purine and pyrimidine synthesis_ & _DNA synthesis_ * Folate deficiency **inhibits synthesis of new cells** resulting in: * **macrocytic anemia** * ******hypochromic, macrocytic RBCs** on blood smear * **hypersegmented neutrophils** possible * **villous atrophy** * **depapillation of the tongue** * increased risk for serious diseases * weakness and fatigue * palpitations * shortness of breath * increased **neural tube defects** in fetuses * **400 mcg/day** supplement recommended for pregnant women * **Hyperhomocysteinemia** commonly accompanies folate deficiency * linked to **increased risk of CAD** * folate supplementation lowers homocysteine levels * **not consistently shown to reduce risk of CAD**

Answer 49

1. Serum folate ↓ 2. RBC folate ↓ 3. Hypersegmented neutrophils appear 4. Mean Corpuscular Volume (MCV) ↑ * months before anemia is apparent 5. Hb levels ↓

Answer 50

**_Vitamin B₁₂_** * **_Sources:_** * Synthesized by microorganisms * Found primarily in **animal sources** * **Meats, fish, dairy, eggs** * **_Absorption:_** requires **gastric acid** (to release the vitamin from food) and **Intrinsic Factor (IF)** secreted by the stomach 1. B₁₂ initially bound to **"R-proteins"** in acidic conditions of stomach 2. released by **proteases in duodenum** 3. binds to **intrinsic factor** 4. very efficiently absorbed (or reabsorbed) in **ileum** by **receptor-mediated process** 5. remaining 1% taken up by diffusion * If absorption mechanisms are intact, B₁₂ stores can last 10-20 years due to recapture * If absorption mechanisms damaged, **anemia can appear within 3-6 months** * **Vegetarians, elderly, and bariatric sx patients** at risk for deficiency

Answer 51

**Involved in only two metabolic pathways:** 1. **Conversion of 5-methyl-THF → THF** * B₁₂ deficiency traps folate in methyl form * folate can no longer be used in purine and TMP synthesis 2. **Conversion of methylmalonic acid → succinyl CoA** * prolonged B₁₂ deficiency results in neuropathy * due to inability to catabolize odd # FAs

Answer 52

* **Common disorder among older adults and vegetarians** * ~ 5-15% in people \> 65 y/o * **Folate can mask a B₁₂ deficiency** * **_Causes:_** * **food-cobalamin malabsorption** * achlorhydria * atrophic gastritis * prolonged PPI use * bariatric surgery * **pernicious anemia** * due to IF deficiency * **inadequate intake of animal sources** * **_Symptoms:_** * megaloblastic anemia * neuropathy * cognitive impairment * psychopathology * elevated levels of **methylmalonic acid (MMA) and homocysteine (HCYS)** * Only hyperhomocystemia seen with folate deficiency * **_Clinical Course:_** * monitoring of Vit B₁₂ concentrations in asymptomatic patients taking PPI for \> 4 years * immediate screening for Vit B₁₂ deficiency if symptoms manifest * given irreversible nature of neurologic changes * **_Treatment:_** * _Supplementation_ with **non-protein-bound B₁₂** * ↓ in MMA and HCYS levels after replacement suggestive of food-cobalamin malabsorption * R/O renal dysfunction as cause of elevated MMA/HCYS * **B₁₂ injections** may be neccessary * used for treatment of pernicious anemia

Answer 53

**B₁₂ deficiency** due to **inability of parietal cells to synthesize Intrinsic Factor (IF)**, resulting in **malabsorption**. * Results in _similar sx as folate deficiency_ * **megaloblastic anemia** and **hyperhomocysteinemia** * **Neuropathy** due to _failure to metabolize odd # FAs_ * Usually treated with B₁₂ injections

Answer 54

**Used for the assessment of B₁₂absorption.**

Answer 55

**_Vitamin B₆_** * **Widely distributed in foods** * Poultry, fish, pork, liver, kidney * Whole grains, carrots, cabbage, peas, potatoes and tomatoes * **Deficiency is rare** * _Large doses_ of B₆ \> 500 mg/day can cause **irreversible peripheral toxic sensory neuropathy** * Abnormal for a soluble vitamin

Answer 56

* Pyridoxine, pyridoxal, and pyridoxamine are precursors to biologically active coenzyme **pyridoxal phosphate (PLP)** * **_PLP functions:_** * Associated with **amino acid metabolism** * **Conversion of tryptophan → niacin** * **Deficiency produces pellagra-like sx** * Involved in **glycogen breakdown** * Factor in conversion of **homocysteine → cysteine** * role in _reducing elevated homocysteine_

Answer 57

**_Vitamin B₂_** * Widely found in a **variety of foods** * **Dairy products, yogurt, cheese, meat, eggs, broccoli,asparagus, and whole grain foods.** * Component of **enzyme prosthetic groups** * Flavin mononucleotide (**FMN**) * Flavin adenine dinucleotide (**FAD**) * FAD and FMN are part of **oxidation-reduction enzymes** * *NADH dehydrogenase* * *Succinate dehydrogenase* * Riboflavin-containing enzymes critical to life * **Uncomplicated riboflavin deficiency uncommon** * Deficiency usually seen with _multiple vitamin deficiencies_ * Has surprisingly _mild symptoms_ * __**dermatitis**, **cheliosis** (fissures at corners of mouth), and **glossitis** (smooth and dark appearing tongue) * corneal vascularization * anemia

Answer 58

**_Vitamin B₇_** * **Widely distributed in foods** * **Deficiency is ordinarily not seen** * _Egg whites_ contain **avidin** which has very strong affinity for biotin * Consumption of **raw egg whites can lead to biotin deficiency** * Functions as **coenzyme in carboxylation reactions** * serves as **carrier of activated CO₂** * binds to specific _lysine residues_ in enzymes * ex. *pyruvate carboxylase*

Answer 59

**_Vitamin B₅_** * Sources are common * **eggs, liver, and yeast** are major sources * **Deficiency is rare** * cooking may destroy some B₅ in foods * deficiency only suspected in recorded cases * **No RDA established** * **Toxicity is rare** * No TUL established * **_Functions:_** * _Pantothenic acid itself_ is a component of the **acyl carrier domain of *fatty acid synthase*** * **Component of CoA** * Functions in the **transfer of acyl groups** in numerous reactions

Exam 2: Nutrition Flashcards

(83 cards)