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Questions and Answers
What happens to glucose during gluconeogenesis?
Inhibition of which compound can affect glycogen breakdown in the muscle?
What is the primary role of hexokinase in muscle cells?
How does high protein consumption affect athletes regarding carbohydrate intake?
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Which of the following amino acids is a precursor to serotonin and melatonin?
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What can excessive protein consumption primarily lead to, especially in athletes?
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In liver cells, which enzyme has an important role in converting glucose to glucose-6-phosphate and is induced by insulin?
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What is the primary function of carnitine in the body?
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Which biochemical process converts glycogen back into glucose?
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What can nitrogen compounds be related to in terms of dietary supplements?
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What is a common cause of Kwashiorkor?
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Which of the following is true regarding the Glycemic Index (GI) of foods?
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What is the recommended daily allowance (RDA) of dietary fiber for men aged 19-50?
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What adverse effect is unlikely to occur at a dosage of 500 mg/kg/day?
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How many disorders are typically screened for in newborn screening?
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In the context of diet and cardiovascular disease (CVD), what should be increased to decrease risk?
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Which of the following best describes Marasmus?
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What is a characteristic symptom of Kwashiorkor?
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Which formula is used to calculate the resting energy estimate (REE) for males?
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What is the kilocalorie value of fat per gram?
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What is the recommended duration of moderate-intensity cardiorespiratory exercise per week for adults?
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Which protein intake is considered the RDA for adults?
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What recommendation is given for resistance training frequency for adults?
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What is the recommended stretching frequency to improve range of motion (ROM) for adults?
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At what point in the body is glycogenesis inhibited?
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What is the protein intake range recommended for athletes?
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What does neuromotor training aim to improve in adults?
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Which is NOT a primary reason to avoid excessive protein intake?
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What is the primary treatment for Phenylketonuria (PKU)?
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Which condition is characterized by high levels of homogentistic acid leading to black urine?
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What common symptom is associated with Methymalonic acidemia?
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For which condition is leucine considered neurotoxic at high levels?
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What is a characteristic symptom of Propionic acidemia?
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What dietary restriction is recommended for individuals with Homocystinuria?
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Which of these conditions is associated with respiratory problems due to biochemical accumulation?
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Tyrosinemia type II is characterized by which of the following symptoms?
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What role does thiamine play in the context of Maple Syrup Urine Disease?
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What complication can arise from urea cycle disorders due to protein metabolism defects?
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What is the primary consequence of untreated phenylketonuria?
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What is the recommended daily intake of methionine for adults?
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What factors can lead to the depletion of essential amino acids?
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Which of the following is a correct statement about PDCAAS?
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What is the upper limit of branched-chain amino acids (BCAA) dosage in divided doses?
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Which amino acid is primarily involved in carnitine and SAM synthesis?
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What is the minimum protein requirement for adults expressed in grams per kilogram of body weight?
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What is the effect of aspartame on individuals with phenylketonuria?
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What role do branched-chain amino acids (BCAAs) play in metabolism?
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What is the impact of supplementing with B6, B9, and B12 on homocysteine levels?
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Study Notes
Energy in Nutrition
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Calculating Energy Requirements:
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Mifflin-St. Jeor Equation: requires weight, height, and age to determine resting energy expenditure (REE).
- Male Equation: REE = 10 * weight + 6.25 * height - 5 * age + 5
- Female Equation: REE = 10 * weight + 6.25 * height - 5 * age - 161
- Total Energy Estimate: Multiply REE by an activity factor to estimate total energy needs.
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Mifflin-St. Jeor Equation: requires weight, height, and age to determine resting energy expenditure (REE).
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Calculating Calories from Macronutrients:
- Fat: 9 kcal/g
- Carbohydrate: 4 kcal/g
- Protein: 4 kcal/g
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Physical Activity Recommendations:
- Cardiorespiratory Activity: Adults should engage in at least 150 minutes of moderate-intensity activity or 30-60 minutes of moderate-intensity activity 5 times per week.
- Resistance Training: Adults should train major muscle groups 2-3 times a week with a variety of movements.
- Flexibility: Adults should engage in flexibility exercises 2-3 days per week.
- Neuromotor Exercise: Adults should engage in neuromotor exercises 2-3 times per week to improve motor skills, proprioception, and physical function.
Protein and Amino acids
- Milk Alternatives in Infants: Commercially available formulas should be used as a primary milk alternative. Goat’s milk is not recommended.
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Protein RDA (Adult): 0. 8g/kg/day.
- Athletes may require 1.2-1.8 g/kg/day.
- No official upper limit for protein, but overconsumption is not recommended.
- World Health Organization (WHO) recommends limiting intake to 1.5 g/kg/day
- Maximizing protein synthesis may require around 100-125 g/day.
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Glycogenesis: Glucose breakdown to form 2 pyruvate.
- Inhibited by ATP.
- 3 irreversible enzymatic reactions: - Hexokinase - Phosphofructokinase (PFK) - Pyruvate kinase
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Glycogenolysis: Glycogen breakdown to glucose for energy.
- Occurs primarily in liver (to increase blood glucose) and muscle (for muscle cell energy).
- Caffeine can inhibit glycogenolysis.
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Gluconeogenesis: Glucose converted to glycogen (storage)
- Occurs primarily in the liver and skeletal muscle.
- Inhibited by AMP.
- First step: Glucose to Glucose-6-Phosphate (G-6-P)
- Hexokinase in muscle
- Glucokinase (inducible by insulin) in liver
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Protein and Athletes:
- Athletes may require 1.2-1.8 g/kg/day of protein.
- Some athletes consume up to 3 g/kg + 1 g/kg in supplemental protein
- WHO indicates little effectiveness with muscle gain and performance.
- May lead to increased nitrogen retention (possible indicator of protein status)
- Strength/power and bodybuilders are at higher risk for excess protein consumption.
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Bone: Protein is acidic.
- Fruits and vegetables are important for supplying bicarbonate as a buffer.
- High protein intake can increase calcium excretion, which is necessary to buffer acidic blood.
- Research on protein's effects on bone is mixed. An increase in protein intake may result in catabolic or anabolic effects, with anabolic effects being more common in older adults (particularly women).
- Increased protein intake can increase serum IGF-1 levels.
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Satiety:
- Protein stimulates the nucleus tractus solitarius and arcuate nucleus in the brain through signaling molecules:
- Cholecystokinin (CCK)
- Peptide YY
- Glucagon-like peptide-1 (GLP-1)
- Protein has strong effects on the brain's reward systems, leading to decreased food cravings.
- Lower levels of activity in limbic regions associated with food motivation are often seen after high-protein breakfast consumption.
- Protein stimulates the nucleus tractus solitarius and arcuate nucleus in the brain through signaling molecules:
Nitrogen Compounds
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Carnitine: Transports fatty acids across the mitochondria membrane.
- Recommended dose: 1-2 g/day for adults.
- Adverse effects: Diarrhea (especially with ketogenic diets due to high fat content).
- Conditions:
- Heart disease (carnitine can improve energy availability to heart cells).
- Carnitine deficiency can lead to impaired metabolism.
- Good sources of carnitine include meats like beef and pork.
- Carnitine absorption saturates around 2g.
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Tryptophan: Precursor to niacin (B3), serotonin, melatonin, and picolinic acid.
- Recommended dose: 1-2 g, 30 minutes before bedtime.
- Adverse effects: Drowsiness, nausea, diarrhea, nystagmus, euphoria, hyperactivity.
- Conditions:
- May be helpful for insomnia (1-2 days at bedtime), as it can increase serotonin and melatonin production.
- Low levels of tryptophan may be caused by conditions such as Crohn's disease, alcohol abuse, lactose intolerance, or fructose intolerance.
- May be helpful for migraines.
- Contraindicated in pregnancy and with antidepressants.
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Glutamine: Alanyl-glutamine is a more stable, better absorbed form of glutamine.
- Conditionally essential amino acid. - Fuel source for small intestine - Increases immune function - Synthesized and stored in skeletal muscle
- Recommended dose: 1-30 g/day.
- Adverse effects: High BUN (blood urea nitrogen) levels with doses above 30 g/day.
- Conditions:
- May help with acute pancreatitis.
- May help with peptic ulcers (0.5 - 1g 2-3 times/day).
- May be beneficial in chemotherapy (24-20 g/day).
- Glutamine depletion can result from physical stress and lower muscle mass.
- Contraindicated conditions: Liver failure and Crohn’s disease
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Methionine: Essential, toxic amino acid.
- Necessary for carnitine and S-adenosyl methionine (SAM) synthesis.
- Recommended dose: 1-6 g/day.
- Adverse effects: High doses (>8g/day), especially on an empty stomach, can potentially increase homocysteine levels.
- Conditions:
- May increase homocysteine levels, which can be linked to an increased risk of heart disease, but some conditions, such as Parkinson's disease, may improve by supplementing with B6, B9, and B12.
- Can lead to pancreatitis (often in combination with selenium, vitamin E, C, beta-carotene).
- Can help with urinary tract infections (UTI) by acidifying the urine.
- Can lead to diaper rash.
- Conditions where methionine restriction is indicated include
- Pancreatitis
- UTI
- Diaper rash
- Parkinson's disease
Miscellaneous
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Phenylketonuria (PKU): A genetic disorder that affects the body's ability to break down phenylalanine, an amino acid.
- Occurs due to a deficiency in the enzyme phenylalanine hydroxylase (PAH).
- Autosomal recessive inheritance pattern (1 in 10,000 births in the US).
- If untreated, PKU can lead to serious neurological problems.
- Treatment: Low-protein diet with phenylalanine-free protein supplements.
- Aspartame (artificial sweetener) contains phenylalanine.
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Protein Digestion & Metabolism:
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Protein Digestibility Corrected Amino Acid Score (PDCAAS):
- Measures the protein quality of a food source by comparing the limiting amino acid in a test protein to a reference protein (egg or milk).
- True digestibility of a protein is determined by testing fecal nitrogen.
- A 100% PDCAAS score indicates complete protein, while a lower score means the protein is less digestible.
- PDCAAS Calculation: PDCAAS (%) = (Amount (mg) of Limiting AA in 1g Test Protein) / (Amount (mg) of Same AA in 1g Reference Protein) * True Digestibility
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PDCAAS Scores:
- 100%: Milk protein, egg white, ground beef, tuna, some other natural animal products
- 94%: Soy
- Reference protein:
- Infant: Human milk
- Other: Use specific chart
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Protein Digestibility Corrected Amino Acid Score (PDCAAS):
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Protein Requirements:
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Adults:
- Minimum: 0.8 g/kg/day
- AMDR: 10-35% of total energy intake.
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Children:
- Preterm: 3.5-5 g/kg/day
- 0-12 months: 1.5 g/kg/day
- 1-3 years: 1.1 g/kg/day
- 4-13 years: 0.95 g/kg/day
- 14-18 years: 0.85 g/kg/day
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Adults:
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Branched Chain Amino Acids (BCAA): Consists of leucine, isoleucine, and valine.
- Essential amino acids that are thought to support muscle protein synthesis.
- Metabolized primarily in skeletal muscle.
- Leucine oxidation produces more ATP than glucose oxidation, making it a more efficient fuel during fasting.
- Recommended dose: Up to 20 g/day in divided doses
- Upper limit: Up to 500 mg/kg/day in healthy men.
- Adverse effects: Unlikely, but may be related to some conditions, such as diabetes and heart disease
- Conditions:
- Liver failure
- BCAAs may help reduce post-exercise muscle soreness, but evidence for improved performance is limited.
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Newborn Screening: Involves testing for 31 disorders, including 6 amino acid disorders, 5 fatty acid disorders, and other conditions with nutritional components.
- Blood spot screening is performed:
- First screening: 24-36 hours after birth.
- Second screening: 5-10 days old.
- Third screening: In case of false-positive results.
- Blood spot screening is performed:
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Marasmus vs. Kwashiorkor:
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Marasmus: Severe wasting due to prolonged undernourishment.
- Symptoms: Underweight, inadequate muscle and body fat, low bone density, drooping skin.
- Treatment: Complete nutrition with adequate macros.
- Kwashiorkor: Edematous wasting due to low protein intake. - Symptoms: Edema in lower limbs, face, and belly (due to low protein in the blood, leading to fluid shifting from vessels into the interstitial space); inadequate protein in the blood. - Treatment: Dietary focus on increasing protein intake.
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Marasmus: Severe wasting due to prolonged undernourishment.
Carbohydrates
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Glycemic Index (GI):
- Measures how quickly a food increases blood glucose levels after consumption.
- GI is calculated by comparing the blood glucose response to a given amount of carbohydrate in a test food to that of a reference food (usually white bread).
- Values:
- High GI: >70
- Moderate GI: 56-69
- Low GI: <= 55
- Factors influencing GI:
- Temperature of food
- Cooking method
- Processing
- Ripeness
- Variety (fruits and vegetables)
- Location of growth
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Description
Test your knowledge on calculating energy requirements in nutrition using the Mifflin-St. Jeor Equation. This quiz covers calorie calculations from macronutrients and physical activity recommendations for adults. Improve your understanding of how to estimate total energy needs effectively.