Title: Nutrition And Diet — LearnCoachAssist

Q: What is nutrition?
A: Nutrition is the science that studies how food affects the body, including the processes of ingestion, digestion, absorption, and utilization of nutrients for growth, maintenance, and repair.
It involves macronutrients, micronutrients, and water to support health.

Q: What are macronutrients?
A: Macronutrients are nutrients required in large amounts, including carbohydrates, proteins, and fats, which provide energy and building blocks for the body.
They are measured in grams and supply calories: 4 kcal/g for carbs and proteins, 9 kcal/g for fats.

Q: What are the primary functions of carbohydrates?
A: Carbohydrates are the body's main energy source, providing 4 kcal per gram, and are essential for brain function and physical activity.
They are broken down into glucose for immediate use or stored as glycogen in the liver and muscles.

Q: What are proteins composed of?
A: Proteins are made of amino acids, of which there are 20 types, including 9 essential ones that must come from diet.
They build and repair tissues, produce enzymes and hormones, and provide 4 kcal per gram.

Q: What are the types of dietary fats?
A: Dietary fats include saturated, unsaturated (monounsaturated and polyunsaturated), and trans fats.
Unsaturated fats, like those in olive oil and fish, support heart health, while saturated and trans fats should be limited.

Q: What are micronutrients?
A: Micronutrients are vitamins and minerals needed in small amounts for metabolic processes, immune function, and bone health.
They do not provide calories but prevent deficiencies like scurvy or rickets.

Q: What is the role of water in nutrition?
A: Water is essential for digestion, nutrient transport, temperature regulation, and waste elimination, comprising 60% of body weight.
Daily needs vary but average 2-3 liters from fluids and food.

Q: What is a calorie?
A: A calorie is a unit of energy, specifically the amount needed to raise 1 gram of water by 1°C; dietary Calories (kcal) measure food energy.
Daily intake depends on age, sex, activity, averaging 2000-2500 kcal for adults.

Q: What are the main food groups in a balanced diet?
A: The main food groups are fruits, vegetables, grains, proteins, and dairy, as per MyPlate guidelines.
Half the plate should be fruits and vegetables, with whole grains and lean proteins filling the rest.

Q: What does RDA stand for and what is its purpose?
A: RDA (Recommended Dietary Allowance) is the average daily nutrient intake level sufficient for 97-98% of healthy individuals.
It guides dietary planning to prevent deficiencies.

Q: What is BMI and how is it calculated?
A: BMI (Body Mass Index) estimates body fat using weight in kg divided by height in meters squared (kg/m²).
Categories: under 18.5 (underweight), 18.5-24.9 (normal), 25-29.9 (overweight), 30+ (obese).

Q: What is dietary fiber and why is it important?
A: Dietary fiber is indigestible plant material that promotes digestive health, lowers cholesterol, and stabilizes blood sugar.
Aim for 25-38g daily from fruits, vegetables, and whole grains.

Q: What are simple vs. complex carbohydrates?
A: Simple carbs (sugars) digest quickly for fast energy; complex carbs (starches) digest slowly, providing sustained energy.
Prefer complex like whole grains over simple like candy to avoid blood sugar spikes.

Q: What distinguishes complete from incomplete proteins?
A: Complete proteins contain all 9 essential amino acids (e.g., meat, eggs); incomplete lack some (e.g., grains, legumes).
Combine incomplete sources like beans and rice for completeness.

Q: What are essential fatty acids?
A: Essential fatty acids like omega-3 (ALA, EPA, DHA) and omega-6 (linoleic acid) cannot be synthesized by the body and must be obtained from diet.
They support brain health, inflammation control, and cell membranes.

Q: What is the function of vitamins?
A: Vitamins are organic compounds that regulate metabolism, support immunity, and act as antioxidants.
They are fat-soluble (A, D, E, K) stored in fat or water-soluble (B, C) excreted in urine.

Q: Name key minerals and their roles.
A: Key minerals include calcium for bones, iron for oxygen transport, potassium for nerve function, and magnesium for muscle relaxation.
Deficiencies lead to issues like osteoporosis or anemia.

Q: What is a balanced diet?
A: A balanced diet provides adequate nutrients in proper proportions from all food groups to meet energy and health needs.
It emphasizes variety, moderation, and whole foods over processed ones.

Q: What is the glycemic index?
A: Glycemic index (GI) measures how quickly foods raise blood sugar; low GI (≤55) like oats is preferable for steady energy.
High GI foods like white bread cause spikes and crashes.

Q: Why is vitamin C important?
A: Vitamin C is an antioxidant that supports immune function, collagen synthesis for skin and wounds, and iron absorption.
Sources: citrus fruits, peppers; deficiency causes scurvy.

Q: What is vitamin D's primary source and function?
A: Vitamin D is synthesized via sunlight or from fortified foods/fish, aiding calcium absorption for bone health.
Deficiency leads to rickets in children or osteomalacia in adults.

Q: What role does iron play in the body?
A: Iron forms hemoglobin to transport oxygen in blood and myoglobin in muscles.
Heme iron from meat absorbs better; deficiency causes anemia, fatigue.

Q: Why is calcium crucial for health?
A: Calcium builds and maintains bones/teeth, supports muscle contraction, nerve signaling, and blood clotting.
Dairy, greens; pair with vitamin D for absorption.

Q: What are omega-3 fatty acids?
A: Omega-3s (EPA, DHA from fish; ALA from plants) reduce inflammation, support heart/brain health.
Aim for 250-500mg EPA/DHA daily.

Q: What are antioxidants?
A: Antioxidants like vitamins C/E, beta-carotene neutralize free radicals, preventing cell damage and chronic diseases.
Found in berries, nuts, vegetables.

Q: What are probiotics?
A: Probiotics are live beneficial bacteria (e.g., Lactobacillus) in yogurt that support gut microbiome, digestion, and immunity.
Prebiotics (fiber) feed them.

Q: What causes malnutrition?
A: Malnutrition results from undernutrition (deficiencies), overnutrition (excess calories), or imbalances.
Leads to stunting, obesity, or diseases like kwashiorkor.

Q: What is the Mediterranean diet?
A: The Mediterranean diet emphasizes fruits, vegetables, whole grains, fish, olive oil, nuts, limiting red meat/sweets.
Linked to lower heart disease, longevity.

Q: Describe a vegan diet.
A: A vegan diet excludes all animal products, relying on plants for protein, calcium, B12 (supplement needed).
Benefits: heart health; risks: deficiencies if unplanned.

Q: What is intermittent fasting?
A: Intermittent fasting cycles eating/fasting (e.g., 16:8 method), promoting weight loss, insulin sensitivity.
Not for everyone; consult doctor.

Q: How does diet affect obesity?
A: Obesity arises from chronic calorie surplus, high sugar/processed foods promoting fat storage.
Balanced deficit via whole foods aids weight management.

Q: What dietary changes help diabetes?
A: For diabetes, focus on low-GI carbs, fiber, lean proteins, healthy fats to stabilize blood sugar.
Limit refined sugars, monitor portions.

Q: What diet supports heart health?
A: Heart-healthy diets like DASH reduce sodium, boost potassium-rich fruits/veggies, whole grains, limit saturated fats.
Lowers blood pressure, cholesterol.

Q: What is basal metabolic rate (BMR)?
A: BMR is calories burned at rest for vital functions; calculated via Harris-Benedict equation factoring age, sex, weight, height.
60-75% of daily expenditure.

Q: What is diet-induced thermogenesis?
A: Diet-induced thermogenesis (DIT) is energy used to digest/process food, 10% of expenditure, higher for proteins.
Contributes to total energy balance.

Q: What is nutrient timing?
A: Nutrient timing optimizes intake around exercise (e.g., carbs/protein post-workout) for recovery, performance.
Carbs pre-workout fuel energy.

Q: What are symptoms of vitamin B12 deficiency?
A: Vitamin B12 deficiency causes fatigue, anemia, neurological issues like numbness, memory loss.
Common in vegans, elderly; sources: meat, fortified foods.

Q: How do you read a nutrition label?
A: Check serving size, calories, % Daily Value for nutrients; limit sodium/sugars under 5% DV, choose high fiber/protein over 20%.
Ingredients list first by weight.

Q: What is ketosis?
A: Ketosis occurs in low-carb states (keto diet) where body burns fat for ketones as fuel instead of glucose.
Used for weight loss, epilepsy.

Q: What is the gut microbiome?
A: Gut microbiome is trillions of microbes influencing digestion, immunity, mood via fiber-rich diet.
Dysbiosis links to obesity, IBS.

Q: What are sports nutrition basics?
A: Athletes need higher carbs for energy (6-10g/kg), proteins (1.2-2g/kg) for repair, hydration.
Timing: fuel pre-event, recover post.

Q: What is orthorexia?
A: Orthorexia is obsession with 'healthy' eating, leading to restrictive behaviors harming social/nutritional health.
Differ from balanced mindful eating.

Q: Describe personalized nutrition.
A: Personalized nutrition tailors diet to genetics, microbiome, lifestyle via tests for optimal macros, allergens.
Emerging field for precision health.

Q: What role does diet play in inflammation?
A: Anti-inflammatory diets rich in omega-3s, antioxidants (berries, turmeric) reduce chronic inflammation; pro-inflammatory: sugars, trans fats.
Links to arthritis, cancer.

Q: What is the alkaline diet myth?
A: Alkaline diet claims food pH alters blood (fixed at 7.4); no evidence for disease prevention.
Focus on whole foods instead.

Q: Explain food synergies.
A: Nutrient synergies like vitamin C boosting iron absorption or fat aiding vitamins A/D/E/K.
Whole foods provide better combos than isolates.

Q: What is metabolic syndrome?
A: Metabolic syndrome clusters high blood pressure, sugar, waist circumference, triglycerides, low HDL.
Diet: Mediterranean lowers risk.

Q: Describe epigenetics and diet.
A: Diet influences epigenetics (gene expression changes), e.g., folate for DNA methylation, preventing cancers.
Not altering DNA sequence.

Q: What are ultra-processed foods?
A: Ultra-processed foods (sodas, chips) high in sugar/fat/salt, additives; linked to obesity, disease.
Limit to <20% intake.

Q: How does sleep affect nutrition needs?
A: Poor sleep disrupts hunger hormones (ghrelin up, leptin down), increasing appetite for junk food.
Aim 7-9 hours for metabolic health.

Q: How does soluble fiber differ from insoluble fiber in mechanism?
A: Soluble fiber dissolves in water to form a gel that slows gastric emptying, binds bile acids, and lowers LDL cholesterol (e.g., oats, psyllium). Insoluble fiber adds bulk and accelerates transit time to prevent constipation (e.g., wheat bran, vegetables). Both are needed; aim for the 25-38 g/day total.

Q: What is the difference between RDA, AI, and UL for nutrients?
A: RDA (Recommended Dietary Allowance) meets needs of ~97-98% of a population; AI (Adequate Intake) is set when evidence is insufficient for an RDA; UL (Tolerable Upper Intake Level) is the maximum daily intake unlikely to cause adverse effects. Exceeding UL risks toxicity for fat-soluble vitamins and minerals like iron.

Q: Why can excess water intake be dangerous?
A: Excessive water in a short period dilutes blood sodium, causing hyponatremia. Symptoms include headache, nausea, seizures, and in severe cases cerebral edema or death. Endurance athletes and extreme water-loading protocols are most at risk; kidneys can only process ~0.8-1.0 L/hour.

Q: What is the difference between heme and non-heme iron absorption?
A: Heme iron (from animal sources like red meat, shellfish) absorbs at 15-35% and is enhanced by meat/factor (MFP). Non-heme iron (from plants, legumes) absorbs at 2-20% and is enhanced by vitamin C but inhibited by phytates, polyphenols, calcium, and tannins in tea/coffee.

Q: Which vitamins are fat-soluble and what risks arise from excess?
A: Fat-soluble vitamins are A, D, E, and K; excess is stored in adipose and liver, raising toxicity risk. Hypervitaminosis A causes liver damage and birth defects; excess D causes hypercalcemia and kidney stones. They require dietary fat for absorption and are not excreted in urine like B and C.

Q: What is the role of the glycemic load (GL) versus glycemic index (GI)?
A: GL = (GI × grams of carbohydrate) / 100 and reflects the actual blood sugar impact of a realistic portion. GI ranks quality of carbs alone; GL multiplies by quantity. A watermelon has high GI (~72) but low GL (~5) per typical serving, while a bagel has high GI and high GL.

Q: How does protein quality get measured by PDCAAS and DIAAS?
A: PDCAAS (Protein Digestibility-Corrected Amino Acid Score) rates protein from 0-1 based on human amino acid needs and digestibility, capped at 1.0. DIAAS (Digestible Indispensable Amino Acid Score) measures digestibility at the ileum and can exceed 1.0, providing a more accurate modern standard for evaluating proteins like whey or pea.

Q: What is the thermic effect of food highest for, and why?
A: Protein has the highest thermic effect at 20-30% of its calories, followed by carbs (5-10%) and fats (0-3%). Digesting protein requires more ATP for deamination, urea synthesis, and gluconeogenesis, which is why high-protein diets modestly raise total daily energy expenditure.

Q: How does chronic high sugar intake lead to insulin resistance?
A: Repeated glucose spikes cause sustained hyperinsulinemia; cells downregulate GLUT4 receptors and receptors become desensitized. Pancreatic beta cells compensate until exhausted, progressing to type 2 diabetes. Visceral adiposity worsens resistance via free fatty acids and inflammatory adipokines.

Q: What distinguishes type 1 from type 2 diabetes nutritionally?
A: Type 1 is autoimmune beta-cell destruction requiring insulin therapy; nutrition focuses on carb counting and timing. Type 2 involves insulin resistance and is heavily managed by weight loss, low-GI diets, and reduced refined carbohydrates; both benefit from fiber and balanced macros.

Q: What are the dietary sources and functions of vitamin K2?
A: Vitamin K2 (menaquinone) is found in natto, fermented cheeses, egg yolks, and butter from grass-fed cows. It activates osteocalcin to direct calcium into bone and matrix Gla-protein to keep it out of arteries, supporting cardiovascular and skeletal health beyond K1's clotting role.

Q: Why is folate critical in early pregnancy?
A: Folate is required for DNA synthesis, methylation, and neural tube closure between days 21-28 of gestation, often before pregnancy is detected. Deficiency causes spina bifida and anencephaly. RDA jumps to 600 µg/day in pregnancy; synthetic folic acid is more bioavailable than food folate.

Q: What is the difference between omega-3 ALA, EPA, and DHA?
A: ALA (alpha-linolenic acid, plant-based) must be converted to EPA then DHA, but conversion is <10% efficient in humans. EPA supports anti-inflammatory eicosanoids and mood; DHA is structural in retinal and neuronal membranes. Direct sources: fatty fish, algae oil, krill.

Q: How does sodium restriction affect blood pressure?
A: Sodium drives extracellular fluid volume; excess raises blood pressure especially in salt-sensitive individuals. The DASH diet with <2300 mg sodium/day reduces systolic BP by 5-6 mmHg; the stricter 1500 mg target adds another ~2-3 mmHg reduction, comparable to one antihypertensive medication.

Q: What are FODMAPs and why are they restricted in IBS?
A: FODMAPs (Fermentable Oligo-, Di-, Mono-saccharides And Polyols) are short-chain carbs poorly absorbed in the small intestine, drawing water and being fermented by colonic bacteria to cause gas. A low-FODMAP diet reduces bloating, pain, and altered motility in 70% of IBS patients.

Q: What is the difference between LDL-C, LDL-P, and apoB?
A: LDL-C measures cholesterol mass inside LDL particles; LDL-P counts the number of particles; apoB counts all atherogenic particles (LDL, VLDL, Lp(a)). Small dense LDL particles (Pattern B) are more atherogenic per unit cholesterol, so apoB and LDL-P predict risk better than LDL-C alone.

Q: What is the carnivore diet and what are its nutritional gaps?
A: The carnivore diet consists only of animal products (meat, fish, eggs, dairy) and excludes all plants. While eliminating refined carbs and plant toxins, it lacks fiber, vitamin C, vitamin K1, magnesium, and phytochemicals; long-term risks include gout, dyslipidemia, and gut dysbiosis are hypothesized.

Q: How does caffeine affect hydration and exercise performance?
A: Moderate caffeine (3-6 mg/kg) is ergogenic, increasing adrenaline, fat oxidation, and alertness without significant diuresis at habitual intakes. Acute high doses can dehydrate and cause jitters; the EFSA safe adult intake is up to 400 mg/day (excluding pregnant women, who should limit to 200 mg).

Q: What are the stages of the Dukan diet?
A: The Dukan diet has four phases: Attack (pure protein, 1-7 days), Cruise (alternates protein with non-starchy veggies), Consolidation (reintroduces carbs/fats with one celebration meal/week), and Stabilization (maintenance with one protein-only day/week). It is high-protein, low-fat, very low-carb.

Q: What is the difference between HDL and LDL cholesterol?
A: LDL (low-density lipoprotein) transports cholesterol from liver to tissues; high levels promote arterial plaque. HDL (high-density lipoprotein) does reverse cholesterol transport from tissues back to liver for excretion. Target LDL-C typically <100 mg/dL; HDL-C should be >40 mg/dL in men, >50 mg/dL in women.

Q: How does the body regulate iron absorption?
A: When body stores are low, enterocytes upregulate ferroportin and the liver releases hepcidin suppression, increasing duodenal absorption. Hepcidin rises with iron repletion and inflammation, sequestering iron in macrophages and reducing dietary absorption to prevent overload.

Q: What are polyphenols and what is their bioavailability?
A: Polyphenols are plant compounds (flavonoids, resveratrol, catechins) with antioxidant and signaling effects. Bioavailability is often <10%, but gut microbes metabolize them into active metabolites. Best sources: berries, cocoa, green tea, olive oil, coffee; benefits include reduced CVD and cognitive decline risk.

Q: What is the difference between satiety and satiation?
A: Satiation is the process that stops eating during a meal, driven by gastric distension and gut hormones (CCK, GLP-1). Satiety is the suppression of hunger between meals. High-volume, high-protein, high-fiber foods increase both; energy-dense, hyperpalatable foods undermine satiation.

Q: Why is breakfast inclusion still debated in nutrition science?
A: Some observational studies link breakfast eating to lower BMI, but randomized trials show no consistent weight-loss advantage. Breakfast skippers may compensate later; individual responses vary by chronotype and circadian rhythm. Quality matters more than timing — sugary cereal is worse than skipping breakfast.

Q: What is the MIND diet and what evidence supports it?
A: The MIND diet (Mediterranean-DASH Intervention for Neurodegenerative Delay) combines Mediterranean and DASH with specific brain-healthy foods (leafy greens, berries, nuts, fish). Cohort studies show 53% reduced Alzheimer risk with strict adherence, but RCT evidence for cognitive decline prevention remains limited.

Q: How does meal frequency affect metabolism?
A: Metabolic rate is determined by total intake and composition, not meal frequency per se. Spreading protein across 3-4 feedings optimizes muscle protein synthesis vs. a single bolus. Frequent small meals do not inherently "stoke the metabolism" beyond the thermic effect of the same total calories.

Q: What is the role of leucine in muscle protein synthesis?
A: Leucine is the key anabolic signal that activates mTORC1, triggering translation initiation and muscle protein synthesis. A dose of ~2.5-3 g leucine per meal maximizes MPS; older adults are less sensitive, requiring higher per-meal protein (30-40 g) to overcome anabolic resistance.

Q: What is the difference between hunger and appetite?
A: Hunger is the physiological need for food driven by glucose, ghrelin, and gastric signals. Appetite is the psychological desire to eat, influenced by sight, smell, memory, stress, and social context. Mindful eating addresses appetite; balanced macros and meal timing address hunger.

Q: How do polyphenols in coffee affect health?
A: Coffee polyphenols (chlorogenic acids) improve insulin sensitivity, hepatic glucose metabolism, and provide antioxidant effects. Habitual coffee intake (3-5 cups/day) is linked to lower risk of type 2 diabetes, Parkinson's, and liver disease. Decaf retains most polyphenols; unfiltered coffee raises LDL via cafestol.

Q: What is the difference between fasting glucose and HbA1c?
A: Fasting glucose is a point-in-time blood sugar measurement; HbA1c reflects average glycemia over ~3 months by quantifying hemoglobin glycation. HbA1c ≥6.5% diagnoses diabetes; prediabetes is 5.7-6.4%. HbA1c can be falsely low in anemia or high in iron deficiency.

Q: What are the risks and benefits of the paleo diet?
A: Paleo excludes grains, legumes, dairy, refined sugar, and processed foods, emphasizing meat, fish, vegetables, fruits, nuts, and seeds. Benefits: higher fiber, lower sodium, weight loss. Risks: calcium and vitamin D shortfalls, expense, exclusion of legumes (a top fiber source) without clear evolutionary justification.

Q: How do dietary cholesterol and blood cholesterol relate?
A: Hepatic synthesis downregulates when dietary cholesterol rises, so for most people blood cholesterol is only modestly affected by dietary cholesterol. However, ~25% are "hyper-responders" whose LDL rises more sharply. The 2020-2025 DGA still suggests keeping intake low for those at risk.

Q: What is resistant starch and how does it benefit gut health?
A: Resistant starch escapes digestion in the small intestine and reaches the colon, where bacteria ferment it into short-chain fatty acids (especially butyrate). Butyrate fuels colonocytes, lowers inflammation, and improves insulin sensitivity. Sources: cooled cooked potatoes, green bananas, legumes, whole grains.

Q: What is the BRAT diet and when is it appropriate?
A: The BRAT diet (Bananas, Rice, Applesauce, Toast) is a short-term bland regimen historically used for acute diarrhea or gastroenteritis. It is low in protein, fat, and certain micronutrients and is not recommended beyond 24-48 hours; oral rehydration solution is now the primary intervention.

Q: How does chronic alcohol consumption affect nutrition?
A: Alcohol provides 7 kcal/g of empty calories, displaces nutrient-dense foods, and impairs absorption of thiamine, folate, B12, and zinc. Liver damage reduces vitamin A storage and impairs gluconeogenesis. Heavy drinking causes Wernicke-Korsakoff syndrome and alcoholic liver disease independent of diet quality.

Q: What are electrolytes and what foods supply them?
A: Electrolytes (sodium, potassium, chloride, magnesium, calcium, phosphate) carry charges for nerve impulses, muscle contraction, and fluid balance. Sodium: salt, processed foods. Potassium: bananas, potatoes, beans. Magnesium: nuts, dark chocolate, leafy greens. Imbalances cause cramps, arrhythmias, fatigue.

Q: How does glycemic control affect athletic performance?
A: Stable blood glucose spares muscle glycogen and delays fatigue; high-GI pre-race meals risk reactive hypoglycemia mid-event. Endurance athletes benefit from carb loading (8-12 g/kg/day for 2-3 days pre-event) and 30-60 g/hr during exercise >90 minutes.

Q: What is sarcopenic obesity and how is it addressed?
A: Sarcopenic obesity is low muscle mass combined with high adiposity, common in older adults and driven by inflammation, inactivity, and anabolic resistance. Treatment combines resistance training (primary) with adequate protein (1.2-1.5 g/kg/day), vitamin D, and modest calorie deficit to preserve lean mass.

Q: What are the dietary guidelines for hypertension (DASH specifics)?
A: DASH emphasizes fruits (4-5 servings), vegetables (4-5), whole grains (6-8), low-fat dairy (2-3), and lean protein; limits red meat, sweets, and sodium. The diet provides ~4700 mg potassium, 1200 mg calcium, 500 mg magnesium daily, lowering systolic BP by 8-14 mmHg in hypertensives.

Q: What is the role of selenium and what are its food sources?
A: Selenium is a trace mineral incorporated into selenoproteins, including glutathione peroxidase, which protects against oxidative damage. Brazil nuts are the richest source (1 nut ≈ 68 µg); other sources include tuna, eggs, sunflower seeds. UL is 400 µg/day; deficiency is linked to Keshan disease.

Q: What is the difference between food allergy and food intolerance?
A: Food allergy is an IgE-mediated immune reaction (e.g., peanuts, shellfish) potentially causing anaphylaxis, even from trace amounts. Food intolerance is non-immune (e.g., lactose intolerance from lactase deficiency) causing digestive symptoms proportional to dose. Skin-prick and IgE tests distinguish the two.

Q: What is the function of iodine and what happens in deficiency?
A: Iodine is required for thyroid hormone synthesis (T3/T4); deficiency causes hypothyroidism, goiter, cretinism in utero, and impaired neurodevelopment in children. Sources: iodized salt, seaweed, dairy, fish. Adults need 150 µg/day; pregnant women 220-250 µg/day to support fetal brain growth.

Q: What is the role of choline in the diet?
A: Choline is an essential nutrient for cell membranes (as phosphatidylcholine), acetylcholine (a neurotransmitter), and methylation via betaine. Eggs and liver are top sources; deficiency causes fatty liver and neural tube defects. AI is 425 mg/day for women, 550 mg/day for men.

Q: What are short-chain fatty acids and why are they important?
A: Short-chain fatty acids (SCFAs) — acetate, propionate, butyrate — are produced by colonic fermentation of fiber. Butyrate is the preferred fuel for colonocytes; propionate supports liver gluconeogenesis; acetate contributes to lipogenesis. SCFAs also bind GPR receptors to influence immunity and appetite.

Q: What is reverse dieting and who uses it?
A: Reverse dieting gradually increases caloric intake by ~50-100 kcal/week after prolonged restriction to restore metabolism without rapid fat regain. Used by physique competitors and chronic dieters. Risks: over-restriction may have already lowered metabolic rate; benefits over intuitive eating remain contested.

Q: What are whole foods vs. processed foods on the NOVA scale?
A: NOVA classifies foods into four groups: 1) unprocessed/minimally processed (apples, milk), 2) processed culinary ingredients (oil, salt), 3) processed foods (cheese, bread), 4) ultra-processed (sodas, instant noodles). Ultra-processed items comprise ~50% of calories in many Western diets and drive chronic disease risk.

Q: What are the dietary sources and importance of magnesium?
A: Magnesium is a cofactor in 300+ enzymatic reactions, including ATP use, DNA synthesis, and muscle/nerve function. Top sources: pumpkin seeds, spinach, almonds, black beans. Deficiency contributes to insomnia, cramps, hypertension, and type 2 diabetes; RDA is 310-420 mg/day depending on age/sex.

Q: What is the difference between soluble and insoluble fiber sources?
A: Soluble fiber sources: oats, barley, psyllium, beans, apples, citrus. Insoluble fiber sources: wheat bran, corn, nuts, vegetables, whole grains. Most plant foods contain both in varying ratios. Soluble fiber is fermented more by gut bacteria, producing more SCFAs.

Q: What is the function of vitamin A and what are its forms?
A: Vitamin A exists as retinol (animal sources: liver, eggs, dairy) and provitamin A carotenoids (plant sources: carrots, sweet potatoes, spinach). It supports vision (rhodopsin), immunity, and epithelial integrity. Excess preformed retinol is teratogenic; carotenoids are safer as conversion is regulated.

Q: What are net carbs and how are they calculated?
A: Net carbs = total carbohydrates − dietary fiber − (some formulas subtract sugar alcohols and allulose). The rationale is that fiber and certain sugar alcohols don't raise blood glucose meaningfully. Legally in the US, "net carbs" is not regulated, so values on labels can vary and may be misleading.

Q: How do legumes compare nutritionally to grains?
A: Legumes (beans, lentils, chickpeas) generally have 2-3× the protein of grains, much higher fiber, more folate and iron, and a lower glycemic index. They also contain phytates that reduce mineral absorption; soaking, sprouting, or fermenting mitigates this. Combining legumes with grains yields complete protein.

Q: What is the role of zinc in immunity and wound healing?
A: Zinc is essential for thymulin activity, neutrophil function, and T-cell maturation; deficiency impairs wound healing and increases infection risk. Top sources: oysters, beef, pumpkin seeds, lentils. Phytates bind zinc; supplementation (typically 15-30 mg/day) is used to treat acute diarrhea in children in low-resource settings.

Q: How does the body synthesize vitamin D?
A: UVB radiation converts 7-dehydrocholesterol in skin to cholecalciferol (D3), which is hydroxylated in the liver to 25(OH)D and again in the kidney to active 1,25(OH)₂D (calcitriol). Latitude, season, skin pigmentation, sunscreen (SPF ≥8 blocks UVB), and age all influence synthesis; many adults need supplementation.

Q: What is the difference between hunger hormones ghrelin and leptin?
A: Ghrelin is secreted by stomach cells when empty, signaling hunger to the hypothalamus and stimulating appetite. Leptin is secreted by adipocytes proportional to fat stores, signaling satiety and suppressing appetite. In obesity, leptin resistance develops — high leptin but blunted signaling — so the brain perceives starvation.

Q: What are the dietary recommendations for chronic kidney disease?
A: CKD diets restrict sodium (<2300 mg/day), potassium (often <2000-3000 mg/day in later stages), and phosphorus (especially additives like sodium phosphate). Protein is moderated to 0.6-0.8 g/kg/day in advanced CKD to reduce uremic load, with adequate calories to prevent catabolism.

Q: What is the difference between fructose and glucose metabolism?
A: Glucose raises insulin and is used by all tissues. Fructose is metabolized almost entirely in the liver, where it is converted to triglycerides via de novo lipogenesis, promoting hepatic steatosis and uric acid production. Fructose does not stimulate insulin or leptin, contributing to passive overconsumption.

Q: How does dietary fat affect satiety and total calorie intake?
A: Fat delays gastric emptying, providing sustained satiety, but is energy-dense at 9 kcal/g. High-fat palatable foods can override satiety signals (Hedonic pathway), driving passive overconsumption. Combining fat with protein and fiber produces the strongest satiety effect per calorie.

Q: What is the glymphatic system and how does diet influence it?
A: The glymphatic system clears brain metabolites (including β-amyloid) during sleep via perivascular flow. Chronic sleep disruption impairs clearance, raising neurodegeneration risk. Diets high in saturated fat and alcohol suppress glymphatic function; omega-3s and fasting-mimicking patterns may support it.

Q: What is the dietary management of celiac disease?
A: Celiac disease requires strict, lifelong avoidance of gluten (wheat, barley, rye, and contaminated oats). Healing requires months to years on a gluten-free diet; cross-contamination (shared toasters, fryers) is a frequent cause of persistent symptoms. Nutrient deficiencies (iron, calcium, B12, folate) should be screened.

Q: What is the difference between simple sugars: glucose, fructose, sucrose?
A: Glucose is a monosaccharide and the body's preferred energy. Fructose is a monosaccharide metabolized mainly in the liver. Sucrose is a disaccharide of glucose + fructose. High-fructose corn syrup is ~55% fructose / 45% glucose. Excess fructose is most associated with NAFLD and uric acid elevation.

Q: What is refeeding syndrome and who is at risk?
A: Refeeding syndrome occurs when severely malnourished patients are refed too quickly; insulin surges drive phosphate, potassium, and magnesium into cells, causing hypophosphatemia, cardiac failure, and rhabdomyolysis. Risk groups: anorexia, chronic alcoholism, post-bariatric, refugees. Prevention: start at 5-10 kcal/kg/day with thiamine and electrolyte monitoring.

Q: What is the role of biotin (vitamin B7) in metabolism?
A: Biotin is a coenzyme for carboxylases involved in fatty acid synthesis, gluconeogenesis, and amino acid catabolism. Deficiency (rare, but seen with raw-egg-white avidin consumption) causes dermatitis, alopecia, and neurological symptoms. Biotin can interfere with lab tests (troponin, thyroid) — an important clinical caveat.

Q: What is the dietary approach to PCOS?
A: PCOS management emphasizes a low-GI diet to improve insulin sensitivity, with adequate protein (≥20% of calories), high fiber, and anti-inflammatory fats (omega-3, olive oil). Modest weight loss (5-10%) restores ovulation. Myo-inositol supplementation (4 g/day) shows promise for improving insulin sensitivity and fertility.

Q: What are food intolerances to FODMAPs: specific examples?
A: Lactose (milk), fructose (apples, mango, high-fructose corn syrup), fructans (wheat, onion, garlic), GOS (legumes, cashews), polyols (sorbitol in stone fruits, xylitol in sugar-free gum). Symptoms are dose-dependent and overlap with IBS; a structured 6-week elimination followed by reintroduction identifies triggers.

Q: How does calcium interact with iron absorption?
A: Calcium (from supplements or dairy) inhibits both heme and non-heme iron absorption when consumed simultaneously (>300 mg dose). Spacing calcium and iron-rich meals by 2+ hours avoids this. Vitamin C counteracts calcium's effect; meat factor enhances non-heme iron independent of calcium.

Q: What is the role of nitrates in dietary performance?
A: Beetroot juice (high in dietary nitrate) is converted to nitric oxide, improving vasodilation, oxygen efficiency, and time-trial performance in endurance athletes. Effects peak 2-3 hours post-ingestion; chronic dosing (~5-7 mmol/day) sustains benefit. Mechanism is independent of stimulants.

Q: What is the difference between vegan, vegetarian, and pescatarian diets?
A: Vegan: excludes all animal products including dairy, eggs, honey. Vegetarian (lacto-ovo): excludes meat and fish but includes dairy/eggs. Pescatarian: excludes meat and poultry but includes fish and seafood. Plant-based diets lower CVD risk but require planning for B12, iron, omega-3, calcium, zinc.

Q: What is time-restricted eating and is it distinct from intermittent fasting?
A: Time-restricted eating (TRE) confines eating to a window (e.g., 8-10 hours/day) without calorie restriction. It overlaps with intermittent fasting (16:8, 18:6 protocols). Evidence supports modest weight loss and improved insulin sensitivity even without calorie deficit, possibly via circadian alignment; effects vary by individual chronotype.

Q: What are the dietary sources of vitamin E?
A: Vitamin E (tocopherols, especially alpha-tocopherol) is found in wheat germ oil, sunflower seeds, almonds, hazelnuts, spinach, and avocado. It is a lipid-soluble antioxidant protecting cell membranes from oxidation. RDA is 15 mg/day; high-dose supplements (>400 IU) have shown increased mortality risk in meta-analyses.

Q: What is the difference between HDL2 and HDL3?
A: HDL particles vary in size and function. HDL2 is larger, more buoyant, and more efficient at reverse cholesterol transport; HDL3 is smaller and denser. Higher HDL2 is associated with lower CVD risk; simply raising HDL-C with drugs has not consistently lowered events, suggesting HDL function matters more than quantity.

Q: What is the role of betaine in methylation?
A: Betaine (trimethylglycine) donates methyl groups in the remethylation of homocysteine to methionine, complementing folate and B12 pathways. Found in beets, spinach, quinoa, and whole grains. Adequate intake lowers homocysteine, which is a risk factor for CVD and cognitive decline.

Q: How does the body adapt to a ketogenic diet?
A: Within 3-7 days of carbs <50 g/day, glycogen stores deplete, insulin drops, and the liver converts fatty acids to ketones (β-hydroxybutyrate, acetoacetate). The brain shifts to ~70% ketone-derived energy. "Keto-adaptation" takes 2-6 weeks; electrolytes, hydration, and gradual carb reduction ease the "keto flu."

Q: What is the alkaline phosphatase connection to nutrition?
A: Alkaline phosphatase (ALP) is a zinc-dependent enzyme elevated in bone and liver disease. Low zinc, B6, magnesium, or protein status can depress ALP; conversely, low ALP is associated with zinc deficiency and hypothyroidism. ALP also helps cleave lipopolysaccharides in the gut, linking nutrition and immune tolerance.

Q: What are the recommendations for added sugar intake?
A: The WHO recommends limiting added sugars to <10% of total energy (ideally <5%) for adults. The AHA sets stricter targets: 25 g/day for women, 36 g/day for men, <25 g/day for children. Excess added sugar (especially in beverages) drives obesity, NAFLD, dental caries, and insulin resistance.

Q: How do probiotics and prebiotics work together?
A: Prebiotics (inulin, FOS, GOS, resistant starch) selectively feed beneficial bacteria; probiotics introduce live strains. Combined as "synbiotics," they improve colonization and SCFA production. Effects are strain-specific: Lactobacillus rhamnosus GG for antibiotic-associated diarrhea, Saccharomyces boulardii for traveler's diarrhea.

Q: What is the protein leverage hypothesis?
A: The protein leverage hypothesis proposes that humans prioritize a fixed absolute protein intake (~15-20% of energy) and overeat calories from carbs/fat when dietary protein is diluted by processed foods. This may explain rising obesity rates with ultra-processed, low-protein-dense diets.

Q: How does vitamin K1 differ from vitamin K2?
A: Vitamin K1 (phylloquinone) is found in leafy greens and primarily supports hepatic clotting factor synthesis. Vitamin K2 (menaquinone, MK-4 to MK-10) is produced by gut bacteria and fermented foods; it activates extrahepatic proteins for bone and vascular health. They share the same cofactor cycle but distinct tissue roles.

Q: What is the dietary management of gout?
A: Gout management reduces purine-rich foods (organ meats, shellfish, anchovies) and fructose, increases low-fat dairy and water, and limits alcohol (especially beer and spirits). Vitamin C supplementation (500 mg/day) modestly lowers urate. The DASH diet lowers gout incidence independent of weight change.

Q: What is the difference between simple and refined carbohydrates?
A: Simple carbohydrates refer to sugars (monosaccharides/disaccharides) by chemistry; refined carbohydrates refer to processing (e.g., white flour, white rice) which strips fiber and micronutrients. Both raise blood glucose quickly. Whole-food sources of simple sugars (fruit, milk) include fiber and nutrients that blunt glycemic impact.

Q: What are free sugars and why are they targeted by policy?
A: Free sugars are monosaccharides and disaccharides added to foods by the manufacturer, cook, or consumer, plus sugars naturally present in honey, syrups, fruit juices, and concentrates. Whole fruit sugars are excluded. UK policy (sugar tax) and WHO guidelines target free sugars because they drive energy overconsumption without satiety.

Q: What is the dietary management of GERD?
A: GERD management: avoid trigger foods (citrus, tomato, chocolate, mint, caffeine, alcohol, fatty/fried foods, carbonation), eat smaller meals, avoid lying down within 3 hours of eating, elevate the head of bed, and maintain healthy weight. There's limited RCT evidence; weight loss and elevation are the most consistently effective.

Q: What is the role of polyphenols in the gut-brain axis?
A: Polyphenols (berry anthocyanins, cocoa flavanols, tea catechins) modulate the gut microbiome, increasing Bifidobacteria and Lactobacillus. Their metabolites cross the blood-brain barrier and influence neuroinflammation, BDNF, and synaptic plasticity. Observational links to reduced depression and cognitive decline are compelling but mechanistically complex.

Q: How does chronic inflammation manifest and how does diet help?
A: Chronic inflammation presents with elevated CRP, IL-6, TNF-α, fatigue, joint pain, and metabolic dysfunction. Anti-inflammatory diets (Mediterranean, whole foods, omega-3s, polyphenols) lower these markers; pro-inflammatory patterns (trans fats, refined sugar, processed meat) raise them. The Dietary Inflammatory Index quantifies this.

Q: What is the MUFAs vs. PUFAs vs. SFAs distinction?
A: SFAs (saturated fats): butter, palm oil, lard — generally raise LDL. MUFAs (monounsaturated): olive oil, avocado, nuts — lower LDL, maintain HDL. PUFAs (polyunsaturated): sunflower, soybean, fish oils — lower LDL but in excess may oxidize; provide essential linoleic and alpha-linolenic acids.

Q: What is the difference between complete and complementary proteins?
A: A complete protein supplies all 9 essential amino acids in adequate proportions in a single food (e.g., eggs, quinoa, soy). Complementary proteins are two or more incomplete sources that together supply all EAAs (e.g., rice + beans, hummus + pita). Modern nutrition views daily intake rather than per-meal as adequate.

Q: What is functional fiber and how does it differ from dietary fiber?
A: Functional fiber is isolated, extracted, or synthetic non-digestible carbs with proven health benefits (e.g., inulin, psyllium, polydextrose). Dietary fiber is intrinsic, intact, non-digestible carbs in plants. Total fiber = dietary + functional. Many processed foods add functional fiber to boost fiber content on labels.

Q: What is the role of CLA (conjugated linoleic acid)?
A: CLA is a fatty acid found in ruminant meat and dairy, with isomer-specific effects. The c9,t11 isomer may modestly reduce body fat and improve insulin sensitivity in some trials; the t10,c12 isomer reduces milk fat but causes insulin resistance at high doses. Evidence is mixed; whole-dairy CLA is well tolerated.

Q: What is the relationship between diet and non-alcoholic fatty liver disease (NAFLD)?
A: NAFLD is driven by excess fructose, refined carbs, saturated fat, and insulin resistance. Treatment: 7-10% weight loss, Mediterranean or low-carb diet, avoiding alcohol entirely, omega-3 supplementation (though evidence is mixed), and exercise. Coffee consumption (≥2 cups/day) is associated with reduced fibrosis progression.

Q: What is the "French paradox" and is it real?
A: The French paradox refers to lower CVD mortality despite high saturated fat intake. Partial explanations: high Mediterranean pattern, red wine polyphenols (resveratrol), longer eating times, less snacking, and underreporting of coronary events in older French cohorts. The paradox weakens when diet quality and physical activity are controlled.

Q: What are prebiotics and what are their clinical effects?
A: Prebiotics are substrates selectively used by host microorganisms conferring health benefits. Confirmed prebiotics: inulin, FOS, GOS, lactulose, resistant starch. Clinical effects: improved mineral absorption, softer stools, lower triglycerides, modest immunity support, possible reduced anxiety via gut-brain axis.

Q: How does biotin deficiency present and how is it treated?
A: Biotin deficiency causes scaly dermatitis, alopecia, conjunctivitis, and lethargy. At-risk groups: infants, long-term anticonvulsant users, raw-egg consumers (avidin binds biotin), and parenteral nutrition without biotin. Treatment: 5-10 mg/day oral biotin; clinical response within weeks.

Q: What is the energy density of common macronutrients in kcal/g?
A: Alcohol: 7 kcal/g. Fat: 9 kcal/g. Carbohydrates and protein: 4 kcal/g each. Fiber: typically 2 kcal/g (sometimes 0) due to partial fermentation. Knowing energy density helps explain why high-fat foods (butter, oils, nuts) deliver more calories per gram than fruits or vegetables.

Q: What are the glycemic thresholds for diagnosis?
A: Diabetes: fasting glucose ≥126 mg/dL, 2-hour OGTT ≥200 mg/dL, HbA1c ≥6.5%, or random glucose ≥200 mg/dL with symptoms. Prediabetes: fasting 100-125 mg/dL, 2-hr OGTT 140-199 mg/dL, HbA1c 5.7-6.4%. Diagnosis requires repeat testing unless classic hyperglycemia symptoms are present.

Q: What are the dietary considerations for hypothyroidism?
A: Hypothyroidism: iodine adequacy is essential but excess worsens autoimmune thyroiditis; selenium and zinc support conversion of T4 to T3. Avoid soy and high-fiber supplements within 4 hours of levothyroxine; calcium and iron also impair absorption. Whole-food iodine (seaweed, dairy) is generally safe at RDA.

Q: What is the role of the endocannabinoid system in appetite?
A: The endocannabinoid system (CB1 receptors) regulates hedonic appetite, food reward, and energy balance. Endocannabinoids (anandamide, 2-AG) rise in hunger and fall after eating. CB1 antagonism (rimonabant) caused psychiatric depression and was withdrawn. THC in cannabis activates CB1, inducing "the munchies" especially for sweet/fatty foods.

Q: What is the difference between brown and white adipose tissue?
A: Brown adipose tissue (BAT) contains uncoupling protein 1 (UCP1) and generates heat via non-shivering thermogenesis; activated by cold and certain foods. White adipose tissue (WAT) stores triglycerides. Beige/brite adipocytes can be induced in WAT by exercise, cold, and some dietary compounds (capsaicin, catechins), a target for obesity research.

Q: What are the dietary strategies for managing hypertension?
A: Key strategies: DASH diet pattern, sodium reduction (<2300 mg/day, ideally 1500 mg), potassium increase (3500-4700 mg/day from produce), adequate magnesium and calcium, weight loss, limiting alcohol, and emphasizing whole foods. Combined effect can rival single-drug antihypertensive therapy in mild-to-moderate hypertension.

Q: What is the MUFAs content of common cooking oils?
A: Olive oil: ~73% MUFA. Canola oil: ~62% MUFA, 30% PUFA. Peanut oil: ~46% MUFA, 32% PUFA. Sunflower oil (high-oleic): ~80% MUFA. Avocado oil: ~70% MUFA. High-oleic oils are stable for cooking; smoke point varies (extra-virgin olive ~190-215°C; avocado ~270°C).

Q: What is the role of choline during pregnancy?
A: Pregnancy increases choline demand for fetal brain and liver development; high maternal intake (930 mg/day) supports memory and reduces neural tube defect risk. Choline also lowers homocysteine. Eggs (especially yolks), lean beef, and soybeans are top sources; many prenatal vitamins lack adequate choline.

Q: What are the dietary sources of vitamin B6?
A: Vitamin B6 (pyridoxine and related forms) is found in chickpeas, salmon, tuna, chicken, potatoes, bananas, and fortified cereals. It is a cofactor for amino acid metabolism, neurotransmitter synthesis, and homocysteine conversion. RDA is 1.3-2.0 mg/day; deficiency causes peripheral neuropathy, sideroblastic anemia, seizures.

Q: What is the difference between energy balance and macronutrient balance?
A: Energy balance compares calories in vs. out and determines weight change. Macronutrient balance refers to relative proportions of protein, carbs, and fat; it influences metabolic health, hormones, and body composition independent of total calories. Both matter: a person can be in energy balance but macro-imbalanced (e.g., very low protein with high refined carb).

Q: What is the thermic effect of protein in weight management?
A: Protein's thermic effect (~20-30%) means ~80 kcal are "wasted" per 100 g of protein. A high-protein diet can increase 24-hour energy expenditure by 50-100 kcal/day. Combined with protein's satiety, this modestly favors fat loss over iso-caloric lower-protein diets in clinical trials.

Q: What is the role of vitamin B12 and what causes its deficiency?
A: Vitamin B12 (cobalamin) is required for DNA synthesis, myelin formation, and homocysteine remethylation. Deficiency causes megaloblastic anemia, neuropathy, and cognitive decline. Causes: pernicious anemia (loss of intrinsic factor), vegan diets without supplements, metformin, PPI use, gastric bypass, age-related atrophic gastritis.

Q: How do polyphenols interact with statins and other drugs?
A: Grapefruit flavonoids inhibit CYP3A4, increasing blood levels of statins, calcium channel blockers, and many drugs. Apple, pomegranate, and citrus juices can have milder effects. Conversely, polyphenols may enhance endothelial function additively with statins. Patients on multiple medications should consult providers about fruit/juice interactions.

Q: What is the dietary management of chronic kidney disease (CKD) stages?
A: Stage 1-3 CKD: moderate protein (0.8 g/kg/day), sodium <2300 mg, manage potassium based on labs. Stage 4-5: protein 0.6-0.8 g/kg, phosphorus restriction (avoid additives), potassium <2000-3000 mg, often fluid restriction. Working with a renal dietitian is essential; plant-based diets may slow progression.

Q: What is the dietary role of pre-workout fueling?
A: Pre-workout meals 2-3 hours before exercise should be carb-focused (1-4 g/kg) with moderate protein and low fat/fiber to minimize GI distress. A snack 30-60 min pre-workout (~30 g carbs) for fast fuel works for many. Fasted training is acceptable for some but may reduce high-intensity output.

Q: What is the difference between soluble and insoluble plant sterols?
A: Plant sterols (phytosterols) and stanols compete with dietary cholesterol for micelle formation, lowering LDL by 7-12% at 2 g/day intake. They are fat-soluble and added to margarines, milks, and supplements. They may slightly reduce absorption of fat-soluble vitamins; supplementation is not necessary for general population with healthy diets.

Q: What is the role of TMAO from dietary choline?
A: Gut microbes convert dietary choline and L-carnitine (from red meat, eggs) to trimethylamine (TMA), which the liver oxidizes to TMAO. Elevated TMAO is associated with atherosclerosis and CVD events. Vegetarians/vegans produce less TMA. Eggs, however, do not raise CVD risk in most prospective studies despite TMAO generation.

Q: What is the dietary management of hypertriglyceridemia?
A: Triglyceride management: reduce added sugars and refined carbs, increase omega-3s (or 2-4 g/day EPA/DHA under medical guidance), limit alcohol, lose weight, replace saturated fat with MUFAs and PUFAs, and increase fiber. Severe hypertriglyceridemia (>500 mg/dL) requires low-fat diets to prevent pancreatitis.

Q: What is the difference between gelatin and collagen supplements?
A: Gelatin is cooked collagen (denatured, partial amino acid profile); hydrolyzed collagen peptides are smaller, more bioavailable, and may stimulate fibroblast activity in skin and joints. Both are incomplete proteins lacking tryptophan. Evidence for skin elasticity and joint pain reduction is modest but supportive.

Q: What is the role of iodine during pregnancy and lactation?
A: Iodine requirements rise during pregnancy (220 µg/day) and lactation (290 µg/day) to support fetal and infant thyroid hormone synthesis. Severe deficiency causes cretinism; mild deficiency lowers IQ. Iodized salt, prenatal vitamins with iodine, and dairy are reliable sources; seaweed (kelp) varies widely in content.

Q: What are the dietary considerations for SIBO?
A: Small intestinal bacterial overgrowth (SIBO) management uses a low-FODMAP or specific carbohydrate diet (SCD) to reduce fermentable substrate, often combined with antibiotics (rifaximin). Symptoms include bloating, distension, malabsorption, B12/iron deficiency. Long-term restriction risks nutritional inadequacy; dietitian supervision is important.

Q: What is the difference between LDL-C and non-HDL cholesterol?
A: LDL-C measures cholesterol in LDL particles only; non-HDL-C = total cholesterol − HDL-C and includes cholesterol in VLDL, IDL, Lp(a), and remnant particles. Non-HDL-C better predicts atherosclerotic risk, especially in metabolic syndrome, diabetes, and hypertriglyceridemia, where VLDL is elevated. Goal: non-HDL-C 30 mg/dL above LDL-C target.

Q: What is the role of vitamin K1 in blood clotting?
A: Vitamin K1 (phylloquinone) is the cofactor for γ-glutamyl carboxylase, which activates clotting factors II, VII, IX, X, and proteins C and S. Anticoagulants like warfarin block vitamin K epoxide reductase, requiring consistent dietary K1 intake. Sources: leafy greens (kale, spinach), broccoli, Brussels sprouts.

Q: How does protein intake affect satiety hormones?
A: Protein stimulates GLP-1, CCK, and PYY release from the gut, suppressing appetite; it lowers ghrelin more than carbs/fats do. Whey protein is most satiating per gram, followed by casein and soy. A high-protein breakfast can reduce total daily intake in adults; effects are dose-dependent up to ~30 g per meal.

Q: What is the role of polyphenols in cardiovascular health?
A: Polyphenols (flavanols in cocoa, anthocyanins in berries, hydroxytyrosol in olive oil) improve endothelial function via increased nitric oxide bioavailability, reduce LDL oxidation, and modestly lower blood pressure. Effects are dose-dependent; whole-food sources consistently outperform supplements in cohort studies.

Q: What is the difference between fruit juice and whole fruit?
A: Whole fruit retains fiber (3-8 g/serving) and requires chewing, slowing glucose absorption. Juice removes fiber and concentrates natural sugars (a glass of OJ ≈ 3 oranges worth of sugar without satiety). WHO classifies fruit juice as a free sugar; one serving per day of whole fruit is associated with lower diabetes risk, while juice shows neutral to adverse associations.

Q: What is the difference between essential and conditionally essential amino acids?
A: Essential amino acids (9) must be obtained from diet (histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, valine). Conditionally essential (e.g., glutamine, arginine, cysteine, tyrosine) become essential under stress, illness, prematurity, or metabolic disorders when synthesis is insufficient.

Q: What is the role of fasting insulin and HOMA-IR?
A: Fasting insulin reflects basal pancreatic output; HOMA-IR = (fasting insulin × fasting glucose) / 405 estimates insulin resistance. HOMA-IR >1.9-2.5 suggests resistance; lower is better. Lifestyle interventions (weight loss, low-GI diet, exercise, sleep) and metformin can lower HOMA-IR before frank type 2 diabetes develops.

Q: What is the difference between pancreatic and salivary amylase?
A: Salivary amylase (ptyalin) initiates starch digestion in the mouth; pancreatic amylase continues in the small intestine. Both hydrolyze α-1,4 glycosidic bonds into maltose and oligosaccharides. Individual copy number variation in the AMY1 gene affects starch digestion efficiency and possibly glycemic response.