Nutrition And Diet
How does meal frequency affect metabolism?
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.
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.
Vitamin D is synthesized via sunlight or from fortified foods/fish, aiding calcium absorption for bone health.
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.
Nutrition And Diet
What is vitamin D's primary source and function?
The Mediterranean diet emphasizes fruits, vegetables, whole grains, fish, olive oil, nuts, limiting red meat/sweets.
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.
Vitamin D is synthesized via sunlight or from fortified foods/fish, aiding calcium absorption for bone health.
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.
Nutrition And Diet
What is the carnivore diet and what are its nutritional gaps?
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.
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.
Gut microbiome is trillions of microbes influencing digestion, immunity, mood via fiber-rich diet.
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.
Nutrition And Diet
What is the role of selenium and what are its food sources?
Obesity arises from chronic calorie surplus, high sugar/processed foods promoting fat storage.
RDA (Recommended Dietary Allowance) is the average daily nutrient intake level sufficient for 97-98% of healthy individuals.
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.
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.
Nutrition And Diet
What is the role of water in nutrition?
Intermittent fasting cycles eating/fasting (e.g., 16:8 method), promoting weight loss, insulin sensitivity.
Water is essential for digestion, nutrient transport, temperature regulation, and waste elimination, comprising 60% of body weight.
Ultra-processed foods (sodas, chips) high in sugar/fat/salt, additives; linked to obesity, disease.
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.
Nutrition And Diet
How do you read a nutrition label?
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.
Check serving size, calories, % Daily Value for nutrients; limit sodium/sugars under 5% DV, choose high fiber/protein over 20%.
Calcium builds and maintains bones/teeth, supports muscle contraction, nerve signaling, and blood clotting.
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.
Nutrition And Diet
What are net carbs and how are they calculated?
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.
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.
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.
Vitamin C is an antioxidant that supports immune function, collagen synthesis for skin and wounds, and iron absorption.
Nutrition And Diet
Describe a vegan diet.
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.
Vitamins are organic compounds that regulate metabolism, support immunity, and act as antioxidants.
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.
A vegan diet excludes all animal products, relying on plants for protein, calcium, B12 (supplement needed).
Nutrition And Diet
What are ultra-processed foods?
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.
Ultra-processed foods (sodas, chips) high in sugar/fat/salt, additives; linked to obesity, disease.
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.
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.
Nutrition And Diet
What is the role of vitamin B12 and what causes its deficiency?
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.
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.
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.
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.
Nutrition And Diet
What is the difference between soluble and insoluble plant sterols?
Proteins are made of amino acids, of which there are 20 types, including 9 essential ones that must come from diet.
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.
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.
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.
Nutrition And Diet
What is the difference between vegan, vegetarian, and pescatarian diets?
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.
A vegan diet excludes all animal products, relying on plants for protein, calcium, B12 (supplement needed).
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.
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.
Nutrition And Diet
What is functional fiber and how does it differ from dietary fiber?
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.
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.
Orthorexia is obsession with 'healthy' eating, leading to restrictive behaviors harming social/nutritional health.
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.
Nutrition And Diet
What are essential fatty acids?
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.
For diabetes, focus on low-GI carbs, fiber, lean proteins, healthy fats to stabilize blood sugar.
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.
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.
Nutrition And Diet
How does chronic alcohol consumption affect nutrition?
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.
Poor sleep disrupts hunger hormones (ghrelin up, leptin down), increasing appetite for junk food.
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.
Simple carbs (sugars) digest quickly for fast energy; complex carbs (starches) digest slowly, providing sustained energy.
Nutrition And Diet
What are the dietary considerations for SIBO?
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.
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.
The main food groups are fruits, vegetables, grains, proteins, and dairy, as per MyPlate guidelines.
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.
Nutrition And Diet
What is the role of the glycemic load (GL) versus glycemic index (GI)?
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.
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.
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.
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.
Nutrition And Diet
What is the function of vitamins?
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.
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.
Vitamins are organic compounds that regulate metabolism, support immunity, and act as antioxidants.
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.
Nutrition And Diet
What is the role of CLA (conjugated linoleic acid)?
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.
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.
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.
Heart-healthy diets like DASH reduce sodium, boost potassium-rich fruits/veggies, whole grains, limit saturated fats.
Nutrition And Diet
What is the function of iodine and what happens in deficiency?
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.
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.
The Mediterranean diet emphasizes fruits, vegetables, whole grains, fish, olive oil, nuts, limiting red meat/sweets.
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.
Nutrition And Diet
What is the dietary management of gout?
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.
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.
Carbohydrates are the body's main energy source, providing 4 kcal per gram, and are essential for brain function and physical activity.
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.
Nutrition And Diet
What is the difference between complete and complementary proteins?
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.
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.
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.
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.
Nutrition And Diet
What is the role of TMAO from dietary choline?
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.
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.
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.
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.
Nutrition And Diet
How does dietary fat affect satiety and total calorie intake?
Check serving size, calories, % Daily Value for nutrients; limit sodium/sugars under 5% DV, choose high fiber/protein over 20%.
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.
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.
Dietary fats include saturated, unsaturated (monounsaturated and polyunsaturated), and trans fats.
Nutrition And Diet
What are the dietary recommendations for chronic kidney disease?
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.
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.
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.
Heart-healthy diets like DASH reduce sodium, boost potassium-rich fruits/veggies, whole grains, limit saturated fats.
Nutrition And Diet
What are whole foods vs. processed foods on the NOVA scale?
Vitamin C is an antioxidant that supports immune function, collagen synthesis for skin and wounds, and iron absorption.
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.
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.
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.
Nutrition And Diet
What are the types of dietary fats?
Dietary fats include saturated, unsaturated (monounsaturated and polyunsaturated), and trans fats.
Athletes need higher carbs for energy (6-10g/kg), proteins (1.2-2g/kg) for repair, hydration.
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.
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.
Nutrition And Diet
What are the dietary sources of vitamin E?
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.
A vegan diet excludes all animal products, relying on plants for protein, calcium, B12 (supplement needed).
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."
Micronutrients are vitamins and minerals needed in small amounts for metabolic processes, immune function, and bone health.
Nutrition And Diet
What is time-restricted eating and is it distinct from intermittent fasting?
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.
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.
Gut microbiome is trillions of microbes influencing digestion, immunity, mood via fiber-rich diet.
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.
Nutrition And Diet
What are macronutrients?
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.
Diet-induced thermogenesis (DIT) is energy used to digest/process food, 10% of expenditure, higher for proteins.
Macronutrients are nutrients required in large amounts, including carbohydrates, proteins, and fats, which provide energy and building blocks for the body.
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.
Nutrition And Diet
What is the function of vitamin A and what are its forms?
Calcium builds and maintains bones/teeth, supports muscle contraction, nerve signaling, and blood clotting.
Macronutrients are nutrients required in large amounts, including carbohydrates, proteins, and fats, which provide energy and building blocks for the body.
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.
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.
Nutrition And Diet
What is metabolic syndrome?
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.
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.
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).
Metabolic syndrome clusters high blood pressure, sugar, waist circumference, triglycerides, low HDL.
Nutrition And Diet
What is the relationship between diet and non-alcoholic fatty liver disease (NAFLD)?
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.
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.
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.
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.
Nutrition And Diet
What is sarcopenic obesity and how is it addressed?
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.
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).
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.
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.
Nutrition And Diet
What are the recommendations for added sugar intake?
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.
Dietary fiber is indigestible plant material that promotes digestive health, lowers cholesterol, and stabilizes blood sugar.
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.
Diet-induced thermogenesis (DIT) is energy used to digest/process food, 10% of expenditure, higher for proteins.
Nutrition And Diet
What is resistant starch and how does it benefit gut health?
Ketosis occurs in low-carb states (keto diet) where body burns fat for ketones as fuel instead of glucose.
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.
Intermittent fasting cycles eating/fasting (e.g., 16:8 method), promoting weight loss, insulin sensitivity.
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.
Nutrition And Diet
What is the role of polyphenols in the gut-brain axis?
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.
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.
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.
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.
Nutrition And Diet
What is the Mediterranean diet?
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.
RDA (Recommended Dietary Allowance) is the average daily nutrient intake level sufficient for 97-98% of healthy individuals.
The Mediterranean diet emphasizes fruits, vegetables, whole grains, fish, olive oil, nuts, limiting red meat/sweets.
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.
Nutrition And Diet
What are antioxidants?
Vitamin B12 deficiency causes fatigue, anemia, neurological issues like numbness, memory loss.
The main food groups are fruits, vegetables, grains, proteins, and dairy, as per MyPlate guidelines.
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.
Antioxidants like vitamins C/E, beta-carotene neutralize free radicals, preventing cell damage and chronic diseases.
Nutrition And Diet
How does the body regulate iron absorption?
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.
Proteins are made of amino acids, of which there are 20 types, including 9 essential ones that must come from diet.
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.
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.
Nutrition And Diet
What is refeeding syndrome and who is at risk?
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.
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.
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.
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.
Nutrition And Diet
What are the main food groups in a balanced diet?
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.
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.
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."
The main food groups are fruits, vegetables, grains, proteins, and dairy, as per MyPlate guidelines.
Nutrition And Diet
What is the role of choline during pregnancy?
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.
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.
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.
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.
Nutrition And Diet
What are probiotics?
Probiotics are live beneficial bacteria (e.g., Lactobacillus) in yogurt that support gut microbiome, digestion, and immunity.
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.
The main food groups are fruits, vegetables, grains, proteins, and dairy, as per MyPlate guidelines.
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.
Nutrition And Diet
What is the difference between LDL-C, LDL-P, and apoB?
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.
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.
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.
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.
Nutrition And Diet
What is the dietary management of celiac disease?
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.
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.
Omega-3s (EPA, DHA from fish; ALA from plants) reduce inflammation, support heart/brain health.
RDA (Recommended Dietary Allowance) is the average daily nutrient intake level sufficient for 97-98% of healthy individuals.