Human Nutrition, Macronutrients/Micronutrients/Water, Special Topics in Nutrition, Weight Control, Pregnancy & Breastfeeding, Food Allergies & Intolerances, Nutrition & Aging, and Infancy Through Adolescence, condensed to the highest-yield facts.
| Topic | One-glance facts |
|---|---|
| Essential nutrient (3 criteria) | A specific biological function is identified → omitting it causes decline in that function → replacing it restores normal function. 6 nutrient classes: carbohydrate, protein, lipid, vitamin, mineral, water. |
| kcal/g factors | Carbohydrate 4 kcal/g, protein 4 kcal/g, fat 9 kcal/g, alcohol 7 kcal/g (alcohol is calorie-yielding but not a nutrient — no essential function). |
| Macro vs. micronutrients | Macronutrients (carbohydrate, protein, lipid) needed in gram quantities and provide calories. Micronutrients (vitamins, minerals) needed in mg/mcg quantities and provide 0 calories. |
| Key metric conversions | 1 lb = 454 g; 1 kg = 1000 g = 2.2 lb; 1 L = 1000 mL; 1 tsp ≈ 5 mL; 1 cup ≈ 240 mL; 4 g sugar ≈ 1 tsp; 6 g salt ≈ 1 tsp. |
| BMI classification | 18.5–24.9 healthy; 25–29.9 overweight; 30–34.9 Class 1 obesity; 35–39.9 Class 2; ≥40 Class 3. 2018 CDC: 26% normal weight, 72.5% overweight (BMI ≥25), 41% obese (BMI ≥30). |
| Standard American Diet (NHANES 2018) | Protein 15.8% kcal (range 10–35%), carbohydrate 46.7% kcal (range 45–65%), fat 35.8% kcal (range 20–35%, slightly above top of range) — carb/protein sit low, fat sits high. |
| Nutrient density vs. energy density | Nutrient-dense = large nutrient amount per calorie (fat-free milk, vegetable soup). Energy density = kcal per gram of food weight: very low <0.6 kcal/g, low 0.6–1.5, medium 1.5–4, high >4 kcal/g. |
| Dietary Guidelines limits | Saturated fat <10% kcal, added sugars <10% kcal, sodium <2,300 mg/day, alcohol ≤1 drink/day women / ≤2 drinks/day men. 2020 label update added a separate Added Sugars line. |
| Topic | One-glance facts |
|---|---|
| Carbohydrate RDA & glycemic index | RDA 130 g/day adults (45–65% kcal); glucose is the preferred fuel (red blood cells use ONLY glucose). Glycemic index ranks how fast a carb raises blood glucose. Added-sugar limits: FNB upper limit 25% of kcal; AHA ~100 kcal/day (24 g, 6 tsp) women, 150 kcal/day (36 g, 9 tsp) men. |
| Fiber types | Insoluble/nonfermentable (cellulose, lignin — whole grains, bran) ↑ fecal bulk, ↓ transit time. Soluble/viscous (pectin, gums, psyllium) is fermented by colonic bacteria and reduces cholesterol absorption. >60 g/day fiber requires extra fluid and may impair mineral absorption. |
| Fatty acid types | Saturated: no double bonds, solid, animal fat. Monounsaturated: 1 double bond (oleic acid, omega-9), liquid, olive/canola oil. Polyunsaturated: omega-3 (first double bond 3 carbons from omega end — ALA, DHA, EPA) vs. omega-6 (6 carbons from omega end — linoleic acid); both essential, must come from diet. |
| Lipoproteins & CVD fat targets | Chylomicron/VLDL carry triglyceride; LDL carries cholesterol to cells ("bad"); HDL returns cholesterol to liver ("good," highest protein content, most dense). Fat 20–35% of kcal, saturated fat <7–10% (AHA); no formal dietary cholesterol limit. |
| Protein balance & malnutrition | RDA ≈0.8 g/kg healthy body weight (10–15% kcal; UL ~35%/170 g). Positive balance = net gain (growth/pregnancy), negative = net loss (illness/starvation), equilibrium = intake matches breakdown. Kwashiorkor: protein-deficient, edema masks wasting, 60–80% normal weight-for-age. Marasmus: protein AND calorie-deficient, <60% normal weight-for-age, rapid onset, no edema. |
| Vitamin solubility & toxicity | Fat-soluble (A, D, E, K) absorbed with dietary fat, not readily excreted — A/D/E can accumulate to toxicity (A most common). Water-soluble (B-complex, C) generally excreted in urine, except B6 and B12 which store in the liver. Vegan diets risk deficiency of B12, D, calcium, iron, zinc, and omega-3s. |
| Minerals: major vs. trace | Major (larger amounts): calcium (~1200 g body content), phosphorus, magnesium, sulfur, sodium/potassium/chloride. Trace (small amounts): iron, zinc, selenium, iodine, copper, fluoride, chromium, manganese, molybdenum. Classified by quantity, not clinical importance; toxicity is mostly a supplement problem. |
| Water & electrolyte targets | Body water 50–70% of weight. Fluid targets: ~2.2 L/day (9 cups) women, ~3 L/day (13 cups) men. Sodium AI 1,500 mg/day, DV/UL 2,300 mg/day. Potassium AI/DV 4,700 mg/day. DASH diet (high K⁺/Ca²⁺/Mg²⁺, low fat/sodium) lowers systolic BP 8–14 points — the single biggest non-drug intervention listed besides weight loss. |
| Topic | One-glance facts |
|---|---|
| Malnutrition etiologies & diagnosis | 3 types: starvation-related (simple), chronic disease-related, acute disease/injury-related (stress starvation). ASPEN diagnosis requires 2 of 6 criteria. 20–50% of hospitalized US adults are malnourished; only 5–8% are diagnosed. Significant weight loss = 2% in 1 week, 5% in 30 days, 7.5% in 3 months, or 10% in 6 months; %loss = (UBW − current weight) ÷ UBW. |
| Malnutrition lab markers | Albumin: half-life 3 weeks. Prealbumin: 3 days. Retinol binding protein: 12 hours (most sensitive to acute change). Transferrin: 8–10 days. All are confounded by inflammation, liver/renal disease, and hydration — use to trend response, not to diagnose alone. |
| Enteral vs. parenteral nutrition | Guiding principle: "if the gut works, use it." Enteral is more physiologic, lower risk, cheaper, can meet 100% of needs. Parenteral reserved for ileus/intolerance, obstruction, hemodynamic instability, severe malabsorption, major GI bleed, or gut-rest surgery. PPN has limited osmolarity/calories; TPN (central line into SVC) delivers full calorie/protein/micronutrient needs. |
| Refeeding syndrome | Feeding a severely malnourished patient shifts catabolism → anabolism (dextrose → insulin), driving electrolytes intracellularly: hypophosphatemia, hypokalemia, hypomagnesemia (arrhythmia risk). Give thiamine (B1) before any dextrose, continue 5–7 days, to prevent Wernicke's/Korsakoff. Start at ~50% of estimated kcal needs and advance gradually over about a week. |
| Nutrition by disease state | CKD 3–5: restrict sodium, phosphorus, potassium, protein; add fluid restriction at CKD 4–5. Chronic liver disease: increase (don't restrict) protein, favor plant/dairy sources, sodium 1,500–2,000 mg/day if ascites present. Diabetes: favor complex over refined carbs; plate method = ½ nonstarchy vegetables, ¼ carbohydrate, ¼ protein. |
| Specialized nutrition support timing | Consider SNS after >5–7 days of inadequate intake in adults (3–5 days children, 1–3 days infants). Not obligatory in futile-care/end-of-life situations — no evidence enteral feeding helps dementia patients; residents have a federally protected right to informed decisions about feeding tube placement. |
| Topic | One-glance facts |
|---|---|
| Energy balance components | BMR 60–80% of total daily needs (lean body mass is the biggest driver), physical activity 15–30%, thermic effect of food (TEF) 8–15% (highest for protein). ~3,500 kcal ≈ 1 lb of weight change. Adaptive thermogenesis = nonvoluntary heat production (fidgeting, shivering, brown fat). |
| BMI categories (WHO) | Underweight <18.5 (severe <16.00, moderate 16.00–16.99, mild 17.00–18.49); normal 18.50–24.99; overweight (pre-obese) ≥25.00 (25.00–29.99); obese Class I 30.00–34.99, Class II 35.00–39.99, Class III ≥40.00. |
| Fat distribution: android vs. gynoid | Android ("apple," waist >40" men / >35" women): visceral, near the liver, driven by testosterone/alcohol — linked to insulin resistance, fatty liver, T2DM, high lipids, heart disease. Gynoid ("pear," hips/thighs): driven by estrogen/progesterone, lower risk. Acceptable body fat: women 23–31% (obese >35%), men 13–21% (obese >25%). |
| Weight-loss plan design | Weight-loss triad: calorie restriction + physical activity + behavior modification. Target 1–2 lb/week loss (~500 kcal/day deficit); maintenance period after losing 10% of body weight before further loss. Crash diets are the primary cause of regain. Average calorie needs: women 1,800–2,400 kcal/day, men 2,400–3,200 kcal/day. |
| Weight-loss medications | Orlistat inhibits intestinal lipase (~30% less fat digestion). Phentermine = appetite suppressant. Liraglutide slows gastric emptying/↑satiety. Semaglutide = GLP-1 agonist. Medication candidacy: BMI ≥30, or ≥27 with an obesity-related comorbidity. |
| Bariatric surgery options | Candidacy: BMI ≥40, or ≥35 with a comorbidity. Gastric bypass = greatest weight loss but highest deficiency risk (reroutes intestine). Sleeve gastrectomy removes 80–85% of the stomach, irreversible. Adjustable banding = lowest deficiency risk and reversible, but least weight loss. Ileal transposition = best glycemic control. |
| Underweight & food insecurity | Underweight = BMI <18.5. Very-low-calorie diet (400–800 kcal/day, medically supervised) is for BMI ≥40 patients who've failed other approaches. 44.2 million people lived in food-insecure US households in 2022; resources include WIC, Summer EBT, and school meal programs. |
| Topic | One-glance facts |
|---|---|
| Folic acid dosing | Preconception: 0.4 mg/day (no NTD history) or 4 mg/day (prior affected pregnancy). During pregnancy: 0.6 mg/day. |
| Organogenesis | Weeks 3-8 of embryonic development — most critical window; maternal hyperglycemia here raises congenital malformation risk. |
| Macronutrients | Protein 1.1 g/kg/day (~71 g, ~20% kcal). Fat 20-35% kcal (<10% saturated). Carbs min 175 g/day (~50% kcal), fiber 28 g/day. |
| Key micronutrients | Iron 27 mg/day. Omega-3 200-300 mg/day. Calcium 1,000 mg/day. Vitamin D 600 IU. Iodine 220 mcg. Choline 450 mg. Vitamin A 770 mcg (excess is teratogenic). |
| Caloric needs by trimester | 1st: no increase. 2nd: +340 kcal/day. 3rd: +450 kcal/day. Total weight gain 25-35 lb (1-5 lb 1st tri, ~1 lb/week after). |
| Food safety | Avoid high-mercury fish (shark, swordfish, king mackerel, marlin, tilefish, bigeye tuna); 2-3 servings/week low-mercury fish instead. Caffeine <200 mg/day. Avoid unpasteurized dairy/juice, raw sprouts, undercooked meat. |
| Physiology of lactation | Prolactin → milk production. Oxytocin → let-down (ejection) reflex. Breastmilk stages: colostrum → transitional → mature; foremilk (watery, first) vs. hindmilk (creamy, later). IgA ~90% of mature milk's immunoglobulins. |
| Breastfeeding nutrition | +500 kcal/day, 70 g/day protein, 1,000 mg calcium, 500 mcg folic acid, 120 mg vitamin C, ~3-4 L water. AAP/WHO: exclusive breastfeeding to 6 months. Cow's milk not before 12 months. |
| Topic | One-glance facts |
|---|---|
| Allergy vs. intolerance | Food allergy = adverse reaction involving an immune response. Food intolerance = adverse reaction with no immune involvement (e.g. lactase deficiency). |
| IgE vs. non-IgE reactions | IgE-mediated (early onset): soon after ingestion, often violent, can be anaphylaxis. Non-IgE-mediated (late onset): later, subtler (diarrhea, eczema, colitis). |
| Diagnosis steps | History → physical exam → elimination diet (1-2 wk) → food challenge (only if anaphylaxis isn't a risk) → blood test → skin test. |
| GI conditions & meds | GERD/heartburn — avoid acidic/spicy/carbonated, small low-fat meals. Ulcers — H. pylori/NSAIDs; PPIs (omeprazole) inhibit H+ secretion, H2 blockers (famotidine) block histamine's acid-stimulating effect. IBS — low-FODMAP diet. |
| Celiac disease | Immune-mediated reaction to gluten (wheat/rye/barley) in genetically predisposed people; flattens villi, impairs absorption; ~1% of US population. Treatment: eliminate gluten. |
| Nonceliac gluten sensitivity | Gluten-triggered symptoms (GI distress, fatigue, headache, joint pain) without villi damage — same elimination treatment as celiac despite the different mechanism. |
| Epidemiology & prevention | Childhood food allergies rose 50% (1997-2011). Hygiene hypothesis: under-exposure to antigens may sensitize the immune system to food proteins instead. 2019 AAP: early peanut introduction (4-6 mo) reduces peanut allergy risk. |
| Allergen labeling & outcomes | 2006 law mandates labeling of 8 major allergens: milk, egg, fish, shellfish, peanut, tree nut, wheat, soy. ~80% of young children outgrow food allergies by age 3. |
| Topic | One-glance facts |
|---|---|
| Adulthood & aging | Nutrients switch from growth to maintenance; peak performance until ~age 30; after 30-40 cell breakdown exceeds renewal. Reserve capacity keeps organs working with fewer cells until it is exhausted. |
| Metabolism & calories | Basal metabolic rate falls ~2% per decade (~100-150 kcal less/day for a 70-yr-old man). Same intake → weight gain, so prioritize nutrient-dense calories (no empty calories). Exercise can halt/reverse lean-mass loss. |
| Macronutrients | Protein 1.0-1.2 g/kg/day (preserve muscle/bone; excess strains kidneys). Fiber 25-35 g/day. Saturated fat <10% of kcal. Water 6-8 8-oz glasses (thirst sensitivity fades; dehydration → disorientation). |
| Micronutrients | Vitamin D 600 IU (51+)/800 IU (70+). Calcium 1,200 mg. Vitamin B12 ↓ with low stomach acid (anemia, cognitive decline). Zinc ↓ → ↓immunity. Iron with vitamin C. Carotenoids (lutein/zeaxanthin) → prevent cataracts & macular degeneration. |
| DETERMINE screen | Disease, Eating poorly, Tooth loss/pain, Economic hardship, Reduced social contact, Multiple medications, Involuntary weight change, Needs assistance, Elderly (>80) — warning signs of poor nutrition. |
| Genetics & Blue Zones | Thrifty phenotype = fewer calories, stores fat easily; spendthrift = burns energy fast, less weight gain. Blue Zones (Okinawa, Sardinia, Nicoya, Ikaria, Loma Linda) follow a Mediterranean pattern; olive oil = main fat. |
| Body composition & systems | Sarcopenia = loss of lean mass; sarcopenic obesity = muscle loss + fat gain. Preserve bone: weight-bearing exercise + vitamin D/calcium/protein, avoid smoking/alcohol/cola. Diuretics leach potassium. |
| Community programs | Older Americans Act Nutrition Program: congregate meals (central site) and Meals on Wheels (delivered to homes); plus commodity distribution, SNAP, and food cooperatives. |
| Topic | One-glance facts |
|---|---|
| Infant growth | Weight doubles by 4-6 mo, triples by 1 yr; length +50% in yr 1; brain grows fastest in yr 1. Growth-chart percentile = rank vs 100 peers (50th = average). Overfeeding ↑ number of fat cells. |
| Failure to thrive & energy | Affects 5-10% of infants; ~80% have no apparent disease; poverty is the biggest environmental risk. ~700 kcal/day at 6 mo; high needs from rapid growth & high surface area (heat loss). |
| Breast milk & formula | Breast milk: fat up to 55% of cal, carb ~35-40%, protein <10%; flavors of mother's diet transfer. Formula fortified except fluoride. No cow's milk until age 1 (protein too high). High protein strains immature kidneys. |
| Key infant nutrients | Vitamin K injection at birth. Vitamin D 400 IU/day <1 yr. Iron stores depleted by 4-6 mo → iron-fortified foods. No fluoride <6 mo. No supplemental water in first 6 mo (dehydrate easily). |
| Introducing solids | Ready ~6 mo, added to (not replacing) milk/formula. One food at a time, wait ~7 days, start with 1 tsp iron-fortified rice cereal. Avoid honey (Clostridium botulinum). Cup by 1 yr, wean bottle by 18 mo. |
| Toddler & school-age | Iron-deficiency anemia peaks 6-24 mo. Whole milk to age 2, then reduced-fat. Excess sodium common. Picky eaters may need 10+ exposures. Limit screen time <2 h/day; cholesterol screen ages 9-11; ~80% of obese teens become obese adults. |
| Teenagers | Growth spurt: girls gain fat + lean, boys gain lean. Calcium 1,300 mg/day, vitamin D 600 IU. Menstruating girls may need iron. Limit caffeine ≤100 mg/day; ~40% eat fast food on a given day. |
| Food allergies | Allergy = immune response; intolerance = not. 8 leading allergens: milk, egg, fish, crustacean shellfish, tree nut, peanut, wheat, soy (FALCPA labeling). Introducing foods <4 mo ↑ risk; ~80% outgrow by age 3. |