Exam 5 Vitamins & Minerals Quick Review

Active forms: retinol (animal), retinal, retinoic acid; provitamins: β-carotene (highest activity), α-carotene, β-cryptoxanthin
Non–provitamin carotenoids: lycopene, lutein, zeaxanthin
Transport: bound to retinol-binding protein (RBP); protein deficiency ↓ RBP → ↓ vitamin A delivery
Deficiency
- Short-term: night blindness
- Long-term: xerophthalmia, keratinization, impaired immunity
Toxicity: preformed vitamin A only; β-carotene not toxic (↓ conversion rate, storage in adipose, skin yellowing only)
Major roles: vision cycle, gene expression, cell differentiation, immunity, antioxidant (carotenoids)
Sources: liver, fortified milk, eggs; orange/dark-green produce (carotenoids)

Skin 7-dehydrocholesterol + UV → previtamin D₃ → liver $25\,(OH)D$ → kidney $1,25\,(OH)_2D$ (calcitriol)
Target organs: intestine (↑ Ca/P absorption), bone (mobilize Ca/P), kidney (↓ Ca excretion)
Borderline low intake → ↓ bone density, ↑ fall/fracture risk; high-risk: limited sun, dark skin, elderly, obesity, sunscreen, northern latitudes, winter
Sun synthesis reduced by latitude, season, SPF, clothing, age, skin melanin; sunlight alone unreliable
RDA $15\,\mu g\,(600\,IU)$ ; UL $100\,\mu g\,(4000\,IU)$

Functions: antioxidant, collagen synthesis, ↑ non-heme Fe absorption, immune support
Common cold: may slightly ↓ duration/severity; not preventive for most people
Dose effects (Fig 10-17): < $10\,mg$ → scurvy; > $200\,mg$ saturates tissues; > $2000\,mg$ GI distress (UL $2000\,mg$ )
Historical deficiency: sailors on long voyages ⇒ scurvy (defective collagen → bleeding gums, petechiae); British navy issued limes (“limey”)
↑ needs: smokers (+ $35\,mg$ ), trauma, infections
RDA: men $90\,mg$ , women $75\,mg$

Coenzyme: TPP in energy metabolism, decarboxylation
Alcoholics: ↓ intake, impaired absorption, ↑ excretion → deficiency
Asia: polished rice led to beriberi; rice bran cured symptoms
Wernicke-Korsakoff: neurological disorder in chronic alcoholism (eye movement, ataxia, confusion)

Coenzymes: NAD, NADP (redox)
Early 1900s South-West US & institutions: corn-based, low protein diets ⇒ pellagra (4 D’s)
Native Americans treated corn with lime (nixtamalization) → ↑ niacin bioavailability
Pharmacologic (> $1\,g$ ) nicotinic acid ↓ LDL & TG, ↑ HDL; side effects: flushing, liver toxicity, gout, hyperglycemia
Synthesis: tryptophan → niacin; $60\,mg$ Trp ≈ $1\,mg$ niacin equivalent; requires B₆, Fe, riboflavin

Coenzyme: PLP in amino-acid metabolism, neurotransmitters, heme
Unique: water-soluble yet stored in muscle → risk of neurotoxicity with megadoses (> $100\,mg$ )
Secondary deficiency: alcoholism, oral contraceptives
Isoniazid (TB drug) binds B₆ → deficiency; supplements given

Added to enrichment later (neural tube defect prevention)
Absorption: polyglutamate → monoglutamate, absorbed, methylated in intestine; activation requires B₁₂ (methyl transfer)
↑ need: pregnancy, growth, cancer, burns
Healthy GI needed; alcohol damages GI & ↑ loss
Antagonist drugs: methotrexate, sulfa antibiotics, anticonvulsants
DFE: $1\,\mu g$ food folate = $0.6\,\mu g$ synthetic with food = $0.5\,\mu g$ empty-stomach

Absorption: stomach HCl + pepsin release B₁₂ → binds R-protein → duodenum frees B₁₂ → binds intrinsic factor → ileal absorption → transcobalamin II transport
Secondary deficiency: lack of IF (pernicious anemia, gastric surgery), achlorhydria; supplements ineffective without IF → need injections or nasal
Primary deficiency risk: vegans, breast-fed vegan infants
Relationship with folate: B₁₂ regenerates folate; high folate masks B₁₂ deficiency → irreversible nerve damage

Bone (99%): structure, Ca bank; Fluid (1%): nerve transmission, muscle, clotting, BP
Blood Ca regulated by PTH, calcitriol, calcitonin; diet low Ca → PTH ↑ bone resorption, kidney reabsorption, calcitriol ↑ absorption
Low-Ca diet does NOT ↓ blood Ca, but weakens bone
Absorption ↑ by vitamin D, lactose, growth, pregnancy; ↓ by oxalates, phytates, high fiber, excess Na/protein; excretion ↑ by high Na & protein
AI adults $1000\,mg$ (≈ 3 cups milk/yogurt or 2 oz cheese)
Peak bone mass ~age $30$ ; low peak → higher osteoporosis risk
Osteopenia: low bone density; Osteoporosis: porous bones, fractures later life
Risk factors: female, age, Caucasian/Asian, petite, low peak mass, low Ca/Vit D, sedentary, smoking, alcohol, menopause
Supplements: avoid Ca-dolomite, Ca-bone meal (Pb contamination); carbonate with meals (↑ acid), citrate anytime
Interaction: do NOT take Fe supplements with Ca

Functions: fluid balance, nerve impulse, muscle, acid-base
AI $1500\,mg$ (19-50 y); UL $2300\,mg$
High intake: processed foods (> $75\%$ of intake); table salt only minor share; need to read labels
Dehydration: thirst, fatigue, dizziness; chronic mild dehydration → UTI, kidney stones, constipation
Heat exhaustion: heavy sweating, rapid pulse, faint; Heat stroke: no sweat, high $T$ , confusion
Thirst lags; drink $~500\,mL$ per lb lost; dilute fluids during exercise

Storage: ferritin (mucosa, liver), hemosiderin (overflow); transport: transferrin
Heme Fe: meat, fish, poultry; highly absorbed (≈ $25\%$ )
Non-heme Fe: plants, dairy, eggs; lower absorption (≈ $17\%$ )
Enhancers: MFP factor, vitamin C, acids; Inhibitors: phytates, tannins, Ca, polyphenols, fiber
Meal planning: pair legumes with tomatoes or meat; avoid tea/coffee with meals
Vegetarians need ≈ $1.8\times$ RDA due to lower bioavailability

AI: men $3400\,mg$ , women $2600\,mg$
1 banana ≈ $450\,mg$ → inadequate alone; multiple bananas ↑ kcal, ↓ variety; better sources: potatoes, legumes, dairy, leafy greens, citrus, melon
No bananas required – wide distribution in whole foods
Low K intake ↑ risk of hypertension, stroke
High K intake marker for diets high in fruits/vegs & low in processed foods