1.4 Nutrition
Key Takeaways
- The six essential nutrient categories are carbohydrates, proteins, fats, vitamins, minerals, and water — each serves specific functions in the body
- Macronutrients (carbohydrates, proteins, fats) provide energy measured in calories: carbs and protein yield 4 cal/g, fat yields 9 cal/g
- MyPlate guidelines recommend filling half the plate with fruits and vegetables, one-quarter with grains, and one-quarter with protein
- Therapeutic diets are prescribed for specific conditions: diabetic diet (carb counting), cardiac diet (low sodium/fat), renal diet (restrict potassium/phosphorus/sodium)
- BMI (Body Mass Index) is calculated as weight (kg) / height (m)² and classifies weight status: <18.5 underweight, 18.5-24.9 normal, 25-29.9 overweight, 30+ obese
- Medical assistants provide dietary education as directed by the provider, including food diary instructions, portion guidance, and therapeutic diet teaching
Last updated: March 2026
Nutrition
Proper nutrition is fundamental to health maintenance and disease management. Medical assistants must understand nutritional principles to support patient education and reinforce provider-directed dietary recommendations.
Essential Nutrients
| Nutrient | Function | Sources | Calories/gram |
|---|---|---|---|
| Carbohydrates | Primary energy source; fuels brain and muscles | Bread, pasta, rice, fruits, vegetables | 4 cal/g |
| Proteins | Build and repair tissues; enzymes and antibodies | Meat, fish, eggs, beans, dairy | 4 cal/g |
| Fats (Lipids) | Energy storage, insulation, hormone production, absorb fat-soluble vitamins | Oils, nuts, butter, avocado | 9 cal/g |
| Vitamins | Regulate body processes; coenzymes | Fruits, vegetables, fortified foods | 0 cal |
| Minerals | Structural components; regulate body processes | Dairy, meat, vegetables, grains | 0 cal |
| Water | Transport, temperature regulation, chemical reactions | Water, beverages, foods | 0 cal |
Key Vitamins and Their Functions
| Vitamin | Function | Deficiency | Food Sources |
|---|---|---|---|
| A | Vision, immune function, skin health | Night blindness | Carrots, sweet potatoes, liver |
| B1 (Thiamine) | Energy metabolism, nerve function | Beriberi | Whole grains, pork, legumes |
| B12 | Red blood cell formation, nerve function | Pernicious anemia | Meat, fish, dairy, eggs |
| C | Collagen synthesis, immune function, antioxidant | Scurvy | Citrus fruits, peppers, strawberries |
| D | Calcium absorption, bone health | Rickets (children), osteomalacia (adults) | Sunlight, fortified milk, fatty fish |
| E | Antioxidant, cell membrane protection | Hemolytic anemia | Nuts, seeds, vegetable oils |
| K | Blood clotting, bone metabolism | Bleeding disorders | Leafy greens, broccoli, liver |
| Folic acid (B9) | DNA synthesis, red blood cell formation | Megaloblastic anemia, neural tube defects | Leafy greens, fortified grains, beans |
Fat-soluble vitamins: A, D, E, K — stored in body fat; can accumulate to toxic levels Water-soluble vitamins: B-complex, C — not stored; excess excreted in urine; need daily intake
Key Minerals
| Mineral | Function | Deficiency | Sources |
|---|---|---|---|
| Calcium | Bones, teeth, muscle contraction, nerve function | Osteoporosis | Dairy, leafy greens, fortified foods |
| Iron | Hemoglobin formation, oxygen transport | Iron-deficiency anemia | Red meat, beans, fortified cereals |
| Potassium | Fluid balance, nerve function, muscle contraction | Muscle weakness, arrhythmias | Bananas, potatoes, oranges |
| Sodium | Fluid balance, nerve impulses | Hyponatremia (rare) | Salt, processed foods |
| Magnesium | Enzyme function, muscle/nerve function | Muscle cramps, weakness | Nuts, whole grains, leafy greens |
| Zinc | Immune function, wound healing | Impaired immunity, slow wound healing | Meat, shellfish, legumes |
Therapeutic Diets
| Diet | Indication | Key Modifications |
|---|---|---|
| Diabetic diet | Diabetes mellitus | Consistent carbohydrate counting, low glycemic index foods, limit simple sugars |
| Cardiac/heart-healthy | Heart disease, hypertension | Low sodium (<2,000 mg/day), low saturated fat, high fiber |
| Renal diet | Chronic kidney disease | Restrict potassium, phosphorus, sodium, and possibly protein and fluid |
| DASH diet | Hypertension | High fruits/vegetables/whole grains, low sodium, low saturated fat |
| Low-residue/low-fiber | Crohn's disease, diverticulitis flare | Limit fiber, raw fruits/vegetables, whole grains |
| High-fiber | Constipation, diverticulosis | Increase fiber to 25-35 g/day, increase fluids |
| Gluten-free | Celiac disease | Eliminate wheat, barley, rye, and cross-contaminated foods |
| Clear liquid | Pre-surgery, acute GI illness | Broth, gelatin, clear juices, popsicles |
| Full liquid | Post-surgery transition | All clear liquids plus milk, cream soups, pudding |
| Soft/mechanical soft | Difficulty chewing/swallowing | Soft, easy-to-chew foods; no raw vegetables or tough meats |
BMI Classification
| BMI | Classification |
|---|---|
| < 18.5 | Underweight |
| 18.5 - 24.9 | Normal weight |
| 25.0 - 29.9 | Overweight |
| 30.0 - 34.9 | Obese (Class I) |
| 35.0 - 39.9 | Obese (Class II) |
| ≥ 40.0 | Morbidly obese (Class III) |
BMI Formula: Weight (kg) ÷ Height (m)² = BMI
Test Your Knowledge
Which macronutrient provides the MOST calories per gram?
A
B
C
D
Test Your Knowledge
A patient with chronic kidney disease would most likely be placed on which type of therapeutic diet?
A
B
C
D
Test Your Knowledge
Vitamins A, D, E, and K are classified as fat-soluble vitamins. What is the clinical significance of this classification?
A
B
C
D