3.3 Health, Nutrition & Disease

Health and Nutrition on the NEX

Health topics make up roughly 8 items (~13%) of the 60-question Science section. They connect basic biology to patient-care reality, and many are pure recall — fast points if the vitamin-deficiency pairs are memorized.

The Six Essential Nutrients

Carbohydrates provide 4 kcal/g, protein 4 kcal/g, and fat 9 kcal/g — fat is the most calorie-dense, a frequently tested number.

Vitamins: Water-Soluble vs. Fat-Soluble

The single most tested vitamin idea: fat-soluble A, D, E, K accumulate and risk toxicity (hypervitaminosis), while water-soluble vitamins are flushed out and rarely toxic. Memorize the deficiency pairs:

Disease Concepts

Communicable (infectious) diseases spread person to person via pathogens; non-communicable (chronic) diseases do not.

Trap: diabetes and heart disease are not contagious — tuberculosis (caused by Mycobacterium tuberculosis) is the communicable answer in most item sets.

The defining viral fact: viruses cannot reproduce on their own and must hijack a host cell — which is also why antibiotics (which target bacteria) do not work against viral infections.

The Immune System

Vaccination trains the adaptive system to make memory cells without causing the disease, so a later real exposure is met quickly — the basis of immunity.

Homeostasis and Feedback

Homeostasis is maintaining a stable internal environment (temperature, pH, glucose, fluids) despite external change.

• Negative feedback (common): the body reverses a change. Temperature rises, sweating and vasodilation cool the body, then stop. Blood glucose rises, insulin lowers it.
• Positive feedback (rare): the body amplifies a change until a process completes. Labor contractions trigger more oxytocin and stronger contractions until delivery; blood clotting recruits more platelets until the wound seals.

Trap: body-temperature and blood-sugar control are negative feedback; only completion-driven events like labor and clotting are positive. Chronic-disease risk factors — smoking, inactivity, poor diet, excess alcohol, obesity, and chronic stress — overload these systems and are tied to heart disease, type 2 diabetes, COPD, and certain cancers.

Macronutrients, Calories, and Balanced Intake

Beyond the deficiency tables, the NEX expects a working sense of energy balance. Weight is gained when calories consumed exceed calories burned and lost when the reverse is true. Because fat carries nine kilocalories per gram versus four for carbohydrate and protein, fatty foods are the most calorie-dense and the easiest to over-consume. A balanced plate emphasizes whole grains, vegetables, fruits, lean protein, and water while limiting added sugars, saturated fat, and sodium. Excess sodium raises blood pressure, which links diet directly to the hypertension and heart-disease risk factors above.

Fiber, a non-digestible carbohydrate, supports digestion and helps regulate blood glucose and cholesterol. These ideas connect the chemistry of macromolecules to the health applications nurses use daily.

Disease Transmission and Prevention

When a question describes how an illness spreads, classify the route. Direct contact transmission passes a pathogen through touch or bodily fluids, as with many skin infections and sexually transmitted infections. Droplet transmission spreads through coughing or sneezing over short distances, as with influenza. Airborne transmission lingers in fine particles over longer distances, as with tuberculosis and measles. Vector-borne transmission uses an organism such as a mosquito, as with malaria. Foodborne or waterborne transmission spreads through contaminated intake.

The most effective everyday prevention measure is hand hygiene, followed by vaccination, safe food handling, and isolation of contagious patients. Recognizing the transmission route is often the key to answering an applied health item, because it determines which precaution a nurse would choose.