Nutrition is all about understanding the nutrients in food, how our bodies use them, and the connection between diet, health, and disease.
Nutritionists rely on concepts from molecular biology, biochemistry, and genetics to figure out how nutrients impact the body.
They also explore how dietary choices can lower disease risk, what happens when someone gets too much or too little of a nutrient, and how allergies function.
Nutrients keep us nourished. Proteins, carbs, fats, vitamins, minerals, fiber, and water are all essential nutrients. Without the right balance, the chances of developing certain health problems go up.
This article breaks down the different nutrients we need and why. It also explains the roles of dietitians and nutritionists.
Macronutrients
These are nutrients we need in larger amounts.
Carbohydrates
Sugars, starches, and fiber are all types of carbs.
Sugars are simple carbs—easy for the body to break down and absorb quickly. They give fast energy but don’t keep you full for long and can spike blood sugar. Frequent spikes raise the risk of type 2 diabetes and related issues.
Fiber is also a carb. Some types get broken down for energy, others feed gut bacteria, and some pass right through.
Fiber and unprocessed starches are complex carbs. They take longer to digest, keeping you full and reducing the risk of diabetes, heart disease, and colon cancer. They’re a healthier pick than sugars and refined carbs.
Proteins
Proteins are made of amino acids—natural organic compounds.
There are 20 amino acids, some of which are essential, meaning we must get them from food. The body makes the rest.
Some foods (like meat and dairy) provide complete protein, containing all essential amino acids. Others have partial mixes.
Most plant-based foods don’t offer complete protein, so vegans should eat a variety of foods daily to get all essential amino acids.
Fats
Fats are crucial for:
- Lubricating joints
- Helping organs produce hormones
- Absorbing certain vitamins
- Reducing inflammation
- Supporting brain health
Too much fat can lead to obesity, high cholesterol, liver disease, and other issues. But the type of fat matters—unsaturated fats (like olive oil) are healthier than saturated fats (found in animal products).
Water
Our bodies are up to 60% water, and we need it for countless processes. Water has no calories and doesn’t provide energy.
While many recommend 2 liters (8 glasses) a day, water also comes from foods like fruits and veggies. Proper hydration makes urine pale yellow.
Needs vary based on body size, age, activity level, climate, and health.
Micronutrients
These are vitamins and minerals needed in smaller amounts. Some foods (like fortified cereals) have added micronutrients.
Minerals
We need carbon, hydrogen, oxygen, and nitrogen—plus minerals like iron, potassium, and more.
A balanced diet usually covers mineral needs, but deficiencies may require supplements.
Key minerals:
- Potassium – An electrolyte supporting kidneys, heart, muscles, and nerves. Too little raises blood pressure and stroke risk; too much harms those with kidney disease. Sources: Bananas, avocados, lentils.
- Sodium – Regulates fluids and nerve/muscle function. Too little causes fatigue; too much raises blood pressure. Limit to 2,300 mg/day (1 tsp salt).
- Calcium – Builds bones/teeth and supports nerves/heart. Too little weakens bones; too much causes kidney stones. 1,000–1,200 mg/day.
- Phosphorus – Strengthens bones/teeth. Deficiency is rare; excess usually comes from supplements. 700 mg/day.
- Magnesium – Aids muscle/nerve function and blood pressure. Too little causes fatigue; too much affects digestion. 320–420 mg/day.
- Zinc – Boosts immunity/wound healing. Deficiency is rare; excess causes nausea. 8–11 mg/day.
- Iron – Forms red blood cells. Too little causes anemia; too much is toxic. 8–18 mg/day (women need more).
- Manganese – Supports energy/bone health. Rarely deficient; excess causes tremors. 1.8–2.3 mg/day.
- Copper – Helps energy production. Deficiency is rare; excess harms the liver. 900 mcg/day.
- Selenium – Vital for thyroid/reproductive health. Too little raises heart disease risk; too much causes hair loss. 55 mcg/day.
Vitamins
These come in two types:
- Water-soluble (B vitamins & vitamin C) – Not stored; must be consumed regularly.
- Fat-soluble (A, D, E, K) – Stored in fat; excess can be harmful.
Antioxidants
These (like vitamins C and E) fight free radicals, which damage cells.
Dietitian vs. Nutritionist
- Dietitians (RD/RDN) – Require a degree, internship, exam, and ongoing education. Work in healthcare, research, or food science.
- Nutritionists – Study nutrition informally/officially but lack RD credentials. Often work in food tech or wellness.
The Bottom Line
Nutrition is about how food fuels the body. Eating varied, whole foods—especially plants—while limiting processed fats, sugars, and salt, supports health.
Popular diets (vegan, Mediterranean, keto, etc.) can work if they’re plant-heavy, fiber-rich, and nutrient-dense. But there’s no universal “best” diet—genetics, health, and lifestyle matter.