Nutrition, nourishment, or aliment, is the supply of materials – food – required by organisms and cells to stay alive. In science and human medicine, nutrition is the science or practice of consuming and utilizing foods.
In hospitals, nutrition may refer to the food requirements of patients, including nutritional solutions delivered via an IV (intravenous) or IG (intragastric) tube.
Nutritional science studies how the body breaks food down (catabolism) and how it repairs and creates cells and tissue (anabolism). Catabolism and anabolism combined can also be referred to as metabolism. Nutritional science also examines how the body responds to food.
Fast facts on nutrition
The human body requires seven major types of nutrients.
Not all nutrients provide energy but are still important, such as water and fiber.
Micronutrients are important but required in smaller amounts.
Vitamins are essential organic compounds that the human body cannot synthesize.
What is nutrition?
As molecular biology, biochemistry, and genetics advance, nutrition has become more focused on metabolism and metabolic pathways – biochemical steps through which substances inside us are transformed from one form to another.
Nutrition also focuses on how diseases, conditions, and problems can be prevented or reduced with a healthy diet.
Similarly, nutrition involves identifying how certain diseases and conditions may be caused by dietary factors, such as poor diet (malnutrition), food allergies, and food intolerances.
Dietitian vs. nutritionist
A registered dietitian nutritionist (RD or RDN) studies food, nutrition, and dietetics through an accredited university and approved curriculum, then completes a rigorous internship and passes a licensure exam to become a registered dietitian.
A nutritionist (without the title of an RD or RDN) studies nutrition via self-study or through formal education but does not meet the requirements to use the titles RD or RDN. The two terms are often interchangeable, but they are not identical.
Dietetics is the interpretation and communication of the science of nutrition; it helps people make informed and practical choices about food and lifestyle in both health and disease.
Part of a dietician’s course includes both hospital and community settings. Dietitians work in a variety of areas, from private practice to healthcare, education, corporate wellness, and research, while a much smaller proportion work in the food industry.
A dietitian must have a recognized degree or postgraduate degree in nutrition and dietetics and meet continuing education requirements to work as a dietitian.
Nutritionists sometimes carry out research for food manufacturers.
Nutrition is the study of nutrients in food, how the body uses nutrients, and the relationship between diet, health, and disease.
Major food manufacturers employ nutritionists and food scientists.
Nutritionists may also work in journalism, education, and research. Many nutritionists work in the field of food science and technology.
There is a lot of overlap between what nutritionists and dietitians do and study. Some nutritionists work in a healthcare setting, some dietitians work in the food industry, but a higher percentage of nutritionists work in the food industry and in food science and technology, and a higher percentage of dietitians work in healthcare, corporate wellness, research, and education.
A nutrient is a source of nourishment, a component of food, for instance, protein, carbohydrate, fat, vitamin, mineral, fiber, and water.
Macronutrients are nutrients we need in relatively large quantities.
Micronutrients are nutrients we need in relatively small quantities.
Macronutrients can be further split into energy macronutrients (that provide energy), and macronutrients that do not provide energy.
Can fat be good for you?
We explain the different types of fats, which are considered good and bad, and what foods they can be found in.
Macronutrients that do not provide energy
These do not provide energy, but are still important:
Fiber consists mostly of carbohydrates. However, because it is not easily absorbed by the body, not much of the sugars and starches get into the blood stream. Fiber is a crucial part of nutrition, health, and fuel for gut bacteria.
For more details go to “What is fiber? What is dietary fiber?”
About 70 percent of the non-fat mass of the human body is water. It is vital for many processes in the human body.
Nobody is completely sure how much water the human body needs – claims vary from 1-7 liters per day to avoid dehydration. We do know that water requirements are very closely linked to body size, age, environmental temperatures, physical activity, different states of health, and dietary habits; for instance, somebody who consumes a lot of salt will require more water than another similar person.
Claims that ‘the more water you drink, the healthier you are’ are not backed with scientific evidence. The variables that influence water requirements are so vast that accurate advice on water intake would only be valid after evaluating each person individually.
Micronutrients are required in smaller quantities:
Minerals are found in a range of food types.
Dietary minerals are the other chemical elements our bodies need, other than carbon, hydrogen, oxygen, and nitrogen.
People with a well-balanced diet will, in most cases, obtain all the minerals they need from what they eat.
Minerals are sometimes added to certain foods to make up for any shortages.
The best example of this is iodized salt – iodine is added to prevent iodine deficiency, which affects about 2 billion people, globally; it causes mental retardation and thyroid gland problems. Iodine deficiency remains a serious public health problem in over half the planet.
Experts at the University of Florida say that 16 key minerals are essential for human biochemical processes:
What it does – a systemic (affects entire body) electrolyte, essential in co-regulating ATP (an important carrier of energy in cells in the body, also key in making RNA) with sodium.
Deficiency – hypokalemia – can profoundly affect the nervous system and heart.
Excess – hyperkalemia – can also profoundly affect the nervous system and heart.
What it does – key for producing stomach acid, important in the transport of molecules between cells, and vital for the proper functioning of nerves.
Deficiency – hypochloremia – low salt levels, which, if severe, can be very dangerous.
Excess – hyperchloremia – usually no symptoms, linked with excessive fluid loss.
What it does – a systemic electrolyte, and essential in regulating ATP with potassium. Important for nerve function and regulating body fluid levels.
Deficiency – hyponatremia – causes cells to malfunction; extremely low sodium can be fatal.
Excess – hypernatremia – can also cause cells to malfunction, extremely high levels can be fatal.
What it does – important for muscle, heart, and digestive health. Builds bone, assists in the synthesis and function of blood cells.
Deficiency – hypocalcaemia – muscle cramps, abdominal cramps, spasms, and hyperactive deep tendon reflexes.
Excess – hypercalcemia – muscle weakness, constipation, undermined conduction of electrical impulses in the heart, calcium stones in the urinary tract, impaired kidney function, and impaired absorption of iron, leading to iron deficiency.
What it does – important for the structure of DNA, transporter of energy (ATP), component of cellular membrane, helps strengthen bones.
Deficiency – hypophosphatemia, an example is rickets.
Excess – hyperphosphatemia, often a result of kidney failure.
What it does – processes ATP; required for good bones and management of proper muscle movement. Hundreds of enzymes rely on magnesium to work properly.
Deficiency – hypomagnesemia – irritability of the nervous system with spasms of the hands and feet, muscular twitching and cramps, constipation, and larynx spasms.
Excess – hypermagnesemia – nausea, vomiting, impaired breathing, low blood pressure. Very rare, but may occur if patient has renal problems.
What it does – required by many enzymes. Important for reproductive organ growth. Also important in gene expression and regulating the nervous and immune systems.
Deficiency – short stature, anemia, increased pigmentation of skin, enlarged liver and spleen, impaired reproductive function, impaired wound healing, and immune deficiency.
Excess – suppresses copper and iron absorption.
What it does – required for proteins and enzymes, especially hemoglobin, the oxygen-carrying compound in blood.
Deficiency – anemia.
Excess – iron overload disorder; iron deposits can form in organs, particularly the heart.