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.

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

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.

Nutrition

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.

Types

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.

Energy macronutrients

Energy macronutrients provide energy, which is measured either in kilocalories (kcal or calories) or Joules. 1 kilocalorie (calorie) = 4185.8 joules. Energy macronutrients include:

Carbohydrates – 4 kcal per gram

Carbohydrate molecules include monosaccharides (glucose, fructose, galactose), disaccharides, and polysaccharides (starch).

Nutritionally, polysaccharides are favored over monosaccharides because they are more complex and therefore take longer to break down and be absorbed into the bloodstream; this means that they do not cause major spikes in blood sugar levels, which are linked to heart and vascular diseases.

Proteins – 4 kcal per gram

There are 20 amino acids – organic compounds found in nature that combine to form proteins. Some amino acids are essential, meaning they need to be consumed. Other amino acids are non-essential because the body can make them.

Fats – 9 kcal per gram

Fats are triglycerides – three molecules of fatty acid combined with a molecule of the alcohol glycerol. Fatty acids are simple compounds (monomers) while triglycerides are complex molecules (polymers).

Fats are required in the diet for health as they serve many functions, including lubricating joints, helping organs produce hormones, assisting in absorption of certain vitamins, reducing inflammation, and preserving brain health.