Nutrients Introduction – 6 Major Classes of Nutrients and their Functions

Learn about the six major classes of nutrients (carbohydrates, proteins, lipids, vitamins, minerals & water) and their functions in our body. Understand the difference between essential and non-essential nutrients, energy-yielding and non-energy yielding nutrients, organic and inorganic nutrients, macro and micronutrients, building elements of nutrients, and calculate potential energy in food.

Nutrients are the substances available in food. Our body uses energy for every activity, either it is our physical movement, thinking about something or any internal metabolic process. Nutrients provide us this energy to perform all these tasks. Nutrients are essential for our growth & development, maintaining cells & tissues and support thousands of body processes that go on inside every day. In simple words, nutrients support our life. There are so many nutrients that can be categorized under 6 major classes of carbohydrates, proteins, lipids, vitamins, minerals, and water.

Essential and Non-essential Nutrients

Our body can make some nutrients as per its needs. So, these nutrients are called non-essential nutrients. Non-essential means, it is not necessary to take these nutrients from food.

There are many other nutrients that our body cannot make, or cannot make in sufficient amounts. These nutrients are called essential nutrients. Essential means, it is necessary to take these nutrients from food or any other source. 45 essential nutrients should be present in our food.

Please note, don’t be confuse about essential and non-essential nutrients. Always eat a diet, rich in all nutrients for good health.

Nutrients in Foods & Our Body

Foods are made of nutrients. Chemical analysis shows that an apple is almost 84% water. If we remove all the water from apple, the remaining part is carbohydrates, proteins, and lipids. If we further remove these three parts, we will find vitamins and minerals in a very small amount.

60% of human body is water

In the same way, if we analyze our body, it is almost 60% water. Further 15-30% is fat. Remaining is mostly protein, carbohydrates, and minerals. There are vitamins also in a very small amount.

So, you can see that the nutrient composition of our food and our body is almost the same. But why this is so? Because our tissues and cells are made of the food we eat. In simple words, we are what we eat.

There are also many other substances in our food. For instance, phytochemicals, zoochemical, alcohol, caffeine, additives, pigments, etc. Phytochemicals are compounds available in plants the same as zoochemical in animals. Phytochemicals and zoochemical don’t fit in the nutrient’s definition but very beneficial for our physical health. These compounds work as antioxidants and prevent oxidative damage to cells and tissues. Research suggests that these compounds can reduce the risk of heart disease and cancer.

Energy Yielding Nutrients

Proteins, carbohydrates, and lipids (triglycerides only) are the three classes of nutrients which supply the body with energy. So, these three classes of nutrients are called energy-yielding nutrients. The human body can break down these nutrients and can use the released energy.

This energy is measured in calories. A calorie is such a small unit of energy that a banana can provide more than 1,00,000 calories. Just for the sake of convenience, energy is calculated in 1000 calorie metric units, called “kcalories” or “kilocalories”. In simple words, 1 kcalorie or 1 kilocalorie means 1000 calories, but in general books and magazines, the word “calorie” is used instead of “kcalories” and “kilocalories”. So, when you read that a banana provides you 100 calories, it simply means 100 kilocalories.

Potential energy in nutrients:

Carbohydrates4 calories
Protein4 calories
Fat9 calories
Alcohol (not a nutrient)7 calories

Alcohol is not counted as a nutrient but just for your information, 1 gram of alcohol provides 7 calories. Don’t say cheers because alcohol is very harmful to our health. We will discuss alcohol in some other article.

How to Calculate Potential Energy in Foods

It is really easy to calculate the potential energy available in foods. Just multiply the amount of protein (in grams) by 4, multiply the amount of carbohydrate (in grams) by 4, multiply the amount of fat (in grams) by 9 and make a total of all the values. We need almost 2000 calories every day and our body gets all these calories from food.

Here is a calculation of energy available in one large slice of white bread.

  • Step 1 : Total fat 1 gram x 9 calories = 9 calories
  • Step 2 : Total carbohydrates 15 grams x 4 calories = 60 calories
  • Step 3 : Total proteins 3 grams x 4 calories = 12 calories
  • Step 4 : Total of 9 + 60 + 12 = 81 calories

If you understand please calculate the calories in this food and comment below.

Organic and Inorganic Nutrients

We can divide 6 classes of nutrients into organic and inorganic categories. Carbohydrates, proteins, lipids, and vitamins are organic because these have a carbon element in the structure. Mineral and water, both are inorganic because these don’t have a carbon element. Carbon is an element that is found in all organic (living) matter, but not in inorganic (non-living) matter. In simple words, organic means chemical compounds with carbon in them.

Alanine 3D Molecule/ L-alanine-3D-balls/ Black part is carbon

Here you can see this alanine amino acid molecule structure which is a protein. The black part of this molecule is the carbon element.

Water 3D Molecule/ Water-3D-balls/ No Carbon

Here is a molecule with 2 hydrogens (white parts) and 1 oxygen (red part), without any carbon element. This is a molecule of water.

Macronutrients and Micronutrients

We can divide classes of nutrients based on how much quantity of them we need in our diet, as macro and micro. Carbohydrates, Proteins, and Fats are called macronutrients because we need many grams of them each day. Vitamins and minerals are called micronutrients because we need only a few milligrams or micrograms.

Now we discuss all 6 classes of nutrients in brief.


Carbo means carbon, hydrate means water, which is a combination of oxygen and hydrogen. So, carbohydrate means “hydrate of carbon” which is made of carbon, hydrogen, and oxygen. Carbohydrates are available in almost every food, especially in grains, rice, pulses, vegetables, fruits, and dairy products. The dietary fiber, which is a long chain of sugars, available in food is also a type of carbohydrate, but not considered as a nutrient, because our body cannot digest (break down) fiber. Yes, the body cannot break down fiber but it is very important for our digestive system. All other types of carbohydrates are broken down by our body and converted into glucose (a simple sugar compound) which is a primary source of energy for our body.


All fats and oils are lipids, but all lipids are not fat. Because there are many other types of lipids, fatlike substances as cholesterol and phospholipids, etc. Same as carbohydrates, lipids are also made of carbon, hydrogen, and oxygen. Lipids are very essential for our health as they provide us energy, provide structure to our body cells, carry fat-soluble vitamins (A, D, E & K), and produce hormones. We get lipids from dairy products, meat products, coconuts, olives, avocado, almonds, seeds, etc.


Proteins are made of amino acids. There are 20 standard amino acids. All these amino acids form a short chain together, which is called the amino peptide. Many of these amino peptides, together, form long chains, which is called protein. The body breaks down the protein into amino acids and these amino acids combine with the body’s amino acids to make hundreds of different amino acids. Our body can use protein as an energy source. Proteins provide us a body structure, take part in different functions of blood, cell membranes, immune factors, and enzymes.

The structure of a protein is different from carbohydrates and lipids because protein has a nitrogen element additional to oxygen, carbon, and hydrogen.

Here is a picture of alanine amino acid which is a protein. The blue part of this molecule is nitrogen. Lipids and carbohydrates don’t have nitrogen element in their molecular structure.


Vitamins are organic compounds made of carbon, nitrogen, hydrogen, oxygen, phosphorus, sulfur, etc. Vitamins don’t provide us energy but help in all the metabolic processes in the human body. Without the help of vitamins, our body cannot use energy from carbohydrates, proteins, and fats. There are 13 vitamins and we need every vitamin for some particular function. For instance, a vitamin helps us to see, a vitamin supports healthy hairs, another vitamin takes part in hormone production.

We can divide all 13 vitamins into 2 categories as fat-soluble and water-soluble. We get vitamins from fruits, vegetables, plants, dairy products, meat products, etc. Any vitamin deficiency can be a reason for any disease, as well as an overdose of vitamins can also cause an issue.

Elements in the six major classes of nutrients.


Minerals are very simple substances and essential for our health, the same as vitamins. We can divide all minerals into 2 categories based on the amount we need, as macro and micro. Macro-minerals mean the minerals we need in large quantities as calcium, phosphorus, magnesium, sodium, potassium, chloride, and sulfur. Micro-minerals mean the minerals we need in small quantities as zinc, iron, manganese, copper, selenium, molybdenum, iodine, and fluoride. Microminerals are also called trace minerals. We get minerals from plant and dairy products.


Now, in the end, we talk about the most important nutrient, water. 60% of our body is water. 92% of human blood is water. 71% of the earth’s surface is covered with water. Water is everywhere, even in the air as water vapor. Water as a nutrient helps our body to maintain temperature, transport other nutrients and wastes, lubricate our joints, provides a framework for every chemical reaction in the body, and many more. We can live many days without other nutrients but not without water. We get water, not only from liquids but also from fruits, vegetables, and milk, etc. because almost every food contains water.

We shall discuss all these nutrients in detail in further articles. Thank you.

Published: May 3, 2020

Author: Vikas Dhavaria

A free spirit who loves to read books. Interested in philosophy, logic and mathematics.

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