What Are Nutrients and Why Do You Need Them?

Learn about the different nutrients.

You hear or see the word 'nutrient' quite often when you learn about foods, diet and weight loss. So, what exactly are nutrients? The general dictionary definition of 'nutrient' is something that provides nourishment. But, in nutrition, the nutrients are more specific. There are six categories of nutrients, all of which are necessary to sustain life:

  • Carbohydrates
  • Proteins
  • Fats
  • Vitamins
  • Minerals
  • Water

Grouping the Nutrients

Humans like to put things into categories and nutrients can be grouped by their chemical structure or by what they do in your body. In nutrition, we look at two main groups, the macronutrients and the micronutrients. Water, however, is in its own group.

Carbohydrates, proteins, and fats are called macronutrients, because they're large, and energy nutrients because they provide the fuel your body needs to do things. Vitamins and minerals are called micronutrients because they're much smaller in comparison. That doesn't mean they're less important; they're still essential nutrients, but you only need little bits.

Micronutrients can be classified by whether or not they're soluble in fat. Vitamins A, D, E, and K are fat-soluble, and the B-complex vitamins and vitamin C are water-soluble. Minerals are grouped as major minerals or trace minerals, depending upon how much of each mineral is necessary.

You can also group nutrients by whether they are organic or not, by which I mean organic chemistry, not organic farming or food production. Water and minerals are inorganic while all the rest are organic because they contain carbon atoms.

Why Nutrients Are Important

They provide energy. Carbohydrates, fats, and proteins provide the energy your body needs to carry out all the biochemical reactions that occur throughout the day (and night).

The energy is measured in calories (kilocalories, technically, but we usually just call them 'calories'). Gram for gram, fat has more calories than either carbohydrates or protein; one gram fat has nine calories, and the other two have four calories per gram.

They're necessary for body structures. Fats, proteins, and minerals are used as raw materials to build and maintain tissues, organs and other structures such as bones and teeth. Carbohydrates aren't on this list, but your body can take any extra carbohydrates and convert them into fat, which can be stored in adipose tissue.

They help regulate body functions. All six classes are involved in regulating various body functions such as sweating, temperature, metabolism, blood pressure, thyroid function, along with many others. When all of the different functions are in balance, your body is said to be in homeostasis.

Not Quite Nutrients, But Still Important

You might have read about phytonutrients, which aren't included in the major classes. Probably because they're fairly new in the world of nutrition research and aren't essential for survival. Phytonutrients are chemical compounds found in plants that offer potential health benefits.

Since they typically occur in foods that are also nutritious, it can be difficult to know how much of the health benefit is due to the regular nutrients or the phytonutrients. Some better-known phytonutrients include polyphenols and carotenoids.

Fiber is a type of carbohydrate that your body can't digest so it doesn't provide energy or structure. Fiber is necessary for digestive system function because it adds bulk to stool, so it is easier to eliminate. There are two types of fiber: soluble fiber that dissolves in water and insoluble fiber that doesn't dissolve.

Alcohol (the active ingredient in adult beverages) has calories (about 7 per gram; a little more than carbs and protein, but a little less than fats), but it isn't classified as a nutrient because it isn't necessary for life.


Gropper SS, Smith JL, Groff JL. "Advanced Nutrition and Human Metabolism." Fourth Edition. Belmont, CA. Wadsworth Publishing Company, 2005. 

Smolin LA, Grosvenor, MB. "Nutrition: Science and Applications." Third Edition. Wiley Publishing Company, 2013. 

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