Food provides the body with the nutrients it needs for energy, growth, repair, and reproduction. Nutritionists divide nutrients into two main groups: macronutrients and micronutrients. Macronutrients, needed in greater quantities, include carbohydrates, fats, and proteins. These are the foods our bodies use for energy and growth. Micronutrients, which are required in smaller amounts, include vitamins and minerals. Most foods contain a combination of the two groups.

An essential nutrient is a nutrient required for normal body functioning that cannot be synthesized by the body, or cannot be synthesized in amounts adequate for good health, and thus must be obtained from a dietary source. Essential nutrients are also defined by their importance in  human diet. Nutrients work (together) synergistically with other nutrients.

Categories of essential nutrients include vitamins, dietary minerals, essential fatty acids, and essential amino acids. Water and oxygen are also essential nutrients.

There are 14 essential vitamins:

Vitamin A, Choline (vitamin Bp), Vitamin B1, B2, B3, B5, B6, B7, B9, B12, Vitamin C, Vitamin D, Vitamin E, and Vitamin K.

There are 17 essential minerals:

Calcium, Chloride, Chromium, Cobalt, Copper, Iodine, Iron, Magnesium, Manganese, Molybdenum, Nickel, Phosphorous, Potassium, Selenium, Sodium, Sulfur and Zinc.

There are 2 essential fatty acids:

α-Linolenic acid and Linoleic acid

There are 8 essential amino Acids for adults:

Isoleucine, Lysine, Leucine, Methionine, Phenylalanine, Threonine, Tryptophan and Valine.

There are 2 essential amino acids for children that are not required for adults:

Histidine and Arginine

All of these nutrients combine to allow our bodies to function normally. A deficiency can undermine our natural ability to sustain health and prevent and fight diseases and disorders.

In a larger context, these essential nutrients, along with water and energy (calories), are so vital to human life that an entire organ system, the digestive system, is always at work ready to provide our body with these essential nutrients from the diet we eat.