Six Essential Nutrients for Our Body

Nutrients are chemical substances the body requires to sustain essential functions and are optimally obtained by eating a balanced diet. Six essential nutrients are vital for human health: carbohydrates, proteins, lipids, vitamins, minerals, and water

As we eat, foodstuffs are digested and absorbed. The products of digestion circulate in the blood, enter various tissues, and are eventually taken up by cells and oxidized to produce energy. The diet also provides precursors, such as essential fatty acids and amino acids that our body can not synthesize, for the biosynthesis of compounds necessary for anatomical structure or physiological functions.

In discussions of metabolism and nutrition, energy is expressed in calories.

Caloric content of fuels

FuelKcal/g
Carbohydrate4
Protein4
Fat9

Carbohydrates

Carbohydrates are essential macronutrients that are the primary energy source for humans and play roles in gut health and immune function. Oxidation of 1 gram of carbohydrates to CO2 and H2O  in the body produces about 4 kcal of energy [1]. For healthy children and adults, carbohydrates should make up approximately 45 to 65% of energy intake. 

Dietary fibers are plant polysaccharides like pectin and cellulose found in whole grains, fruits, vegetables, and legumes and play a major role in gut health and lower the risk of coronary artery disease. The recommended fiber intake is greater than 38 g for men and 25 g for women.

The major carbohydrates in the human diet are starch, sucrose (table sugar), lactose (milk sugar), glucose, fructose, maltose, and galactose. Optimal carbohydrate intake consists of fiber-rich, nutrient-dense whole grains, fruits, vegetables, legumes, and less added sugar [2].

Digestion converts the larger carbohydrates to monosaccharides, which are absorbed into the bloodstream. Glucose, a monosaccharide, is the predominant sugar in human blood.

Read more about types of carbohydrates found in food.

Proteins

These are essential macronutrients composed of amino acids that are joined to form linear chains. Proteins are the structural components of cells and tissues. Adequate consumption of protein is needed to maintain lean muscle mass. Proteins also serve as enzymes (catalysts of biochemical reactions) and regulate cell and body processes (as enzymes).

Healthy dietary patterns include consuming a variety of protein foods in nutrient-dense forms. Proteins are available in food sources like meats, poultry, and eggs; seafood; and nuts, seeds, and soy products [3].

The digestive process breaks down proteins into their constituent amino acids, which enter the blood. Complete oxidation of one gram of proteins yields approximately 4 kcal of energy, and byproducts such as CO2, H2O, and NH4+ are formed [1]. The recommended protein intake is 0.8 to 1 gram per kilogram of body weight per day [4].

Lipids

Lipids are essential macronutrients composed of triglycerides (triacylglycerols). A triacylglycerol molecule contains three fatty acids esterified into one glycerol molecule. Lipids are the body’s main source of stored energy, contribute to cellular structure and function, regulate temperature, and protect body organs. 

Lipids are found in fats, oils, meats, dairy, and plants [5]. Total fat should contribute less than 30%, and saturated fat should meet <10% of total calories requirements. The amount of saturated fat is given in upper limits because of that type of fat’s ability to raise blood cholesterol levels.

Lipids are more reduced than other biomolecules and yield more energy when oxidized.  The complete oxidation of one gram of fat into CO2 and H2O in the body releases approximately 9 kcal of energy, more than twice the energy yield from an equivalent amount of carbohydrate and protein [1]. 

Approximately 5 to 10% of the daily fat energy intake should consist of omega-6 (n-6) polyunsaturated fatty acids such as linoleic acid. Omega-3 (n-3) polyunsaturated fatty acids such as α-linolenic acid should meet 0.6 to 1.2% daily fat energy intake [2]. 

Vitamins

Vitamins and minerals are considered micronutrients and play essential roles in metabolism. These are a diverse group of organic molecules required in minimal quantities (in the microgram or milligram range) in the diet for health, growth, and survival. 

Vitamins are organic micronutrients classified as either water-soluble or fat-soluble. The classification has little relationship to their function but is related to absorption and transport.

Most vitamins are used as precursors for coenzymes, organic molecules that assist enzymes in catalyzing biochemical reactions. However, some vitamins also act as hormones. 

Water-soluble vitamins 

Thiamin, riboflavin, niacin, pantothenic acid, vitamin B6, biotin, vitamin B12, folate, and vitamin C are water-soluble vitamins. Find more about each of these vitamins;

  1. Thiamin (Vitamin B1)
  2. Riboflavin (Vitamin B2)
  3. Niacin (Vitamin B3)
  4. Pantothenic Acid (Vitamin B5)
  5. Vitamin B6
  6. Biotin (Vitamin B7)
  7. Folate (Vitamin B9)
  8. Vitamin B12 (Cobalamin)
  9. Vitamin C (Ascorbic acid)

Fat-soluble vitamins 

Vitamins A, D, E, and K are essential fat-soluble vitamins.

  1. Vitamin A (Retinol)
  2. Vitamin D (Cholecalciferol)
  3. Vitamin E (Tocopherol)
  4. Vitamin K (Phylloquinone; Menaquinone)

Minerals

These are inorganic micronutrients required in the diet. Minerals are classified as macro or major minerals and micro or trace minerals, depending on the amounts required. 

Table: Minerals Required in the Diet

Macro MineralsMicro (Trace) Minerals  
Sodium aIodine
Potassium aSelenium
Chloride aCopper
CalciumZinc
PhosphorousIron
MagnesiumManganese b
 Fluoride b
 Chromium b
 Molybdenum b

a Electrolytes
b Ultratrace minerals

Macrominerals 

Macrominerals are required in amounts greater than 100 mg daily and include calcium, phosphorous, magnesium, sodium, potassium, and chloride. Calcium and phosphorous are structural components of bones and teeth, while phosphorous is required for ATP formation. Magnesium activates many enzymes and also forms a complex with ATP. 

Sodium (Na+), potassium (K+), and chloride (Cl-) are the major electrolytes. Electrolytes are inorganic ions dissolved in our body’s fluid compartment and are used to establish ion gradients across membranes, maintain water balance, and neutralize positive and negative charges on proteins and other molecules. 

Microminerals

Microminerals are those nutrients required in amounts less than 100 mg daily, including iron, copper, zinc, selenium, and iodine. Iron is a component of hemoglobin (the oxygen-carrying protein in the blood) and is required by many enzymes in oxidation-reduction reactions. 

Water 

It is required in large amounts but does not yield energy. Water constitutes 1/2 to 4/5 of the weight of the human body. Daily water intake depends on the balance between the amount produced by body metabolism and the amount lost through the skin, expired air, urine and feces. 

We need about eight cups of water each day and more if we are sweating or have a fever or diarrhea. In addition to drinking water, we get water from soups, tea, coffee, juices, and fruits and vegetables.

  1. Guenther PM, Jensen HH. Estimating energy contributed by fiber using a general factor of 2 vs 4 kcal/g. J Am Diet Assoc. 2000 Aug;100(8):944-6. [PubMed Central]
  2. Trumbo P, Schlicker S, Yates AA, Poos M., Food and Nutrition Board of the Institute of Medicine, The National Academies. Dietary reference intakes for energy, carbohydrate, fiber, fat, fatty acids, cholesterol, protein and amino acids. J Am Diet Assoc. 2002 Nov;102(11):1621-30. [PubMed Central]
  3. Pasiakos SM, Agarwal S, Lieberman HR, Fulgoni VL. Sources and Amounts of Animal, Dairy, and Plant Protein Intake of US Adults in 2007-2010. Nutrients. 2015 Aug 21;7(8):7058-69. [PubMed Central]
  4. Acheson KJ. Diets for body weight control and health: the potential of changing the macronutrient composition. Eur J Clin Nutr. 2013 May;67(5):462-6. [PubMed Central]
  5. Del Razo Olvera FM, Melgarejo Hernández MA, Mehta R, Aguilar Salinas CA. Setting the Lipid Component of the Diet: A Work in Process. Adv Nutr. 2017 Jan;8(1):165S-172S. [PubMed Central]

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