The big 3 – Macronutrients

Nutrient is a component in food that organism uses to survive and grow. Macronutrients are types of food or chemical elements that humans consume in everyday life. There are three primary macronutrients: carbohydrate, proteins and fats. Each of them has their nutritional value. There are also more macronutrients that has nutritional value like alcohol and those that don’t provide nutritional value like water, fiber, micronutrients.

PROTEINS

Proteins are one of the building blocks of body tissue but they can also serve as a fuel source. They provide 4 kcal per gram of energy. Amino-acids build proteins and they are stored in cells and bound with enzymes. Body can only take limited amount of proteins (amino-acids) so the excess is dissolved as energy source or stored as fat.

Essential amino acids and non-essential amino acids are two sorts of amino acids. There are 9 amino acids our body needs but cannot produce for itself so it must be obtained through food while there is 11 non-essential amino acids can be produced by our own body.

FATS

Fats are composed of three fatty acid chains thus they are called triglycerides. Fats are broken down to glycerol and fatty acids. Glycerol can be converted to glucose and become a source of energy. Metabolized fat releases 9 kcal per gram. There are unsaturated and saturated fat.

 

Unsaturated fat

Saturated fat

Monounsaturated fat

Polyunsaturated fat (essential fats omega 3 and omega 6)

Trans fat

Interesterified fat

 

Fats are important part of any diet because some vitamins like A,D,E,K are not absorbed if they are not bound to fat.

CARBOHYDRATE

Carbohydrates are common source of energy but no carbohydrate is an essential nutrient in humans. Carbs produce 4 kcal of energy per gram.

Monosaccharides are the simplest carbohydrates that cannot be broken down to smaller carbohydrates. They are the major source of fuel for metabolism. Glucose is most important simple sugar in human body and only fuel brain can use beside ketone bodies. Besides sugars, human body needs non-starch polysaccharides knows as fiber. They cannot be metabolized or absorbed by humans but with their volume they speed up the process of elimination and prevent constipation.

Unused glucose is metabolized in liver in glycogen. The body stores glycogen in liver and muscles. But there is limited capacity. Liver can store about 100g of glycogen and muscles around 500g, the rest is stored as adipose tissue (fat).

 

Sugars

Polysaccharides

MONOSACCHARIDES

DISACCHARIDES STARCH

NON-STARCH

Glucose

Galactose

Fructose

Xylose

Sucrose

Lactose

Maltose

Trehalose

Amylose

Amylopectin

 

Cellulose

Hemicellulose

 

 

ALCOHOL

Alcohol is also a nutrient that yields energy. One gram of alcohol produces 7 kcal of energy. Human body produces around 3 gram of ethanol per day merely through fermentation.

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