Macronutrients are the type of foods which are required by the body in larger quantity, macronutrients involve protein, lipids, and carbohydrates.
Protein as a macronutrients:
Protein is the most abundant substance in the body,(other is water), there are twenty different amino acids which create proteins. Some amino acids synthesized properly in the body are known as non-essential amino acids and some amino acids have to take from the diet they are known as essential amino acids.
Leucine, lysine, isoleucine, methionine, valine, tryptophan, threonine, phenylalanine are essential amino acids. Arginine and histidine have inadequate synthesis during infancy so they are essential during infancy, they both have an important role in the growth of the infant.
The function of the protein as a macronutrients:
- Protein as a macronutrients is a source of energy for the body.
- It helps in the growth of the child.
- Protein as a macronutrients is necessary for the formation of digestive juice, hormones, vitamins, plasma protein, enzymes, hemoglobin.
- Proteins help to maintain acid-base equilibrium.
If excess protein is taken, it is not used by the body to build tissues or to provide energy to the body instead of, converted to fat by the liver and stored in body tissues.
How much protein to be taken as a macronutrient:
- An average adult requires 1.0 g/kg of body weight of protein as a macronutrient.
- 15 grams/kg body weight per day, in addition, must be taken during in latter half of pregnancy.
- Additional daily intake of 25 grams/kg body weight is required during lactation (first six months) and 18 grams during 6-12 months of lactation.
Sources of protein as macronutrients:
A complete protein is that protein which contains all the essential amino acids, in the same amounts as the human body requires for maintenance for its proper growth. Animal origin protein has a higher content of all essential amino acids, than protein derived from vegetable sources so animal origin protein is considered as a biologically complete protein as in vegetable origin protein there is a lack of one or more essential amino acids. Protein taken from rice and potato are good vegetable proteins.
High-quality protein must be complete and must be digestible, this is measured by the biological value of protein. Egg protein is called a reference protein as it is both complete and easily digestible.
Carbohydrate as macronutrients :
Carbohydrates as macronutrients give energy, had a contribution to the taste and texture of food and are essential for the assimilation and digestion of other foods. Carbohydrates protect the protein to be used for energy.
Carbohydrates are of two types:
- Simple carbohydrates: monosaccharides (deoxyribose, galactose, glucose, ribose, fructose)and disaccharides (sucrose, maltose, lactose).
- Complex carbohydrates: Polysaccharides (fiber, glycogen, starch).
Carbohydrates is obtained from grains vegetable fruits and legumes, this type of diet is low in fat and high in fiber vitamin, minerals, and energy. These diets contribute to lower rates of undernutrition, obesity, cardiovascular disease and diabetes. Excess consumption of carbohydrates in the form of sweets leads to dental caries, excessive weight gain, cataract ischemic heart diseases.
The deficiency of carbohydrates as micronutrients in the diet leads to ketosis, depression, loss of energy, breakdown of body protein. The excess of carbohydrates is converted to fat.
Role of fibers:
- They are important because they have water-holding, bile binding capacity and for the growth of the normal microflora the intestine.
- Water-soluble fiber like gums and pectin helps in lowering blood cholesterol and limits the absorption of glucose.
- Fibers which are insoluble in water helps as a stool softener.
- A high fiber diet is an advocate for chronic constipation, diabetes, increased cholesterol level, and obesity.
- Low fiber diet is very helpful in irritable bowel syndrome, chronic colitis and chronic gastrointestinal obstruction of partial type.
Cereals, vegetables, dried beans, and fruits are rich in fibers. Water-soluble fibers are found in fruits and vegetables. Avoid excess intake of fibers as they lead to decreased bioavailability of minerals and lead to increased gas in the abdomen and low appetite.
Lipid as macronutrient:
- Lipids as macronutrients work as insulators of the body and are concentrated sources of energy.
- Lipids as macronutrients are the carrier for vitamins which belongs to the fat-soluble category.
- Lipids include sterols (cholesterol), lecithin as phospholipids, fats, and oils as triglycerides.
What is the recommended quantity of fat?
- 10 percent maximum for saturated fats.
- 300 mg per day maximum for cholesterol.
- Excess fat leads to obesity non-insulin-dependent diabetes mellitus, cancer, hypertension, etc.
Cholesterol is a lipid very important to good health, but intake must be within the limit, as the carbohydrate is synthesized in the body from fat or carbohydrates and protein the scarcity of carbohydrate in the body usually does not occur. Cholesterol is an important part of the cell membrane. Cholesterol is only found in animal foods like ghee, cheese, liver, kidney, eggs.
- They are those lipids that are abundant.
- Food lipids constitute 95% of triglycerides and the lipids which are stored in the body are 99% of triglycerides.
Saturated fatty acids: They are derived from animals (leaving coconut oil) and remain solid at 20-30 degrees centigrade.
Unsaturated fatty acids: They remains liquid in room temperature and obtained from vegetable seeds etc. Fatty acids with one unsaturated link can be synthesized in the body , but polyunsaturated fatty acids (PUFA) cannot be adequately synthesized in the body.
There are two Important families of PUFA :
- Omega 6 fatty acids: Linoleic acid (18:2 omega 6) and Arachidonic acid.
- Omega 3 fatty acids: Liniloc acid (18:3 omega 3), Eicosapentaenoic acid (EPA), Docosahexaenoic acid (DHA).
These PUFA must be available in the diet for good health and hence called essential fatty acids.
Essential fatty acids:
- Essential fatty acids are necessary components of the cell membrane, they provide at least 3% of energy.
- Eicosapentaenoic acid (EPA) and Docosahexaenoic acid (DHA) lowers cholesterol in blood and triglyceride concentration, these serve as an important constituent for the synthesis of eicosanoids, which plays an important role in the regulation of blood pressure, lipid concentration, immune response and inflammatory response to infection and the injury.
- EPA favors atherogenesis which means formation of fatty deposits in arteries.
Vegetable oils are a good source for supplying Omega 6 lipids but they lack the desired quantity of omega 3 lipids.
Omega 3 fatty acids are more abundantly found in fish and other seafood.
Deficiency of essential fatty acids may lead to growth retardation, reproductive failure, skin disorders, decreased myocardial contractibility, renal hypertension, and hemolysis and more prone to infections. Selective deficiency of omega 6 fatty acids may cause skin changes while deficiency of omega 3 fatty acids results in visual and neurological symptoms.