Chapter 3 :- Macro Nutrients

 Simple Carbohydrates vs Complex Carbohydrates:

Simple Carbohydrate	Complex Carbohydrate
Simple carbohydrates contain single molecule or smaller chains of sugar.	Complex carbohydrates contain longer chains of sugar molecules than simple carbohydrates.
Simple carbohydrates are quicker to digest than complex carbohydrates.	Complex carbohydrates take longer to digest and are a more stable source of energy.
Simple carbohydrates are in foods such as table sugar and syrups.	Complex carbohydrates are present in foods such as bread and pasta.
Milk and milk products contain simple carbohydrate. These foods do not contain fiber but are rich in protein, calcium, and vitamin D	Complex carbohydrates found in whole foods tend to be highly nutritious

Deficiency of carbohydrates -

The daily diet should not contain less than 100 g of carbohydrate. Carbohydrate deficiency is uncommon in our country as diets are cereal based. A deficiency of carbohydrate in the diet results in utilization of fat for energy. In severe deficiency, incomplete oxidation of fats causes ketone bodies to accumulate in the blood. 

Excess Carbohydrates-

1. Excessive consumption of refined sugars could be one of the causes of dental caries or tooth decay. 
2. Excessive sugar depresses the appetite, provides hollow calories, and could result in malnutrition. 
3. High intake of sugar and refined carbohydrates increase the blood triglyceride levels leading to heart diseases.
4. When excessive carbohydrates are consumed, they are converted into fat and deposited in the adipose tissue, which could lead to obesity, i.e., body weight of 20 percent or more than the desirable weight. 
5. Excessive fiber could irritate the intestinal lining, causing cramps or bloating due to gas formation. 
6. Excessive fibre interferes with the absorption and availability of mineral elements such as iron and calcium. 

(A.) Carbohydrates:-

a.) Definition:-

Carbohydrates are a major source of energy for humans, providing approximately 45 percent to 80 percent of the total calorie intake in different income groups. Since they are a relatively inexpensive source of energy compared to fats and proteins,they form the bulk of the diet of humans throughout the world. 

          They are mainly present in food in the form of sugars,starches,and fibres. A study of the various types of carbohydrates is necessary because the kind and proportion of different forms of carbohydrate present in food have a direct bearing on our health. 

         Three groups of carbohydrates are of importance in our diet from the nutritional point of view, namely sugars,starches, and fibres. The sugar and starch that we consume is ultimately broken down to glucose in the digestive tract and absorbed into the blood circulation. In the human body, glucose is removed from blood by the tissue cells and used as a source of energy. Some glucose is converted to glycogen, also called animal starch, and stored in the muscle and liver as a reserve store of energy. 

Glucose-------> Energy +CO2 + H20

                                         Waste products of                                                             metabolism 

Definition- Carbohydrates are polyhydroxy aldehydes or polyhydroxy ketones, or substances that yield such compounds on hydrolysis. Carbohydrates are organic compounds made up of carbon, hydrogen, and oxygen. These are called carbohydrates because hydrogen and oxygen are present in the same proportion as found in water. 

b.) Classification (mono,di and polysaccharides) :-

Carbohydrates,which are of importance in the diet, are classified on the basis of the number of sugar units present in them.

 They may also be classified as:

Available carbohydrates- Carbohydrates which can be digested in the human body and yield energy when they are oxidized in the body. 

Unavailable carbohydrates- Carbohydrates which cannot be digested because the human body does not contain the enzymes for their breakdown. Unavailable carbohydrates do not provide any energy to the body but are necessary as they perform some important functions in the body such as regular elimination of faecal waste. 

c.) Dietary Sources:-

Daily diet should provide up to 50-70 percent kcal of energy from carbohydrate, which means that the diet of an individual who needs 2,400 kcal should consume 60 percent of 2,400 ,i.e., 1,440 kcal or 360 g of carbohydrates/day . Carbohydrates are not only an economical source of energy but are also readily available and easy to store as they have a long shelf life. 

              All foods of plant origin contain carbohydrates in varying amounts. With the exception of milk, animal foods do not contain carbohydrate. Although milk is not consumed as a source of carbohydrate, some milk products, such as khoa and milk powder, contain significant amount of carbohydrate lactose. 

               The important sources of carbohydrates in the diets of Indians are cereals and millets, roots,tubers,pulses, sugar, and jaggery. 

All sugars provide 4 kcal/g of energy. The carbohydrate and calorie content of a food can be reduced by using sugars which are sweeter than sucrose so that the quantity of sugar required will be less. 

d.) Functions:-

1. The chief function of carbohydrate is to provide energy to the body so that it can carry out day-to-day work and maintain body temperature. All carbohydrates except fibre provide 4 kcal/g of energy. It is the cheapest source of energy available. 
2. Glucose is the only form of energy used by the central nervous system. When blood glucose levels fall, the brain does not receive energy and convulsions may occur. 
3. Carbohydrates spare proteins from being broken down for energy and are used for body building and repair. In carbohydrate deficient diets, proteins meant for body building and repair are oxidized to meet the most important and primary need of the body, i.e., energy. 
4. They are required for complete oxidation of fat. In a deficiency, fats are broken down rapidly for energy and intermediate products such as ketones are formed in large amounts resulting in a condition called ketosis. 
5. Carbohydrates can be converted into non-essential amino acids, provided a source of nitrogen is available. 
6. The sugar lactose helps in the absorption of the minerals calcium and phosphorus. 
7. Lactose helps certain bacteria to grow in the intestine. This bacterial flora is capable of synthesizing B-complex vitamins in the gut.
8. Dietary fibre plays an important role of increasing faecal mass by absorbing and holding water, stimulating peristalsis,and eliminating faecal waste. 
9. Fibre also helps in lowering blood cholesterol levels by binding bile acids and cholesterol. 

e.) Significance of dietary fibre (Prevention/treatment of disease) :-

• Dietary fiber refers to the total amount of naturally occurring material in plant foods, which is not digested.
• The terms roughage, bulk, and unavailable polysaccharides are synonymous with fiber.
• Fibers cannot be digested by human enzymes.
• Dietary fiber or roughage does not provide humans with but performs many important functions in the body.
• Fiber can absorb and hold water thereby increasing faecal bulk.
• This acts as a laxative and reduces intraluminal pressure in the colon preventing diverticulosis.
• Insoluble fiber prevents constipation by stimulating peristalsis in the large intestine.
• The contraction of muscular walls of the digestive tract is stimulated by fiber.
• Fiber increases water absorption, forming a larger, softer stool that rapidly passes through the colon.
• Soluble fiber binds bile acids and cholesterol and is beneficial to people suffering from coronary heart disease.
• Fiber reduces the triglyceride and cholesterol levels in blood.
• Fiber is beneficial to people on weight reduction regime. It provides satiety value to the meal because of more chewing required and at the same time does not add to the calorific value of the meal. 
• It helps in lowering blood sugar levels in diabetic individuals by slowing down carbohydrate absorption and lowers the insulin requirement. Regular intake of fiber may prevent cancers of the colon and rectum.
• Food such as whole grain cereals, fruits, and vegetables, especially when the peel and seeds are edible, are rich sources of fiber. 
• The fiber content of the daily diet should be approximately 30-40 g/day.

(B.) Lipids:-

a.) Definition:-

• Fats and oils belong to a group of compounds called lipids,which are insoluble in water but soluble in fat solvents. 
• Like carbohydrates, they are mainly made up of carbon, hydrogen, and oxygen. 
• They contain much smaller proportions of oxygen than carbohydrates and larger proportions of carbon and hydrogen. 
• Hence, they are a more concentrated source of energy, providing two and a quarter times more energy than carbohydrates and proteins.
• The lipids of importance to our health are fatty acids, fats,oils, phospholipids, lipoproteins, and sterols.

b.) Classification: Saturated and unsaturated fats:- 

Saturated Fatty Acids-

• Fats that are tightly packed are called saturated fats. There are some exceptions, but most are solid at room temperature.
• These are found in animal foods such as meat, butter, cheese, and egg yolk and in plant foods such as coconut oil, palm oil, and cocoa butter. 
• Hydrogenated fats used in bakery products and confections have a high percentage of saturated fatty acids. 
• Stearic acid, palmitic acid, myristic acid, and butyric acid are some of the saturated fatty acid. 
• A maximum of 10% of our total calories should come from saturated fats.

Sources of saturated fat include:

• Red meat
• Some pork and chicken products
• Dairy products including butter, shortening and cheese
• A diet high in saturated fat may raise your low-density lipoprotein (LDL)cholesterol levels. This will raise your risk of heart disease and type 2 diabetes.

Unsaturated Fatty Acids-

• Unsaturated fats are loosely packed. They tend to be liquid at room temperature.
• Replacing saturated fat with unsaturated fat can improve your health. Unsaturated fat comes from plants. It’s found in:
• vegetable oils, olives, nuts and seeds, some fish
• There are two main types of unsaturated fat:

Monounsaturated fats-

• Monounsaturated fats can help improve your cholesterol levels and lower your risk of cardiovascular disease. It may also help you control your insulin levels and blood sugar.

Foods that contain monounsaturated fats include:

• olive oil
• peanut oil
• canola oil
• avocados
• most nuts
• most seeds

Polyunsaturated fats-

• Your body needs polyunsaturated fats to function. This type of fat helps with muscle movement and blood clotting. Since your body doesn’t make it, you have to get it in your diet.
• Polyunsaturated fats can be further divided into two types: omega-3 and omega-6 fatty acids.
• Omega-3 fatty acids may be beneficial to the heart. 
• Omega-3 fatty acids can be found in:fatty fish, such as sardines, tuna, salmon, trout, mackerel, and herring
• ground flax and flaxseed oil
• non-hydrogenated soybean oil
• safflower oil
• sunflower oil
• canola oil
• walnuts
• sunflower seeds
• chia seeds
• hemp seeds

Unsaturated Fatty Acids-

Polyunsaturated fats can be further divided into two types: omega-3 and omega-6 fatty acids.
Omega-6 fatty acids may also help protect against cardiovascular disease. But there’s debate about the inflammatory role of omega-6’s
Omega-6 fatty acids can be found in:
safflower oil
soybean oil
sunflower oil
walnut oil
corn oil
Research has found that repeatedly heating oils can decrease their antioxidant activity and increase free radical production, which may lead to poor health effects. Avoid overheating or burning of oils to keep their nutrient content.

Essential Fatty Acids-

• EFAs are a special type of “good fat”. They are also essential nutrients; sometimes called vitamin F. 
• Essential nutrients are necessary for life, but must be obtained through diet because the body cannot make them. 
• EFAs are required for the proper structure and function of every cell in the body, and are important for optimal health. 
• EFAs increase the absorption of vitamins and minerals; nourish the skin, hair and nails; promote proper nerve functioning; help produce hormones; ensure normal growth and development; and prevent and treat disease.
• The two primary EFAs are known as linoleic acid (omega-6) and alpha-linolenic acid (omega-3).

c.) Dietary Sources:-

• Most foods except the bread cereal group and the vegetable fruit group (except olives and avocado) contain varying percentages of lipids.
• Some fats are visible such as fats and oils added to food or used for frying. 
• Many sources are hidden or invisible such as the fats and oils naturally present in the food, e.g., milk, egg yolk, oily fish, and meat. 
• Both visible and invisible sources must be taken into account while calculating the fat content of a meal.

Plant sources-

• All oils and oilseeds like groundnut, sesame, soya bean, rice bran, coconut, almond, cashew nut, corn, safflower, sunflower, and all hydrogenated fats and margarine are sources of lipids.

Animal sources- 

• Mutton, pork, fish, poultry, milk, and milk products such as butter, cream, yoghurt, cheese, eggs and organ meats.

Invisible sources- 

• Invisible sources of fats are nuts, salad dressings, flesh food, desserts, cookies, cakes, milk, eggs, milk based sweetmeats, etc., which are rich in fat, but the fat is not visible.

d.) Functions:-

Energy- Fats are a concentrated source of energy in our diet. One gram of fat/oil gives 9 kcal when it is oxidized in the body. All tissues, except those of the central nervous system and brain, can utilize fat as a source of energy. 

Protein sparing action- The kilocalories from fat spare dietary proteins from being oxidized for energy. An adequate intake of fat in the diet allows proteins to perform their main functions of growth and maintenance. 

Thermal insulation- Subcutaneous fat acts as an insulation and helps in retaining body heat. 

Protection of vital organs- Fat provides a protective padding to vital organs from mechanical shock and keeps them in place. 

Absorption of fat-soluble vitamins- Fat is necessary for the absorption of fat-soluble vitamins A,D,E,and K.

Essential fatty acids- An adequate intake of fats/oils is necessary to meet the body’s requirements for linoleic and linolenic acids. 

Satiety value- Fats slow down the secretion of gastric juice and speed of digestion. 

Food is more flavoursome because of volatile essential oils naturally present and fats used for cooking. A well-cooked meal containing fats is more satisfying than a meal devoid of fats.

Synthesis of cell membranes- Fats are an important constituent of all cell membranes. 

Synthesis of hormones- The lipid cholesterol is necessary for the synthesis of some hormones, e.g., sex hormones. 

e.) Significance of Fatty acids (PUFAs,MUFAs,SFAs,EFA ) in maintaining health:-

Monounsaturated fatty acid (MUFA) and polyunsaturated fatty acid (PUFA) fats are healthy to eat as they increase the good cholesterol and lower the bad cholesterol in our body.
The saturated fatty acid (SFA) fats on the other hand increase the level of bad cholesterol and decreased the level of good cholesterol, thereby causing the risk of coronary heart ailments. 

Tips to consume healthy forms of fat-

f.) Cholesterol- Dietary sources and the Concept of dietary and blood cholesterol:-

• It is a fat like substance present in food. 
• It is different in structure from triglycerides, as it has a ring structure. It is present in all cells of the body and in large amounts in brain and nerve tissue. 
• Cholesterol if consumed in excess is responsible for diseases of the cardiovascular system. 
• The normal blood cholesterol level for adults should be below 200mg/100ml blood. 

The human body gets cholesterol from two sources:

• Synthesis in the liver 
• Food rich in cholesterol (meat, poultry and full-fat dairy products)

Functions of cholesterol-

1. Cholesterol is a precursor of all steroid hormones, e.g., sex hormones. 
2. A precursor of Vitamin D, 7-dehydrocholestrol is present in the skin which is irradiated by ultra violet (UV) rays of sunlight to form vitamin D.
3. It is required for formation of bile.
4. It is an essential constituent of cell membranes. 

Two main forms of Cholesterol-

• LDL (low-density lipoprotein)

LDL cholesterol is often referred to as “bad cholesterol” because too much is unhealthy.

• HDL (high-density lipoprotein)

HDL is often referred to as “good cholesterol” because it is protective.

Dietary Cholesterol-

Dietary cholesterol is found in animal-based products including meat, fish, eggs, as well as poultry and dairy. Red meat will have more cholesterol than chicken and fish, but shrimp and eggs have been known to be the worst cholesterol culprits of the group.

Blood cholesterol-

Lipoproteins carry cholesterol in the blood. The two main types that carry cholesterol to and from cells are called low-density lipoproteins (LDL-C) and high-density lipoproteins (HDL-C).
The lower the density of the lipoproteins the more fats it contains. High-density lipoprotein (HDL cholesterol) is called the ‘good cholesterol’ because it helps to keep cholesterol from building up in the arteries. Low-density lipoprotein (LDL cholesterol) is called the ‘bad cholesterol’ because it is the main source of cholesterol build-up and blockage in the arteries. Statin medication work to reduce this LDL-C.

(C.) Proteins:-

a.) Definition:-

• It is the only nutrient that can make new cells and rebuild tissues. 
• Proteins are large, complex, organic compounds made up of carbon, hydrogen, oxygen, and nitrogen. 
• The presence of nitrogen distinguishes proteins from carbohydrates and fats. 
• Apart from nitrogen, elements such as sulphur, phosphorus, copper, and iron are also found in some proteins. 
• The basic units from which proteins are built are the amino acids. Each amino acid contains a carboxyl group (COOH) or acid group and an amino group (NH2) or basic group. 

Proteins consist of chains of amino acids that are linked to each other by a peptide linkage (-CO-NH-).

The protein content of any food can be estimated by measuring the nitrogen content of the food. Since proteins contain 16 percent nitrogen, each gram of nitrogen measured is equal to 6.25 g of protein. 

b.) Classification based upon amino acid composition:-

1. Essential Amino Acids:- Those amino acids which cannot be synthesized in sufficient amounts by the body and must be provided by the diet are called essential amino acids. The human adult requires 8 essential amino acids, while growing children require 10 essential amino acids. Essential amino acids are indispensable to life. 
2. Non-essential Amino Acids:- All amino acids are required by the body for tissue synthesis and repair. Non-essential amino acids does not mean that these amino acids are not required by the body. They are termed non-essential because they are not dietary essentials. If they are lacking in the diet, they can be synthesized by the body from other amino acids. The 22 amino acids present in proteins could be compared with the letters of the Roman alphabet and the innumerable words present in our dictionary. Similarly, innumerable proteins can be formed by using the 22 amino acids in varying sequences and quantities. 

c.) Dietary Sources:-

Proteins are present in both plant and animal foods.

Animal food sources:-
Animal food sources provide the highest quality or complete proteins such as eggs, milk and milk products (cheese, paneer, mawa, milk powder, curds, condensed milk),meat, fish, shellfish, poultry, and organ meat.

Plant food sources:-

• Pulses, especially soya bean (43 per cent protein) and its products such as soya milk textured vegetable proteins: nuts and oilseeds-groundnuts and gingelly seeds are important sources of protein in the Indian diet. 
• Cereals contain 6-12 per cent partially complete proteins and as they form bulk of the diet, they contribute significantly to the protein content.
• Vegetables contain a small percentage of good quality protein (approx 1-3 percent).
• Fruits do not contribute towards protein content of the diet.

d.) Functions:-

Proteins perform three main functions

1. Structural function 
2. Regulatory function 
3. Energy 

1.) Structural function- 

Growth: The primary function of food protein is the synthesis of body cells. Proteins are the major constituent of muscles, organs, endocrine glands, and collagen. Collagen is the main structural protein of bones, tendons, ligaments, skin, blood vessels, and connective tissue. All enzymes and some hormones, e.g., insulin are made up of proteins. Proteins are required for the formation and growth of all these substances. During periods of rapid growth, additional proteins are needed for synthesis of body components.

Maintenance or wear and tear: Protein is required by all age groups for continuous maintenance of all the cells in the body. Cells have a varying life span and proteins are needed to replace the old or worn out cells.

2.) Regulatory function- 

• Haemoglobin, an iron containing protein in the red blood cells, performs an important role by transporting oxygen to the tissue cells. 
• Plasma proteins maintain water balance and regulate the osmotic pressure in the body. 
• Antibodies that are protein in nature perform a protective function by increasing the body’s resistance to disease. 
• All enzymes and some hormones, e.g. insulin are made up of protein. The hormone insulin regulates blood sugar levels. Enzymes act as specific catalysts to metabolic process in the body.  
• Some amino acids have specific functions, e.g. tryptophan serves as a precursor for niacin, a complex vitamin. The amino acid tyrosine in combination with iodine forms the hormone thyroxine. 

3.) Energy-

Like carbohydrates, proteins too provide 4 kcal/g when broken down in the body. If the diet does not supply adequate calories from carbohydrates and fats, the proteins from the diet will be oxidized to meet the energy needs of the body. Protein is used by the body as a source of energy only when no other source of energy is available.

e.) Methods of improving quality of protein in food (special emphasis on Soya proteins and whey proteins) :-

Animal protein contains all essential amino acids in correct proportions and amounts and is good quality proteins. Four essential amino acids are in short supply in plant proteins. They are lysine, methionine, threonine, and tryptophan. Proteins in plant foods are generally deficient in one or two essential amino acids. Cereals are poor in lysine and pulses are poor in methionine.

Protein will be synthesized only when all amino acids, which form the protein, are present simultaneously. Vegetable proteins are partially complete proteins. These two points should be kept in mind while improving the protein quality of a meal.


The protein quality of a mainly vegetarian diet can be improved in the following ways:-

1. By including a small quantity of complete protein food in every meal. Complete protein foods such as milk, curds, paneer, cheese, buttermilk, and eggs could be used in small quantities in various preparations instead of including it in one meal only, e.g. cereal and milk, egg or cheese sandwiches, french toast, raitha, curd rice, or buttermilk at all meals in place of bowl of curd in one meal. 
2. Correct mixtures of plant foods could provide all essential amino acids in suitable proportions and amounts. Cereal and pulse combinations will complement each other as cereals provide methionine, which is lacking in pulses, and pulses provide lysine, which is lacking in cereals, when cereal and pulses are consumed together in the same meal, e.g. missie roti, thalipeeth, puran poli, idli, and rajma chawal. This is possible because the same amino acids are not missing from all plant foods. 
3. Synthetic amino acids may be added to processed foods to compensate for the amino acid deficient in them, e.g., lysine enriched bread. Textured  vegetable proteins are used successfully to improve the protein quality and reduce the cost of protein rich foods.
4. When plant proteins are consumed with a small quantity of animal protein, the quality of the mixture is likely to be as effective as if only animal protein has been consumed. A good rule while planning menus would be to include some animal proteins at each meal instead of concentrating it all in one meal.

Whey Protein:-

• Whey protein is a mixture of proteins isolated from whey, which is the liquid part of milk that separates during cheese production.
• Milk actually contains two main types of protein: casein (80%) and whey (20%).
• Whey is found in the watery portion of milk. When cheese is produced, the fatty parts of the milk coagulate and the whey is separated from it as a byproduct.
• If you've ever opened a yogurt container to see liquid floating on top — that’s whey. Cheesemakers used to discard it before they discovered its commercial value.
• After being separated during cheese production, whey goes through various processing steps to become what people generally recognize as whey protein — a powder that is added to shakes, meal replacements and protein bars .
• Whey protein doesn't taste very good on its own, which is why it’s usually flavored. Chocolate-, vanilla- and strawberry-flavored powders are popular.
• It's important to read the ingredients list, as some products may have unhealthy additives like refined sugar.
• Taking whey protein is a convenient way to add 25–50 grams of protein on top of your daily intake.
• This can be important for bodybuilders and gym enthusiasts, as well as people who need to lose weight or are simply lacking protein in their diet.

Soy Protein:-

• Soybeans are among the best sources of plant-based protein.
• The protein content of soybeans ranges from 36 to 56% of the dry weight .
• One cup of boiled soybeans (172 g) contains around 29 grams of protein .
• The nutritional value of soy protein is good, although the quality is not quite as high as animal protein .
• The main types of protein in soybeans are glycinin and conglycinin, which make up approximately 80% of the total protein content. These proteins may trigger allergic reactions in some people.
• Consumption of soy protein has been linked with a modest decrease in cholesterol levels.

Key Terms:-

• Dietary fibre- Term used to describe the unavailable polysaccharides, such as cellulose, hemicellulose,pectin, gums,mucilages,seaweeds, and lignin (a non-carbohydrate) ,which are not digested by humans but are necessary in the diet. 
• Hollow calories or empty calories- Term used to describe foods which only supply energy and have very few or no nutrients. 
• Insulin- A hormone secreted by the pancreas, which regulates carbohydrate metabolism. 
• Invert sugar- Mixture of glucose and fructose, sweeter than sucrose, produced by hydrolysis of sucrose, and prevents crystallization in confectionery items. 
• Lignin- A substance which is not a carbohydrate but present along with carbohydrates in the cell wall of plants and forms part of dietary fibre. 
• Amino acids- They are organic acids that contain an amino group (NH2) and an acid or carboxyl group (COOH ) attached to the same carbon atom. They are the basic units from which proteins are built. 
• Collagen- The intracellular cementing protein/structural protein in bone, cartilage, connective tissue, etc.
• Essential Amino Acid- An amino acid that cannot be synthesized by our body and needs to be supplied by our diet. 
• Non-essential amino acid- An amino acid that can be synthesized in the body and need not be present in the diet. 
• Peptide linkage- The linkage between the amino group of one amino acid and the carboxyl group of another amino acid.
• Adipose tissue- It is a fatty tissue. 
• Essential fatty acid- The fatty acid linoleic and linolenic acid which cannot be synthesized by the body and should be supplied by the diet. It serves as a precursor for arachidonic acid.
• Obesity- A condition of overweight in which weight exceeds more than 20 percent of desirable body weight. 
• Omega-3 fatty acids- Long-chain polyunsaturated fatty acids with the first double bond between carbons 3 and 4 from the omega or methyl end (omega means last).