Everything you need to know about carbohydrates, proteins, and fats

The majority of people today are becoming more body-conscious than ever. With an increase in awareness of the advantages of a healthy body in this pandemic time, the demand for a perfect diet to stay healthy has increased. However, a balanced diet is not just about eating healthy but also about the appropriate amount of food eaten. This means you need to consider the number of carbohydrates, proteins, and fats to be included in your diet.

These three macronutrients provide significant energy which is measured in the body as calories. However, they differ in the number of calories delivered to the body and their physiology.

1 gm of Carbohydrates = 4 kcal

1 gm of protein = 4 kcal

1 gm of fat = 9 kcal

A balanced diet containing 2100 kcal consisting of 58% carbohydrate, 12% protein, and 30% fat is recommended for a healthy person. If you do the above calculation, this diet would contain about 305 gm of carbohydrate, 63 gm of protein, and 70 gm of fat.

Carbohydrates

Physiology

Carbohydrates digestion begins in the mouth via the release of salivary amylase. Polysaccharides (long-chain carbohydrates) are broken down into smaller disaccharides and monosaccharides till they reach the small intestine and are absorbed.

Carbs are divided into simple and complex. Simple carbohydrates are small monosaccharides that are quickly absorbed from the intestine. Hence, they are the quickest source of energy i.e. they quickly increase the blood sugar. Complex carbohydrates are polymers of simple carbohydrates that take time to get digested and absorbed.

As carbohydrates are consumed, the blood sugar rises. This causes stimulation of the pancreas which releases insulin. Insulin acts mainly on three tissues: Liver, Muscle, and Adipose tissue. Insulin promotes glycogen (storage form of glucose) synthesis from glucose in the liver and muscle. When the liver and muscle are filled with glycogen, the liver starts converting glucose into fatty and triglycerides. Insulin promotes triglyceride synthesis in adipose tissue. Due to all these reasons, insulin problems can lead to diabetes mellitus.

To record the number of carbohydrates present in food and their effect on blood glucose levels, Glycemic Index is used. It is a number from 0 to 100 assigned to food, with pure glucose arbitrarily given the value of 100. It represents the relative rise in the blood glucose level two hours after consuming that food.

Foods

Foods with a low glycemic index (less than 55) cause a gradual increase in blood sugar but for a long period of time. These foods are beneficial for diabetics. These include: include soy products, beans, fruit, milk, pasta, grainy bread, porridge (oats), and lentils.

Foods with medium glycemic index (55 to 70) include: quick oats, brown rice, and whole wheat bread.

Foods with a high glycemic index (greater than 70) quickly increase the blood sugar. These foods increase the risk of type 2 diabetes, heart disease, obesity, and ovulatory infertility. These foods include white bread, corn flakes, white potatoes, pretzels, rice cakes, and popcorn.

Proteins

Physiology

Proteins are complex structures comprised of a combination of 20 different amino acids. Proteins serve as structural support, biochemical catalysts, hormones, enzymes, building blocks, and initiators of cellular death. As these are large complex molecules, metabolism of proteins is slow. As a result, they provide energy for a longer duration.

Amino acids are classified into 3 types:

• Essential – These 9 amino acids cannot be generated by the human body and hence essential in the diet. These are Histidine, Isoleucine, Leucine, Lysine, Methionine, Phenylalanine, Threonine, Tryptophan and Valine.
• Non-Essential – There are five amino acids termed non-essential because they can be obtained from foods and also generated within the body. These are Alanine, Asparagine, Aspartic acid, Glutamic acid, and Serine. 
• Conditionally Essential – There are six amino acids termed conditionally-essential because healthy bodies can generate them under normal physiologic conditions. They become essential under certain conditions like starvation or inborn errors of metabolism. These are Arginine, Cysteine, Glutamine, Glycine, Proline, and Tyrosine.

Proteins are building blocks of the body. They are used for growth and maintenance as well as for the majority of biochemical reactions in the body. Hence, proteins are not used much for obtaining energy. When excess proteins are consumed, proteins are converted into fatty acids.

During the fasting stage, glucose is obtained from gluconeogenesis and glycogenolysis. However, once the glycogen stores are empty, proteins are broken down and converted into glucose for energy.  But proteins are needed for the maintenance of the body and biochemical reactions too. And also, there is no storage form of protein. Hence, the body shifts from using glucose to ketones due to which proteins are spared.

Foods

Always choose high quality and highly protein-rich foods. Deficiency of proteins can lead to wasting of muscles, weakening of immune response, organ failure, etc. These foods include:

• Lean meats like beef, lamb, etc.
• Poultry like chicken, turkey, etc.
• Eggs
• Cottage cheese
• Greek Yogurt
• Fish and Seafood
• Legumes
• Beans like black beans, kidney beans, etc.
• Nuts like almonds, sesame seeds, cashews, walnuts, macadamias, etc.
• Protein Powders are also available.

Fats

Physiology

Fats are mainly composed of fatty acids and glycerol. Fats and other lipids are important for the formation of phospholipid bilayer cell membranes and several hormones. Excess fats are stored in adipose tissues mainly present beneath the skin (subcutaneous fat), around internal organs (visceral fat), in bone marrow (yellow bone marrow), and in the breast (breast tissue).

Fatty acids are divided into 2 types: Saturated and Unsaturated.

Saturated fatty acids do not have any double bond in their structure. These are mostly unhealthy fats which increase the blood cholesterol level and induce the risk of atherosclerosis and other heart diseases.

Unsaturated fatty acids contain 1 or more double bonds in their structure. These are generally ‘good’ fats. They reduce the amount of LDL cholesterol and thus reduce the risk of atherosclerosis and other heart diseases. These are either monounsaturated (1 double bond) or polyunsaturated (more than 1 double bond).

Only a few unsaturated fatty acids are synthesized by the human body. Rests are essential fatty acids that are consumed via diet. These fatty acids are absorbed in the small intestine and stored in the form of triglycerides in adipose tissue. Linoleic acid and arachidonic acid are omega-6 fatty acids whereas linoleic acid is an omega-3 fatty acid. Out of these essential fatty acids, omega-3 fatty acids are correlated with a decrease in cardiovascular diseases and serum triglycerides.

Most double bonds are in cis-configuration in fatty acids. However, trans-double bonds can be found in processed foods due to the partial hydrogenation of vegetable oils used in their preparation. These are solid at cool temperatures. Like saturated fatty acids, trans-fatty acids decrease the fluidity of cell membranes and increase the risk of cardiovascular disease.

Foods

Palmitic acid (16C) and Stearic acid (18C) are saturated fatty acids. Foods containing saturated fatty acids are mostly derived from animals. These are Dairy products (milk, cheese, butter), Meat (pork, lamb, chicken), ice-cream, processed meat like burgers, kebabs, etc. Sweets and pastries also contain high saturated fatty acids. Coconut oil and palm oil are the only two oils containing saturated fatty acids more.

Most of the unsaturated fatty acids are plant-derived. Unsaturated fatty acids are divided into monounsaturated and polyunsaturated.

Foods containing monounsaturated fatty acids are Oils (sunflower oil, peanut oil, canola oil, olive oil), Nuts (almonds, peanuts, macadamia, cashews), Avocados, etc.

Foods containing polyunsaturated fatty acids are Oils (soybean oil, flax oil, safflower oil, corn oil), Seeds (sunflower seeds, flax seeds), Walnuts, Fish (salmon, tuna, mackerel), etc.

Linoleic acid, Eicosapentaenoic acid (EPA), and Docosahexaenoic acid (DHA) are omega 3 fatty acids. The richest source of omega-3 fatty acids is Fish (salmon, mackerel, tuna, herring, sardines). Seeds (flax seeds, chia seeds), Walnuts, Oils (soybean oil, canola oil), Eggs, Kidney Beans, etc. also contain omega-3 fatty acids.

Trans-fatty acids are processed fatty acids that are unhealthy. Foods containing trans-fatty acids are Baked foods (cake, cookies, doughnuts, pizza dough), Fried foods (French fries, fried chicken), Packaged foods (microwave popcorns, chips), Margarine, Vegetable Shortening, etc.