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The Role of Proteins, Fats and Carbohydrates in Our Diet and Health

Our diet consists of three major building blocks, the so-called macronutrients – the proteins, fats and carbohydrates. They are all essential for our existence and good health. We cannot do without any of these three critical components. If you managed to eliminate any of them from your diet, you would surely die. Proteins form the structure of every cell in our bodies. Carbohydrates, including sugars and starches, are the body’s chief source of fuel. And fats serve as a storage of energy and certain fat soluble vital nutrients. When it comes to diet and nutrition, the question is not whether we need any of them, but rather in what proportions they do us the most good.


Proteins are large, complex molecules composed of smaller building units called amino acids, attached to each other in long chains. There are many different types of proteins in our body and their functions vary. They can act as antibodies, enzymes, signal transmitters, transporters or structural components in our cells. Our bodies can manufacture most of the amino acids necessary to make proteins themselves. However, there are nine essential amino acids that can only be obtained from the food we eat. Meat, fish, poultry, eggs and dairy products are all concentrated sources of protein. Proteins are also present in many plants, but in order to get all the essential amino acids from plants, certain varieties must be eaten in combination with others, such as rice served with beans.

Certain groups of people such as infants, children, breastfeeding and pregnant women and the elderly need more protein than others. Getting too little protein can lead to stunted growth in children and reduced immunity to disease and lack of energy in both young and old. When protein intake drops too low for too long, the body starts depleting its own protein from muscle and other tissue. This condition is called protein deficiency and it sometimes happens to vegans and vegetarians. However, most people in Western world have the opposite problem. They eat nearly twice as much as the recommended 56 grams of protein a day for men and 46 grams a day for women. Any excess protein you ingest is either burned as energy or converted to fat. But, since the body cannot store proteins in their original form, they must be supplied by our diet every day.


Carbohydrates are the body’s main source of energy. Depending on their chemical structure, they come in two forms, simple and complex. Carbohydrates are in the digestive tract broken down into glucose (simple sugar), which is used as a source of energy to fuel cells, organs and tissues. The glycemic index is used to classify carbohydrates according to their potential to raise your blood sugar (glucose) level. In general, simple carbohydrates have a high glycemic index, while complex carbohydrates, which break down more slowly in the digestive system, release glucose (blood sugar) more gradually into the bloodstream and thus tend to have a low glycemic index.

Simple carbohydrates, also known as sugars, are made of just one or two molecules of simple sugar (monosaccharide). Because they are easy to digest, they happen to be the quickest form of energy. Sugars come in different forms and under several names, including fructose, glucose, lactose and sucrose. Natural sugars are found in fruit, milk, honey and vegetables. Refined sugars, such as table sugar (sucrose), have been stripped of other valuable nutrients such as vitamins, minerals and fiber, retaining little more than their calories. Refined sugars are often abundant in foods that also happen to be loaded with fat, such as desserts, candy and cakes, contributing little to your health but a lot to your waistline. For more information on sugars, please visit this link.

Complex carbohydrates, also known as starches, are made of several sugar molecules bonded together. They must be split apart in the digestive system into simple sugars (glucose) before they can be absorbed, thus providing a more lasting source of energy than sugars (simple carbohydrates). As an important dividend, the foods rich in complex carbohydrates are also loaded with vitamins and minerals. Dietary fiber is a complex carbohydrate too, with longer molecule than starches and it is more or less indigestible. Complex carbohydrates are found in vegetables including potatoes and legumes, some fruits and grains including rice and corn but especially in whole-grains.


The fats are compounds consisting of fatty acids linked to an alcohol via an ester bond. The major form of fats present in our bodies and food are triglycerides. When fats are broken down and transported in the bloodstream, they are called free fatty acids. They fulfil many crucial functions in our body such as acting as messengers, helping proteins to do their job and starting chemical reactions that help control growth, reproduction, immune function, etc. Free fatty acids that float through the bloodstream supply back-up energy for the body and help to produce compounds that regulate blood clotting, blood pressure and inflammation. Riding in the free fatty acids are the fat-soluble vitamins A, D, E and K, traveling through the body to perform their own vital roles. In today’s Western world it is practically impossible to develop a fat deficiency.

Dietary fat is high in calories when compared with other macronutrients. Every gram of fat contains more than double the calories of the gram of protein or carbohydrate. Because the standard American diet gets about 35% of its calories from fat, which is more than the recommended 30% maximum, excess calories are piling on. Add a lack of physical activity to that and the result is an obesity epidemic. Worse yet, it is hardly a coincidence that in westernized countries with diets predominantly based on animal products and typically high in fat, people have much higher rates of cancer of the colon, rectum, pancreas, breast, prostate and endometrium than in countries with vegetarian-based diets where modest amounts of fat are consumed. Read this post for more information on the role of fats in the human body.

Getting the Right Balance of Macronutrients

Is there an ideal balance of macronutrients? With so many extreme diets providing us different macronutrient ratios there seems to be no simple answer to this question. Some sports nutritionists recommend a 60/20/20 diet (carbs/proteins/fats). This diet mainly suits endurance athletes. Other nutrition experts recommend a more evenly balanced 40/30/30 or 50/20/30 diet with low glycemic index. If you have a sedentary lifestyle, you should probably aim for one of these more balanced diets. But these ratios are meaningless, if you overeat. It is the absolute amount of carbohydrates, fats and protein that matters. Keep in mind that even a high-carbohydrate, low-fat diet such as a 60/20/20 diet will put on extra pounds if it is too high in calories and you lack adequate physical activity. Therefore, it is the complex carbohydrates low in calorific value that are the centerpiece of good nutrition. Most experts now agree that a low-fat, high-fiber diet can help fend off cardiovascular diseases, diabetes, obesity and even certain types of cancer.

Cholesterol and Diet

Cholesterol has the tendency to build up inside some people’s arteries, causing cardiovascular disease. For the majority of the population, this does not happen enough to lead to problems. However, since it is hard to tell in advance whether or not cholesterol will someday affect you, the safest course is to keep your total blood cholesterol level below 200mg per deciliter. Cholesterol is most abundant in eggs and organ meats such as liver. Eating animal fats also tends to raise cholesterol levels, as does eating partially hydrogenated vegetable oils containing trans fats. Trans fats not only increase the blood levels of bad cholesterol (LDL), they also lower the levels of good cholesterol (HDL). That means keeping certain foods to a minimum, while eating others in different forms. Fiber can help to remove excess cholesterol from the bloodstream, whereas some minerals and vitamins, such as calcium, niacin, vitamins C and E, may reduce your cholesterol levels as well.

“Healthy” Fats

Not all dietary fats are bad. Some are even good for your heart. But unfortunately, they are as bad for your waistline as any other type of dietary fat. There are some elements in certain types of fatty acids that work together to promote health and growth. These beneficial elements can be found mainly in unsaturated fats (both mono- and polyunsaturated fats), but much less so in saturated fats and trans fats. They can help you lower cholesterol levels and reduce the risk of cardiovascular disease. Here are some of them:

Omega-3 fatty acids are polyunsaturated fatty acids. This family of fatty acids is derived from alpha-linolenic acid (ALA) and includes eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). They cannot be manufactured by our body. Omega-3 fatty acids are essential for eye and brain development and normal growth and they reduce the risk of developing coronary heart disease by preventing the toxic mess of white blood cells and cholesterol from sticking to the insides of blood vessels and building up as plaque. Latest research suggests that omega-3 fatty acids may also be beneficial in the treatment and prevention of other conditions such as rheumatoid arthritis, asthma, depression, ADHD and Alzheimer’s disease. These good fats can be found in canola, rapeseed and flaxseed oils, tree nuts (e.g., walnuts), green plants and especially in cold-water fish such as albacore tuna, herring, lake trout, mackerel, salmon, sardines and swordfish.

Omega-6 fatty acids are polyunsaturated fatty acids. They start with linoleic acid, from which gamma linoleic acid (GLA) and arachidonic acid (AA) are derived. Linoleic acid cannot be synthesized from other nutrients in the body and must be obtained from food. It is essential for maintaining the health of your skin and hair. Rich sources of omega-6 fatty acids include corn, soybean and other vegetable oils, seeds and oils from seeds, nuts and meat from animals that eat corn.

Omega-9 fatty acids are monounsaturated fatty acids. They help lower the bad and raise the good cholesterol levels and even help control blood sugar. Some studies suggest that these fats may also help prevent breast cancer. Unlike omega-3 fatty acids or omega-6 fatty acids, omega-9 fatty acids are not considered to be essential fatty acids because our body makes them as it needs them. Omega-9 fatty acids are found in olive and other vegetable oils as well as in animal fat.