The Importance of Food in the Human Body

Food provides nutrients that the body needs for good health. Nutrients include proteins, fats and carbohydrates (including dietary fibre), as well as vitamins and minerals.

Eating a balanced diet means eating a variety of foods from the 5 main groups every day, in the recommended amounts. It also involves avoiding some kinds of food, such as sugary drinks and foods high in saturated fats.

Carbohydrates

Carbohydrates are the body’s primary energy source and are used as fuel for the brain, muscles and other cells. During digestion, carbohydrates are broken down into glucose – a form of sugar that the body uses for energy. The body can also use other types of fuel, such as fat or protein, but carbohydrate is the preferred fuel for most cells and tissues, including the brain.

Foods that contain carbohydrate include fruits, vegetables, whole grains and legumes. During digestion, complex carbohydrates (starches) and naturally occurring sugars are broken down into simpler, more easily absorbed sugars. Added sugars are found primarily in foods such as soft drinks, candy and baked goods, while naturally occurring sugars are found in milk, fruit, vegetables and whole grains.

The majority of carbohydrates should come from complex carbohydrates (starches) and naturally occurring (unrefined) sugars rather than from added sugars. Evidence suggests that a diet high in refined sugar is associated with adverse health outcomes, while diets rich in complex carbohydrates and dietary fiber are associated with better outcomes. Therefore, various empirical indexes reflecting carbohydrate quality have been proposed. A ratio of total carbohydrate to dietary fiber, such as a 10:1 carbohydrate-to-fiber ratio, appears to be the best strategy for promoting the choice of healthier carbohydrates.

Fats

Fats provide 9 kcal per gram of energy, more than double that of carbohydrates (4 kcal/g) and protein (2 kcal/g). Fats help build cell membranes, nerve tissue (including the brain), hormones, and other essential body structures. In addition, they absorb and transport certain fat-soluble vitamins, such as A, D, E and K.

Dietary fats come from both animal and plant sources. The human body can make some of its own fats, called fatty acids, but it must get other types through food. These include the omega-3 fatty acids, which are found in oily fish like mackerel and salmon, and the omega-6 fatty acids, which are in plant-based oils such as soybean, sunflower and corn oils and in walnuts, flaxseeds and sesame seeds.

Unhealthy fats are saturated and trans fats, which raise cholesterol levels and increase the risk of heart disease. Saturated fats are found mainly in animal products and some processed foods. Trans fats are a type of unsaturated fat that’s made by adding hydrogen to vegetable oils. They increase LDL (“bad”) cholesterol and decrease HDL (“good”) cholesterol, which also increases the risk of heart disease.

Proteins

The third macronutrient, proteins are a group of molecules that make up enzymes and other structures in the body. They are also an important source of energy. Proteins are made of chains of amino acids containing hydrogen, carbon and nitrogen, arranged in different ways. There are 20 different amino acids that can be linked together in a variety of combinations to form various proteins.

The body cannot produce amino acids and must get them through the diet. Nine amino acids are considered essential, which means they must be ingested. Other amino acids are nonessential, which means the body can generate them under normal physiologic conditions. These include the amino acids found in dietary proteins and those generated from other sources, such as gut microflora or the breakdown of protein in the body.

Research suggests that replacing red meat and processed meats with beans, soy foods, nuts, fish and poultry reduces the risk of cardiovascular disease and other diseases. This is probably due to the composition of the protein “packages” from these sources, which tends to be more diverse than those found in red meat and dairy products.

Minerals

The body needs minerals, such as potassium and iron, to work properly. They are called micronutrients because the body requires them in very small amounts. Manufacturers sometimes add them to foods, for example in fortified cereals. Most people get the minerals they need through a varied and balanced diet.

The main nutrients found in the human body are proteins, carbohydrates (sugars, dietary fiber and starches), fats, oils, minerals and vitamins. These are the building blocks of cells that give us life and perform vital functions.

Food provides these materials in the proportions that are best suited to an individual’s genetic make-up and lifestyle.

Staple foods should be the largest portion of any meal because they provide a dependable supply of energy and protein. These include grain foods (such as rice, maize, barley and wheat), legumes (beans, peas, lentils and groundnuts) and root crops (such as potatoes, cassava and yams). Meat, fish, eggs and dairy products provide protein, extra energy and important vitamins and minerals. They also help strengthen muscles and enhance the immune system.

Vitamins

A wide variety of health conditions are caused or affected by food. Some, such as food poisoning and bacterial infections from contaminated food, are directly caused by the consumption of certain foods, while others such as hypertension from excessive salt intake or heart disease from consuming fatty and partially hydrogenated oils, can be prevented with a healthy diet and vitamin supplements.

Water-soluble vitamins, such as vitamin C, are necessary in small amounts and also function as antioxidants, protecting cells from damage. They are found in green vegetables, citrus fruits, berries and red and orange peppers as well as in beef liver, chicken breast, brown rice and fortified cereals. Fat-soluble vitamins are stored in fat tissue and absorbed by the body from foods such as avocados, olive oil and nuts.