Our bodies need a certain amount of nutrients on a regular basis to be able to function. In order to supply our bodies with these nutrients we need to eat a balanced diet. Eating well helps us to achieve and maintain body compositions that enable us to do strenuous mental and physical work and remain healthy.

Everybody will have a different calorie intake and it will most likely vary from day to day. But it is essential that we give our body what it needs to function well. This is why governments, universities, and health centres around the world have developed food guides and food pyramids in an effort to help people understand how to eat healthily.

What makes up a balanced diet?

While many nutrients can be synthesized by the body, other nutrients, namely essential nutrients, cannot. Therefore, we must supply them through our diet – the foods we eat and drink.

Essential nutrients include 9 of the 20 amino acids found in proteins, certain fatty acids found in fats and oils, and a number of minerals and vitamins. Nutrients are generally divided into 2 categories: macronutrients and micronutrients.

Other substances, such as fibre, are recommended by physicians, nutritionists, and other primary health care providers to improve movement in the gastrointestinal tract, moderate changes in blood sugar and cholesterol that occur after we've eaten, and increase the elimination of cancer-causing substances produced by the bacteria in the large intestine.

Macronutrients include fats, proteins, carbohydrates, and some minerals, and our bodies need these in large quantities on a daily basis. They make up the bulk of our diet and supply the energy and building blocks we need for growth, activity, and maintenance. When these foods are digested they are turned into their basic units, namely sugars from carbohydrates, fatty acids and glycerol from fats, and amino acids from proteins. The energy content derived from each is measured in calories.

Typically, our individual calorie intakes vary greatly depending on physical activity, age, sex, and availability. But the recommended averages are generally agreed to be as follows: older adults, children, and sedentary women need roughly 1,600 calories per day; active women, older children, and sedentary men need roughly 2,000 calories per day; and young men and active adolescent boys need roughly 2,400 calories per day.

Macrominerals include calcium, sodium, and chloride, and our bodies need roughly 1 to 2 grams of each per day. Water is also a macronutrient and we need 1 mL for each calorie of energy we expend, or about 2,500 mL (2.6 quarts) per day. Our bodies also need about 3 to 5 grams of potassium, 300 to 400 milligrams of magnesium, and about 700 milligrams of phosphorus per day.

Essential fatty acids include linoleic acid, linolenic acid, arachidonic acid, eicosapentaenoic acid, and docosahexaenoic acid. Linoleic acid and linolenic acid are found in vegetable oils. Eicosapentaenoic acid and docosahexaenoic acid are essential for brain development and are found in fish oils.

Micronutrients include vitamins and trace minerals, and our bodies need them to metabolize the macronutrients. Micronutrients are usually required in small amounts – from milligrams to micrograms. Essential trace minerals include iron, zinc, copper, manganese, molybdenum, selenium, iodide, and fluoride. With the exception of fluoride, all these minerals activate enzymes that help our bodies metabolize food.