The nutrients our bodies need can be divided into two categories: macronutrients (those we need in large amounts) and micronutrients (those we need in small amounts). The macronutrients are carbohydrates, proteins, fats and water. Micronutrients are vitamins and minerals.
Carbohydrates are a large group of compounds that are composed of carbon, hydrogen and oxygen molecules arranged into ring-like structures called saccharides. The main function of carbohydrates is to provide energy. Carbohydrates come in two main forms: simple and complex. The body converts both simple and complex carbohydrates into glucose, which is used to fuel the body’s energy needs.
Simple carbohydrates, also called sugars, consist of one saccharide molecule or two molecules attached together. Their names usually end in "-ose" (e.g., glucose, sucrose and fructose). They tend to taste sweet. Sugars occur naturally in foods such as fruit, berries and milk. They are also found in concentrated amounts in table sugar, honey, maple syrup and molasses. Simple carbohydrates are small molecules so they are easily absorbed into the bloodstream and quickly raise blood sugar levels. A diet high in sugars contributes to weight gain, which is associated with diabetes, heart disease and other health problems. Sugar also increases the risk for cavities. Although there is no recommended amount for sugars in the diet, the consensus among nutrition experts is to limit "added" sugars. Added sugars include those found in processed foods (e.g., cakes), candies, soft drinks and sugary cereals as well as sugars that are added at the table (e.g., sugar added to coffee, tea or cereal). Several prominent organizations — including the World Health Organization and the American Heart Association — have issued recommendations to keep added sugars to no more than 10% of daily calories, preferably less. Based on a 2,000 calorie a day diet, this would translate to no more than 12 teaspoons of added sugar. Keep in mind that a 355 mL can of non-diet soft drink typically contains 10 teaspoons of added sugar!
The second type of carbohydrates is the complex carbohydrates, which are also called starches. They consist of many saccharide molecules linked together in chains. Because they are larger molecules, they tend to be absorbed more slowly and therefore keep blood sugar levels more stable. Sources of complex carbohydrates include grain products (e.g., bread, cereal, rice, pasta and oats), vegetables (e.g., potatoes, carrots) and legumes (e.g., peas and beans). Whole grains are an excellent option since they are not refined and retain much of their nutritional strengths.
Each gram of carbohydrates provides four calories of energy. It is recommended that the majority of our daily calories — between 50 and 65% — come from carbohydrates. If you eat according to Canada's Food Guide, you will meet your carbohydrate needs and the proportion of simple and complex carbohydrates will be favourable to your health.
Proteins build and repair muscles, skin and other tissues and are an integral component of hormones and enzymes, which regulate the body’s processes. Proteins are also essential for building the cells of the immune system. Proteins are composed of basic units called amino acids, which are linked together in various combinations to create thousands of different proteins. There are 22 amino acids, 13 of which are called "non-essential" because the body can make them. The other nine "essential" amino acids must come from the foods we eat since the body cannot make them.
Animal food sources of protein are referred to as "complete" protein because they contain all 22 amino acids. Sources include meat, poultry, dairy products, eggs and seafood. With the exception of soybeans and quinoa, all plant proteins lack one or more of the essential amino acids, so they are called "incomplete" proteins. Depending on the foods they include in their diet, some vegetarians and all vegans need to pay attention to the protein in their diet. Plant foods that contain a substantial amount of protein include beans, lentils, soy products (e.g., tofu) and nuts.
One gram of protein provides four calories of energy. In a healthy, balanced diet, protein should contribute 10 to 15% of daily calories. If you eat according to Canada's Food Guide, you will meet your daily protein requirements. Contrary to popluar belief, those seeking to build muscle do not need to consume a large amount of protein.
Fat stores energy, insulates the body and its organs, is a component of hormones and other important substances and provides essential fatty acids that the body cannot produce. It also transports the fat-soluble vitamins A, D, E and K throughout the body. High fat consumption is linked with cardiovascular disease and some cancers. The health effects are related to the type of fat in the diet, rather than the amount. However, since fat provides a concentrated source of energy, high consumption of any type of fat can contribute to weight gain, which increases the risk of many health problems.
In general, fat occurs as triglycerides, which are formed by attaching three fatty acid molecules to a molecule of glycerol. These fatty acids can be saturated or unsaturated. (Unsaturated fatty acids can be either monounsaturated or polyunsaturated.) Dietary fats contain a combination of saturated and unsaturated fatty acids. A dietary fat is called "saturated" if it contains predominantly saturated fatty acids and "unsaturated" if it contains predominantly unsaturated fatty acids. (The terms "monounsaturated fat" and "polyunsaturated fat" refer to dietary fats that are rich in these types of fatty acids.) The body can produce some fatty acids, so they are referred to as "non-essential." Those that the body cannot produce are called "essential" fatty acids. We must get these from our diet.
Saturated fat has been dubbed "bad fat" because eating too much of this type of fat negatively affects blood cholesterol levels, which contributes to an increased risk for cardiovascular disease (e.g., heart attack, stroke). Saturated fat typically comes from animal sources and is often solid at room temperature. Sources include meat, lard, animal shortening and dairy products such as cheese, butter, sour cream and milk. Unsaturated fat has been linked to a reduced risk of cardiovascular disease, so it is often referred to as "good fat." Unsaturated fat typically comes from plant foods and is liquid at room temperature. Sources include olive oil, canola oil, soybean oil, peanut oil, avocados and nuts.
Fat is calorie dense. One gram of fat provides nine calories — more than twice the amount in proteins or carbohydrates. It is recommended that fat contribute 20 to 30% of daily calories in a healthy diet. Most of that fat should be the unsaturated type. If you follow Canada’s Food Guide, you will achieve these recommended amounts.
You may have heard that you should drink "eight glasses of water a day," but there is no evidence to support this idea. Instead, your daily water needs depend on your size, activity level, the weather and what food and drinks you have consumed. Water needs are greater with increased physical activity and when the weather is hot. Unlike the other nutrients, there is no recommended daily amount of water that we should consume. Men should aim for 3.5 litres a day and women should aim for 2.75 litres a day. Obviously you will need more if you are active or if the weather is hot.
Canada’s Food Guide recommends that you make water your drink of choice. Although all beverages contain water, many also contain other nutrients that can negatively affect health when consumed in large amounts. Non-diet soft drinks, fruit flavoured drinks and sweetened hot and cold drinks contain a lot of sugar and calories. Drinking a lot of these contributes to an increased risk for overweight and diabetes.
Lab tests show that the quality of tap water and bottled water are the same, so take advantage of the water stations on campus and fill your reusable water bottles and help save the environment — and some money — along the way.
Although the body needs vitamins and minerals in small amounts, these amounts are critical for optimal functioning. A deficiency of a vitamin or mineral can lead to serious health consequences. Taking large amounts of a vitamin or mineral (i.e., a megadose) over time can also negatively affect health.
If you follow the recommendations in Canada's Food Guide and enjoy a variety of foods, you will meet your vitamin and mineral needs.
Vitamin and mineral supplements are not recommended for the majority of people. However, supplements are recommended for specific groups to meet their nutrient needs, such as an iron supplement for those with anemia or a folic acid supplement for women who are pregnant or planning to become pregnant.