Aside from air, water and shelter, food is essential for survival. Food provides the energy our bodies need to stay alive. Macronutrients are nutrients in food that provide calories or energy. Without these substances the body would not be able to grow, metabolize or perform other crucial functions. The three (3) macronutrients are carbohydrate, protein and fat. Each macronutrient is essential for survival, in ways that go beyond providing calories for fuel. They are used for very specialized functions, optimal functional performance and overall good health.
If you look across the row of magazines at any supermarket checkout you’ll see countless fad diets claiming to shed pounds … fast! If you look closely at the fine print, some significantly limit (or eliminate) the amount of one or two macronutrients to get results. Although this can result in short term weight loss, the long term effects can be dangerous.
Carbohydrates for Survival
As it relates to macronutrients, we consume carbohydrates in the largest amounts (one gram of carbohydrates is equivalent to 4 calories). The United States Department of Agriculture (USDA) recommends 45 to 65 percent of a person’s dietary calories come from carbohydrates. We need carbohydrates in this quantity because:
- Carbohydrates are the body’s main source of fuel.
- Carbohydrates are easily converted to usable energy in the body.
- All tissues of the body can use glucose (the most important carbohydrate) for energy.
- Carbohydrates are needed for the proper function of the central nervous system, brain, kidneys and muscles (including the heart).
- Carbohydrates are important for intestinal health and the elimination of waste.
- Carbohydrates can be stored (in the muscles and liver) and used for energy at a later time.
Carbohydrates are mainly found in starchy foods (i.e. potatoes and whole grain foods), fruits, milk and yogurt. Fiber, a specific type of carbohydrate, is not easy to digest. Fiber passes through the intestinal tract to aid in the removal of waste out of the body. Diets high in fiber have been shown to decrease the risk of heart disease, obesity and associated metabolic disease.
Carbohydrate is the most important source of energy when exercising. No matter the activity, glycogen provides the energy that fuels muscle contractions. Glycogen is utilized during short, intense bouts of exercise (i.e. sprinting, lifting weights or explosive jumping) because it is easily accessible. Glycogen also supplies energy during the first few minutes of any sport and is required during long, slow exercise to break down fat into a form the muscle can use for sustained energy. Adequate glycogen stores in the body also ensures protein is not broken down and used for fuel.
Protein for Survival
The USDA recommends 10 to 35 percent of calories come from protein (one gram of protein is equivalent to 4 calories) to reduce the risk of chronic disease while providing adequate intakes of essential nutrients. According to a recent study in the American Journal of Clinical Nutrition (2008), the majority of Americans are receiving at least the minimum amount of protein recommended in their diet. We need this amount of protein to facilitate:
- Tissue repair
- Immune function
- The production of hormones and enzymes
- The production of energy (when carbohydrate is not available)
- The maintenance of lean muscle mass
Protein is found in meats, poultry, fish, cheese, milk, nuts and legumes. When we eat these foods our bodies break down the protein in the food into amino acids (the building blocks of protein). Essential amino acids can only be found in the foods we eat (i.e. valine, tryptophan and leucine). Non-essential amino acids are those our bodies can produce on their own (i.e. alanine, glutamic acid and aspartic acid). Protein from animal sources contain all of the essential amino acids, unlike plant-based sources of protein.
Many studies have shown that individuals who engage in regular exercise training require more dietary protein than sedentary individuals. Adequate amounts of protein intake is an important component of an overall exercise training program, essential for proper recovery, immune function and the growth and maintenance of lean muscle mass.
Fat for Survival
Although fat is perceived as being unhealthy and “bad for you”, some fats are essential for good health and survival. The USDA recommends 20 to 35 percent calories come from fat (one gram of fat is equivalent to 9 calories). We need this amount of fat in our diet for:
- Normal growth and development
- Maintaining cell membranes
- Providing protection for the internal organs
- Energy (the most concentrated source of energy; responsible for aerobic energy metabolism)
- Absorbing specific vitamins (i.e. A, D, E, K and carotenoids)
Fat is found primarily in meat, poultry, nuts, dairy products, oils, lard and fish. Three main types of fat include: saturated fat, unsaturated fat (mono- and polyunsaturated) and trans fat. Saturated fat (found in foods that come from animals) and trans fat (found in partially hydrogenated vegetable oil) have been shown to increase the risk for heart disease. Unsaturated fat (found in nuts, seeds, olives, legumes and avocados) as a replacement for saturated fats has been shown to significantly decrease the risk of developing heart disease.
The body’s glycogen stores can only provide enough energy for anywhere from 90 to 180 minutes of exercise before fatigue sets in. When this occurs the body is forced to slow down or stop (i.e. hitting the “wall” in running). The body then turns to it’s other main source of energy … fat. Typically, the body has approximately 50,000 to 60,000 kcal (calories) of energy stored as fat compared to only about 1,500 kcal of glycogen.
Macronutrients and Exercise
For those of you who are active and working towards specific health and fitness goals, be sure to include carbohydrate, protein and fat into your nutrition plan. These macronutrients are essential for proper functioning of the body and overall athletic performance. Without adequate amounts of each the body is more susceptible to impaired function and chronic disease.
For more information on USDA Dietary Reference Intakes for macronutrients, click here.