Biology » Human Biology » Nutrients and Balanced Eating

Food and Nutrients

Are these really good for you?

Fresh fruit and vegetables. Every child’s favorite. Especially those vegetables. When your mother tells you to “eat your vegetables,” there is a reason for that. Yes, they are actually good for you.

Food and Nutrients

Did you ever hear the saying, “You are what you eat”? It’s not just a saying. It’s actually true. What you eat plays an important role in your health. Eating a variety of the right types of foods promotes good health and provides energy for growth and activity. This is because healthful foods are rich in nutrients. Nutrients are substances the body needs for energy, building materials, and control of body processes. There are six main classes of nutrients: carbohydrates, proteins, lipids, water, vitamins, and minerals. These six classes are categorized as macronutrients or micronutrients depending on how much of them the body needs.


Nutrients the body needs in relatively large amounts are called macronutrients. They include carbohydrates, proteins, lipids, and water. All macronutrients except water can be used by the body for energy. (The energy in food is measured in a unit called a Calorie.) The exact amount of each macronutrient that an individual needs depends on many factors, including gender and age. Recommended daily intakes by teens of three macronutrients are shown in Table below. Based on your gender and age, how many grams of proteins should you eat each day?

Gender/AgeCarbohydrates (g/day)Proteins (g/day)Water (L/day) (includes water in food)
Males 9–13 years130342.4
Males 14-18 years130523.3
Females 9-13 years130342.1
Females 14-18 years130462.3
  • Carbohydrates include sugars, starches, and fiber. Sugars and starches are used by the body for energy. One gram of carbohydrates provides 4 Calories of energy. Fiber, which is found in plant foods, cannot be digested but is needed for good health. Simple carbohydrates are small carbohydrates found in foods such as fruits and milk. These carbohydrates include lactose, fructose and glucose. Complex carbohydrates are much larger molecules. Starch, which is a complex carbohydrate found in vegetables and grains, is made of thousands of glucose units bonded together.
  • Dietary proteins are broken down during digestion to provide the amino acids needed for protein synthesis. Any extra proteins in the diet not needed for this purpose are used for energy or stored as fat. One gram of proteins provides 4 Calories of energy. Eating protein provides the amino acids for your cells to produce your own antibodies, muscle fibers and enzymes (as well as many other types of proteins).
  • Lipids provide the body with energy and serve other vital functions, such as protecting neurons and providing the membranes that surround all cells. One gram of lipids provides 9 Calories of energy. You need to eat small amounts of lipids for good health. However, large amounts can be harmful, especially if they contain saturated fatty acids from animal foods. 
  • Water is essential to life because biochemical reactions take place in water. Most people can survive only a few days without water.


Nutrients the body needs in relatively small amounts are called micronutrients. They include vitamins and minerals. Vitamins are organic compounds that are needed by the body to function properly. Several vitamins are described in Table below. Vitamins play many roles in good health, ranging from maintaining good vision to helping blood clot. Vitamin B12 is produced by bacteria in the large intestine. Vitamin D is synthesized by the skin when it is exposed to UV light. Most other vitamins must be obtained from foods like those listed in Table below.

VitaminFunctionGood Food Sources
Agood visioncarrots, spinach
B12normal nerve functionmeat, milk
Cmaking connective tissueoranges, red peppers
Dhealthy bones and teethsalmon, eggs
Enormal cell membranesvegetable oils, nuts
Kblood clottingspinach, soybeans

Minerals are chemical elements that are essential for body processes. They include calcium, which helps form strong bones and teeth, and potassium, which is needed for normal nerve and muscle function. Good sources of minerals include leafy, green vegetables, whole grains, milk, and meats.

Vitamins and minerals do not provide energy, but they are still essential for good health. The necessary amounts can usually be met with balanced eating. However, people who do not eat enough of the right foods may need vitamin or mineral supplements.


  • Nutrients are substances that the body needs for energy, building materials, and control of body processes.
  • Carbohydrates, proteins, lipids, and water are nutrients needed in relatively large amounts.
  • Vitamins and minerals are nutrients needed in much smaller amounts.

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