How Nutrients Work in Our Body

Nutrients from food are absorbed by the body as it passes through the digestive system:

  • Nutrients are essential for cell growth, maintenance and repair.
  • Nutrients provide energy to enable your body to function efficiently.
  • Nutrients, along with fiber and water, are essential to your good health.

Although nutrients can work alone, each depends upon the others to be the most effective. The main nutrients are the macronutrients, carbohydrates, proteins, and fats – and the micronutrients, vitamins and minerals.

What Macronutrients Do

Macronutrients Are Essential for Good Health:

  • They assist in breaking down carbohydrates and fats, which provide energy to the body.
  • They assist in the absorption of protein, which provides the building blocks necessary for cell growth and repair.

What Micronutrients Do

Vitamins and minerals do not in themselves provide energy, but macronutrients depend on them to regulate the release of energy from food.

  • Vitamins are organic substances.
  • They activate enzymes, which are proteins that act as catalysts to speed up biological reactions that take place in your body.
  • Your body produces a certain amount of vitamins D and K, but all other vitamins come from your diet or supplementation.

Minerals are inorganic substances that originate from rocks and ores and enter the food chain through the soil.

  • We get minerals either by eating plants grown on mineral-rich soil or by eating animals that have fed on these plants.
  • Calcium, magnesium and phosphorus are the major constituents of bone.
  • Sodium and potassium control your body’s water balance.
  • Other minerals (chromium, iron, and magnesium) are needed for various chemical processes to take place in the body.
  • Omega Fatty Acids
  • Phytonutrients, also referred to as phytochemicals, are compounds that act as a natural defense system in plants, and that also have a beneficial effect on human health.

Role of Carbohydrates in Good Nutrition

The word “carbohydrate” means “carbon plus water.” Plants use sunlight (photosynthesis) to convert water and carbon dioxide into carbohydrates and oxygen.

Key Functions

  • When your body needs energy, it looks for carbohydrates first.
  • If you are not consuming enough carbohydrates, your body will look for other sources of energy, such as proteins found in muscle tissue. Proteins, however, are not efficient sources of energy for the body.
  • Carbohydrates also protect your muscles and help regulate the amount of sugar circulating in your blood so that all the cells get the energy they need.

Food Sources

Carbohydrates come in two forms: simple and complex. Both are composed of units of sugar. The difference is how many sugar units they contain, and how they link together.

  • Simple carbohydrates are sugars that give you instant energy and typically have no nutritional value. These include sweets, candy, and soda.
  • Complex carbohydrates release energy slowly and often contain fiber. These “healthier” forms of carbohydrates include bread, pasta, rice, potatoes, cereals and legumes.


Carbohydrates typically consist of 45 – 60% of your total caloric intake.

  • Research suggests that adult individuals should consume a minimum of 120 – 125 grams of carbohydrates per day to satisfy basic needs.

Check with your local market for the recommended daily intake of carbohydrates.

Safety Evidence

If you consume excess carbohydrates and participate in little or no physical activity, these excess carbohydrates will be converted and stored in the body as fat – which may lead to weight gain and other health risks.

Role of Protein in Good Nutrition

Protein is an essential nutrient whose name comes from the Greek word “protos,” which means “first.” To visualize a molecule of protein, think of a very long chain with links. These links represent amino acids, the building blocks of protein, which are essential for cell regulation, growth, and repair.

Key Functions

  • The body uses protein to build new cells, maintain tissues and regulate cell function.
  • About half of the protein consumed daily is converted into enzymes, the specialized “worker proteins” that regulate the speed of biological reactions in your body and permit it to perform functions such as digesting food and assembling or dividing molecules to make new cells and chemical substances. To perform these functions, enzymes often need specific vitamins and minerals.

To make all the proteins that the body needs, 22 different amino acids are required. Nine are considered to be essential, meaning they are not synthesized by the body and must be obtained from food. Our bodies can produce the other 13 from fats, carbohydrates, and other amino acids. So, these are referred to as non-essential amino acids.

Food Sources

  • Meat, poultry, fish, eggs, cheese, nuts, legumes, and soy


It is possible to consume too much protein. The amount of protein needed for good health varies.

  • An average healthy adult man or woman needs about 0.8 grams of protein per every kilogram (2.2 pounds) of body weight.
  • As you grow older, new proteins are synthesized less efficiently, and muscle mass (protein tissue) diminishes while fat content stays the same or rises. This is why muscle seems to “turn to fat” in old age.
  • Infants, adolescents, pregnant women, individuals with injuries, and athletes may often require more protein on a daily basis.

Check with your local market for the recommended daily intake of protein.

Safety Evidence

Several medical conditions make it difficult for people to digest and process proteins properly. As a result, waste products build up in different parts of the body. Check with your physician for individual safety concerns you may have.

Role of Fats in Good Nutrition

Fats are essential for good health. They aid in energy production, cell building, oxygen transport, blood clotting, and the production of extremely active hormone-like substances called prostaglandins.

Fats can be saturated, polyunsaturated, or monounsaturated. Our bodies can produce both monounsaturated and saturated fats. Polyunsaturated fats, or essential fatty acids, cannot be produced in the body and must come from the diet.

Key Functions

  • Fat is mostly stored in the body’s adipose (fat) cells but is also found in blood plasma and other body cells.
  • Fat insulates your body, cushions vital organs, and can be converted into energy.
  • Fat is used to build new cells and is critical for normal brain development and nerve function.
  • Fat is also needed to carry and help absorb fat-soluble vitamins, such as vitamins A, D, E, and K, and carotenoids.

Food Sources

Fat is twice as calorie-dense (1 gram = 9 calories) as carbohydrates or protein (1 gram = 4 calories). Although there are health benefits associated with olive and canola oils, they are still high in calories (1 tbsp = 120 calories). In addition, many processed foods and fast foods are high in fat, especially saturated fat.

  • Mono-unsaturated fats are found in olive and canola oils.
  • Saturated fats are found in animal products such as butter, cheese, whole milk, ice cream, cream, and fatty meats, as well as some vegetable oils – coconut, palm, and palm kernel oils.
  • Polyunsaturated fats are found in safflower, sunflower, corn, and soybean oils.

Usage: Upper Limits

Carbohydrates typically consist of 45 – 60% of your total caloric intake.

  • Keep total fat intake between 20 and 35 percent of calories, with most fats coming from sources of polyunsaturated and monounsaturated fatty acids, such as fish, nuts, and vegetable oils.
  • Consume less than 10 percent of calories from saturated fats.
  • Consume less than 300 mg/day of cholesterol.
  • Keep trans fatty acid consumption as low as possible. Any packaged goods containing “partially-hydrogenated vegetable oils,” “hydrogenated vegetable oils,” or “shortening” most likely contain trans fats.

Check with your local market for the recommended daily intake of fats.

Safety Evidence

All healthy people need some fats in their diet to aid in many bodily functions. The risks from fat intake come from eating too much fat on a long-term basis.

For healthy adults, 30% or less of total calories should come from foods high in fat, according to general guidelines. Of that 30%, 10% or less should come from foods high in saturated fats.


Kevin McNabb

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