Stedman's Medical Dictionary defines nutrients as components of food essential for the body's growth, functioning and maintenance. A healthy diet must contain various nutrients. The seven main nutrients are protein, carbohydrates, fats, vitamins, minerals, water and antioxidants. Protein, carbohydrates and fats provide calories and also perform other functions. The body uses them in large quantities. Although vitamins, minerals and antioxidants do not provide any calories, they are essential for good health.
Protein
Proteins are building blocks of all organs and systems in the human body. This includes muscles, major vital organs like heart and liver, blood, skin, and immune and hormonal systems.
Carbohydrates
Carbohydrates, or "carbs," supply all body cells with energy and are an important part of a healthy diet. Complex carbohydrates are more nutritious than simple or refined ones. Besides energy, complex carbohydrates provide fiber, vitamins, minerals and antioxidants.
Fats
Although some fats contribute to high cholesterol, certain fats are necessary for normal function of the body. The U.S. Department of Agriculture's Dietary Guidelines for Americans recommend replacing saturated and trans fatty acids with mono- and polyunsaturated ones for optimal health. Monounsaturated and polyunsaturated fats, especially omega-3 oils, offer considerable health benefits. In addition, fats help absorption of certain vitamins, minerals and antioxidants.
Vitamins
All vitamins fall into two groups: fat-soluble and water-soluble. There are four fat-soluble vitamins -- A, D, E and K -- that mostly occur in the fats and oils of foods. Functions of fat-soluble vitamins in the body are diverse. Vitamin E supports growth, vitamin A helps with vision, vitamin K aids in blood clotting, and vitamins D and K are essential to proper bone development.
All the other vitamins are water-soluble. All B vitamins are essential for metabolism of carbohydrates, proteins and fats. Vitamin C acts mostly as an antioxidant protecting the body from dangerous substances called oxidants.
Minerals
Among the major minerals are calcium, potassium, sodium and iron. In addition to major minerals, the body needs various minerals in trace amounts, such as zinc and selenium. Although the body uses minerals in small amounts, deficiency in any of the minerals may cause serious health problems.
Water
Water is one of the essential elements of the human diet. The human body consists of about 60 percent water. Every day, the average adult loses more than 8 cups of water simply by living. The body needs to replenish these losses to prevent dehydration. In addition, some vitamins, minerals and antioxidants need water for their absorption and action.
Antioxidants
Antioxidants are small molecules that counteract oxidative stress and help the body to stay healthy. The majority of antioxidants come from plant sources: fruits, vegetables and whole grains. Examples of antioxidants are polyphenols in green tea, anthocyanins in purple berries, resveratrol in red wine and lycopene in tomatoes. Some vitamins such as C, A and E, as well as minerals like selenium and zinc, are also potent antioxidants.
References
- "Stedman's Medical Dictionary, 27th Edition"; 2000
- USDA: Dietary Guidelines for Americans 2010: Foods and Nutrients to Increase
- "Textbook of Medical Physiology, 10th Edition"; A. Guyton, et al.; 2000
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