WHAT IS NUTRITION AND WHY IS GOOD NUTRITION SO IMPORTANT?

Whereas food is the source of nutrients that your body needs, nutrition is about more than just food.Nutrition is the science that studies how the nutrients and compounds in foods nourish you, help you function, and affect your health.

Your body needs all the nutrients to function properly. A chronic deficiency of even one nutrient will negatively affect your body’s ability to function in the short term. Chronic deficiencies, excesses, and imbalances of many nutrients can also affect your long-term health.

Good nutrition plays a role in reducing the risk of four of the top ten leading causes of death in the United States, including the top three—heart disease, cancer, and stroke—as well as diabetes. Nutrition also plays an important role in preventing other diseases and conditions that can impede your lifestyle. A healthy diet can help keep your bones strong and reduce your risk of osteoporosis. Eating right will help you better manage your body weight, which in turn will reduce your risk of developing obesity, diabetes mellitus, and high blood pressure.

You are a product of what you eat, what you don’t eat, or what you may eat too much of. You want to eat the best combination of a variety of foods to meet your nutritional needs and to be healthy. To do that, you need to understand the roles of the essential nutrients in your body and which foods to eat to get them.

What Are the Essential Nutrients and Why Do You Need Them?

The classes of nutrients that we introduced earlier are all essential because you must have them in order to function. (Alcohol, in contrast, is not an essential nutrient; even though it provides energy in the form of kilocalories, your body does not need it to function.) Your body is, in fact, made up of the same essential nutrients that are found in foods.

Carbohydrates, lipids (fats), and proteins are called macronutrients, because you need higher amounts of them in your diet.Vitamins and minerals, though equally important to your health, are considered micronutrients because you need them in lesser amounts. You need to consume the final nutrient, water, in copious amounts daily so that you are well hydrated.

Kilocalories from the macronutrients are used as energy during the process of metabolism, and many vitamins and minerals are essential to this process.Vitamins and minerals are also needed for growth and reproduction and to help repair andmaintain your body.

Although each nutrient is unique, they are all equally important, as they work together in numerous ways to keep you healthy.An imbalance of just one will affect your health. Let’s take a closer look at the macro- and micronutrients, and water.

Carbohydrates, Fats, and Proteins Provide Energy

Carbohydrates, fats (lipids), and proteins are the energy-providing nutrients, because they contain calories. When we talk about energy, we mean that your body breaks down these nutrients and “burns” them to fuel your activities and internal functioning. One calorie equals the amount of energy needed to raise the temperature of 1 kilogram (a liter) of water 1 degree Celsius. Carbohydrates and protein provide4 calories per gram, and fats provide 9 calories per gram. The number of calories in a given food can be determined by measuring the weight, in grams, of each of the three nutrients in one serving of the food.

The amount of calories that you need daily to maintain your weight is estimated based on your age, gender, and activity level. However, you need these nutrients for many reasons beyond their providing energy.You must consume a healthy combination of carbohydrates, fats, and protein so that excesses, deficiencies, and imbalances don’t occur that may increase your risk of chronic diseases.

Carbohydrates supply the simple sugar, called glucose, that your cells use as the major energy source to fuel your body.Most of your daily calories should come from carbohydrates. Fats are another major fuel source.They also help cushion your organs to prevent damage and act as insulation under your skin to help maintain your body temperature. Proteins can be used as energy, but are better used to build and maintain your tissues, muscles, and organs. You also need protein to make most enzymes and some hormones, to help transport other nutrients, and for a healthy immune system. A healthy diet should provide adequate amounts of carbohydrates and fats for energy, and enough protein to maintain and repair your body.

Carbohydrates, fats, and proteins are all organic because they contain the element carbon. They also contain two other elements, hydrogen and oxygen. Proteins also contain nitrogen, while carbohydrates and fats do not.

Vitamins and Minerals Are Essential for Metabolism

You need vitamins and minerals to use carbohydrates, fats, and proteins and to sustain numerous chemical reactions. A deficiency of vitamins and minerals can cause ill effects ranging from fatigue to stunted growth, weak bones, and organ damage.

Many vitamins and minerals aid enzymes, which are substances that speed up reactions in your body. For example, many of the B vitamins function as coenzymes in the metabolism of carbohydrates and fats.Many minerals, such as calcium and phosphorus, work with protein-containing hormones and enzymes to maintain and strengthen your teeth and bones. The fate of carbohydrates, protein, and fats in your body is very much dependent upon your consuming enough vitamins and minerals in your daily diet.

Vitamins are organic compounds that usually have to be obtained from your foods. Your body is able to make some vitamins, such as vitamin D, but sometimes cannot make enough of it to maintain good health. In these situations, your diet has to supplement your body’s efforts.

Minerals are inorganic substances that play a role in body processes and are key to the structure of some tissues, such as bone. A deficiency of any of the minerals can cause disease symptoms. Anyone who has ever suffered from iron-deficiency anemia can tell you that falling short of your daily iron needs, for example, can cause fatigue and interfere with your ability to function.

Water Is Vital for Many Processes in Your Body

Although plain water does not provide energy or calories, it is vital to many key body functions, and staying hydrated is therefore an important part of staying healthy. As part of the fluid medium inside your cells, water helps chemical reactions, such as those involved in the production of energy, take place.Water also bathes the outside of your cells, playing a key role in transporting vital nutrients and oxygen to, and removing waste products from, your cells.Water helps maintain your body temperature and acts as a lubricant for your joints, eyes, mouth, and intestinal tract. It surrounds your organs and cushions them from injury.

How Should You Get These Important Nutrients?

There is no question that you need all six classes of nutrients to function properly. But is there an advantage to consuming them through food rather than taking them as supplements? Is there more to a healthy diet than just meeting your basic nutrient needs? Let’s look at these questions in more detail.

The Best Way to Meet Your Nutrient Needs Is with a Well-Balanced Diet

Many foods provide a variety of nutrients. For example, low-fat milk is high in carbohydrates and protein and provides a small amount of fat. Milk is also a good source of the vitamins A, D, and riboflavin, as well as the minerals potassium and calcium, and is approximately 90 percent water by weight.Whereas milk contains a substantial variety of all six classes of nutrients, a single food item doesn’t have to provide all nutrients in order to be good for you. Rather, a well-balanced diet composed of a variety of foods can provide you with all of these important nutrients.

A well-balanced diet will also provide other dietary compounds, such as phytochemicals and fiber, that have been shown to help fight many diseases. At least 900 different phytochemicals have been identified in foods and more are likely to be discovered.

Don’t assume that these compounds can be extracted from foods, put in a pill, and still produce the same positive effect on your health. The disease-fighting properties of phytochemicals likely go beyond the compounds themselves, and work with fiber, nutrients, or unknown substances in foods to provide a synergistic, positive effect on your health.

Fiber is the portion of plant foods that isn’t digested in the stomach and small intestine. Some foods, such as whole grains, fruits, and vegetables that are high in fiber, are also phytochemical powerhouses. Studies have shown that diets rich in these foods fight many diseases. Also, let’s not forget some of the obvious benefits of getting your nutrients from food. The delicious texture and aroma of foods, coupled with the social interaction of meals, are lost when you pop a pill to meet your nutrient needs. That said, some individuals should take a supplement if food alone can’t meet their needs.

You Can Meet Some Nutrient Needs with a Supplement

Although many people can get all their nutrients through their diet, others have diet restrictions or higher nutrient needs such that they would benefit from taking a supplement in addition to consuming a healthy diet. For example, someone who is lactose intolerant (meaning they have difficulty digesting milk products) may have to meet his or her calcium needs from other sources. A calcium supplement could be an option for these individuals. Pregnant women should take an iron supplement because their increased need for this mineral is unlikely to be met through the diet alone. As you can see, a well-balanced diet and dietary supplements aren’t mutually exclusive. In some situations, they should be partnered as the best nutritional strategy for good health.

Even with an abundance of foods and the availability of supplements for those who may need them, the diets of Americans aren’t as healthy as they could be. Let’s find out why this is the case.

By Joan Salge Blake in "Nutrition and You", second edition, Pearson, USA, 2012, excerpts pp.8-12. Adapted and illustrated to be posted by Leopoldo Costa.