What you eat is important to overall health. The term diet doesn’t necessarily mean a restriction; it simply refers to what a person eats. Nutrition is the content of food and the amounts of specific nutrients. In a world in which there are so many choices for food, it is more important than ever to understand the nutrients that foods provide and which foods contribute to poor health.

There are very serious consequences of having poor nutrition or a diet that is not balanced. A poor diet can lead to malnutrition, obesity and related diseases, chronic illness, and even a risk of earlier death. Diet also impacts mental health, contributing to body image and overall sense of well-being. If you need help with your nutrition or losing weight, a registered dietitian can provide guidance and knowledgeable advice.

How Nutrition and Diet Impact Health

Understanding nutrition is important for everyone, even healthy adults. Children and teens need good nutrition for growth and development, but adults also need to eat well to maintain normal function and to stay healthy. People who are ill or living with chronic diseases need good nutrition to ensure the body is able to function as well as it can and to address specific health needs.

Nutrition, when good, is not always noticeable. Someone who is healthy and eats well is likely to have a strong immune system, a healthy weight, normal blood pressure and blood cholesterol levels, and a low risk of chronic diseases as well as positive overall wellness.

When nutrition is poor, the effects are more noticeable. Poor nutrition can cause specific nutrient deficiencies, for instance. Not eating enough or eating too much can cause a person to be under or overweight. Consuming too many calories can lead to obesity, which contributes to diabetes, heart disease, high blood pressure, sleep apnea, arthritis, gallbladder disease, certain types of cancer, and other illnesses.

Diet can also impact mental health. Eating disorders, for instance, are very serious mental illnesses related to eating and body image. They can cause a person to eat too little or to binge, consuming large quantities at once. A poor diet and being overweight can lead to low self-esteem and feelings of depression.


A balanced diet includes the right amounts and types of three macronutrients: fat, protein, and carbohydrates. These are called macronutrients because they are needed in large amounts as compared to micronutrients, vitamins and minerals. Fat is important for protecting organs, insulating the body, transporting certain vitamins, and as a reserve source of energy. Fats are found in animal products, nuts, seeds, and oils. Between 20 and 35 percent of daily calories should come from fats, and only 10 percent should be from saturated fats, which are found in animal products and a few plant oils.

Carbohydrates are the primary energy source in the diet, and they are particularly important for fueling brain function. Carbohydrates may be complex as in grains and vegetables, or simple as in sugars found in fruit and added to foods. Between 40 and 60 percent of daily calories should come from carbohydrates, depending on a person’s activity level. Athletes and active people need more.

Protein provides structure in tissues in the body and is important for metabolism, transport systems in the body, and hormones. Protein is also important for muscle mass and enzymes that regulate processes in the body. A diet should include between 0.4 grams per pound of body weight and 0.9 grams per pound, depending on activity level. Protein is found in meat and dairy, beans, legumes, whole grains, nuts and seeds, soy products, and to a lesser extent in vegetables.


Micronutrients are much more numerous than macronutrients and include vitamins and proteins, which are needed for proper functioning but in much smaller amounts. Some of these are considered trace nutrients because the amounts needed in the diet are even smaller. Because there are so many of them, to get adequate amounts of vitamins, like vitamins C and D, or minerals like iron, calcium, and potassium, it is important to eat a variety of healthful foods.

Eating only a few different types of food can lead to deficiencies in micronutrients, which can lead to health problems that range from mild to serious. For instance, not getting enough iron can cause anemia. This causes fatigue but over the long term can cause serious damage to the body and even lead to death if not corrected. A deficiency in vitamin D, especially in children, can lead to soft and malformed bones.

Dietary Guidelines for Americans

The federal government sets dietary guidelines to give individuals an idea of how and what to eat for optimal health. The current guidelines are the eight edition of this advice and are set to be reviewed again after 2020. They are different from previous guidelines in that they suggest certain eating patterns rather than focusing on specific foods:

  • Eat foods that are dense with nutrients, including vegetables, fruits, whole grains, lean meats, seafood, and low-fast dairy.
  • Avoid foods that have a lot of salt, trans fats, saturated fats, cholesterol, refined grains, and added sugar.
  • Most of the calories in the diet should come from plant-based foods, like vegetables, fruits, nuts, beans, and grains.
  • Eat enough foods that are rich in calcium, the equivalent of three cups of low fat milk per day.
  • Eat portion sizes that are moderate.
  • Avoid alcohol or drink in moderation, which is one drink per day for women and two per day for men.
  • Include physical activity to balance out calorie intake.

Healthful and Nutritious Foods

It can be hard to keep up with all kinds of trends on diet and nutrition reported in the news, but following the government’s basic guidelines and understanding the types of foods you should eat most of the time and those to limit or avoid is an easy way to eat well. First, it is important to eat a variety of nutritious foods to ensure you get all of your micronutrients. Include a big range of fruits and vegetables, plus smaller amounts of nuts and seeds.

For macronutrients, choose lean proteins, like lean meats, seafood, soy products, and beans or legumes combined with whole grains. Carbohydrates should largely come from whole grains, like whole wheat bread or pasta, brown rice, oats, and other grains. Carbohydrates also come from beans, legumes, and vegetables. Healthful fats include fatty fruits like avocado, low-fat dairy products like skim milk and yogurt, nuts, seeds, fatty fish like salmon, and certain vegetable oils, like olive oil. It is also important to drink plenty of water, eight to ten cups per day.

Foods to Limit or Avoid

Foods that provide less nutrition or that have ingredients that are not good for health and wellness should be avoided or at least limited. These include fast food and junk food, highly processed foods, foods with trans fats or saturated fats, and foods with a lot of added salt or sugar. Added sugar is a particular problem. The American Heart Association recommends that men eat no more than nine teaspoons of added sugar a day and women no more than six, and yet most people eat much more because it is hidden in so many processed foods.

Working with a Registered Dietitian

For most healthy adults, eating well is simple. It isn’t always easy to eat well and to avoid junk foods, but the basic concepts are to eat a variety of whole foods and to avoid or limit unhealthy fats, salt, sugar, and processed foods. For people with special health needs, including those who need to lose weight, who struggle with eating disorders, or who have specific illnesses like diabetes or cancer, eating nutritiously can be more complicated.

If you have special needs, working with a registered dietitian nutritionist can be helpful. These are trained and licensed professionals who can give you expert advice, provide meal plans, and track your goals. Before you work with a dietitian, make sure you talk to your doctor. A good dietitian will want to know your medical history and to communicate with your doctor.

Nutrition and diet are important for overall health and wellness. Good nutrition promotes health and helps individuals lower their risks for illness and disease. Bad nutrition can do a lot of damage, contributing to or causing illness. If you have questions about your own nutrition, talk to your doctor and work with a recommended dietitian to get your health on track.