The food we eat gives our bodies the "information" and materials they need to function properly. If we don't get the right information, our metabolic processes suffer and our health declines.
If we get too much food, or food that gives our bodies the wrong instructions, we can become overweight, undernourished, and at risk for the development of diseases and conditions, such as arthritis , diabetes , and heart disease .
In short, what we eat is central to our health.
Consider that in light of Webster's definition of medicine: "The science and art dealing with the maintenance of health and the prevention, alleviation, or cure of disease." Food acts as medicine, to maintain, prevent, and treat disease.
The nutrients in food enable the cells in our bodies to perform their necessary functions. This quote from a popular textbook describes how the nutrients in food are essential for our physical functioning.
"Nutrients are the nourishing substances in food that are essential for the growth, development and maintenance of body functions. Essential meaning that if a nutrient is not present, aspects of function and therefore human health decline.
When nutrient intake does not regularly meet the nutrient needs dictated by the cell activity, the metabolic processes slow down or even stop."
- Perspectives in Nutrition , Wardlow and Insel
In other words, nutrients give our bodies instructions about how to function. In this sense, food can be seen as a source of "information" for the body. See examples in Food As Information .
Thinking about food in this way gives us a view of nutrition that goes beyond calories or grams, good foods or bad foods. This view leads us to focus on foods we should include rather than foods to exclude.
Instead of viewing food as the enemy, we look to food as a way to create health and reduce disease by helping the body maintain function.
The nutrients in food give our bodies the information and materials they need to function properly. But our daily diets may not always be providing all the information our bodies need.
We all know that we need to get a basic balance of nutrients every day. But we may not be aware that the Standard American Diet (SAD) lacks nutrients. Moreover, some of our processed foods include chemically-altered fats and sugars that may be giving our bodies the wrong signals.
If you are interested in more specific information on the nutrients you need and how best to get them, see the section, What Do Specific Foods Do?  This information springs from research coming out of an area of healthcare called Functional Medicine, which is a dynamic approach to assessing, preventing, and treating complex and chronic diseases, and includes research about the role that nutrition plays.
As a society we are facing significant health problems.
Many researchers now believe that these problems are partly related to diet. While they used to believe that diseases-such as type II diabetes , obesity, heart disease , stroke, and certain cancers  - were caused by a single gene mutation, they are now generally attributing these conditions to a network of biological dysfunction. And the food we eat is an important factor in that dysfunction, in part because our diets lack the necessary balance of nutrients (Proceedings of the Nutrition Society, 2004).
To prevent the onset of these diseases, we need to know how multiple nutrients in a diet interact and affect the human body's functions, according to the Nutrition Society, Europe's largest nutritional organization.
One component of Functional Medicine focuses on how diet impacts health and function. When Functional Medicine practitioners examine the role of nutrition in chronic disease, they look at multiple systems, such as the digestive system, the immune system, and the detoxification system, because of the interconnections between those systems. For instance, because 80% of the immune system is contained in the gastrointestinal system, a person's issues with immunity could be related to faulty digestion.
Functional Medicine maintains that chronic disease is almost always preceded by a period of declining health in one or more of the body's systems. Thus, these practitioners seek to identify early the symptoms that indicate underlying dysfunction, possibly leading to disease.
One of the ways Functional Medicine seeks to address declining health is to provide the foods and nutrients needed to restore function. This is a cost effective, non-invasive intervention that aims to stop the progression into disease.
When taking a nutritional approach to health and disease, it is important to understand that one disease might have multiple causes, and one underlying dysfunction might cause multiple diseases. Cardiovascular disease  may be among the clearest examples of this concept.
Researchers have shown that the development of heart disease  can be triggered by multiple factors. These factors include insulin resistance, elevated homocysteine, oxidative stress, elevated cholesterol, hypertension, heavy metal toxicity, stress , and inflammation. Each of these factors can be influenced by nutrition and each, in turn, impact our nutritional needs. This applies both to the prevention and treatment of these factors (Textbook of Functional Medicine).
For example, a 2007 study shows the importance of optimal mineral balance and how a deficiency in mineral balance can contribute to the development of congestive heart failure (Cardiovascular & Hematological Agents in Medicinal Chemistry, 2007).
During her initial visit, Lynn (53), just had one goal: "I need to get healthy!" Her cholesterol was elevated (including triglycerides), and she had taken Lipitor for five years. Her blood pressure had been elevated in the past. She had acid reflux and had been on Zantac for 15 years.
She slept poorly and experienced sleep apnea and extreme fatigue. She was taking hormone replacement therapy for hormonal headaches that had plagued her for years. She had experienced swollen, painful joints for many years, which had developed into osteoarthritis. Her bowels tended toward constipation, and she craved bread and sweets.
The nutritionist noted her systemic inflammation, water retention, swelling, and constipation  and suspected a food sensitivity. She suggested that Lynn eliminate corn, dairy, and wheat from her diet; keep track of her body's reaction to the changes; and then gradually introduce these foods one at a time.
When Lynn returned four weeks later, she had determined through the elimination diet that she had a corn sensitivity. Since eliminating corn, she reported feeling much better, and the pain in her back and legs had diminished. Her constipation was relieved and much of the swelling and fluid retention also improved. Lynn reported that "I lost only five pounds, but I feel smaller."
Returning at eight weeks, Lynn reported that the, "changes have been easy." She had lost 20 pounds and her energy was much improved: "I wake up ready for the day." She was walking a mile and a half each day and her cravings for sugar had also diminished, much to her delight. She reported feeling more in control of her eating.
At 12 weeks, Lynn said the changes were becoming habit. "I feel so much better." Her energy continued to improve; she had lost a total of 27 pounds, and she experienced less pain.