One Man's Food is Another's Poison
As you may already know, metabolism is simply the sum total of all the chemical and biological activities that are necessary to sustain life. Although these life functions -- or metabolic activities -- are many and diverse, they can be summarized as follows: nutrition, transport, respiration, synthesis, regulation, growth and reproduction.
In order to sustain life, all these metabolic activities require energy. The air, water, sunlight, and food (nutrients) which we acquire from our environment are used by our body to produce this vital, life-sustaining energy.
The raw materials in the foods we eat (vitamins, minerals, enzymes, etc.) are particularly important, since they're used by our bodies to repair, rebuild and heal tissue. But foods and nutrients are also essential because they provide the fuel that is oxidized (burned or combusted) in our cells to provide energy for all metabolic activities.
In fact every biochemical process in your body is entirely dependent on the rate, quality and amount of energy available to you. When optimum energy is available to your body on all levels -- to all your cells, organs, glands and systems -- then optimum (balanced and efficient) functioning of your body, or good health, is possible.
It is on the cellular level that all metabolic activity takes place and efficiency or inefficiency is determined. Each cell in your body is like a biochemical factory built to fulfill a specific metabolic function. As food passes through the digestive tract, it is absorbed into the bloodstream where it is transported to the cells. Once nutrients arrive at the cells, they are assimilated into the cells, and then utilized by the cells for the production of energy and for the fulfillment of the cells' "programmed" function
We all need a full spectrum of nutrients. But, different people have genetically programmed requirements for different amounts of the various nutrients. It is these differing genetic requirements that explain why a given nutrient can cause one person to feel good, have no effect on another, and cause a third person to feel poorly.