Vitamin B6 is a type of micronutrient--a nutrient needed in very small quantities. It is found in a wide variety of foods such as meat, bananas, beans, peanut butter, vegetables, salmon, tuna fish and fortified breakfast cereals. Along with seven other vitamins it is part of the vitamin B complex. Together they help govern much of the metabolism--the matrix of chemical reactions that sustain life. However, vitamin B6 cannot be used as energy directly.
The energy present in nutrients is measured by a unit known as a calorie. In technical terms, a calorie is the amount of energy required to raise a single gram of water 1 degree Celsius. The calories that exist in nutrients are actually chemical energy. This is the energy that exists in the bonds of molecules such as the sugar glucose.
Human cells use a molecule known as ATP, or adenine triphosphate, for energy. ATP contains three phosphorus atoms. When one of them is severed, enough energy is released to power such functions as muscle contractions. ATP is metabolized through the process of cellular respiration, which first requires some sort of input molecule like glucose. There are only three organic nutrients that can be metabolized into ATP by the cells: carbohydrates, fats and proteins. Therefore, they are the only nutrients that can be said to contain calories. As useful as vitamin B6 is to the human body, it does not exist in a form that can be used as energy.
According to the Office of Dietary Supplements, vitamin B6 does play a key role in the production of energy. It is essential to the metabolism of hemoglobin, which transport oxygen through the blood. Oxygen is needed to complete the metabolism of ATP. Vitamin B6 also helps maintain blood glucose within a normal range. When caloric intake is low, vitamin B6 helps convert stored carbohydrates or other nutrients to glucose in the blood. Mostly, however, vitamin B6 is involved in protein metabolism.
Vitamins are a set of molecules known as cofactors. They bind to enzymes to help them facilitate chemical reactions in order to metabolize target molecules. Therefore, they can only metabolize energy that already exists in the cells. They cannot be thought of as packets of energy that can boost the functions of the body in and of themselves.
Energy metabolism is based on a complex set of factors, so vitamin B6 supplementation is not necessarily going to enhance energy production in a well-nourished individual. And at some point consumption actually becomes dangerous. The Food and Nutrition Board of the Institute of Medicine has established an upper tolerable intake level at 100 mg per day for all adults. Too much vitamin B6 can cause nerve damage in the arms and legs.