Cellular respiration refers to all of the chemical reactions in your cells that are required to release energy from nutrients. Like other B vitamins, vitamin B6, or pyridoxine, is an essential co-factor in many of those reactions. It is particularly important for amino acid metabolism, but is also necessary for the metabolism of fats and carbohydrates.
Amino Acid Metabolism
Vitamin B6 is an important co-factor in many enzymes involved in the metabolism of amino acids, the building blocks of proteins in your cells. One such group of enzymes, known as the transaminases, is essential for converting amino acids from one form to another. Transaminases linked to vitamin B6 help to create several critical compounds in the Krebs cycle, a series of biochemical reactions that plays a role in the oxidation of fats and carbohydrates for energy.
Your liver can convert amino acids, as well as lactic acid, into glucose, or blood sugar, a process called gluconeogenesis. Glucose from gluconeogenesis provides an important source of energy for cell respiration, especially during exercise and when you're fasting. Vitamin B6-containing enzymes play important roles in those reactions. Vitamin B6 is also involved as a coenzyme in fat and lipid metabolism and assists with the conversion of amino acids into fats.
Cells in your liver and muscles store carbohydrates in the form of glycogen, or animal starch. Glycogen consists of long chains of glucose molecules strung together like beads on a string. When cells need energy, those glycogen molecules can be broken off to provide glucose in a process called glycogenolysis. The enzyme responsible for glycogenolysis, called phosphorylase, also uses vitamin B6 as a co-factor. Glycogenolysis also provides an important source of energy during exercise and when you're fasting.
Vitamin B6 Requirements
The recommended dietary allowance of B6 for adult men and women, as set by the National Institute of Medicine, is 1.3 mg per day. Older adults need more, however. The RDA for men over 50 is 1.7 mg per day, while for women over 50 it is 1.5 mg. Vitamin B6 is found in many foods. The best sources are fish, liver and other organ meats, starchy vegetables and non-citrus fruits.