Pyridoxal is a derivative compound of pyridoxine more commonly known as vitamin B6. Two other forms of vitamin B6 are closely related compounds known as pyridoxamine and pyridoxine. The human body metabolizes it and the other two forms of vitamin B6 into one compound that can be used by the body through processing in the liver. This common form of the three bases for vitamin B6 is known as pyridoxal 5-phosphate (P5P), or just pyridoxal phosphate.
The vitamin B6 acts as a coenzyme in the body, which means it serves as a transfer site for a chemical reaction caused by another enzyme, referred to as a transaminase. This allows the human body to synthesize complex molecules that are essential to human health, known as amino acids. Cysteine is one of the important amino acids that pyridoxal plays a key role in synthesizing from methionine, another amino acid. Pyridoxal also breaks down the essential amino acid tryptophan into vitamin B3, commonly known as niacin, and is useful in over 100 other types of coenzyme reactions in the body.
While vitamin B6 is commonly available as a nutritional supplement, the need for it is rather small, at 2 milligrams per day for the average adult. Deficiencies, however, can have adverse health effects, such as causing facial skin lesions or promoting conditions of hypertension and myochardial ischemia. A lack of sufficient quantities of pyridoxal in the diet over an extended period of time can be a contributing factor to convulsive seizures and other adverse effects. Vulnerable segments of the population that seem to lack adequate amounts of pyridoxal include women, adolescent girls, and seniors. It is a common component of many meats and vegetables in the diet, but vitamin B6 levels are often reduced during food preparation as well.
Since vitamin B6 shares the same limitation of the 20 essential amino acids that the human body cannot synthesize on its own from precursor chemicals, it must be continually supplied by the diet. Two versions of vitamin B6, including pyridoxal and pyridoxamine, are found in meats such as liver, beef, and fish, which can be a limited part of commonly-consumed foods for women or people on restrictive diets who are attempting to lose weight. This explains why these groups tend to have lower levels of vitamin B6. Pyridoxine is primarily derived from plants and seeds and is also the source for creating vitamin B6 supplements. Regardless of which of the three compounds are consumed as a regular source of the vitamin, estimates are that around 60% of this vitamin content is lost during food processing and storage such as in freezing, canning, or cooking.