What Is the Chemical that Causes Fatigue?

There are hundreds of potential causes of fatigue, including viral causes, vitamin deficiencies, anemia, and cancer. But there is one fatigue-producing chemical to which nearly everyone is exposed at some point in life, and it's often used as a natural sleep aid and anti-depressant.

Tryptophan

• Tryptophan is one of the essential amino acids in the human diet, most commonly identified as L-tryptophan. It is used as a building block in human metabolism, to make such proteins as serotonin and melatonin.

Drowsiness

• Tryptophan is widely believed to cause drowsiness, since it is a complex chemical that requires metabolizing---hence that feeling of fatigue after a heavy Thanksgiving dinner (though the amount of food and alcohol likely contributes as well).

Essential

• As an essential amino acid, L-tryptophan is one that the body does not produce. Therefore, it must be ingested through the diet.

Sources

• Tryptophan is present in some very common foods, including egg whites, soybeans, cod, and turkey.

Supplements

• L-tryptophan is an effective sleep aid, available only by prescription. But 5-hydroxytryptophan (5-HTP) (which L-tryptophan forms in the blood anyway) is available over the counter as a natural sleep aid and antidepressant.