A trip to the health food store can be daunting these days. The consumer is typically confronted by shelf after shelf of vitamins, minerals, herbs, and other so-called natural substances, all touted as enhancing well-being in some way. Many of these over-the-counter products make subtle claims about their effects on mood, thinking, or energy -- without providing scientific data to back up those claims.
Because many of these preparations are classified as "food substances," the U.S. Food and Drug Administration (FDA) cannot regulate them as real drugs. In effect, it's up to the FDA to prove that a food substance is unsafe, rather than the job of the manufacturer to show it is safe. What is the evidence that vitamins, minerals, or similar substances have an effect on mood disorders? And can these substances actually improve moods or even treat depression?
Serotonin acts as a neurotransmitter, a type of chemical that helps relay signals from one area of the brain to another. Although serotonin is manufactured in the brain, where it performs its primary functions, some 90% of our serotonin supply is found in the digestive tract and in blood platelets.
Vitamin deficiencies are rare in the United States and other developed countries. In fact, vitamin excess may now be more common than vitamin deficiency. When deficiencies do occur, they're usually due to food fads that lead to medical conditions from poor absorption of nutrients in the intestine, or inborn errors in the way nutrients are handled. Alcoholism is also a major cause of vitamin deficiencies, owing to poor nutrition, impaired absorption of nutrients, and other factors. The elderly and those with mental illness or mental retardation are also at risk, usually due to poor nutrition and self-care.
Occasionally there are individuals whose depression, anxiety, or memory problems are caused by a deficiency in some vitamin, mineral, or trace element -- most commonly, one of the B complex vitamins. Deficiencies of thiamine (vitamin B1), niacin, pyridoxine (B6), or cobalamin (B12) sometimes produce mental or emotional problems, including depression. Folic acid deficiency may cause problems with mood and mental function. While only a small minority of severely depressed persons suffer from such vitamin deficiencies, this problem must be ruled out when the clinical picture raises suspicions -- for example, when a depressed individual has a history of bowel surgery that may have led to malabsorption of B vitamins. If depression is due to a vitamin deficiency, treatment must include replacement or supplementation of the vitamin before the patient can fully recover.