Niacin has been an important boon to the field of orthomolecular psychiatry for its use in a variety of mental disorders. It was initially well demonstrated to be helpful for the neuroses and psychoses described as the "dementia of pellagra," the niacin deficiency disease. Since then, it has been used in high amounts, well over 100 mg. per day and often over 1,000 mg. per day (up to 6,000 mg.), to treat a wide variety of psychological symptoms, including senility, alcoholism, drug problems, depression, and schizophrenia. Niacin has been helpful in reversing the hallucinatory experience, delusional thinking or wide mood and energy shifts of some psychological disturbances. Though this therapy has its skeptics, as does all application of nutritional medicine, some studies show promising results in treatment of schizophrenia with niacin and other supplements. Other studies show little or no effect. More research is definitely needed on niacin's effect in mental disorders.

People on high blood pressure medicines and those who have ulcers, gout, or diabetes should be very careful taking higher-dose supplements of niacin because of its effect of lowering blood pressure, its acidity, its liver toxicity, its potential to raise uric acid levels, and its effect in raising blood sugar--though recently niacin has been shown to have a positive effect on glucose tolerance (it is part of glucose tolerance factor) and, thereby, on diabetes as well. Exercise and niacin are helpful for people with adult diabetes through their positive effects on blood sugar and cholesterol.

Deficiency and toxicity: As with the other B vitamins, there are really no toxic effects from even the high doses of niacin, though the "niacin flush" previously described may be uncomfortable for some. However, with the use of high-dose niacin in recent years, the occasional person experiences some minor problems, such as irritation of the gastrointestinal tract and/or the liver, both of which subside with decreased intake of niacin. In addition, some people taking niacin experience sedation rather than stimulation.

Deficiency problems have been much more common than toxicity, and for a long period of history, the niacin deficiency disease, pellagra, was a very serious and fatal problem. Characterized as the disease of the "three Ds," pellagra causes its victims to experience dermatitis, diarrhea, and dementia. The fourth D was death.

As described previously, the classic B3 deficiency occurs mainly in cultures whose diets rely heavily on corn and where the corn is not prepared in a way that releases its niacin. One of the first signs of pellagra, or niacin deficiency, is the skin's sensitivity to light, and the skin becomes rough, thick, and dry (pellagra means "skin that is rough" in Italian). The skin then becomes darkly pigmented, especially in areas of the body prone to be hot and sweaty or those exposed to sun. The first stage of this condition is extreme redness and sensitivity of those exposed areas, and it was from this symptom that the term "redneck," describing the bright red necks of eighteenth- and nineteenth-century niacin-deficient fieldworkers, came into being.

In general, niacin deficiency affects every cell, especially in those systems with rapid turnover, such as the skin, gastrointestinal tract, and nervous system. Other than photosensitivity, the first signs of niacin deficiency are noted as decreased energy production and problems with maintaining healthy functioning of the skin and intestines. These symptoms include weakness and general fatigue, anorexia, indigestion, and skin eruptions. These can progress to other problems, such as a sore, red tongue, canker sores, nausea, vomiting, tender gums, bad breath, and diarrhea. The neurological symptoms may begin with irritability, insomnia, and headaches and then progress to tremors, extreme anxiety, depressionÑall the way to full-blown psychosis. The skin will worsen, as will the diarrhea and inflammation of the mouth and intestinal tract. There will be a lack of stomach acid production (achlorhydria) and a decrease in fat digestion and, thus, lower availability from food absorption of the fat-soluble vitamins, such as A, D, and E. Death could occur, usually from convulsions, if the niacin deficiency is not corrected.