Vitamins & Nutritional Supplements for Seasonal Depression

L-tryptophan is the amino acid used by the body to manufacture serotonin. Several trials, some controlled, have shown that experimentally inducing a tryptophan deficiency in people with SAD who are in remission brings about a relapse of depressive symptoms. This suggests that supplemental L-tryptophan might be helpful in SAD. In small, preliminary trials, 4 to 6 grams of L-tryptophan given in divided amounts daily was as effective as light therapy and more effective than placebo. L-tryptophan may be of particular use in people with winter depression who do not benefit from light therapy. In a preliminary trial, people with SAD who responded only partially or not at all to bright light therapy were given 1,000 mg of L-tryptophan three times daily in addition to 10,000 lux light therapy for 30 minutes every morning. Sixty-four percent of them had significant improvement in depressive symptoms while receiving both L-tryptophan and bright light therapy. L-tryptophan is currently available by prescription only.

5-HTP is a substance related to L-tryptophan that increases serotonin production and has shown antidepressant activity. It may also be useful in the treatment of SAD, but there is currently no research testing this possibility.

Vitamin D is well known for its effects on helping to maintain normal calcium levels, but it also exerts influence on the brain, spinal cord, and hormone-producing tissues of the body that may be important in the regulation of mood. A double-blind study found that mood improved in healthy people without SAD who received 400 or 800 IU per day of vitamin D for five days in late winter...