This Old Turkey of a Theory Is Depressingly Inaccurate

Aram Bakshian's review of "Foods That Harm; Foods That Heal" (Books, April 27) quotes the book as stating that: "Turkey, with its tryptophan, may help with depression, but sugary foods will not." All of that statement was scientifically incorrect when first published in the 1997 version of the book and remains every bit as incorrect now.

Turkey protein, the source of amino acids, contains proportionately no more tryptophan than any other animal protein (e.g., egg albumin) and like all other proteins actually decreases the amount of tryptophan that gets into the brain (and can be converted to serotonin, which may have antidepressant properties). That's because tryptophan competes with other amino acids, which are far more abundant in protein, in crossing the blood-brain barrier. So paradoxically, the more turkey protein one eats, the lower brain tryptophan levels become, and the less serotonin is synthesized.

Sugary or starchy foods contain no tryptophan in their sugars or starches. However, also paradoxically, these foods raise brain tryptophan levels because they cause insulin to be secreted, and insulin selectively lowers blood levels of the amino acids that compete with tryptophan for passage across the blood-brain barrier. They also increase brain serotonin synthesis and can exhibit antidepressant effects.

All of this has been known for four decades and confirmed in hundreds of scientific publications. It explains a number of phenomena that Journal readers might have experienced, such as the fact that the Atkins Diet, popular a decade ago, which encouraged people to eat high-protein but low-carbohydrate meals, often exacerbated their depression and insomnia by decreasing the release of brain serotonin. It also explains the tendency of many people experiencing seasonal depression, or the depression associated with premenstrual syndrome, to become carbohydrate cravers.

Prof. Richard Wurtman, M.D.

Massachusetts Institute

of Technology

Cambridge, Mass.