of broccoli or Brussels sprouts to get the same amount of
choline as found in one single egg yolk.)
Serotonin: The Mood Neurotransmitter
Growing up in New York City, I would always feel my
spirits drop come the fall. The impending winter months of
long, dark days with little sun exposure gave rise to a kind
of depression known as seasonal affective disorder, or SAD.
Also known as winter depression, SAD affects an estimated
ten million people in the United States—and while the
majority of those affected are women, everybody is at risk.
When I was seventeen, I learned that the skin made
vitamin D from exposure to the sun, and I realized that my
lack of sun exposure during those dark months was likely
compromising my body’s vitamin D production. I had a
hunch that my mood, the limited sun I was receiving, and
the reduced vitamin D that I was synthesizing might all
somehow be related. So I self-prescribed a vitamin D
supplement to see if that would improve my mood. Lo and
behold, I felt better.
Was this a placebo effect? One can never be sure—a
double-blind trial this was not. However, nearly two decades
since my experiment, scientists have discovered a
mechanism that might very well explain the improvement I
felt. It turns out that healthy serotonin levels may actually
rely on vitamin D, as vitamin D helps to create serotonin
from its precursor, the amino acid tryptophan. This is an
important insight, particularly in light of research estimating