It's one of the most intriguing discoveries about diet. People who consume a diet low in fats and especially low in cholesterol are at risk for depression and suicide.
The first clue that low-fat diets might have anything to do with depression or self-directed violence turned up a few decades ago, quite by surprise. Large community-based studies of heart disease prevention strategies showed that among persons with the lowest cholesterol levels, there was a increased incidence of death not caused by illness, primarily to suicide, accidents, and violence.
At first, it defied comprehension. And to a considerable degree it still does, twenty-something years later.
But the link between cholesterol lowering and suicide may run directly through brain serotonin pathways, with side stops to depression, irritability, impulsiveness, and aggression. Or it may run more indirectly through metabolic pathways of brain serotonin, the neurotransmitter most associated with depression. Whatever the link is, it's complex, because it hasn't been easy to pin down.
Not that there is a whole industry of people trying to hunt it down. To some degree, the issue pits hearts against minds, or the interests of cardiologists against those of psychiatrists and neuroscientists. Cardiologists, for the most part, along with many public health experts, are focused on the need for much of the American population to reduce their risk of heart disease by cutting their intake of dietary fats. They have lots of evidence to back them up. And they don't seem over-eager to vigorously pursue whether there may be an unusual behavioral hazard associated with cholesterol-lowering strategies.