YOU’RE NOT exactly sure how it happened, but somehow you’ve managed to plough
your way through three helpings of turkey, two helpings of sprouts, which you
don’t even like, a whole plate of Aunt Edna’s festive cheese balls and the
chimney off the gingerbread house. Like everyone else, you’re slumped in your
chair with a self-satisfied grin on your face, glowing happily, drinking your
last egg-nog before bed. It’s a lovely scene, but there might be something
nastier ahead of you than a few extra inches on your waistline.
We’ve all heard the story a thousand times—eating too much food just
before bed can give you bad dreams. Especially if it’s spicy, or fermented, and
definitely if it’s cheese that smells like your sock drawer. I’ve noticed it. My
mom’s warned me about it. It’s established fact, isn’t it?
Well, not exactly. There is something called “The Pickled Walnut Theory”,
says Tore Nielsen, a sleep researcher from the Dream and Nightmare Laboratory at
the Sacred Heart Hospital in Montreal, Canada. The theory simply says you can
get nightmares from what you eat (apparently especially if it’s a pickled
walnut). But that’s about it, says Nielsen, no explanation provided. “A lot of
dream experts pooh-pooh this as a kind of myth,” he says. “But my opinion is
that it’s very likely.” And there is some evidence to back Nielsen up. Sort
of.
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That evidence mainly revolves around a number of neurotransmitters in the
brain that control the amount of time you spend in rapid eye movement (REM)
sleep, one of the most rejuvenating bits of our night and also the phase when
you’re most likely to dream. Eating foods containing particular chemicals can
bump the levels of neurotransmitters up and down, playing havoc with dreams.
For example milk, considered by most parents and researchers to be a
soporific, contains tryptophan, an amino acid that is also used by doctors to
relieve nightmares. Tryptophan increases the brain’s levels of serotonin, a
neurotransmitter that can cut down on your REM sleep. Ironically, that means
warm milk probably diminishes the amount of restful sleep you get at night, but
it also simmers down your dreams—bad or good. (What that might mean for
Santa, with the billions of milk-and-mince-pie donations, is anybody’s
guess.)
So it’s probably not tryptophan in cheese that’s responsible for its
nightmarish reputation. But it might be the tyramine—a chemical that
bumps up noradrenalin levels in the brain. High noradrenalin, like serotonin,
tends to be associated with less REM sleep, and so less dreaming. But
noradrenalin also makes blood vessels constrict and blood pressure rise, and
that could make the dreams you do have racy, even nightmarish, suggests Nielsen.
The more aged the cheese, or the more rancid, the more tyramine it’ll have.
Ditto for overripe mandarin oranges. And if the cranberries in the sauce have
gone off, then hold on to your reindeer, it could well be a bumpy night.
If food can be linked to bad dreams, then perhaps that even explains the
nightmarish visitations experienced by Ebenezer Scrooge on Christmas Eve. He
tucks into a late-night nosh and then sits down to a pan of gruel when his
long-dead business partner Jacob Marley, looking awfully ghost-like and making
frightening chain-scraping noises, appears to waft through the door. Scrooge,
who has perhaps read up on the effects of tyramine, proclaims wisely, “You may
be an undigested bit of beef, a blot of mustard, a crumb of cheese, a fragment
of an underdone potato. There’s more of gravy than of grave about you, whatever
you are!”
The trouble is that not everyone is convinced by the possible links between
food and bad dreams. “There’s no evidence that spicy food causes nightmares,”
says Ernest Hartman, a psychiatrist at the sleep clinic at Newton-Wellesley
Hospital in Newton, Massachusetts, and arguably the world expert on nightmares.
The whole thing about cheese, as far as he’s concerned, is a myth.
But maybe the explanation isn’t so chemically complicated. Maybe it’s just
that cheese, like most dairy products, is notoriously difficult to digest,
suggests Rafael Cabeza, a neuropharmacologist from the University of Texas at El
Paso. Get a tummy full of it, and you may spend the night tossing and turning.
The more often you wake up, the more likely it is that your dreams are
interrupted and so you remember them. If they are bad dreams that can leave you
with the impression of a night plagued by nightmares.
Apart from pungent cheese, a bellyful of Christmas cheer could also trigger a
nightmare or two. Take mulled wine. Aside from the double dose of tyramine
you’ll get from the alcohol and the fermenting oranges, there’s more trouble
brewing. Go to bed the worse for wear, and you’ll initially dream less because
alcohol suppresses REM sleep. Once that effect wears off, usually around the
early hours of the morning, your brain “rebounds” and crams as much REM sleep
into as short a time as possible. Your dreams get more vivid, sometimes even
frightening. It’s like someone shouting in your ear when you expect them to
whisper, says Nielsen.
Things get worse if you’re trying to go cold-turkey on cigarettes and have a
nicotine patch or two stuck to your tummy. The patch increases levels of
dopamine, another neurotransmitter, which has been tentatively linked to
increasing REM sleep. People who use patches often complain of nightmares. And
if you’re doped up on beta-blockers for your high blood pressure that could
cause trouble too. These drugs initially increase noradrenalin, suppressing REM
sleep. But just as with booze, you may get a rebound effect and an onslaught of
early-morning dreaming.
Then there’s the issue of just how you fall into bed after the season’s
festivities. “The way we sleep, the postures we assume, even the way we touch
our spouse, that affects our dreams,” says Nielsen. Hartman says that his
patients seem to complain more of nightmares when they sleep on their backs,
although he doesn’t know why this might be so. The Netherlanders of the Middle
Ages, on the other hand, were apparently so convinced of the importance of
posture that they slept in cupboard-like vertical spaces called “box beds” to
stop the bad dreams triggered, they believed, by their diet rich in salted
fish.
Today the jury is out on whether food, including salted fish and Christmas
binges, can really cause nightmares. But we could soon know the truth now that
Nielsen’s on the case. “It would be an interesting research project,” he muses.
“You could probably get a pizza company to sponsor you…”