15 hours ago
Nightmares? It Might Be Something You Ate
This transcript has been edited for clarity.
Welcome to Impact Factor , your weekly dose of commentary on a new medical study. I'm Dr F. Perry Wilson from the Yale School of Medicine.
When the ghost of Jacob Marley sits across from Ebenezer Scrooge in A Christmas Carol , he observes that the miser doesn't believe in him. Scrooge, with forced bravado, says he's right. The ghost may be in actuality, 'an undigested bit of beef, a blot of mustard, a crumb of cheese… There's more of gravy than of grave about you!'
And so we see that, even in 1843, people believed that there was some link between the food we eat and the nightmares that plague us at the witching hour.
But… is it true? Does the dinner plate affect the nightmare state? Does a late-night snack make your dreams more wack?
The inspiration for today's little reverie is a perplexingly-entitled study, 'More dreams of the rarebit fiend: food sensitivity and dietary correlates of sleep and dreaming,' appearing in Frontiers in Psychology .
To save you the googling, 'dreams of the rarebit fiend' were a series of comics published in the early 1900s which would depict a nightmare of a poor individual who would wake in the last panel and lament eating some food or another.
Rarebit is a cheese-on-toast dish which, if you've never had it, can still be found at Mory's here in New Haven.
In any case, I think the Scrooge reference is a bit more familiar than the comic, but maybe the Dickens estate is litigious.
Before we dig into this study, let's think through what mechanisms there may be for food to impact dreaming. Is there biologic plausibility here?
One hypothesis, the 'food specific effects' hypothesis, suggests that certain foods have a chemical or chemicals that directly impact dreaming. There is precedence for this — certain drugs, for example, are notorious for causing weird dreams. I was on mefloquine traveling in Africa once, and I still remember the surreal dreams I had on the antimalarial. Planes flying backward against an orange-colored sky. Weird stuff.
There's also the 'food distress' hypothesis. This is the idea that certain foods hurt us a bit. Maybe they are spicy or make us gassy or whatever, and it's actually that pain or discomfort that prompts the bad dreams.
Finally, we have the 'sleep-effects' hypothesis, which is the idea that certain foods decrease the quality of our sleep — like coffee or alcohol. And that poor sleep quality predisposes to bad dreams.
So we have a number of ways that it is plausible that food may impact your dreaming… but does it? To try to figure this out, the researchers conducted a fairly detailed survey study.
More than 1000 individuals — mostly undergraduate students, mostly women — were surveyed. While they were relatively healthy overall, 13.8% reported having a medical condition and 17.1% a psychiatric condition. The average PHQ4 score for anxiety and depression was 9.5 — which is in the mild-to-moderate range: typical of modern 20-somethings. It's also worth noting that 32.4% reported sensitivity to some type of food.
Nearly one third of participants reported a high frequency of recalled nightmares — more than one per week — and women tended to recall more dreams and had more nightmares than men.
Did these individuals feel like what they ate affected their dreaming? Not really. Just 59 individuals, (5.5%) said that they thought there was any relationship between the food they ate and the qualia of their dreams. That said, those 59 people were much more likely to have frequent nightmares.
This is notably lower than the 17.8% of individuals who said food affected their dreaming in the author's prior study which was published a decade ago. That study had a smaller sample size but still focused on undergraduate students, so I think there is comparability here.
We have a dramatic reduction in the perception of a link between food and dreaming. We'll get to whether there is a real link in a minute, but why are younger people less likely to believe this these days? We can only guess. It might be a secular trend towards more data-driven, scientific, or at least quasi-scientific explanations of phenomena. The food/dream hypothesis does give old-wives-tale vibes, right? Perhaps the relevance of this idea has decreased in the public consciousness as food safety has increased. Or maybe kids these days have inputs into their brains that are way more potent than the slowly digesting cheese steak in their stomachs.
In any case, the researchers asked the 59 people who did feel that food affected their dreaming which types of food had the largest effects. In terms of increasing 'disturbing' dream content, sweets and dairy topped the list. In terms of leading to more pleasant dreams, fruit, vegetables, and herbal tea were up there.
The fact that there was some consistency here lends modest support to the food-specific effect hypothesis. Maybe there is a chemical in dairy foods that gives you bad dreams. If so, Liz Lemon should not be working on her night cheese. And for the three of you who get that reference, I salute you.
What about the food distress hypothesis? I think the data is a bit stronger here. People who were lactose-intolerant, for instance, had a higher frequency of nightmares, even if they didn't consciously believe that food intake affected dreaming.
When the authors dug down into that association, they found that controlling for gastrointestinal (GI) symptoms eliminated the observed relationship.
In other words, the data suggests that the reason people who are lactose intolerant have more nightmares is because people who are lactose intolerant have more GI upset. This is decent evidence for that food-distress hypothesis.
Finally, that sleep-effects hypothesis. Lactose intolerance was associated with worse sleep, but a lot of that effect was mediated through GI upset. So, it seems to me that, if there is any relationship between food and dreaming, it's probably due to the distress that some food causes you as you're sleeping.
Which means, of course, that Scrooge was right. A bit of underdone potato can lead to visions of fettered apparitions chastising you for the chains you forge in life. And though it ended up working out for old Ebenezer, I think most of us would like to avoid nightmares if possible.
In addition to the suggestion that food sensitivities can worsen nightmares, the researchers found that nightmares were more common among people who frequently ate late at night and those who had underlying medical or psychiatric conditions.
In brief, there might be some wisdom contained in the old wives' tales. For a restful and ghost-free night's sleep, it's likely best to slumber without a full belly and to avoid those foods that (for you) cause distress. As for Dickens, he was famously an insomniac, spending long nights walking the streets of London. Staying wide awake all night also avoids nightmares, but I wouldn't recommend it.
