Did you know that the scent of mistletoe stimulates saliva production and that the taste of eggnog boosts serotonin levels? And did you know that second-graders who believe in Santa Claus do worse on standardized tests than non-believers? I bet you didn't and there is a good reason why – these associations have no basis in fact. Still, if enough people were to repeat them, they might easily become accepted as truth. Take, for example, the popular belief that the tryptophan in turkey makes you sleepy. While turkey does contain tryptophan (an amino acid with sleep-inducing properties), it doesn't contain any more of it than beef or chicken. In fact, sunflower seeds and soybeans are both richer in trypotphan than turkey. Which means that the post-Thanksgiving dinner drowsiness you recently experienced was most likely due to other holiday indulgences – such as alcohol and carbohydrate intake.
Last year, in the spirit of dispelling such seasonal myths, the British Medical Journal published a scientific review of some common holiday-related beliefs. I was surprised by some of the content and must admit that in the past I’ve contributed to the urban legends that the article debunks. And I suspect some of you have too. So, this holiday season, I’d like to give us all the gift of some solid scientific evidence.
*Poinsettia plants are not toxic.
A poison control center study reviewing more than 800,000 poinsettia leaf ingestions did not find a single case of significant toxicity. In fact, 96% of ingestions did not even require medical evaluation. And in another study, scientists were unable to kill rats (they are clearly not alone in this predicament) with poinsettia – even after feeding them the equivalent of more than 500 leaves. So, while not to be encouraged, should junior mistake a poinsettia for a festive treat, there is no reason to panic.
*People are not more depressed during the holidays.
A U.S. study spanning 35 years did not find an increase in suicide rates over the holidays – a finding corroborated by evidence from other countries. This is not to say that people don’t get bummed out over the holidays, just that the amount and degree of depression around this time of year is probably no different than during the rest of the year.
*Children who eat sugar are not more hyper; but their parents might be.
Twelve well-designed studies have not found an association between sugary food and hyper-activity levels. Parents, though, are more likely to rate their child's behavior as "hyper-active" after they have watched them drink a sugary drink. So, the sugar-hyper-activity connection may only exist in mom and dad’s mind. The link between sugar and rotten teeth, on the other hand, is quite real so there is good reason to be hyper-active about post-candy tooth brushing.
*Nighttime binging is not more fattening than daytime binging.
This was news to me. I have often warned my patients against feasting late at night and advised them that people who skip breakfast are more likely to gain weight. It turns out that the latter is true, but not because breakfast-skippers binge at night, but rather because they eat more during the rest of the day. Several good studies have failed to establish a connection between late-night eating and obesity. So, feel free to enjoy the occasional midnight snack, but know that the age-old association between holiday-related overeating and weight gain is no myth.
I’m thankful that the British Medical Journal has given us less to stress about these holidays, but also know that there are some genuine seasonal health threats that deserve mention.
*Heart-related deaths are more common during the holidays.
It is not exactly clear why, but very good evidence shows that the rate of heart-related deaths spikes at Christmas and New Years. To minimize your risk of a Merry Christmas Coronary; consume only moderate amounts of calories, salt, and alcohol, avoid excessive exposure to air-based pollutants like smoke from a wood burning stove, and don’t engage in too much robust exertion after big meals. If you experience any new and concerning symptoms (such as feeling like there’s an elephant sitting on your chest), please don’t delay your trip to the hospital until after the presents are all unwrapped.
*Festive dinners tend to get stuck in the esophagus.
Whether it is Christmas goose or Chanukah brisket, one of the biggest risks of a holiday meal is that it won't make it to its intended destination. Getting a chunk of beef lodged in your esophagus may be a good way to limit caloric intake, but it also may lead to a visit to you local Emergency Department and an encounter with a grumpy gastroenterologist. So remember, on Christmas day, the best gift you can give Grandpa may be to remind him to cut his dinner into safely-sized chunks.
*Space heaters have Scrooge-like tendencies.
Not only are space heaters energy hogs, they also poise an under-recognized health risk – an unsightly rash called erythema ab igne. If you spend hours nestled close to a space heater – in the office or bedroom – you are at risk for developing this web-like discoloration which may result in permanent pigmentation changes and perhaps even skin cancer. So, take it easy on your skin (and mother nature) and turn down the space heater.
On that note, I am off to salivate under the mistletoe. Happy Holidays.
Vreeman RC, Carroll AE. BMJ 2008;337:a2769