For a festive feast, concerns of calorie counting and drink moderation get tossed to the side as we indulge in Saturnalian levels of consumption. And if we go in for post-Christmas “detox” diets, it’s presumably because we worry about having “toxed” ourselves in the first place. With this in mind, and while we look forward to the treats and merrymaking to come, it seems like a fun time to take a light-hearted look at some seasonal toxins.
1. Salicylic acid
Cranberry sauce is delicious. After cooking with heaps of sugar and a good slug of port wine, you’d never know that the raw berries started out with an unpleasant bitter-sour flavor. Part of what you’re tasting when you eat a hard, raw cranberry is salicylic acid—a phenolic acid also derived from willow bark. It has anti-inflammatory and antibiotic properties, which make it ideal for use in acne treatments. On the downside, an overdose of salicylic acid can cause stomach bleeding, and patients on blood-thinners such as warfarin are sometimes advised against eating cranberries as the combination may mess with your blood’s ability to clot.
Cloves—which add a seasonal, almost menthol-like aroma and flavor to mince pies—contain the chemical compound eugenol. In one experiment with eugenol, rats exposed to it by inhalation lost weight overnight. But before you go sniffing your way through dozens of mince pies trying to drop a few pounds by Boxing Day, it’s worth noting that the weight loss disappeared after a few days. Other scientists are experimenting with using eugenol as an anesthetic; it can certainly knock out frogs.
Asked to name the best-known poison in popular culture, many people would probably say cyanide. In the kind of gritty, Cold War thrillers often repeated on Christmas TV, biting down on a cyanide pill sometimes spells the frothy-mouthed end for the captured spy. How about a snack to go with that movie—some sugared almonds perhaps? Fortunately for us, wild bitter almonds—which contain quite high levels of cyanide—are banned for culinary use in the United States. The variety we eat are harmless: long-term selection of low-cyanide varieties has domesticated them, effectively "breeding out" the cyanide. Interestingly though, one popular Christmas liqueur—amaretto—is sometimes flavored with extract from apricot kernels, which are related to bitter almonds and do contain some cyanide.
A stick of cinnamon can add depth and spice to the flavor of mulled wine. Increasingly, cinnamon is becoming popular as a flavoring year-round. In Denmark, it’s a traditional ingredient of the regular diet, baked into those delicious Danish pastries. Some Danes didn’t take kindly, then, to scientists raising concerns over the levels of coumarin being ingested as a result of their high cinnamon intake; some news sources even began calling the public outcry "cinnamon-gate." Ingesting too much coumarin can cause liver damage, but you’d have to munch your way through a massive number of cinnamon swirls or drink untold gallons of mulled wine to get anywhere near overdosing on it.
Citrus is one of those scents we associate with the holidays. Our zest for citrus at Christmas has us garnishing paté with lemon slices, guzzling tangerines, baking citrus rind into cakes and puddings, and boiling it in sugar to make candied peel. The zingy aroma of citrus may be tantalizing to us, but it’s a graveyard smell to many insects. Citrus, especially grapefruit, contains a compound called nootkatone, which has been shown to kill insects ranging from mosquitos to bedbugs. We often worry about pesticides on our fruit, but most of us don’t realize we’re ingesting an array of natural ones when we eat citrus peel. But despite being toxic to insects, the FDA has approved nootkatone as a safe additive.
In the UK, roast parsnips—slathered in honey or maple syrup—are considered an essential Christmas dinner accompaniment. This pale root vegetable, a relative of the carrot, contains a compound called psoralen (a furocoumarin, related to the coumarin in cinnamon). Psoralen, also found in celery and turnips, can increase skin sensitivity to UVA light. This makes it effective for treating the skin condition vitiligo and for cosmetic use in tanning (for that roasted-parsnip look, perhaps?), but it is toxic at higher doses. Workers picking parsnips have been known to develop burns and rashes on their hands, which are literally sunburns. And, in rare cases, increased photosensitivity from psoralen can lead to skin cancer.
For a quick, easy, and delicious Christmas dinner starter, prawns with avocado is hard to beat. Your pet parakeet, however, should give it a wide berth. A compound called persin found in avocados is poisonous to many mammals, birds, and fish—but not to humans. There’s debate about the effects of persin on cats and dogs; while it might make your dog a bit sick, it can do serious harm to horses and to ruminants such as cows and goats (as well as to other mammals). It could kill your pet bird or your goldfish. It’s not known why avocados should be safe for humans (some kind of evolutionary adaption to a nutritious food source, maybe), but this kind of “selective toxicity” is more common than you might expect.
“What’s your poison?” Whatever the booze, the “poison” is ethanol. It’s a complex drug, with diverse effects on brain chemistry. Throughout the festive season we ingest it via a sumptuous variety of drink and drink-laced foods. In the UK, brandy or other spirits are glugged into the heavy, dark fruit cake traditionally served when everyone is too full of Christmas dinner to eat another bite. And "flaming" the Christmas pudding, using brandy as fuel, often fails to burn off much of the heady liquor. Though an expected Holiday intoxicant, ethanol can also be found in unexpected places. It’s a main ingredient in some flavoring extracts, so it’s technically possible to overdose on vanilla extract.
Who hasn't stuffed themselves with tasty potatoes during a holiday meal? Roasted, mashed, or baked, this carbohydrate-rich tuber is a festive favorite. Nevertheless, it can also be a bit of a green monster. It’s thought that “greening” in potatoes—hard to spot in red-skinned varieties—indicates the presence of a higher-than-average level of glycoalkaloids. These naturally produced compounds (such as solanine and chaconine) can cause a bitter-tasting, burning sensation in the mouth. Anecdotally, glycoalkaloid toxicity from potatoes has been blamed for headaches and even hallucinations. That’s some crazy monster mash.
Nutmeg—popular for spicing up that bland Christmas turkey and great in eggnog—has a toxic dose of only 2-3 teaspoons. Our seasonal seasoning friend Myristica fragrans also has a cheery red casing, known as mace, which tastes like nutmeg but with a slightly subtler flavor. Both mace and nutmeg (also essential ingredients in Scottish haggis) contain a compound called myristicin, which, taken to excess, can cause transient psychosis.
Before you go trashing your holiday store cupboard, it’s worth remembering that any ingredient can be poisonous when taken in overdose. In toxicology, all substances have an LD50—a dose which will kill 50% of those taking it within a given time period. So Christmas dinner ingredients are really no more “toxic” than some of those we take at other times of the year (the LD50 for coffee is around 25 cups).
So don’t worry. Eat, drink, and be merry, for tomorrow we wake up late, a little groggy, but essentially healthy, perhaps ready to curl up on the couch and read that detox diet book.