The controversial vegetable is a traditional festive staple in countries including the UK.
But it can be a dangerous accompaniment to blood-thinning drugs like Warfarin, as one Scottish patient found out.
The Scottish man was prescribed the drug for heart failure and warned to stay away from green leafy vegetables, especially brussel sprouts.
The vitamin K in the vegetable can interfere with the drug and cause adverse effects including bleeding, which can be fatal.
Despite the advice, the man consumed 15 to 20 brussel sprouts on three to four occasions in one week during the festive period and was admitted to hospital three days after Christmas, where his condition improved.
His treating physicians from the Golden Jubilee National Hospital in Glasgow warned doctors and patients about the dangers of consuming excessive quantities of brussel sprouts at the Christmas table.
"Doctors should consider counselling patients who must remain anticoagulated at all times ... against excessive consumption of this traditional Christmas fare," they wrote in the Medical Journal of Australia today.
Meanwhile, those considering starting Christmas with a grapefruit breakfast or tossing a grapefruit salad might want to check their medication first.
Chemicals in grapefruit called furanocoumarins can interfere with up to 85 known medications, including cholesterol-lowering drugs, and can cause serious side effects in the case of 45 of them.
The fruit interacts with medications to increase the concentration of the drug in the bloodstream, putting patients at risk of overdose.
But Christmas can be a time of overindulgence for everyone, which carries its own risks.
Australasian College for Emergency Medicine president Dr Anthony Cross said emergency departments regularly see the effects of overindulgence at Christmas.
Often, it was a result of too much cheap food and wine, he said.
He suggested people buy a little less, but spend more on quality goods.
"Eat the good stuff and drink the expensive stuff," Dr Cross said.
Heart Foundation clinical issues director Dr Robert Grenfell said heart failure patients needed to watch their fluid intake, particularly alcohol, as it could affect their treatment.
Details about medications that react with grapefruit can be found on the website of the National Prescribing Service: http://www.nps.org.au
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