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From our archives: Right now, it’s peak citrus fruit season - but there can be good reasons for avoiding certain varieties. In this 2022 column from the New Zealand Listener archives, nutritionist Jennifer Bowden explains why.
Question:
A recent column on grapefruit mentioned similar drug interactions with seville oranges. I take medication that stipulates I must avoid grapefruit, but this was the first time I’d seen other citrus fruits mentioned. I made seville marmalade this year for the first time, and my garden has what looks like a lemon tree but is actually a lemonade. Its fruit taste similar to the pomelos I had in China. Do you know if they are a problem with drug reactions?
Answer:
Seville oranges and certain lime varieties are related to grapefruit, all being hybrids of the pomelo, and therein lies the problem. The pomelo and its hybrids contain the group of compounds called furanocoumarins, which can interfere with our body’s metabolism of certain medications. So, caution is warranted when using any medication that interacts with grapefruit, as it will likely interact with pomelos, seville oranges and certain limes, too.
A study published in 2001 found seville orange juice had a similar effect to grapefruit juice on drug metabolism. Drinking a 240ml glass of seville orange juice alongside felodipine (used to treat high blood pressure and angina) resulted in a 76% increase in drug levels, comparable to what occurs with a glass of grapefruit juice. So, caution is warranted and seville orange juice and products (including marmalades) should be avoided when taking medication known to interact with grapefruit, because both the flesh and rind of this orange contain large quantities of furanocoumarins.
I presume doctors and pharmacists mention seville oranges, pomelos and limes less often in relation to drug interactions because these fruit and products made from them are perhaps less commonly consumed than grapefruit.
However, if you take medication known to interact with grapefruit, be aware that seville oranges are often used in marmalade, so check the ingredients list of any marmalade or mixed juice to ensure it doesn’t contain grapefruit or seville oranges.
In general, sweeter citrus varieties such as navel or valencia oranges do not contain the troublesome furanocoumarins. Studies have also found mandarins and small mandarin hybrids to be largely devoid of furanocoumarins. Many lemons have negligible levels, too, although meyers and sweet varieties of limes have intermediate levels of furanocoumarins in their peel, but extremely low levels in their pulp.
The lemonade fruit you mention are a variety of sweet lemon. As they were originally produced from a chance seedling, there is uncertainty about their heritage, but they are believed to be a hybrid of a mandarin and a lemon.
There is no research specifically on the furanocoumarin levels in lemonades, but given what we know about mandarins and lemons, it seems likely they would have intermediate to low levels of furanocoumarins in their flesh and possibly intermediate to low levels in their rind.
Check with your doctor to see whether eating lemonades regularly is affecting the functioning of your medication. Remember that not only the fruit type, but also the quantity eaten, the time between consumption and taking your medication and your individual genetic profile will all influence the size of any interaction with your medication.
In other words, this is not an exact science, which is why drug manufacturers err on the side of caution and recommend avoiding grapefruit and grapefruit products (and other fruits high in furanocoumarins such as seville oranges and pomelos) when taking affected medications.
This article was first published in the NZ Listener’s November 26 - December 2, 2022 edition.
