If you’re dying to eat marmalade but drugs prevent you, help is at hand.
Help is at hand for grapefruit lovers whose medication means eating marmalade can be risky.
Question
I take statins [a cholesterol-lowering medication] and despair of finding a grapefruit-free commercial marmalade. Given the number of older marmaladeconsuming and statin-using people, I’d have thought a savvy producer would make a grapefruit-free marmalade.
Answer
The so-called grapefruit-juice effect is the bane of many Kiwis’ lives. At last count, the juice was known to or predicted to interact with more than 85 drugs, many of them commonly used to lower cholesterol or blood pressure or treat heart arrhythmia, depression, anxiety, allergies, impotence or seizures. However, the University of Florida has developed a grapefruit hybrid that could solve these problems.
Food interactions with prescription drugs are problematic, as they can, and do, alter our body’s metabolising of medication, leading to treatment failure. In developed countries, 85-90% of elderly adults use at least one prescription drug, with many using more than one. In the US, for example, more than a third use five or more. And sadly, it’s this generation that loves grapefruit.
Grapefruit, however, do not love certain enzymes in our gut and liver – in particular, Cytochrome P450 3A4 (CYP3A4). Compounds in grapefruit, called furanocoumarins (FC), inhibit enzymes, such as CYP3A4, and transporters involved in the breakdown and clearance of medicines in the gut. This leads to higher circulating medication levels and an increased risk of an adverse drug reaction or overdose.
More recently, researchers have discovered that grapefruit juice can also reduce some medication levels in the body. Seasonal allergy sufferers, for example, find the antihistamine fexofenadine becomes less effective.
But there is good news on the marmalade front. Barker’s of Geraldine produces two grapefruit-free marmalades: New Zealand lemon & lime, and mandarin with ginger.
Anathoth Farm’s seville orange marmalade is also 100% grapefruit-free, but according to horticultural sciences professor Fred Gmitter, from the University of Florida’s Citrus Research and Education Center, the flesh and rind of seville oranges (sour or bitter) also have big quantities of FCs, so should be approached with care.
His team has developed a tree, known as UF 914, which produces red juicy-fleshed fruit with significantly lower FC levels. “It’s a hybrid of pummelo [a citrus species native to Southeast Asia] with grapefruit, produced by breeding.
“It tastes sweeter than ordinary grapefruit but still retains a lot of the aroma and flavour characteristics of true grapefruit,” says Gmitter.
Focus-group studies with people who like or dislike grapefruit have produced promising results. “The ‘dislikers’ actually enjoyed the 914, with comments such as ‘if grapefruit always tasted like this, I’d buy it’. The
‘likers’ also really enjoyed it.”
Juice from the hybrid has much less impact than grapefruit juice on human cells, Gmitter and colleagues noted in a 2012 study published in the journal Xenobiotica. Their trial with 12 adults showed UF 914 juice had no effect on medication, but interestingly, grapefruit juice also had little effect on some of the 12 participants’ drugs. This supports the idea that humans have huge genetic variations that, when grapefruit juice is consumed, result in a range of effects on medication, says Gmitter.
Unfortunately, his team hasn’t been able to get the estimated US$1 million funding for the large population trial needed to make food-safety claims in the US. And although UF 914 has been made available to Florida’s citrus growers as an experimental option, the release was overshadowed by the rapid spread of citrus greening disease, which has cut production by 70-80%. “Growers are in a panic, and with few exceptions, new varieties have not been widely planted,” including 914, which isn’t very resistant to the disease, says Gmitter. Consequently, UF 914 fruit are not yet on the market.
Perhaps our grapefruit growers will join South African and Chinese producers who are now growing UF 914 under licence. In the meantime, try Barker’s non-grapefruit marmalades.
“The hybrid tastes sweeter than ordinary grapefruit, but still retains a lot of the aroma and flavour characteristics of true grapefruit.”