: Is lemon juice bad for heart failure? Drinking a lot of grapefruit juice is not recommended for patients with heart failure. Does the same apply to lemon juice? and whatever the answer, why? My source for the assertion about

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The study you link explains that the problem with grapefruit juice is its tendency to cause inhibition of the CYP3A4 liver enzyme, which is needed for the metabolism of many medications - including some statins prescribed to lower cholesterol. The wikipedia article on grapefruit explains this further, in particular:

Mechanism of grapefruit–drug interaction

Grapefruit juice contains furanocoumarins. Furanocoumarins
irreversibly inhibit a cytochrome P450 metabolizing enzyme called
CYP3A4, as stated above. CYP3A4 is a metabolizing enzyme for almost
50% of drugs, and is found in the liver and small intestinal
epithelial cells. As a result, many drugs are impacted by
consumption of grapefruit juice. When the metabolizing enzyme is
inhibited, less of the drug will be metabolized by it in the
epithelial cells. A decrease in drug metabolism means more of the
original form of the drug could pass unchanged to systemic blood
circulation. An unexpected high dose of the drug in the blood
could lead to fatal drug toxicity.

The furanocoumarins found in grapefruit juice are natural chemicals.
Thus, they are present in all forms of the fruit, including freshly
squeezed juice, frozen concentrate, and whole fruit. All these forms
of the grapefruit juice have the potential to limit the metabolizing
activity of CYP3A4. One whole grapefruit, or a glass of 200 mL (6.8 US
fl oz) of grapefruit juice can cause drug overdose toxicity.

The article goes on to explain that these furanocoumarins are unique to grapefruit, and I have not heard of any other fruit being associated with grapefruit in drug interaction warnings. However, since grapefruit is a cross of pumelo and a bitter orange, and since pumelo tastes like a big grapefruit, I would be cautious of pumelo.

However, I found no evidence that other common citrus contains furanocoumarins and would cause any adverse effects on drug metabolism. Furthermore, this study found that grapefruit itself lowers cholesterol and recommended it for reducing the risk of heart disease.