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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 grapefruit juice is here

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    Telling us which medications you're on, and what quantity of actual lemon juice you're drinking in a 24 hour period will help you get a better answer. Also, it's reasonable to wait a few days before you accept an answer, particularly if the answer doesn't answer your question. A better answer can pop up days or months from now! – anongoodnurse Jul 15 '15 at 23:05
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    And remember that if a better answer does come along, you can change your selection to have that be your favorite answer. – Chris Jenks Jul 15 '15 at 23:23
  • Somewhere in the back of my brain I seem to recall hearing that lemon is a diuretic, that being said, it seems that it could actually be helpful. However, I understand the concern since grapefruit has come to be on the "blacklist" for people who are on medications, especially cardiac. – L.B. Aug 24 '16 at 12:51
  • is lemon and hot water is harmful for heart decease if we drink it early morning blank stomach – imtiaz Nov 30 '17 at 12:25
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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.

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    I am curious how this relates to heart failure. I understand that grapefruit interferes with the metabolism of medications, but why heart failure? – anongoodnurse Jul 15 '15 at 18:52
  • Thank you for the excellent answer, and a good point from @anongoodnurse, it's because I have been diagnosed and am being treated for heart failure, and it is in that context that I am interested. – Harry Weston Jul 15 '15 at 18:58
  • @anongoodnurse - I amended my answer to point out that the original source simply mentioned some cholesterol-lowering medications (statins) affected by grapefruit consumption. And another link to a study recommending grapefruit to lower cholesterol to reduce the risk of coronary disease. So I don't think it is heart failure in particular for which eating grapefruit is contraindicated - at least no evidence of this has been offered. – Chris Jenks Jul 15 '15 at 19:13
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    I am aware of the relationship between grapefruit juice and decreased efficacy of statins. This still does not answer the OP's question: "Drinking a lot of grapefruit juice is not recommended for patients with heart failure. Does the same apply to lemon juice? [A]nd whatever the answer, why?" – anongoodnurse Jul 15 '15 at 23:00
  • But the study the OP gave as the source for the question is titled "Does grapefruit affect my medicine?" Why would lemons have the same affect on medication metabolism described in that study? – Chris Jenks Jul 15 '15 at 23:25

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