I was reading an article last week when I realized that there was a gross basic error (GBE)  in my knowledge base. Maybe, it would be more accurate to say “another” GBE in my knowledge of how the world works.

I had thought that the terms “citron” and “citrus” were interchangeable. Did I not learn in French class that “citron” means lemon? And then there is “Citroen” which is that dinky little car made in France. Reading the article made it clear that citron and citrus are not interchangeable, but are somehow related.

I had to figure out the difference. I am pretty sure that I know what “citrus” is, but then, what on earth is “citron”?

What Is Citron Fruit?

Citron is also known as “citrus medica,” “Otroj” and “Brain Otroj.” It is a member of the Rutaceae family of plants. It looks like a lemon with rough skin and has a large amount of peel relative to the flesh. It is considered to be an important medicinal plant in Unani and Ayurvedic medicine where both the peel and the whole fruit are used.

Is there a connection between citron and citrus?

Almost all citrus fruits come from five ancestral species:

1. Citrus micrantha (small flowered papeda) gives us Persian limes, Mexican limes and limequats

2. Citron medica gives us Mexican lime, lemon, meyer lemon and Buddha’s hand

3. Pomelo gives us grapefruit, tangelo, meyer lemon, sweet orange, sour orange, lemon and Persian lime

4. Mandarin gives us tangelo, sweet orange, sour orange grapefruit and blood orange

5. Kumquat gives us limequat.

Therefore citron is the parent compound of many citrus fruits but strictly speaking the terms “citron” and “citrus” are not interchangeable.

In this article, we will limit our discussion to “citron.” You may argue and say this is too pedantic. 

Can we not say “like father, like son”?

To be scientific about this, we cannot attribute benefits/risks seen in derivative compounds to the parent compound. Variations on this conversation that can be heard in my house most weekends. Picture the scene.

One evil looking, chemical-laden, fluorescent soda. One child arguing that it says on the bottle that it contains orange. Therefore, it must be healthy. My answer at home is no. Similarly, I am not going to take data on citrus as surrogate data for citron.

The full chemical composition of citrus medica was identified in 2015 (1). It was found to contain 16 constituents including methyl ferulic acid, dihydro-N-caffeoyltyramine,  acacetin, β-ecdysterone, (-)-balanophonin, p-methoxy cinnamic acid, umbelliferone, ferulic acid, pyrocatechualdehyde, diosmetin, 4-methoxy salicylic acid, β-amyrin acetate, epigallocatechin, betulinic acid, lupeol and nicotinamide.

It can be difficult to buy fresh citron in local stores. Citron is more commonly found in diced candy, syrups, preserves or as an ingredient in perfumes. The very fact that fresh citron is hard to source is another reason for my intransigence on sticking to “citron” rather than “citrus.”

Every other wellness blog on citron that I have read uses data from citrus fruits to support health claims for citron. I have no intention of sending HBS readers on a wild goose chase for an exotic fruit unless it has proven health benefits. 

Is There any Research?

There are over 16 publications related to citron which include 1 clinical trial.

To put this into context, there are over 60,000 publications on vitamin C which includes almost 3000 clinical trials.

Does it Improve Immune Function?

There are no studies looking at citron and the immune system.

Does it Protect Against Cancer?

There are no studies looking at citron and cancer.

Does it Boost Cardiovascular Health?

CardiovascularFinally, we have some data to look at. Investigators from Saudi Arabia undertook a study to see if otroj could protect against isoproterenol induced cardiotoxicity in 12-week old laboratory rats (2). The otroj was sourced in a local market in Riyadh. The rats were given a subcutaneous injection of isoproterenol and either a saline placebo or otroj.

They were evaluated, when alive, by EKG recordings and via blood draws from their orbital sinuses (ouch). They were also sacrificed and their heart muscles were studied. As an aside, the investigators used an EKG machine for rats which they bought in Italy (I had never thought about the fact that someone has to make EKG monitors for rats but it seems the Italians saw the opportunity).

Overall the administration of otroj was found to prevent biochemical and histological (changes in the heart tissue) damage. The investigators did not specifically check on the mechanisms of action of otroj but thought that the protective effect was due to phenols in the otroj.

Bottom Line

There are no human clinical data on citron and heart health.

Does It Relieve Pain?

Relieve PainA 2009 study from India looked at the effect of the peel of citron on pain in rats (3). Citrus medica fruits were collected in northern India. The peels were removed, dried and ground into a fine powder.

The rats were exposed to a range of different painful stimuli including injection of carrageenan into the hind paw, being placed on a hot plate or under radiant heat. There was a statistically significant reduction in inflammation and pain in these rats.

There is a 2016 human clinical study on migraine from Iran (4). The investigators used a citron syrup called Sharbat-e-Balang which contains edible Citrus medica L. fruit juice and sugar. Sharaby-e-Balang was compared with propranolol or placebo in 90 patients with migraine. This was a randomized controlled trial which took place over 4 weeks.

The study found that Sharbat-e-Balang was superior to placebo for the metrics of headache frequency, intensity, and duration. It was as effective as propranolol in patients with migraine headache but was less effective than propranolol at reducing headache frequency. The Citron syrup was well tolerated in this particular study.

Bottom Line

There are data to suggest that citron can relieve migraine frequency, intensity, and duration. I am very sympathetic to migraine sufferers but have to say that this is just one short-term study and the citron comes with sugar. I think we have moved on since Dr. Mary Poppins recommended: “a spoonful of sugar to help the medicine go down.”

Is Citron Fruit Safe?

Here we have to infer from the limited available data from the studies that we have looked at thus far. Citron was well tolerated in the clinical trial on migraine (4).

Additionally, toxicity studies done in the cardiac study on rats showed no acute toxicity or death (2).

Conclusions

At the end of this piece of research, all I know for sure is that citron and citrus are not interchangeable terms.

I also know that there is too little published data on citron to draw any meaningful conclusions about its benefits and/or safety and far too little data for me to bother tracking down this hard to find fruit.

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