Lemon

What a lemon actually is

Citrus limon is the offspring of a bitter orange and a citron, crossed somewhere in north-east India or southern China around a thousand years ago. It has no wild ancestor of its own. Almost all the citrus in a shop works this way: citron, pomelo and mandarin are the three original species, and lemons, limes, oranges and grapefruit are all combinations of those three.

Three ancestral species, and a very large family.

The sharpness is citric acid, which makes up around five per cent of the juice and takes it to a pH near two. The smell is something else entirely: limonene, held in oil glands in the peel. That split is why zest smells intensely of lemon while the juice mostly just smells sour.

How lemons ended scurvy

Scurvy killed more sailors than combat did. On long voyages, crews without fresh food developed bleeding gums, wounds that reopened years after healing, and eventually collapse. Nobody knew why.

In 1747 the naval surgeon James Lind ran what is usually called the first controlled clinical trial: six pairs of scurvy patients, six different treatments. The pair given oranges and lemons recovered. The Royal Navy adopted citrus rations in 1795 and the disease all but vanished from the fleet.

The Navy later swapped lemons for cheaper West Indian limes, which carry less vitamin C. The nickname stuck anyway.

The compound behind it was not isolated until the 1930s, and it was named for the job it does: ascorbic acid, from a-scorbutic, meaning against scurvy.

What the vitamin C in lemons actually does

A whole lemon carries around 30 mg of vitamin C, somewhere between a third and a half of an adult’s daily requirement depending on whose figure you use. What that vitamin does is unusually well settled.

It is required to build collagen, the protein holding skin, gums, blood vessels and connective tissue together, which is precisely why scurvy looks the way it does. It contributes to normal immune function. It works as an antioxidant, protecting cells from oxidative damage. All three are established well enough that regulators permit them as claims, which is rare.

And it does one more thing, more specific and more useful than any of those. It unlocks the iron in plants. Iron from meat is absorbed easily. Iron from beans, lentils, spinach and grains is not: it arrives in a form the gut struggles with, and most of it passes straight through. Vitamin C converts that iron into a form the body can take up, and holds it in that form long enough to matter.

If you eat mostly plants, or you run low on iron, this is the most practical thing a lemon does for you. Squeezing lemon over a lentil dish is not decoration.

What else lemons are studied for

Kidney stones. This is the strongest of the rest and it is proper clinical territory. Lemon juice has the highest citrate content of any citrus, and citrate binds calcium in urine so crystals cannot form. Urologists use this directly: in trials, lemon juice raised urinary citrate substantially and cut stone recurrence in people who form calcium stones. The doses are therapeutic rather than culinary, in the region of 60 ml of juice twice a day, so it is a conversation to have with a doctor rather than something to arrange yourself.

Blood sugar. Citric acid slows the stomach emptying and the breakdown of starch, so a sharp dressing alongside a carbohydrate-heavy meal flattens the glucose rise that follows. It is the same mechanism at work in apple cider vinegar, and the effect is modest but consistent.

Blood pressure. A much-quoted Japanese study found lower readings among women who ate lemon daily and walked regularly. That is two variables and a small sample. Interesting, not settled.

What lemons cannot do

Lemon water does not detox you. Detoxification is a job the liver and kidneys do continuously, and nothing in a lemon raises their output. What it does do is make plain water more appealing, so people drink more of it, and being properly hydrated genuinely helps those organs work. The habit is good. The explanation attached to it is wrong.

Lemons do not burn fat. No food removes fat from a particular part of the body. Swapping a sweetened drink for lemon water cuts sugar, and that counts for something, but it is the swap doing the work rather than the lemon.

What lemons are genuinely good for

• Vitamin COne of the few nutrients where the science is closed and the claims are permitted.
• Getting iron out of plantsThe most useful trick on this page, and the least known.
• CitrateMore than any other citrus, and used clinically because of it.
• Making everything else taste like itselfAcid lifts flavour the way salt does, without the sodium.
• Drinking more waterSmall, slightly silly, and completely true.

Who should be cautious with lemons

Lemon is food, and every caution here is about the acid rather than the fruit.

1. Tooth enamelThe substantial one, because enamel does not grow back. Citric acid softens it temporarily, so drink lemon water in one sitting rather than sipping it across a morning, rinse with plain water afterwards, and leave brushing for half an hour. Brushing softened enamel is what does the damage.
2. Reflux, gastritis and ulcersAcid on an already irritated stomach lining is a common trigger.
3. Mouth ulcersCitrus stings them and slows the healing.
4. Citrus allergyUncommon, but real.

Common questions about lemons

This article is for general information and is not medical advice. Natural Elixir is a natural health tonic and is not intended to diagnose, treat, cure, or prevent any disease. Always speak to a healthcare professional before changing your diet, supplements, or medication, and never stop prescribed treatment without medical guidance.