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Today, I was surprised to find a number of sources stating that lemons, while acidic in nature, act as bases once in the body. Here is one such source. I'm unclear whether the claims are based on shoddy science, or if there is any truth to the matter. This person claims that it is due to Na+ and K+ ions in the lemon, which then form strong, fully dissociated bases that counteract the weak citric acid.

However, I'm always skeptical (and rightfully so, I think) of this type of seemingly 'alternative' claim, as they frequently aren't based on the reality of the situation. Can anyone clear up whether this is actually a valid claim?

  • 1
    a mix of weak acid and a weak base can create a stable pH that acts as a buffer; citric acid has the necessary properties to act as a buffer – ratchet freak Jul 7 '14 at 11:34
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    The claim I've heard is that the body creates acid in the stomach: and that if acid (lemon or vinegar) is added to the stomach (by swallowing it) then the body will compensate by creating less acid. I say this as a comment, not because I think it's true, but to add a related claim to the question, in case that helps someone discover evidence of any study. – ChrisW Aug 16 '14 at 12:33
  • That linked source is so ridiculous and lacking in science, it's not even correct on the very simple and well-understood reason why sugar is bad for teeth. – iamnotmaynard Mar 13 '17 at 21:40
8

In the cited website and video, there is a claim that lemons alkalize the body.

This is false. Lemons do not alkalize the body:

  1. The pH of lemon juice is 2-2.6, so lemons are acidic, not alkaline.

  2. The body uses pH buffers to avoid the pH of blood being changed:

When an acid or base is added to the body, the buffers just mentioned bind or release H+, thereby minimizing the change in pH. Buffering in extracellular fluid [including blood] occurs rapidly, in minutes.

Source

So, neither acidic nor alkaline foods change pH of the blood.


Now, from where the claims that lemons alkalize the body originate?

  1. Lemons contain citrate:

Citrus fruits...contain natural citrate and the highest citrate level exists in lemon.

Source

  1. Citrate supplements can be used to alkalinize urine

Citrates are used for alkalinization of urine (as alternatives to sodium bicarbonate) in conditions where long-term maintenance of an alkaline urine is desirable (e.g., management of uric acid and cystine calculi of the urinary tract).

Source

  1. However, this effect doesn't happen from drinking lemonade:

It has been known that citraturic effect of potassium citrate was due to net alkaline load produced by its oxidation to bicarbonate and its renal excretion. In spite of this, lemonade treatment has not caused urinary alkaline load due to low pH of lemon juice.

Source


Conclusions:

  • Lemons do not alkalize the body.
  • Citrate from supplements alkalizes the urine.
  • Citrate from lemons does not alkalize the urine.
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The links above mention a lot of mumbo jumbo but do not give any science based reasoning on how a proton donor, or acid, which increases the concentration of hydrogen ions is somehow able to reduce the concentration of hydrogen ions in the blood. The link authors appear to be alternative medicine practitioners, and presumably alternative science practitioners as well.

The chemical composition of lemon juice [1] is also nothing special to somehow create an alkalising effect on the body's pH.

Citrus fruits in general contain sugars, polysaccharides, organic acids, lipids, carotenoid (pigment), vitamins, minerals, flavonoids, bitter limonoids, and volatile components. The lemon is a good source of potassium (145 mg per 100 g fruit), bioflavonoids, and vitamin C (40 to 50 mg per 100 g, twice as much as oranges). The isolation of vitamin C from lemon juice has been performed. 8 Calcium (61 mg) is also present, along with vitamins A, B 1 , B 2 , and B 3


[1] http://www.drugs.com/npp/lemon.html

The central argument of this answer is theoretical in nature. We do not allow answers based uniquely on common sense or pure logic. Answers which are wholly based on a theoretical model are generally downvoted and may be deleted. See FAQ: What are theoretical answers?

  • It's not really up to the claimant to show how a certain effect happens. The precession of the orbit of Mercury was unexplained by theory for 200 years, yet it remains an experimental fact. – Sklivvz Mar 13 '17 at 23:43
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As a result of multiple linear regression analysis, it was possible that lemon ingestion is involved more greatly with the blood citric acid concentration Δ% and the number of steps with blood pressure Δ%, and it was surmised that the number of steps and lemon ingestion are related to blood pressure improvement by different action mechanisms

(Kato, et al., 2014)

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    Hello and welcome. Can you explain a little better how this answers the question? – Sklivvz Mar 13 '17 at 9:12

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