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I was recently having a discussion with someone about whether lemon water actually increases the pH of your body (by which I assume they mean the blood); their claim was that once Citric acid was metabolised it results in an increase in pH due to the "anionic properties of citric acid".

I looked around on the internet at it would seem that this is a common claim circulating around health forums: Example 1, Example 2, etc.

Now to me this sounds like something which cannot possibly be true and appears to be a crazy health fad (they seem to spuriously appear and gain popularity now and again), and I cannot find any scientific papers or articles to support or refute their claim.

Can anyone provide a reliable scientific reference or provide a reasonable scientific explanation (preferably accessible to a layman with only A-level (college level) understanding of chemistry and biochemistry) which either supports or refute the claim that drinking lemon water (citric acid) increases the pH of the blood?

I have crossposted this to Chemistry.SE as well, as it is a crossover between chemistry and biochemistry.

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The blood pH is tightly controlled since variations are quite dangerous for us. Under normal circumstances the pH is 7.4 (with a normal range between 7.35 and 7.45). Below that we are talking about acidosis, above it about alkalosis. If the blood pH goes about 7.8 or below 6.8, death will occur. This pH is maintained by the Bicarbonate-buffering system, for details see here and here. Food that we take up does not directly influence the blood pH (and there is also no reason for us to do so, since this is tightly controlled and regulated), so this is a health fad. Details that debunk this myth about it can be found here, here and here.

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The website to which you linked states that Lemons have a "moderate to strong alkaline-forming effect"? How is it that something acidic can form this "alkaline-ash"? – Shaktal Dec 27 '13 at 13:42
Food gets metabolized in the body and molecules get modified in this process. If you think of the stomach, this is highly acidiy, while the duodenum is pretty alkalic. This gets often mixed up... – Chris Dec 27 '13 at 13:50

Short Answer:

There was an interesting paper that dealt with the pH of urine when citric acid was consumed.

The summary was: There was no increase in urinary pH or total nitrogen in 24 hours collection of urine.

What This Means:

The food we take does not affect the blood pH directly. Acidic food will cause increased secretion of alkaline components into the digestive tract to neutralize the excess acid. This will cause a fall in the bicarbonate ions concentration (this being the major alkaline buffer) in the blood. This might cause acidosis (depending on how acidic the food is).

The body compensates the decrease in bicarbonate concentration by excreting H+ ions in the urine. Thus urine becomes more acidic when there is a relative state of metabolic acidity in the body. There is also hyperventilation and excretion of more CO2 as this will cause excretion of H+ ions.

HCO3- + H+ ----> H2O + CO2

Incase of alkaline foods, the stomach acid itself would be partly neutralized by the alkali present in food. Thus the body need spend only minimal bicarbonate ions to neutralize the remaining acid.

If there is severe alkalosis body compensates by decreasing the respiratory drive (conserving more H+ ions) and excreting more bicarbonate ions through kidneys.

Compare this with the data obtained from experiment

If consuming citric acid would lower blood pH levels then the urinary pH should increase. As the data shows this is not so, that would mean the citric acid does not contribute to the acidity of food in any significant way even when consumed in large quantities.

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The excellent answers from Chris and One Face have already written about why the claim is wrong, so I'm going to add a hypothesis for how this sort of nonsense could even originate in the first place.

The reason why lemons are acidic is because they contain a lot of citric acid, so in a solution part of this citric acid ionizes to citrate which increases the concentration of H3O+, thus increasing pH. Now imagine some quackjob with poor knowledge of chemistry reading about this, and only picking up the word "citrate".

Citrate is of course a weak base (since 3rd pka of citric acid is 6.40 then pkb of citrate must be 7.60) so if we pour some kind of citrate salt into water we would get a basic solution. So basically, I think that the originators of this fad forgot about or didn't know about the H3O+ ions, which of course do not magically disappear when we ingest lemon juice.

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Also, note that there are a lot of quack treatments that center around supposedly being able to alter the pH of your blood. I think that quackery is why anyone would be interested in altering one's PH deliberately. – swbarnes2 Aug 4 '15 at 20:23
Nowadays you can convince people all kinds of stupid shit by calling it "natural" and wrapping it in a few anecdotes along with some cherry picked (or just completely made up) scientific facts. – Inhibitor Aug 4 '15 at 23:43

I think the answers above have covered the basic breakdown of how our body regulates blood pH and why it is clearly misleading to propose that drinking lemon juice can have a positive effect on acidosis mediated illnesses.

What I would like to add from a more microbial perspective is that a paper by Yoshiake Miyake on the Metabolism of Antioxidant in Lemon Fruit (Citrus limon BURM. f.) by Human Intestinal Bacteria (1997) has shown that Lemon fruit can be an important antioxidant. Antioxidants are known in clinical medicine to be inhibitors of acidosis and is why we recommend blueberries and such to take care of those nasty free radicals and ROS species. What this article suggests though is that they only tested Bacteroides. These little microbes are responsible for some of the breakdown of indigestable plant material, possibly lemons, that occurs within our gut. Recently I read an article, "Impact of diet in shaping gut microbiota revealed by a comparative study in children from Europe and rural Africa", which sequenced the fecal microbiota of 14 children from Africa and 15 Children from the EU to understand if there is an association between diet and gut flora regionally. Although it was a small sample size, it showed that overwhelmingly children from Africa had a significantly higher proportion of Bacteroidetes while also having a higher bacterial gut diversity overall. Children from the EU had a large proportion of Firmiculates because Western diets have the need for Firmiculates to breakdown highly processed foods, sugars, and animal fats. What if it is at the detriment to our balance of gut microbes? Could the lack of complete breakdown and neutralization of acidic fruits such as lemons along with production of acid through protein breakdown be a common cause for the massive increase in non-infectious enteric diseases in the western world?

Just the thoughts of a lowly molecular researcher.


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This is not an answer to the question. Please adapt it to avoid its deletion. – Chris May 17 at 6:09
This is a random comment. Note the format of SE; answers are answers, comments are comments, and quite frankly this doesn't even qualify as a comment... I do like the referencing though - much appreciated. Have a look at the help center to see how the site works. – Christiaan May 17 at 7:56

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