There are so many inaccurate, misleading, and harmful claims about cancer that I could spend years just debunking them. One of the most popular assertions is that acidic blood causes cancer – that is, if you lower the pH of the blood, it creates an environment to let cancer thrive.
Now, I’ve stated this about a hundred times on this blog (I am not kidding) – there are only a handful of scientifically sound methods to potentially lower your risk of cancer. Quit smoking is near the top. Stay out of the sun. Maintain a healthy (that is, very low) weight. Don’t drink alcohol. Get exercise. And a handful more.
And even if you do all of them, you just reduce your absolute risk, not completely eliminate it. You could randomly get a set of mutations – there are several trillion cells in the body, and even if genetic copying in cell division or transcription were 99.999% perfect, it still leaves millions of chances of mutations – that lead to cancer.
And then there are at least 200-250 different cancers, all with different causes, pathophysiologies, prognosis and treatments. In other words, even if you found some miracle way to prevent one cancer 100% of the time, it probably will have no effect on the other 200 or so cancers. We have tended to conflate cancer as one disease, when it is really a large set of diseases that have the same general physiology, but aren’t truly related.
Cancer is scary because it is so random. In many cases, the treatment is so harsh. And people are so interested in anything that may prevent cancer. And if it’s simple like “eat superfoods like kale and blueberries,” or “reduce acid in your blood,” the instinct is to try it out.
But let’s examine how and if acidic blood causes cancer. Spoiler alert – it doesn’t.
Control of blood acidity
Let’s start right at the top (and without apology, a very scientific explanation)– what is the normal pH of blood? Firstly, pH is a numeric scale used to specify the acidity or alkalinity of an aqueous solution, such as blood. A neutral pH (that is, neither acidic or alkaline) is 7.0.
To be honest, pH was my least favorite topic in college chemistry. Professors would say “more acidic” which means pH less than 7.0. And the lower the number, the higher the acidity. And, to make this even more complicated, “more alkaline” means pH higher than 7.0 – and the higher the number means higher the alkalinity.
My head spun around just writing that.
Basically (pun intended), pH measures the number of hydrogen ions in water, which causes acidity, while the lack of them (relatively speaking), causes alkalinity.
The pH of blood runs about 7.34–7.45 in healthy human beings. It’s slightly alkaline (very slightly), and controlled in a very narrow range. The balance between the acid and base of human blood is called acid-base homeostasis.
Essentially, the acid-base balance is tightly regulated by chemical buffers in the blood, the lungs, and the kidneys. They work together in a very complex manner to maintain the blood pH. For example, the lungs can expel more or less carbon dioxide to produce or reduce bicarbonate, which buffers acids. The kidneys help in the same process.
Breathing and kidney function change rapidly to keep the pH at a “normal” level. It is near instantaneous.
There are certain conditions which can cause an altering of blood chemistry and push the blood pH outside of the normal range: metabolic acidosis, respiratory acidosis, metabolic alkalosis, and respiratory alkalosis.
It’s beyond the scope of this article to get into each of these, but an example of metabolic acidosis is when a diabetic becomes uncontrolled with extremely high glucose levels. This leads to a condition called diabetic ketoacidosis (DKA), a dangerous condition. However, even in the most life-threatening DKA, the pH of the blood drops to around 7.0-7.1, still neutral to very slightly alkaline. The reason why it’s so dangerous isn’t necessarily the acidity itself (the body doesn’t dissolve from the acidity), it’s because the lungs and kidneys are working overtime to increase the pH, which leads to other issues like drops in blood potassium.
My point here is that it takes a severe insult to the body’s metabolism and physiology to cause a big change in pH. You cannot simply change the pH of your blood if you’re in good health, which almost all of us are.
For example, the pH of Coca Cola is around 2.5, fairly acidic, mostly in the form of phosphoric acid. If you drank 1 liter of that product, which is quite a bit, you’d have no effect on your blood pH. Now as it hits the mouth, sure, it’s acidic enough to have some very temporary local effect. But a systemic effect on your blood? No.
Even though pH of 2.5 sounds very acidic, it is actually 15 times less acidic than gastric juices which have a pH of 1 (just since someone is checking my math, pH is logarithmic, so 2.5 is approximately 15 times lower acidity than 1.0). Proteins and other chemicals in your stomach generally buffer the gastric acid before it moves too far into the intestines, which means drinking soda all day is not going to change your blood pH.
This is important to note – nearly everyone has normal blood pH. Even diabetics who are well controlled have normal pH. If something is causing your blood pH to vary from normal, the blood pH itself is probably not going to be the biggest worry, but what is causing it to do that will be.
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Why does acidic blood causes cancer
The short answer is “it doesn’t.”
There is some evidence that some cancers may require an acidic microenvironment, meaning the few cubic millimeters around the cancer cells. Moreover, it’s not the body itself that creates this microenvironment, it’s the cancer cells, through independent mutations, that have created it.
So treating this breast cancer may (and there’s not robust evidence) involved attacking the cancer site with an alkaline agent. But read that carefully – attacking the cancer cells themselves. More importantly, this evidence is a mouse model. And let me keep repeating this point – very few therapies that work in mouse models work in humans. And we’re not even sure of anything in the current research.
Furthermore, there’s this belief out there that if you can kill a mouse cell with some substance, then eating a bunch of that substance will kill the cancer. There’s some very preliminary evidence that some components of marijuana may have an effect on mouse cancer cells in vitro. Even if that were true, and the evidence is preliminary, to have a clinical effect, one needs to smoke 1000 joints a day to raise the blood level enough to have that clinical effect.
If marijuana has an anti-cancer effect, the key ingredients will be isolated, and then a safe delivery system will be invented to deliver the ingredient directly to the cancer. The treatment, if it happens, will not be smoking it but maybe by a direct injection of the ingredient into the cancer mass.
Nevertheless, the cancer pseudoscience pushers have leapt onto the “acidic blood causes cancer” nonsense. There is simply no evidence that in the earliest stages of cancer, the blood of the patient has any different pH, other than normal.
In the study I linked above, by Robey and Martin, the researchers suggested that a dose of approximately 12 g of baking soda (sodium bicarbonate, a base or alkaline) per day would buffer the acid produce by a cancer that is around 1 cubic mm in size. In other words, if you could increase the pH around a tiny, almost invisible, cancer, you’d need to deliver that 12 g of baking soda to that site.
And you could not possible consume enough alkaline, like sodium bicarbonate, in sufficient quantity to generally increase the pH of your blood. First, sodium bicarbonate is toxic at high doses (it is a very safe compound, but as we’ve mentioned here before, dose makes the poison). For a normal 65 kg adult, 30 gm of baking soda can cause serious health problems, as a result of the excess sodium and gases released when the baking soda hits the acidic environment of the stomach.
Summary, the TL;DR version
Even if you could identify all the foods that might be alkaline and you might assume would increase your blood pH – forget about it. The stomach is going to buffer the alkaline, since it’s a pH 1.0 environment. Let’s also set aside that the fact that the stomach is a pH 1.0 microenvironment, and stomach cancer is quite rare.
People have this enduring belief that what we eat has some significant impact on our health. Even if kale could prevent one of the 250 cancers, you couldn’t possibly consume enough to have any impact on that cancer. And besides that, the intestinal tract breaks that kale down into simple sugars, amino acids, and nucleic acids that are indistinguishable for all other simple sugars, amino acids and nucleic acids from all other foods.
Yes, eating a “balanced diet” is important and is considered one of the 12 ways to reduce risks of cancer. But it is implausible, if not impossible, to control your blood pH with consumption of anything short of causing immediate harm to yourself. The so-called “ketogenic diet” is supposed to reduce your blood’s acidity – no it doesn’t. And even if it did, could it actually “cure” cancer? That would also be no.
Again, if certain cancers do create an acidic microenvironment, scientists are going to figure out the best way to get an alkaline agent to that cancer directly. It could be as simple as injecting sodium bicarbonate into the tumor mass. Or much more complicated.
But it’s never going to be as easy as eating a spoonful of baking soda – it will not change the pH of the blood in any meaningful way. To the body, that spoonful of baking soda will combine with the acid in the stomach to form water, salt, and carbon dioxide. You’ll burp a lot. But you still have the same risk of cancer.
If you’re reading some pseudoscience on Joe Mercola’s for-profit website about how making your blood more alkaline will prevent cancer? It’s false. Your blood is slightly alkaline naturally, and there is no way to change it. Well, other than having some other medical condition that changes blood pH that will be more critical than worrying about cancer.
- Chin TW, Loeb M, Fong IW. Effects of an acidic beverage (Coca-Cola) on absorption of ketoconazole. Antimicrob Agents Chemother. 1995 Aug;39(8):1671-5. PubMed PMID: 7486898; PubMed Central PMCID: PMC162805.
- Robey IF, Martin NK. Bicarbonate and dichloroacetate: evaluating pH altering therapies in a mouse model for metastatic breast cancer. BMC Cancer. 2011 Jun 10;11:235. doi: 10.1186/1471-2407-11-235. PubMed PMID: 21663677; PubMed Central PMCID: PMC3125283.