RHR: Dispelling the Acid-Alkaline Myth

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This post was originally published on ChrisKresser.com on October 29, 2015

What are the three basic claims of the acid-alkaline hypothesis? I'll clear up the confusion about what it all means for your health.

The basic idea of the acid-alkaline hypothesis is that if we eat acid-forming foods, we get sick, and if we eat alkaline-forming foods, we’ll be healthy and we’ll be protected against disease.  There are three claims of the acid-alkaline hypothesis.  One is that diet affects the pH of our blood.  In other words, how acid-forming or alkaline-forming the foods are that we eat directly affects the pH or acidity of our blood.  Number two would be that our urine pH is an accurate indicator of our health, and by extension, we can use these urine test strips that proponents of the hypothesis recommend and determine, first of all, whether our blood is acidic by measuring our urine acidity, and second of all, by extension, we can use these urine test strips to determine our health.  And then the third claim would be that acid-forming diets contribute to modern disease.

In this episode, we cover:

5:15  What Chris ate today
9:10  What is the alkaline hypothesis?
10:32  Critique of the alkaline hypothesis

Links we discuss

Steve Wright: Good morning, good afternoon, and good evening. You are listening to the Revolution Health Radio Show. I’m your host, Steve Wright, co-author at SCDlifestyle.com.

Now, with me is integrative medical practitioner, healthy skeptic, and New York Times bestselling author, Chris Kresser. Chris, how’s the day going?

Chris Kresser: The day is going great. How are you, Steve?

Steve Wright: Chris, my new word is conflicted.

Chris Kresser: OK, right. Good. You’re moving away from the fine and great and good. I remember now.

Steve Wright: Yeah.

Chris Kresser: All right, you’re conflicted.

Steve Wright: Yeah, it’s 83 outside and we’re inside.

Chris Kresser: Yeah, it’s beautiful here, too. Well, you know, we’re doing this for the benefit of all humankind, so that should be some consolation. Maybe that’s the conflict you’re experiencing.

Steve Wright: Yes, yes. No, I am willingly choosing to be here and do this now.

Chris Kresser: All right.

Steve Wright: But I just wanted to be honest.

Chris Kresser: Good. Well, from what I learned talking to you before this, you’re headed to a music festival this weekend, and I’m headed up to Tahoe with Robb Wolf and Dan Pardi and family, so I guess we can’t complain too much.

Steve Wright: Nope. I think we’ve set up the conditions to be working inside and unplug this weekend.

Chris Kresser: Good. All right.

Steve Wright: So before we get into today’s question, Chris, people are literally dying to know, what have you been eating today?

What Chris Ate Today

Chris Kresser: Well, let’s see. I had some chorizo. We recently bought half a pig from a local rancher, a pastured, acorn-fed pig, and so we have some chorizo from that, which is really delicious. And some plantains fried in some coconut oil and raw sauerkraut, so pretty standard. And I have not eaten lunch. I’ve decided to skip lunch today, so it’s 1:30 when we’re doing this show, and I’ll probably just go through to dinner because I have a lot of stuff going on. That’s my version of intermittent fasting, as we talked about a few shows ago.

Steve Wright: OK, perfect. Well, before we get into the question, I just want to let all the listeners know that this podcast is really created by you and for you. If you’d like your question answered on the show, please go to ChrisKresser.com/PodcastQuestion and submit it there.

So, Chris, what’s the question for today?

Chris Kresser: We have a great question from Melissa, and this is something that comes up a lot, so I’m looking forward to answering. Let’s give it a listen.

Question from Melissa: Hi, Chris. This is Melissa Milam. I am in school right now to become a nutrition therapist, and I run across some conflicting information sometimes, and today I ran across the relationship between protein and calcium metabolism. My textbook states that high dietary protein intakes are known to increase urinary calcium excretion, and some research suggests that animal protein is more detrimental to calcium metabolism, so I just wanted to hear your thoughts on this and see what research you have to offer. Thanks a lot!

Chris Kresser: OK, so what Melissa is really referring to here is the whole acid-alkaline theory, and I’ve actually written a couple of critiques of this hypothesis on my blog a couple of years ago. We’ll put those in the show notes. I’ve also spoken about it, delivered public presentations on this topic recently in two different venues. One was at the Weston Price Wise Traditions Conference a couple of years ago, and the other was just very recently at Paleo f(x) in 2015 in Austin here. But if you didn’t have a chance to go to those conferences and you haven’t read the blog articles, this should at least help clarify this particular part of the hypothesis and Melissa’s question, of course, specifically, and then if you need more background and want to dive a little bit more deeply into this topic — which I recommend; it’s pretty interesting, and there are a lot of misconceptions and misunderstandings out there about it — then you can check out those articles on the podcast or I think you can purchase a recording of both the Wise Traditions presentation and the Paleo f(x) presentation. The Paleo f(x) one is a little bit more recent and had some updated info, so maybe if you had to choose, that would be the best one.

Steve Wright: So, Chris, are you telling me that the acid-alkaline theory, hypothesis, myth — whatever we decide it is today or whatever you tell me it is today — that’s in the medical textbooks and is being taught?

What Is the Alkaline Hypothesis?

Chris Kresser: That’s a good question. There’s part of it that’s in medical textbooks and part of it that’s not, so maybe we should do a little background. The overall acid-alkaline hypothesis, the basic idea is that if we eat acid-forming foods, we get sick, and if we eat alkaline-forming foods, we’ll be healthy and we’ll be protected against disease, and there are three basic claims of the hypothesis. One is that diet affects the pH of our blood. In other words, how acid-forming or alkaline-forming the foods are that we eat directly affects the pH or acidity of our blood. Number two would be that our urine pH is an accurate indicator of our health, and by extension, we can use these urine test strips that proponents of the hypothesis recommend and determine, first of all, whether our blood is acidic by measuring our urine acidity, and second of all, by extension, we can use these urine test strips to determine our health. And then the third claim would be that acid-forming diets contribute to modern disease. Melissa’s question is specifically about third claim, and that’s what we’re going to spend most of the time talking about.

In terms of what’s in medical textbooks and medical studies, you will not find any reliable medical studies or textbooks that claim that what we eat affects the pH of our blood because the pH range of our blood is so tightly controlled by our body that it’s not possible to alter it just by what we eat, and the reason for this is that even slight changes in the pH or acidity of our blood can lead to very, very serious consequences, including death. So it doesn’t make sense from an evolutionary perspective that we would be able to dramatically lower or raise our pH just by what we eat or we could easily kill ourselves off, and that’s not really what evolution is all about. So that first claim is pretty easily dismissed, and the second claim, which is that urine pH is an accurate indicator of health or that our urine pH is a good reflection of our serum pH, you will actually find some studies that make that claim, but they’re also easily dismissed, and there are many more studies that have found that the pH of our urine does not in any way reflect the pH of our blood and, therefore, it’s not a reliable indicator of anything other than how well our kidneys are functioning because one of their main jobs is to buffer the blood and remove any excess acid that might accumulate from protein digestion.

So the first two claims are pretty easily dismissed, and there’s not even very much debate about them in the scientific literature. The third claim, however, is addressed at length in the scientific literature, and if you just do a cursory search, you can find studies that support this idea that consuming acid-forming foods will lead to excess calcium excretion in the urine, and it’s easy to come to the conclusion that acid-forming foods — which would be animal products, among other things — are negative for bone health because of that.

Steve Wright: Before you dive into this third area, really quick, just to summarize, number one, blood pH is way too tightly regulating. That’s a total myth that food affects that.

Chris Kresser: Yeah.

Steve Wright: Number two, the pH of our urine is not related to the pH of our blood. However, the pH of our urine, for those people who have maybe been testing this, it does indicate potential kidney function.

Chris Kresser: Well, it measures how much acid you’re excreting in the urine, specifically, and yeah, that can indicate kidney function, but it’s not necessarily pathology. One of the kidney’s normal jobs is to filter excess acid from the blood, and when it does that, of course, it then is eliminated through the urine. And there’s a whole sustainable process there, where when protein is digested, acids are buffered by these bicarbonate ions that are made by the kidneys, and that reaction produces carbon dioxide, which is an acid, and the carbon dioxide is exhaled by the lungs, which is, by the way, the biggest source of acid elimination in the body by far, that exhalation of carbon dioxide, and it happens very quickly. And then that reaction where the kidneys buffer bicarbonate ions also produces salts, which are then excreted by the kidneys, and during the excretion of those salts, the kidney makes new bicarbonate ions that replace what was used up in the buffering of the acid, and that just produces this ongoing sustainable cycle that’s not adverse for bone health in any way.

We’re starting to kind of jump into the critique, but let me first tell you a little bit more about the hypothesis because, otherwise, the critique won’t make sense. The hypothesis — and, by the way, this is a specific kind of subset of the acid-alkaline hypothesis, which is called the acid-ash theory of osteoporosis, and the basic idea is not as simple and wrong as, you know, eating acid-forming foods raises acid in our blood and that affects our bone health. As we’ve established, that’s not really accepted at all in the scientific literature. This is a little bit more nuanced, and the idea is that when you consume acid-forming foods, it doesn’t change the pH of the blood directly, but the body pulls minerals out of the bone in order to maintain a stable blood pH. So if you continually are eating net acid-forming diets with animal products, then you eventually will pull enough calcium out of your bones that you’ll start experiencing bone demineralization and osteoporosis.

Critique of the Alkaline Hypothesis

That’s the theory, and that’s what Melissa’s nutrition instructors were alluding to. And like I said, if you just do a quick search of the literature, you will find studies that show that eating acid-forming foods does lead to higher calcium levels in the urine, and researchers initially assumed that these higher calcium levels were coming from bone, it was being withdrawn from the bone, as I just said the theory states. The problem is that assumption turned out to be wrong. There was a big meta-analysis in 2009 of five high-quality studies, and they did find a linear association between the amount of acid in the urine and the amount of calcium in the urine, but there was no association between the amount of acid in the urine and calcium levels in the body. So if you put it more simply, if you eat more protein, you will pee out more acid and calcium, but the amount of calcium in your body doesn’t change.

How is that possible? Well, other studies have shown that eating more animal protein actually increases calcium absorption, and this has been shown in human isotope trials where they tracked the progress of calcium through the body, and I have a slide — This is a podcast, so you can’t see this, but in the presentation, a show a slide. It’s a chart that shows as protein increases from 1 gram per kilogram of body weight to 2.1 grams per kilogram of body weight, you see a significant increase in the amount of calcium in the urine. Then they have another figure on the right that shows that as you increase protein by that same amount, there’s a corresponding increase in the amount of calcium that’s absorbed in the intestine into the bloodstream, and that increase in intestinal calcium absorption compensates for any loss of calcium that might happen in the urine, and the overall calcium balance either doesn’t change or it actually even goes up with higher-protein diets.

So as you can see, this is a misconception. Her professors or instructors are saying that high dietary protein increases urinary calcium excretion, and then they make the assumption that, therefore, it’s bad for bone health, but that’s only part of the puzzle, and they’re not understanding the increase in intestinal absorption of calcium that animal protein and protein in general leads to. Does that make sense?

Steve Wright: Oh, it totally makes sense, especially if you take a step back and look at, for instance, I don’t know, eating one cup of meat or one cup of vegetables and the amount of calcium that might be coming in that’s usable in each scenario.

Chris Kresser: Yeah.

Steve Wright: And then trusting that the body knows how to actually regulate its own nutrient stores.

Chris Kresser: Yeah. There are a lot of different ways to look at this, too. We just talked about the mechanistic view of how intestinal calcium absorption compensates for any potential loss in the urine, but there are a lot of other ways to look at it, too. For example, instead of looking at the effects of animal protein on an intermediate marker of bone health, like calcium, why not just look directly at studies that examine the relationship between animal protein intake and more specific markers of bone health, like bone mass or bone microarchitecture or bone strength? It’s the same kind of idea as, you know, instead of looking at the relationship between saturated fat intake and cholesterol, why not just look directly at saturated fat intake and heart disease? Because that’s why we would be looking at cholesterol in the first place, as a predictor for heart disease, right? But you can just look directly at studies that examine the relationship between saturated fat and heart disease, and you see that there isn’t much of a relationship.

Now, in the case of protein and bone health, if you look at these direct markers of bone health, there was, for example, a 2009 meta-analysis in the American Journal of Clinical Nutrition that looked at 61 different studies, and they found a strong positive association between protein intake and bone health. On the other hand, there have been controlled trials where they have experimentally induced protein deficiency — so they’ve dramatically restricted protein intake — and that has led to deterioration of bone mass, microarchitecture, and strength, which are the hallmarks of osteoporosis.

But we can go further. We can also say, what does the research tell us about the importance of protein for bone health? And if you do that kind of review, you will find that there are three potential mechanisms through which higher protein intake positively impacts bone health. Number one is that protein contains a bunch of amino acids that are really important for bone. Number two is that eating more protein increases IGF-1 levels, and IGF-1, in turn, increases bone growth and bone mass. And then number three, eating more protein lowers levels of serum parathyroid hormone, and we know that high levels of serum parathyroid hormone are associated with low bone mineral density, high bone turnover, and an increased risk of fractures.

Steve Wright: Well, I think that sums it up pretty well.

Chris Kresser: I’m not done, though! We have to keep going! So animal protein, I think, is especially important for bone health. So far, we’ve just been talking about the relationship between protein and bone, but we have studies that have shown that changes in muscle and bone mass track together, so that tells us that things that are good for muscle are typically good for bone, and vice versa. And we know that leucine is an amino acid that signals that protein is available for muscle synthesis, and animal proteins typically contain high amounts of leucine, which, of course, then suggests that leucine may play an important role in bone health.

We have observational studies that show that a high intake of animal protein is associated with greater bone mineral density and decreased rates of hip fracture, especially in the elderly. On the other hand, we have studies that show that eating less meat and more plant protein leads to worse bone health. There’s a negative association between vegetable protein and bone mineral density in both sexes, and elderly women on vegetarian diets have been shown to have increased risk of osteoporosis.

And finally, we have the gold standard randomized clinical trials where protein has also been shown to benefit bone. For example, there’s a 2009 trial in the American Journal of Clinical Nutrition that found that in postmenopausal women, increasing protein from 10% of calories to 20% of calories improved intestinal calcium absorption and also decreased urinary DPD, which is a marker of bone breakdown, and an increased IGF-1, which, as we just talked about, has several different positive effects on bone health.

And then the last thing that I’m going to say is there was a really exhaustive review on this topic published in the Nutrition Journal in 2011 that looked at 55 different trials, 22 of them randomized clinical trials, and the authors’ conclusion was this: “A causal association between dietary acid load and osteoporotic bone disease is not supported by the evidence, and there is no evidence that an alkaline diet is protective of bone health.”


Steve Wright: Drop the mic! Point made. There are some fascinating things to take away from this discussion. One quote — and I’ll probably butcher it, so I’ll paraphrase it the best I can — I believe it was Einstein who said, if you give me 60 minutes to solve a problem, I’d spend 55 minutes figuring out the right questions to ask.

Chris Kresser: Yeah.

Steve Wright: And I have made this mistake over and over again. It seems like what happens is we are so quick to try to find the answer that we begin to look for surrogate endpoints that will help us with our biases or help us just make the problem easier. A surrogate endpoint, if you don’t know what that is, it’s — this is from Wikipedia — “a measure of effect of a specific treatment that may correlate with a real clinical endpoint but does not necessarily have a guaranteed relationship.” There’s a lot of surrogate endpoint research out there, and I believe that if you can think about the real endpoint, for instance, if we’re talking about osteoporosis in this case, if that’s the bullseye, you have sort of concentric rings coming out from that of surrogate endpoint data, and some this stuff, there are surrogate endpoints that are so far away from the bullseye that the relationships all break down. So I think one of the take-homes from this giant myth that’s been populated throughout the internet and throughout the world is about asking better questions and trying not to really force the answer too fast.

Chris Kresser: That’s a really great point, Steve. In a way, I mean, that’s largely what this community of explorers and investigators at ChrisKresser.com is all about, continuing to challenge even our cherished beliefs, like the idea that — not that this was a cherished belief for me, but sacred cows, let’s say, like the idea that legumes aren’t paleo and shouldn’t be eaten because they have toxins in them. We have to continually go deeper and challenge our beliefs and continue to ask questions. That’s really what the process of science is all about. Just accepting something at face value because you’ve heard it a few different times or even because a teacher or a professor says it is generally not the best way to acquire knowledge, so kudos to Melissa for asking that question and for getting some clarification. I definitely encourage Melissa and others who want to get more info on this topic to read the two articles, which have a bunch of citations, references that you can pursue if you want to learn more, or to watch the full presentation from Paleo f(x).

I think this is not a harmless theory. You know, some theories are wrong and they’re just relatively harmless, and some theories are wrong and they are definitely potentially harmful. I’ve written a lot about the potential for nutrient deficiencies on a vegetarian diet, and so I’m not going to rehash that here, but if you take an acid-alkaline diet through to its logical conclusion, you’ll end up on a vegetarian or even vegan diet. If you try to maximize the alkaline-forming quality of the diet, then you’ll pretty much be eschewing all animal proteins. And if you do that, you’re going to put yourself at higher risk for things like B12 deficiency, calcium deficiency, zinc deficiency, vitamin D deficiency, EPA and DHA deficiency, and all of the health problems that are associated with that. So it’s not just a benign misunderstanding; it’s a pretty significant one that could negatively impact the health of a lot of people.

Steve Wright: Yeah, I would agree with that 100%. I think it’s also a really great example of how this n=1 experimentation can really fail you. I know of a lot of actual friends, you know, who will try something like this — and I have nothing wrong with people trying things — but they’ll buy into a myth like this, they’ll make changes in their lifestyle that we would generally think are good, for instance, eating more vegetables, eating more fruits, and they may have underlying health conditions that make meat or animal consumption, such as low stomach acid or GI infections or anything, a little harder for them to digest right now. Otherwise, they wouldn’t be searching for better health anyway, and so they reduce their animal consumption, they increase vegetables and berries, they get some feedback from some pH strips, and lo and behold, they’re a changed person in seven days, and now they’re off and running in this direction for a long time. I totally encourage doing tests and things, but what I’m finding more and more is people are forgetting to ask the assumption questions, like, what is this based on? What am I basing my n=1 trials on? And I think this myth, in particular, can cause a lot of harm in people who run with an n=1 idea if they don’t challenge the assumptions behind their own bodies.

Chris Kresser: That’s another great point, Steve. Another example of that would be I just published an article today called “3 Reasons Gluten Intolerance May Be More Serious Than Celiac Disease,” and one of the commenters asked how reliable the tests are and whether you can rely exclusively on elimination provocation, and I think certainly elimination provocation is a very good idea if you don’t have access to this test, and for many years it’s been considered the gold standard for assessing non-celiac gluten sensitivity, but one of my concerns with it is we know there are “silent” forms of celiac disease where people don’t have obvious symptoms even when they eat gluten. The effect of gluten may be immune dysregulation that happens in the background. For example, maybe they start producing antibodies to pancreatic cells that produce insulin, or maybe they start making antibodies to thyroid. You can’t feel that, you know, until it’s already at the point where those organs are damaged and then you start to feel the decline in thyroid hormone production or the decline in insulin production via high blood sugar, and even that a lot of people don’t feel, and the only way they’re going to find out about it is if they get tested.

So my concern is, like, let’s say you have someone who does elimination provocation and they don’t notice any obvious problem with gluten, and then they get a test for gluten intolerance and it turns out that they’re reacting to it. What is the cost for that person of going on to continue to eat gluten? Unfortunately, it could be fairly high. And there’s no way of knowing, necessarily, in that n=1 experiment that it’s a problem. I think there are a lot of situations like this, and I’m glad you brought that up.

Steve Wright: Yeah, my pleasure. It’s taken me seven or eight years now to get to this point, so I think if we’re challenging some people’s beliefs today, and I think if you’re listening to this and feeling a little triggered by Chris and I are talking about right now, just know that we are supporting your changes in your health and we’re just giving you some sort of wisdom as guys who have done it to ourselves and been through long journeys ourselves and then also worked with a lot of people.

Chris Kresser: Yeah, and I would add that there’s a wide range of responses to a vegetarian diet. One of the things that determines how someone will respond is genetic polymorphisms that affect how well we convert inactive forms of nutrients to active forms of nutrients. To use an example, some people are really good at converting beta carotene, which is a vitamin A precursor that’s found in plant foods, into retinol, which is the active form of vitamin A that’s found in animal foods. So if that people goes on a vegetarian, alkaline-based diet, they might not fare as poorly as someone who is almost entirely unable to convert beta carotene into retinol, and there are people like that, actually a fairly substantial number of people. So the first person goes on a vegetarian diet. They do OK. The second person goes on a vegetarian diet, and they start to experience signs of vitamin A deficiency, which can cause a lot of problems very quickly. Again, there’s no one-size-fits-all approach. There’s a lot of different individual variation here that people aren’t even tracking and aren’t even aware of. Like, how would you possibly know that you’re the person that doesn’t convert beta carotene into vitamin A? Your doctor’s not going to test for that. I don’t even know if there are commercial tests for that available.

So there’s a lot to this, and I don’t want to create the impression that you can’t figure it out just by experimenting. I think that’s very important and crucial, but the point we’re trying to make here is there’s a role for continuing to ask questions and asking the right questions and getting help from someone who can guide you through the kinds of testing that can reveal things that aren’t easily determined just through self-experimentation.

Steve Wright: Yeah, that’s great. Well put, and I’m sure we could do a whole episode on the train we’re on right now, but I know you have some commitments today, and I have some other thoughts I’d share, but maybe for another time.

Chris Kresser: Yeah. If someone wants to ask that question, go for it. Maybe you can give them the link.

Steve Wright: All right. Well, thanks, everyone, for listening today.

In between episodes, if you’re not following Chris on social media, go to Facebook.com/KresserInstitute and Twitter.com/ChrisKresser. Follow him there for more updates.


  1. Very interesting. Thank you for this.

    I wrote an article in support of pH testing for NDNR prior to the 2009, 2011 metanalysis articles.

    With my patients I prescribed urine and saliva pH, first morning, for one week. Then had them repeat that once a month or every few months. I never called it a diagnosis of anything, just a way to monitor response to treatment.

    If acidic, which they usually were, then I prescribed more vegetables, not less meat. In my article I cautioned against trying to control pH with diet, as that could lead to protein deficiency and that if you had to control your diet that strictly, there was probably something besides diet contributing to the low pH. Likely chronic inflammation or gut issues.

    I did witness pH numbers moving toward neutral as their health improved. I also saw bone loss reverse.

    One of the most interesting observations was that the sickest patients often had a very high pH. I felt that was possibly from ammonia. This usually normalized during treatment.

    Thanks, Tom Ballard, ND

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