Another day, another diet to debunk

Ah yes, the alkaline diet. I first came across this diet a few years back in my undergrad when I was volunteering at community nutrition table at a local farmer’s market. Here is a reenactment of that experience:

Person: I see you have a Myplate diagram here. Well let me tell you, it’s completely wrong and unhealthy!

Me: Please, explain (insert popcorn.gif. Oh, wait.)

Person: See, too many of the recommended foods are acidic. Those foods lead to bone loss, cancer, and even DEATH!!!!! You need to eat exclusively alkaline food. The alkaline diet can prevent bone loss and even cure cancer!

Me: I’m sorry, but those are some bold claims. I’m fairly certain that food doesn’t affect blood pH because……



Well, alright then. After that experience, I figured it would probably be a good idea to take a look at what this diet was all about and if the current body of evidence supports any of this gentleman’s claims. (spoiler: it doesn’t)

What is the alkaline diet?

The alkaline diet (aka acid alkaline diet, aka alkaline ash diet) is a diet based around the premise that the foods you eat alters the acidity or alkalinity of your body. When you digest a food, the food leaves an ash residue which can be either acidic or alkaline depending on the type of food. Here are examples of acidic or alkaline foods:

Acidic (protein, phosphate, and sulfur containing): Meat, poultry, fish, dairy, eggs, grains, and alcohol

Alkaline(calcium, magnesium, potassium): Fruits, nuts, legumes, vegetables

The belief is that acidic ash makes you vulnerable to illness and disease by causing your blood to become more acidic, while alkaline ash is considered protective. Therefore, this diet makes it seem that the more alkaline foods you choose, the better the health outcomes you can expect. Makes sense in theory right? Well I hate to break it to you but…..

Let me explain.

Let’s talk pH

In order to understand the alkaline diet, it’s pretty important to understand what pH is. pH refers to how acidic or alkaline a particular substance is. pH values range from 0-14:


People who advocate the alkaline diet recommend that you keep your blood pH above 7 (alkaline) for optimal health. There are two major issues with this line of thinking. The first is that your blood’s pH is always slightly alkaline at a pH between 7.35-7.45. It doesn’t fluctuate outside that range. Would you guess what happens if the pH of your blood moves either way outside of that range?

You’ll get very sick and most likely die. That’s a pretty huge problem.

Another problem with this theory is that the pH varies greatly within the human body. Just because your urine pH (which is how proponents of this diet recommend you check your pH) is a certain number, that doesn’t mean it reflects the pH of various other parts of your body. Some parts of the body are acidic, others are alkaline. For instance the stomach is acidic due to the presence of hydrochloric acid which is essential to digest food.

So how does food affect pH?

It’s pretty important that your blood maintains a constant pH or else there can be some pretty nasty consequences (again, death. That’s not good.) This is why the human body has many mechanisms to closely regulate the pH balance of your blood to make sure that doesn’t happen. These mechanisms are known as acid-base homeostasis. The good thing is that these mechanisms make it almost impossible for outside influences (in this case, food) to make a significant change in the pH value of our blood.

So then why do proponents of the alkaline diet say food affects pH? Food can affect the acidity or alkalinity of your urine but that’s about it. Food has minimal affect on your blood’s pH. Just because the pH of your urine is at 8, that doesn’t mean that’s the same pH as your blood. This automatically debunks the argument of the alkaline diet that the foods you eat has any impact on the acidity or alkalinity of your blood.


Another argument that proponents of the alkaline diet push is that acid forming diets can lead to things such as osteoporosis and cancer and in some cases can even cure cancer. Is there any truth to these claims? Let’s take a look at what the evidence has to say.


Many alkaline diet proponents believe that in order to maintain a constant blood pH, the body takes alkaline minerals (i.e. calcium) from your bones to counteract the acids from the acid-forming foods you eat. According to this idea, acid-forming diets cause a loss in bone mineral density and can lead to osteoporosis.

This all sounds well and good in theory but it completely misses one very important aspect of basic human physiology. It completely ignores the fact that we have kidneys. Yeah, these guys right here.

See, our kidneys do a pretty great job of removing acids and regulating blood pH by producing bicarbonate that neutralizes acid in the blood. In addition to your kidneys, your respiratory system also works to control blood pH. It does this by breathing out the carbon dioxide that forms when the bicarbonate from the kidneys interact with the acids in your blood. Both do a pretty good job of making sure your blood doesn’t become too acidic. Do you know what doesn’t play a role in regulating your blood’s pH? YOUR BONES! So it doesn’t make sense that your body has to rely on stripping your bones of important minerals to do something that other organs are perfectly capable of taking care of.

Another problem with the idea that a high acid diet causes osteoporosis is that it ignores one of the major drivers of osteoporosis, a loss in the collagen from bone. Interestingly enough, the loss of collagen is strongly linked with low levels of various acids such as vitamin C. That’s the opposite of what proponents of the alkaline diet would expect.

In addition, there is no evidence of a negative relationship between urine pH and bone health. If anything, there is more research linking high protein diets (acid-forming foods) with healthier bones.


Now let’s move on to the claim that acidic diets increases cancer risk. Proponents of the alkaline diet argue that since cancer only grows in an acidic environment, cancer can be treated or even cured with an alkaline diet.

There are several things wrong with this argument. We’ve already talked about how food doesn’t affect blood pH to a significant degree so we’ll skip that and move to the next one. The other major flaw with this argument is that it assumes that cancer cells only grow in acidic environments. The truth is that cancer cells can grow in alkaline environments too.

If you need more convincing, this thorough review on the relationship between “diet-induced” acidosis and cancer concluded that there is no direct link between the two.

Wrapping it up

As you can see, the alkaline diet has little scientific evidence or basis in human physiology to suggest it is a magic cure all like it’s proponents argue. No, it will not cure cancer or prevent osteoporosis. With that being said, it does have a few good things going for it in which I can get behind. It emphasizes a diet rich in fruits and vegetables and one that focuses on minimally processed foods. Those are two major keys to forming a healthy diet and two things I recommend everyone strive for to achieve optimal health.

Want more information about nutrition counseling and our Fuel program? Contact one of our registered dietitian nutritionists today!

Written by: Jesus Hernandez RDN, LD

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