Followers of the alkaline diet believe it promotes health—but does it?
The alkaline diet seems to be enjoying some renewed popularity these days. I say “renewed” because the idea of eating foods that promote alkalinity in the body has been around for decades. The first paper on the topic, in fact, was published over 100 years ago1. Like most diet fads, the alkaline diet seems to have been rediscovered, and it’s being promoted by followers as a sure path to health and vitality. But what is an alkaline diet? And can it deliver on those promises?
The alkaline diet promotes the idea that eating certain foods and avoiding others will help keep the body from becoming too “acidic.” Alkaline diet proponents believe that taking in too many acid-forming foods upsets the body’s natural acid-alkaline balance, and so an emphasis is placed on eating foods that are said to be more alkaline.
The diet has sometimes been called the “alkaline ash” diet. The idea of it is that you should eat foods that, once metabolized, leave behind an alkaline residue or ash. This dietary ash is pretty much just want it sounds like. It’s what’s left after you burn up everything in that food that can be broken down, primarily a mixture of minerals. Depending upon which minerals are present in a food, the resulting ash is termed either “acid ash” or “alkaline ash.”
Supporters of the alkaline diet believe that eating too many foods that produce acid ash can negatively impact health, and advise a diet rich in foods that produce a more alkaline ash.
The belief is that by tinkering with the body’s acid-base balance and eating more alkaline foods, better health will result. Processed foods, sugar, alcohol, meats, dairy and grains are considered too acidic (and therefore shunned); whereas, fruits, vegetables, nuts and seeds are favored for their alkaline properties.
Those who follow the alkaline diet believe that it helps the body maintain an optimal pH level.
If you’re not familiar with the term, pH is simply a scale that measures how acidic or how alkaline (or “basic”) a liquid substance is. The pH scale ranges from zero to 14: the lower the number, the more acidic the substance is. A pH of seven is considered neutral. As the number rises, the substance is more alkaline (sometimes called basic).
Now, it is true that if the body becomes too acidic, your health will suffer. No argument there. But here’s what is also true: You can’t change the acidity of a healthy body simply by eating certain foods and avoiding others. Let’s look at this issue a little more closely and separate fact from fiction.
First of all, your body doesn’t have a single pH value—it depends on what you’re testing. The pH of the digestive fluids in your stomach are highly acidic (values in healthy people range somewhere between about 1.5 and 2). But the pH of your small intestine, where most of your nutrients are absorbed, is more alkaline, topping out at about 7.4. And the blood of a healthy person is also slightly alkaline: it’s maintained by the body within a very narrow range of about 7.35 to 7.45.
This is an important point, because the chemical reactions in your body can only take place within this pH range. So, your body maintains your blood pH through systems that involve, primarily, your lungs and your kidneys. As long as you’re in good health, you can’t (nor would you want to) change your blood pH through diet. Because if the pH were to stray from these narrow confines, you’d be in serious trouble.
On the other hand, the pH of the urine in a healthy person tends to have a range generally between 6.5 and 8.0, depending on the time of day. Values tend to be higher in the morning, as well as after what’s been eaten. Proponents of the alkaline diet frequently check the pH of their urine with special test strips. They’re aiming for values on the higher end of the scale, which they believe indicates they’re staying on track with the diet and moving the body to a more alkaline state.
This ignores the fact that if your body is functioning properly and you’re healthy, the pH of your urine will naturally fluctuate. And those fluctuations indicate that the body is doing its job to help maintain the pH of the blood within that very narrow, desired range. The pH of the urine is not a reflection of the pH of your blood.
The bottom line is this: There’s no scientific support for the idea that following an alkaline diet will affect the pH of the body in a healthy person. And, as you now know, the idea that you would even want to change the pH of your system doesn’t make sense either.
That said, the alkaline diet does place an emphasis on plant foods in the diet—especially fruits and vegetables—which isn’t a bad thing. After all, these foods offer up an abundance of vitamins, minerals and fiber. So, if there are any positive takeaways from the diet, that would be one.
However, there are also many healthy foods that are not permitted on this plan, including nuts, fish, poultry, eggs, lentils, beans, soybeans and avocado. So, finding enough protein on an alkaline diet could be challenging.
Many believers say that the alkaline diet has brought them benefits, such as weight loss or improved digestive function. But if they are attributing these benefits to the alkaline nature of their diet, they’re focusing their attention on the wrong thing. Watery, high fiber foods—whether acid or alkaline—are filling and satisfying and help promote regularity.
1Sherman HC and Gettler AO. 1913. http://www.jbc.org/content/11/4/323.full.pdf