The Truth About: Alkaline Diets

Last year, it became pretty clear that raw veganism was the new thing. As a committed omnivore through-and-through, I was not interested in partaking, but as a budding dietitian, I was curious about the science. So I checked a book out of the local library and brought it home to read. I won’t name names, but, boy, was it confusing. The author, while obviously passionate, was going on and on about acidic and alkaline foods. Alkaline is good, acidic is bad, and acidic foods are going to cause the downfall of civilization.

This was really my introduction to the pH or Alkaline Diet. I am going to cut raw vegans a little bit of slack by saying that as far as I can tell, I was mislead and this book was not about veganism per se, but rather about the Alkaline Diet and this particular author took it to the extreme of raw veganism. A slight distinction, but an intellectually important one, I think.
In any case, this pH-based diet had me intrigued (if a bit confused).  So, let’s get down to the nitty-gritty. Is this diet a good idea? Scientifically based? Do we have to remember stuff we learned in high school to understand it?

What is the Alkaline Diet?

Basically, the premise of this diet is that some foods can change the acidity or alkalinity of your body–we’re talking acids and bases, y’all. It’s high school chem all over again! Now, according to purveyors of this diet, this question of pH is an important one because cancer cells grow faster in acidic solutions, but alkalinity will kill cancer cells. That, and acidity basically leads to all the Diseases of Civilization (at least according to our diet gurus).
Now, after scaring you half to death with the horrors of being too acidic, the diet guru will explain that certain foods leave behind a residue called ash and it can be alkaline (fresh fruits and veggies) or acidic (everything else–the “big bads” like dairy and meat, but also things like legumes and grains) [1]. I’d like to point out that fruits like citrus are considered alkaline on this diet and that throws me quite through a loop.
Some of the more biochem savvy authors will explain that those “good” foods that are typically acidic (hello, most fruits) outside the body will become alkaline inside the body. There is a chemical explanation about how various minerals “dissociate” from the food and then these minerals enter your bloodstream and can raise or lower the pH (if it’s a fruit or vegetable, it’s obviously raising the pH *cue eyeroll*).

What are the problems with it?

So, how well does this stand up to our friend Science? Not well.
First, remember homeostasis? Keeping everything in balance? Well your body does that super well with pH–it’s a tightly regulated machine. So, the pH of your digestive tract doesn’t affect the pH of your blood. Which is good. We like our blood to have a pH around 7.4 but there is a bit of wiggle room. However, between 7.3 and 7.35, you reach a state called acidosis, which is when your blood is too acidic. A blood pH between 7.45 and 7.5 is called alkalosis, and that is when your is too basic (yep, too basic–it’s a thing). If you have a blood pH below 7.3 and above 7.5, you’re dead. Worry not: your blood is buffered, which means that it is resistant to changes in pH.
There are a few ways you can change you blood’s pH: things like sitting for too long (this stagnates your blood, so extra carbon dioxide ends up dissolving into your blood as an acid), not breathing (again, carbon dioxide has nowhere to go, so it dissolved into your blood), and hyperventilating (suddenly, there is no carbon dioxide at all, and your blood begins to become too alkaline). And your body is really good at bringing your pH back to where it belongs–for instance, by getting you to breathe again when you are acidotic (and thus expelling the excess carbon dioxide). But food really isn’t one of the things that affects blood’s pH.
First, when you eat something–even something as acidic as orange juice (pH of 3.5) or something basic like baking soda (but who would eat that!), it goes to your stomach, which has a pH between 1 and 2 (in layman’s terms: that’s hecka acidic). Basically, anything you eat is going to end up becoming that acidic in your stomach because an enzyme called peptidase (which is the first step in digesting proteins) works best at that pH.
While your stomach is adapted to be so acidic, your intestine is not. That is why when that mixture from your stomach enters the intestine, the pancreas secretes a ton of bicarbonate (a base) to neutralize that stuff. So, everything you eat is at the same pH once you start chemical digestion. The food’s starting pH has little to do with the pH of your digestive tract and the pH of you digestive tract has very little to do with your blood pH.
*Note: it is true that the ash byproduct can change the pH of urine, but that is not important because the pH of urine has nothing to do with the pH of your blood.
Second, in response to that those minerals dissociating and going into your blood stream to change your blood pH, I’d like to point out that none of this is happening in a vacuum. It’s not as though there is nothing else in your blood stream for these minerals to interact with; it’s not like they will have unmitigated effects. Remember, our blood is highly buffered. Those minerals which could effect the pH of, say, plain water, but not our blood because the buffer has weak acid to neutralize a base and weak base to neutralize an acid.
Plus, we have organs to deal with this because our bodies aren’t helpless damsels waiting for food to save us or destroy us. While it is true that as your intestine breaks food down, the nutrients are absorbed through the intestinal wall and into the blood stream, all that blood is funneled straight to the liver. Our livers can store vitamins and minerals. Additionally, you have two kidneys and they will do a water, salt, and pH balance on all your blood when the blood reaches them after reaching the heart. Your kidneys are full of little nephrons which make sure enough water and salt is reabsorbed into your body, excrete the rest, and get rid of extra acidity or alkalinity.
Trust your body, it has this covered.

Bottom line?

Fruits and veggies are great for you, but there are much better reasons to eat them than because they alter your body’s pH balance. Instead, eat ’em cause they taste good, they’re full of vitamins, or they give you that healthy glow.

Resources

Alkaline Diets and Cancer: Fact or Fiction? January 16, 2013. Stephanie Vangsness, M.S., R.D., L.D.N., Brigham and Women’s Hospital

Don’t believe the hype – 10 persistent cancer myths debunked. March 24, 2014. Oliver Childs. Cancer Research UK.

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