The Popular Diet That Ignores Some Basic Biology Facts

The alkaline diet has been touted as a cure for health issues ranging from indigestion to cancer. Some believe it's the answer to the obesity problem that's rampant in our country. But, ultimately, the alkaline diet crumbles at its foundation — because the whole thing is based on a faulty premise.

The crux is this: The modern diet contains a high quantity of foods that make the body acidic, and health can be improved if the pH of the body is brought back into its natural range. To do so, according to the diet, 75% of one's caloric intake must come from alkaline (also known as “basic”) foods. This includes fruits, leafy greens, and root vegetables, all of which have a pH of greater than 7 — a neutral pH. Acidic foods — with a pH of less than 7 — such as sugar, caffeine, and protein, should be avoided. Alkaline dieters keep track of their bodies’ acidity by measuring the pH of their urine, assuming that a basic pH means an alkaline body.

There are a few key problems with this premise. First, the human body possesses a sophisticated pH-regulating system (separate from digestion) that cannot be disrupted by the food we eat. “Our lungs and kidneys are constantly regulating our pH,” says Tanis Fenton, PhD, adjunct assistant professor of community health services at the University of Calgary. Second, even if the foods we ate could change our body’s pH, no food has a lower pH than the human stomach (gastric acid typically falls between a pH of 1.5 and 3.5 — very acidic). So, the pH of the fruits and vegetables that comprise the alkaline diet is irrelevant, since everything we eat ends up with the same pH: that of the highly acidic environment in our stomachs. Thus, the idea that blood pH can be altered by what we eat is simply not true.

Third, bodily fluids we can measure, such as urine or saliva (which are both typically acidic), have no correlation to the pH within the body. Dieticians have performed experiments to see what kind of effect the alkaline diet has on blood pH. They found that although the urine pH changed significantly, the blood pH didn’t change at all. After the body does its job of mining nutrients from our food, it eliminates everything else as waste. If anything, urine that becomes more basic as a result of the alkaline diet is a sign that the organs operate just fine at a neutral pH. In other words, the body is dispelling the excess “basicness” dieters have introduced.

So, where did this alkaline idea emerge? The diet originated 100 years ago, Dr. Fenton explains, during early experiments aimed at understanding the nutritional value of food. Researchers burned different foods, vaporizing their energy-containing components (such as protein, carbohydrates, and fat) and leaving only minerals behind. Much later, other researchers developed a formula called the potential renal acid load (PRAL), which relates the acidity of those mineral ashes to the acidity of urine after the food was consumed. The acid-alkaline hypothesis then ensued, questioning the effect of food pH on body pH.

The hypothesis has only been tested a couple of times. In both cases, it was determined that regardless of PRAL, blood acidity stayed within the physiologically expected pH range of 7.3 to 7.4. Unfortunately, despite a lack of vetting, the acid-alkaline hypothesis has been repackaged as “the alkaline diet.”

People who adopt the alkaline diet probably do feel a lot better, since they are eating so many healthy fruits and vegetables. What’s the harm, then? The diet eliminates immune-system-boosting foods (such as beans and legumes) along with essential fats and oils necessary for cellular health. And, consumers can get duped by products claiming to increase pH, such as water alkalizers and juices, which are nothing more than bogus promises.

One big concern is the fact that alkalinity apostles limit protein, deemed an acidifier to be avoided. The diet restricts most animal protein, but offers few other alternatives. Yet, our bodies need protein to rebuild tissue on a continual basis (more so if you are an athlete). “They are taking it to the extremes, they are saying protein doesn't matter,” says Dr. Fenton. “And, nowhere has science said that protein doesn't matter. Protein matters.”

So, yes, eat green vegetables. They’re still good for you. But, you can skip peeing on pH paper for now.

This post was authored by Rebecca Guenard.