There are so many diets out there it’s tough to keep count. Most of them have the end goal of weight loss—though most of them aren’t ultimately effective or sustainable in achieving that. One of the most talked about diets this year, the alkaline diet, doesn’t necessarily focus on dropping pounds; rather, its alleged purpose is to reduce disease risk. The premise is that by eating foods that promote an alkaline pH in the body, you can optimize your pH and supposedly rid yourself of all the health woes brought on by an acidic, Western diet. That includes everything from cancer to obesity.
Does it work? Experts are extremely skeptical, but it’s not a total throwaway. There are some ways an alkaline diet can benefit your health—just probably not in the way it’s being advertised.
Here’s a quick refresher on pH, and what “acidic” means within the context of the alkaline diet. (It’s not what you think.)
As you may remember from high school chemistry class, pH is a measure of how acidic or basic a substance is. Zero to 6.9 is acidic, 7 is neutral, and anything above that (up to 14) is basic. Basic and alkaline are synonyms. The pH of a healthy human’s blood is a little bit alkaline, at 7.4. The pH of stomach acid is naturally much lower, usually 3.5 or below.
Lauri Wright, Ph.D., R.D., L.D., assistant professor of nutrition at the University of South Florida, explains that the theory behind the alkaline diet is that when we metabolize food, we leave an “ash,” or by-products, that are either acidic or alkaline. “The alkaline diet proponents say that acidic ash is unhealthy.” But that’s not clearly the case.
“Whether a food is considered to be acidic or alkaline depends on its overall effect on the body, or specifically its effect on urinary acid excretion,” not on whether it’s acidic or basic to begin with, Lisa Cimperman, M.S., R.D.N., L.D., a clinical dietitian at University Hospitals Cleveland Medical Center and spokesperson for the Academy of Nutrition and Dietetics, tells SELF. For example, lemons are acidic foods with a pH of 2. But they are broken down into an alkaline substance in our bodies and give our urine a basic pH, so they’re considered alkaline according to the diet’s guidelines.
The alkalinity is measured along the PRAL scale, which stands for the potential renal acid load, aka how acidic they make your pee. Foods that have a negative PRAL score are considered alkaline. This includes lemons and most other fruits and vegetables. Foods with a positive score are considered acidic or acid-forming—this includes grains, animal proteins, and dairy foods, Cimperman explains.
What you eat can affect pH levels in your body, but only to a certain extent.
Eating different foods on the PRAL scale may change the pH of your urine, but urine pH changes quickly and easily, is influenced by many factors, and “is a very poor indicator of body pH or health,” says Wright. Certain foods may also impact urine pH differently when combined with other foods, adds Cimperman, making a single food’s PRAL score irrelevant.