In today’s pop culture vernacular, it’s an insult to be called basic — the opposite of cool and trendsetting. But in the nutrition world, being basic, as in alkaline, is aspirational, with popular books, websites and celebrities all endorsing a pH approach to eating. There is some serious science to back this trend, so it is worth paying attention to, but (surprise, surprise) there is a lot of confusing misinformation and hyperbole out there, too.
The concept of the alkaline diet centers on the well-established fact that different foods affect the body’s pH balance differently. As a rule, fruits and vegetables promote alkalinity, whereas meats, dairy and grains have an acidic effect. It’s not the acid content of the food itself that matters here; it is the way the food has an impact on the pH once it is metabolized. For example, even though oranges and tomatoes are acidic foods, they have an alkaline impact on bodies.
Let’s get one thing straight right away, though: The pH of the blood never varies much. Kidneys and lungs work hard to keep that tightly regulated at about 7.4, because even a small variation in blood pH is life-threatening. So ignore statements such as the one I found on an influential TV doctor’s website, proclaiming that the “typical American diet is full of foods like meat and dairy products that tend to increase the acidity of your blood.”
Although the acid-base balance of blood is constant, the pH inside cells has a somewhat broader range, from slightly acidic to slightly alkaline. Cells function best when they are on the alkaline side, and the way you eat impacts that balance. In a 2012 review published in the Journal of Environmental and Public Health, researchers noted that alkaline diets lead to higher levels of magnesium in cells — a mineral that is required for many enzyme systems, as well as for activating vitamin D, for example. The study also points to documented benefits of an alkaline diet, including preservation of muscle mass with aging.
The pH of urine varies widely, as the urinary tract is on the front line of keeping bodies in acid-base balance. Animal protein, grains, soda, beer and sodium all produce high acid loads for kidneys to process. That acid can be neutralized by the potassium and minerals from fruits and vegetables, but if you don’t get enough of those alkaline foods, urine can wind up chronically acidic, which can contribute to kidney stones and necessitate that bones’ stores of neutralizing minerals be continually tapped, ultimately depleting and weakening them.
But the acid-base equation is only part of the bone-health story, and research has been mixed as to how an alkaline diet affects bones. Besides plenty of acid-balancing potassium and minerals needed to spare their stores, healthy bones also depend on adequate protein. Strict alkaline diets may limit protein-rich foods because of their acid effect, which is a negative for bone health. Focusing on boosting your produce consumption while getting enough protein appears to be the better path to take.
Although there is some solid science indicating that pH matters, many of the benefits touted by alkaline diet proponents, such as healthier bones, reduced risk of chronic disease and weight loss, can be directly traced to the well-known dietary advice to consume more colorful produce and vegetable protein and fewer fatty meats, sweets, refined carbs and sugary drinks. The alkaline diet may sound cutting-edge and innovative, but the most sensible versions boil down to the same advice found in the U.S. Dietary Guidelines.