If you’re trying to eat a healthy diet, you have a lot to keep track of. Do you get enough vitamins, minerals, and fiber (soluble and insoluble)? Enough good fat (from nuts, olive oil, and fish) and not too much bad fat (from meat)? And don’t forget all those phytochemicals that you need to stay healthy.

But what about the acid/alkaline balance of your foods—do you need to consider that, too? Many articles, websites, and ads claim that an acid-boosting diet is unhealthy—perhaps even the cause of most diseases, from cancer and arthritis to depression and diabetes—and they promote special diets or supplements (with names such as Acid2Alkaline or Buffer-pH+) to keep your body from becoming too acidic.

Most of these claims are farfetched or even nonsensical. However, as with many fad diets and supplements, there’s a kernel of truth within them. Research has shown that diet can influence the acidity/alkalinity of the body and that this may affect bone health.

Acidity and alkalinity are measured by the pH scale, which goes from 0 to 14; 7 is neutral, and lower numbers indicate increasing acidity, higher numbers alkalinity. The body keeps its acid balance in the normal range several ways. Acid is excreted by the kidneys and also reduced via exhalation of carbon dioxide. And most important, as far as bone health goes, the body buffers the blood (that is, neutralizes acidity in it) by releasing calcium compounds, which are alkaline.

Where Diet Comes In

The typical Western diet is high in animal protein, which increases the acidity of blood slightly. Fruits and vegetables reduce blood acidity—that is, make it more alkaline. It’s not that meat is acidic, but rather that it contains acid-forming compounds, such as amino acids and phosphorus. Similarly, fruits and vegetables have alkaline-forming compounds (even though many of them taste acidic).

Laboratory studies have shown that an acid-boosting diet can indeed cause bones to release calcium; alkaline-forming foods help prevent this loss. People who eat lots of fruits and vegetables tend to have stronger bones, and this may help explain why. Thus, studies have found that the blood-pressure-lowering DASH diet, which is rich in fruits and vegetables, helps reduce calcium loss.

What about the effect of other foods? Nuts, legumes, some grains (such as rice, pasta, and corn flakes), hard cheeses, and eggs increase acidity; milk and yogurt apparently do not. Sodas, because of the phosphorus they contain, are also high on the acid scale, which is why some studies have linked a very high soda consumption to weaker bones.

There is controversy, however, about how significant the effect of an acid-boosting diet is on bones and the risk of osteoporosis, especially in people who consume adequate amounts of calcium. Since the kidneys help reduce acidity, and kidney function does decline with age, some researchers believe that an acid-boosting diet may help explain some of the bone loss in older people. But so many factors affect bone health—including genetics, physical activity, and many nutrients—that it’s hard to tease out the effect of an acid-boosting diet.