Dawson-Hughes is the director of the Bone Metabolism Laboratory at the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts. She says that most humans reach their maximum bone density by age 25—but after that, things tend to go downhill, especially in middle age. Most men lose about 1 percent of their bone mass annually after age 50, and women lose even more.

“At menopause, women lose roughly 3 percent of their bone mass annually for about five to eight years,” she says. That means more than 20 percent of the body’s total bone density can disappear in less than a decade, leading to osteoporosis, painful fractures and a diminished quality of life.

Because grains contain sulphur compounds, they break down into by-products like sulfuric acid, which in turn leads to an increase in the body’s overall acidity. Although that sounds awfully dramatic on paper, the actual change in blood pH is thankfully minute—on the order of a few tenths of 1 percent—yet even this tiny change may trigger bone loss.

Bones Neutralize the Acid
Dawson-Hughes says that some of this loss is caused by a chemical breakdown that happens when bone touches acidic blood. The rest, however, may be due to a specific defensive mechanism.

“As the pH goes down in the blood just a little bit, that activates a specific receptor in bone, creating a chain of events that results in bone resorption,” she says. “It signals bone to break down, which dumps alkali into the circulation, neutralizing the acid. It’s a defensive response—our bodies are basically defending against a dropping pH.”

Ideally, this defence mechanism should keep our acid-base levels more or less in balance. With high-grain diets continually adding more acid into our bodies, however, this system may kick into overdrive to compensate, leading to accelerated bone loss.

Article found in the Magazine of the Gereald J. and Dorithy Fieldman school of Nutrition Science and Policy and the Jean Mayer USDA Human Nutrition Research Center on Aging.
“TUFTS NUTRITION” summer 2016