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Your gut contains tens of trillions of microorganisms, including at least 1,000 different species of known bacteria. Even though these bacteria are microscopic in size, they are so abundant that they make up 1 to 3 percent of your total body mass! Many of these microorganisms that live in the body are actually beneficial to your health, although some can be harmful. The “good” bacteria in your digestive system protect your body by preventing the growth of “bad” bacteria that can make you sick. They also serve an essential function in food digestion by breaking down foods and proteins and synthesizing vitamins and nutrients. Recently, researchers have shown that gut bacteria, or microbiota, may play a role in diseases such as diabetes, obesity and Alzheimer’s disease, and they can affect distant organs such as the brain and even bone.

One of the ways that the gut affects bone is by regulating mineral absorption. As food passes through the body, the gastrointestinal (GI) system controls the amount of minerals that are absorbed from the food into the bloodstream. Many of these minerals—including calcium, phosphorous, and magnesium—are essential for healthy bones. In fact, studies report that people with GI diseases such as inflammatory bowel disease can experience bone complications.

Other research has added support to the theory that gut bacteria may affect the bone by contributing to the absorption of nutrients. Mouse studies have shown that the presence or absence of gut microbiota can actually change the structure and density of bone. Bone density, or bone mass, is one indicator of how strong and healthy your bones are. It’s not exactly clear how or why gut bacteria affect bone, but researchers believe that one way is by regulating how much calcium is absorbed into the body.

Taking probiotics is known to help maintain a healthy gut microbiota. Probiotics are live bacteria that can be taken by mouth as a dietary supplement. They contribute to the health of the digestive system by promoting the growth of good bacteria and inhibiting harmful bacteria. But new research is showing that they can also have beneficial effects on the bone.

While scientists continue to explore the link between the gut bacteria and bone, a few lifestyle adjustments can help protect your bones:

• Include plenty of calcium and vitamin D in your diet.
• Exercise regularly (preferably with weight-bearing exercises that strengthen your bones).
• Quit smoking and limit alcohol consumption.
• Avoid using steroid drugs, which can weaken your bones.
• Get bone mineral density testing according to the schedule recommended by your doctor.

Naiomy Rios-Arce, BS, is a PhD candidate in the Comparative Medicine and Integrative Biology program in the Department of Physiology at Michigan State University. Her research focuses on understanding the mechanism by which probiotics can affect bone density. Naiomy is originally from Hatillo, Puerto Rico.