Which of the following is a key risk factor for developing osteoporosis later in life?

Smoking is a well-established risk factor for developing osteoporosis later in life. Tobacco use adversely affects bone health by interfering with the body's ability to absorb calcium and by reducing the blood supply to the bones, which is essential for maintaining bone density. In addition, smoking has been linked to lower estrogen levels in women, which further enhances the risk of osteoporosis as estrogen plays a significant role in bone metabolism.

In contrast, a high intake of dairy products generally supports bone health due to their calcium content, which is essential for maintaining bone density. Frequent exercise is beneficial for bone health; it promotes bone strength and density. Low vitamin B12 levels are not as directly linked to osteoporosis compared to smoking and do not have the same level of evidence indicating a strong risk factor for developing the condition. Therefore, smoking stands out as a clear and significant risk factor for osteoporosis.