Does cow’s milk make strong bones?

DEAR DR. ROACH >>

I read that cow’s milk weakens the bones. Is that true? — A.H. DEAR READER >> The preponderance of the evidence is that dairy intake — like cow’s milk, yogurt and cheese — increases bone strength and reduces fracture risk. However, there is not the highest level of evidence to support this. In absence of interventional data (where one group is given cow’s milk and the other given something else), we have to rely on other kinds of evidence, all of which have some potential for bias.

Some of these have shown benefit from drinking cow’s milk; others have not. A 2018 study from the U.S. estimated a 6 to 8 percent reduction in fracture risk from consuming cheese or milk daily. It’s not clear whether it’s the calcium, the vitamin D or something else that may be reducing risk.

Regular exercise is another way to reduce risk of osteoporosis and fractures. Unfortunately, some people will still be at risk for fractures despite an excellent diet and regular exercise, so those at high risk should be screened, and may require medication. You can reduce your chances of needing medication through a good lifestyle, preferably beginning in young adulthood.

DEAR DR. ROACH >> Do all cervical cancers come from HPV? — B.H. DEAR READER >> One study estimated that 99.7 percent of all cervical cancers worldwide are due to infection from human papillomavirus, especially the high-risk strains that are most likely to cause changes in the cells that can become cancerous. However, most cases of HPV are effectively treated by the body, and do not become cancer.

A few cancers do not have evidence for HPV when they are looked at. In one recent study from the U.S., about 10 percent of cervical cancers did not seem to be associated with HPV, but on careful re-evaluation, about half of those did have an association with HPV. Still, there are some cases of cervical cancer that are not due to HPV, and the risk factors for those may include smoking and HIV. This type of cervical cancer has a worse prognosis than HPV-related cervical cancer.

Population-level vaccination of HPV is likely to dramatically reduce cervical cancer, but not eliminate it entirely. For this reason, the Pap smear, which diagnoses cancer and its precursors, is likely to remain an important screening tool.