I diagnosed a patient with osteoporosis. She looked me in the eye and said I must be wrong. I assured her that her bone density was low and asked why she didn’t think the diagnosis could be correct. “I’ve taken a vitamin D supplement and a calcium supplement for years to make sure my bones stay strong. I just can’t have osteoporosis… I’ve done everything right.” She’d never been told about the third nutrient absolutely critical to bone health.