Days are becoming shorter in this part of the world, and it's time to think about vitamin D. This vitamin, along with calcium, is essential to bone health - without vitamin D, our body can't absorb the calcium we consume. When we spend time in the sun, special cells in our skin manufacture vitamin D. But when days are short, the sun's rays become less intense for those of us who live as far north as Portland, Oregon; Boise, Idaho; Chicago, Illinois; or Boston, Massachusetts. Starting in October in these northern states, our skin produces only about half as much vitamin D as in the summer months. What's more, from November through February, we produce none at all. If we don't do something to compensate, we can actually lose bone over the winter.

If you're over age 50 or at risk for osteoporosis, I urge you to consider taking a supplement that contains between 400 and 600 IU of vitamin D, especially during these fall, winter and spring months. Supplementing with vitamin D will reduce the seasonal loss of bone that otherwise happens because of changes in sunlight. Keep your bones strong for a lifetime by making sure that you get plenty of vitamin D.