I recently told you that thousands of people across the country in danger of vitamin D deficiency. Well, now my colleague Taryn has come across another article that demonstrates just how critical it is to keep tabs on your levels of this essential nutrient -- and to make sure it's in a healthy range.

Researchers from three prominent universities have uncovered a significant link between insufficient vitamin D levels and cognitive decline.

When they examined the records of nearly 2,000 subjects, they discovered that lower vitamin D levels corresponded with higher levels of cognitive impairment. In fact, the people who didn't have optimal levels of vitamin D were more than TWICE AS LIKELY to have problems with their brain function.

As I mentioned earlier this week, you should consider having your own levels tested – or re-tested – as soon as possible. If they prove to be low, don't rely on fortified milk or orange juice to bring them up to where they need to be. Neither of these sources are ideal.

Dr. Wright recommends 4,000 IU (International Units) of vitamin D daily for adults and teenagers, 1,000 IU for infants and small children, and 2,000 IU for everyone in between. But, if your levels are low, you may need even more. Work with your doctor to determine your body's current levels, and the vitamin D dose that best suits your needs.