People who are cognitively impaired are more likely to develop dementia and possibly even Alzheimer’s disease. At least 5.2 million Americans currently suffer from Alzheimer's. By 2010, there will be 500,000 new cases each year, and nearly 1 million new cases annually by 2050.

A lack of vitamin D could be one factor contributing to this snowballing epidemic … and one that could easily be remedied.

A study a few years back also found that almost half of elderly women in high-level residential care, though not bedridden, were severely deficient in vitamin D as well.

The problem is two-fold because seniors do not typically spend much time outdoors in the sunshine, and even when they do they may have trouble making enough vitamin D, as the capacity of your skin to absorb vitamin D from sunlight tends to decrease with age.

How Does Vitamin D Impact Your Brain?

It used to be thought that vitamin D’s role in your body was primarily related to your bones.

How wrong we were.

As Dr. Cannell, founder of the Vitamin D Council, explained so well in my February Inner Circle interview with him, vitamin D is not a vitamin, but rather the only known substrate for a powerful repair and maintenance steroid hormone that is involved in numerous functions of your body and organs.

Like all steroid hormones, vitamin D influences your health by regulating the expression of your genes. Vitamin D influences over 2,000 of the 30,000 genes in your body. That is one of the primary reasons it affects so many diseases, from cancer and autism to heart disease, the flu and rheumatoid arthritis.

Researchers are now beginning to realize that vitamin D is intricately involved in maintaining the health of your brain as well, as they’ve recently discovered vitamin D receptors in your brain, spinal cord, and central nervous system.

There’s even evidence indicating vitamin D improves your brain’s detoxification process and induces glioma cell death, making the hormone of potential interest in the management of brain tumors.

For children and pregnant women, getting enough vitamin D is just as crucial as it is for seniors, as it may play a major role in protecting infants' brains from autism.

How Much Vitamin D is Healthy?

The current RDA for vitamin D, developed by the Food and Nutrition Board at the Institute of Medicine of The National Academies, is much, much too low to be beneficial. It is only:

For comparison, consider that in the summertime when you put on your bathing suit and sunbathe for 30 minutes, your body produces about 20,000 IUs of vitamin D -- as much as exists in 200 glasses of milk, or the equivalent of about 50 typical multivitamins!

Ideally, sunbathing is the best way to get your vitamin D. If you have light-colored skin, you can use the color of your skin to tell you when you’ve had enough sun and it’s time to get in the shade (or cover up using a long-sleeved shirt, pants, and a hat). Stay out just long enough so that your skin turns the very lightest shade of pink.

In lightly colored Caucasian skin like many Irish or Scottish have, this typically occurs within a few minutes of ultraviolet exposure. It can take 10 times longer (or more) for darkly pigmented skin to reach this equilibrium concentration of skin vitamin D.

For those in the winter with little or no exposure to sunshine, the next best option would be to use a safe tanning bed. If you do not have access to a safe tanning bed then a vitamin D3 supplement may be appropriate. For dosage, 4,000-5,000 units per day is appropriate for most adults. (If you are very heavy you may need to double that dose, and for children the dose can be half that.)

If you opt to take vitamin D supplements, it is very important that you monitor your vitamin D levels by blood testing, to make sure your levels are therapeutic and not toxic. There is simply FAR too much variability in dosing to not test. Some people may need 20,000 units of vitamin D a day or more and some may actually get to toxic ranges on far lower levels. So you simply MUST test if you opt to take this simpler, but far less ideal way to get your vitamin D.

For an in-depth explanation of what you MUST know before you get tested, please read my updated article Test Values and Treatment for Vitamin D Deficiency.

Making sure that your vitamin D levels are optimized is really one of the most simple yet profound steps you can take for your health, no matter what your age.

It is so important, in fact, that I recently recorded a one-hour lecture all about vitamin D, which I urge you to watch and share with all of your friends and loved ones.