We are a sunshine society, and we take advantage of beaches, pools, and outdoor activities like never before in our history. Usually this time of year we are filling the Internet with warnings about the danger of getting too much sunlight. So it may come as a surprise how common is Vitamin D deficiency.

Vitamin D most famously is found in sunlight, and we've all been told to get at least ten minutes of sunshine to score our recommended daily dose of it. With the bar so low, how can anyone be deficient?

We are getting older, for one thing. Older people make less vitamin D from the same amount of sunlight, and their gut's ability to absorb vitamin D from food and supplements is reduced.

We are getting fatter, for another reason. Obese individuals usually have lower vitamin D levels because the vitamin gets absorbed by fat tissue and it is not easily released into the blood stream. And since the volume of blood that an obese person is moving around is so much larger, what vitamin D does make it into the blood stream is diluted by comparison.

Happily, more of us are wearing sunscreen to minimize our risk of skin cancer, but that's a double-edged sword when it comes to our vitamin D dosing. The higher the SPF, the more UVB radiation we block, the less vitamin D we take in.

The major role of vitamin D is to maintain normal blood levels of calcium and phosphorus. Vitamin D helps the body absorb calcium, which forms and maintains strong bones. It is used alone or together with calcium to improve bone health and decrease fractures. Vitamin D may also protect against osteoporosis, high blood pressure, cancer, and other diseases.

When we don't get enough Vitamin D, we may experience bone pain, muscle cramps, weakness and tingling, and even a loss of height. A long term deficiency in the vitamin can cause rickets, and osteoporosis. Complications of vitamin D deficiency include bone fractures and disability. There is also some research that suggests that vitamin D deficiency may also be linked to the development of hypertension, depression, multiple sclerosis, arthritis, type 2 diabetes, cardiovascular disease, and an increased risk of cancer.

A diagnosis of vitamin D deficiency will include a physical exam, and a blood test to analyze the level of the vitamin in the bloodstream. Your doctor may also schedule X-rays and bone density testing to gauge the health of your bones. Vitamin D deficiency is particularly prone to mi-diagnosis, because the condition usually takes years to develop.

Once properly diagnosed, a vitamin D deficiency can be treated with supplements, either oral or intravenous. Maintenance should include a diet high in vitamin D, which will include fortified milk and dairy products, fortified orange juice, liver, eggs, and oily fish.