In the U.S., inadequate levels of vitamin D are more common than you might think. About 8 percent of Americans are at risk for vitamin D deficiency, according to the National Health and Nutrition Examination Surveys conducted by the Centers for Disease Control and Prevention.

Internationally, the situation is often quite a bit worse, especially in Africa and the Middle East. In the latter, vitamin D deficiency is especially widespread, according to a recent study conducted by the International Osteoporosis Foundation.

Researchers found that in certain Middle Eastern countries, the incidence of vitamin D deficiency is between 75 and 90 percent.

"Vitamin D is an essential component of bone health," said Dr. med Gemma Adib, the report's lead author and the general secretary of the Pan Arab Osteoporosis Society. "It is essential that the region develops vitamin D supplementation strategies based on local data for at-risk groups."

If that weren't discouraging enough, new research has demonstrated that the consumption of vitamin D-rich foods of any kind has dropped in the past three decades.

A study published in the Journal of the American Dietetic Association found that between 1980 and 2009, daily vitamin D consumption from food-based sources decreased by 15 percent among men and 5 percent among women.

Without regular vitamin D intake, bone and respiratory health can be seriously impaired, as can any number of cellular processes within the body, the Office of Dietary Supplements reports.

Foods that naturally contain vitamin D include eggs, fish and mushrooms.

Without adequate food sources of the nutrient, individuals may wish to consider taking dietary supplements or multivitamins in order to maintain their health and well-being.

Researchers at Florida State University came to this conclusion after asking a group of women to consume 100 grams of prunes or of dried apples every day for a year. All participants were also given vitamin D and calcium at levels often found in dietary supplements.

Ultimately, women who consumed prunes exhibited better bone density in their ulnae and vertebrae, which the team attributed in part to the ability of prunes to slow mineral resoprtion in people who are gradually losing bone mass.

"Over my career, I have tested numerous fruits, including figs, dates, strawberries and raisins, and none of them come anywhere close to having the effect on bone density that dried plums, or prunes, have," co-author Bahram H. Arjmandi emphasized.

A study appearing in the Journal of Clinical Endocrinology and Metabolism announced that females between the ages of 14 and 18 may have slightly lower bone mass densities than their peers if they take birth control pills.

The bone mineral loss was relatively minor, researchers said. All participants who took birth control pills experienced a bone growth rate less than 2 percent slower than those not taking oral contraceptives. Also, this disparity only appeared after at least two years of regular use of the Pill.

Still, the authors said that this information may help young women choose a method of contraception that is healthiest for them

The U.S. Surgeon General and the National Osteoporosis Foundation both recommend that women eat foods or take dietary supplements containing vitamin D and calcium, as well as get regular aerobic exercise.

The study, which was presented in Boston at the annual meeting of the Endocrine Society, determined that bisphosphonates—a class of pharmaceutical bone-density drugs—work seven times better if an individual has at least 33 nanograms (ng) of the nutrient per milliliter of blood (ng/mL).

The National Institutes of Health (NIH) states that 20 ng/mL is usually sufficient for healthy adults. That, however, does not appear to be nearly enough for people taking bisphosphonates for accelerated bone loss, said study co-author Richard Bockman. The best indicator of vitamin D status is thought to be 25(OH)D levels in serum. A committee of the Institute of Medicine found that levels of 50 to 125 ng/mL offer the most benefits, while going below or above that range may present deficiency or toxicity risks. To ensure adequate 25(OH)D levels, an adult over the age of 50 should consume at least 800 international units (IU) of vitamin D each day, according to the National Osteoporosis Foundation. Taking a daily dietary supplement is a simple way to do so.

Recently, a group of French researchers determined that a compound found in red wine may help reduce the onset of bone loss brought on by weightlessness, like that experienced by astronauts. The results, which appeared in the Federation of American Societies for Experimental Biology (FASEB) Journal, pointed to resveratrol as the chemical key to bone health in zero Gs.

For the study, scientists dosed laboratory rodents with resveratrol, a compound found in grape skins and wine. After days of simulated weightlessness, those animals given the substance did not display any bone deterioration, muscle loss or insulin resistance, while those given no resveratrol experienced all of these complications.

The team expressed excitement for resveratrol's applications in space and on terra firma.

"For the earthbound, barriers to physical activity are equally challenging, whether they be disease, injury, or a desk job. Resveratrol may not be a substitute for exercise, but it could slow deterioration until someone can get moving again," Gerald Weissmann, editor of the FASEB Journal, concluded.

The report was published in the Journal of Clinical Endocrinology and Metabolism and included a clinical practice guideline (CPG), which is a set of recommendations that physicians can follow when looking at vitamin D levels.

Among other things, the CPG suggested that healthcare professionals routinely test their patients for deficiencies of the nutrient, particularly if a person is part of an at-risk group, such as the elderly or those exposed to little or no sunlight.

The report also stated that for adults of any age, consuming at least 1,500 to 2,000 international units (IU) of the vitamin, if not more, may be needed in order to maintain a blood level of the nutrient above 30 nanograms per milliliter (ng/mL).

The National Institutes of Health (NIH) defines blood levels less than 20 ng/mL as insufficient, while blood levels lower than 12 ng/mL are considered full-blown deficient.

And supporting that finding is a study appearing in the journal Respirology. The study is based on data collected from 112 people with respiratory health concerns.

Scientists noted that individuals with vitamin D deficiencies were almost 13 times more likely to experience negative health consequences, compared to people with adequate nutrient levels.

The study’s authors said that 15 percent of patients with respiratory concerns  had a vitamin D deficiency, which is defined as having fewer than 30 nanomoles of the compound per liter of blood. Likewise, researchers noted that the vitamin D-based effect did not appear to be affected by a person’s age, gender or the state of respiratory function.

Many adults do not get enough sun exposure to account for the recommended daily dose of vitamin D, which is why so many Americans turn to dietary supplements to boost their nutrient levels.

Research published in the journal Nutrients indicates that consuming adequate levels of nutrients may contribute to bone tissue of a higher quality.

Co-author Karen Chapman-Novakofski, Ph.D., of the University of Illinois at Urbana-Champaign (UIUC), and her research partner conducted a survey of more than 200 articles. They determined that consuming dietary supplements containing 1,200 milligrams (mg) of calcium and 1,000 international units (IU) of vitamin D may help elderly Americans safely promote optimal bone health.

In an article in the journal Nutrients, scientists at the University of Illinois at Urbana-Champaign recommended that physicians prescribe over-the-counter calcium supplements for individuals who are at risk for osteoporosis, rather than immediately resorting to prescription medications.

The research team noted that many doctors may balk at such a simple solution because they expect their patients to fail to adhere to a regimen of dietary supplements.

However, bone tissue built through pharmacological means is not always structurally sound, they said, indicating that it may be more effective to treat low bone density the natural way.

By taking vitamin supplements or eating fortified foods, aging Americans may be able to increase their calcium intake to a healthy level.

The National Osteoporosis Foundation recommends that adults over the age of 50 consume 1,200 milligrams (mg) of calcium and at least 800 international units (IU) of vitamin D each day.