By Mary I. O’Connor, MD, and Laura L. Tosi, MD
Not just for women: Is vitamin D the key to bone health?
Although men sustain fewer hip fractures than women, their recuperation is significantly more difficult. More men are underdiagnosed and undertreated for osteoporosis after a hip fracture (only about 1 percent of males are discharged with treatment, compared to 25 percent of females), and few FDA-recommended pharmacologic treatments for men with osteoporosis exist. Although osteoporosis is four times as likely to develop in women than men, severe osteoporosis resulting in disability and death is more likely to occur in men.
Healthy bones go through a continual process of remodeling, in which small amounts of old bone are removed and replaced by new bone. As we age, we lose more bone than we gain. Because bone loss from osteoporosis cannot be replaced, treatment focuses on preventing additional bone loss. The key to building and maintaining strong bones is weight-bearing exercise and adequate dietary nutrients such as calcium. Taking calcium is not enough, however; in both men and women, vitamin D is a critical component of calcium absorption and is also known to significantly improve muscle strength.
Vitamin D, a group of fat-soluble vitamins that are related to steroids and essential for normal bone and tooth structure, has several forms. Many organs—including the brain, heart, gut, muscle, pancreas, skin, and kidney—as well as the immune system have vitamin D receptors. When vitamin D is absorbed, the liver and kidney chemically convert it to 1,25 dihydroxyvitamin D, which makes it physiologically active and allows it to act as a hormone, telling the intestines to increase the absorption of both calcium and phosphorus. Working with other hormones, vitamins, and minerals, vitamin D then promotes bone mineralization.
Essential for bone and muscle health
A significant link exists between vitamin D and reducing falls; based on a meta-analysis of five randomized clinical trials, ambulatory and institutionalized older individuals with stable health taking vitamin D had up to a 22 percent reduction in the number of falls compared to those not receiving vitamin D. In both men and women, patients treated with vitamin D showed significant improvement in stability and walking.
Vitamin D deficiency can compromise bone quality and play a large part in the development of osteoporosis and osteomalacia. Studies have shown that hypovitaminosis D (concentrations lower than 20 ng/mL) will actually increase the risk of falls and fractures. Mild to moderate deficiency may cause nonspecific, diffuse musculoskeletal pain. Patients with a severe deficiency may also have deep bone pain, diffuse muscle weakness, proximal weakness, hip pain, problems walking with a normal gait, and difficulty performing everyday activities such as climbing stairs.
Sources of vitamin D
The body receives vitamin D from dietary sources, supplements, and skin synthesis. Only a few foods—such as egg yolks, fatty fish (salmon, etc.) and cod liver oil—naturally contain vitamin D. Many foods—including milk, breakfast cereal, some orange juices, and even some waters—are fortified with vitamin D. Multivitamin supplements usually contain vitamin D and calcium.
Vitamin D is also absorbed into the body through skin synthesis; UV radiation converts 7-dehydrocholesterol (a lipid in the dermis) to previtamin D3. However, skin synthesis declines with age as the epidermis thins, resulting in loss of lipid contents and decreased blood flow to the skin. Many experts agree that adequate amounts of vitamin D can be absorbed with just 10 to 15 minutes of sun exposure on the hands and arms two or three times per week. Geography, however, plays a major role in the efficacy of sun synthesis. For example, in northern cities like Boston and Seattle, skin synthesis is ineffective in producing vitamin D between November and February, regardless of the amount of time a person spends in the sun. In Los Angeles and Atlanta, however, vitamin D synthesis is adequate throughout the year.
We’re not getting enough
Vitamin D insufficiency is common in adolescents and adults living north of 32° north latitude (Boston is at 35°). In Boston, a study of 8,000 healthy adults showed that 30 percent had low concentrations of vitamin D at the end of winter, and 11 percent still had low concentrations of vitamin D at the end of the summer.
Even in South Florida, a low concentration of vitamin D is common. An analysis of 212 adults showed 38 percent of men and 40 percent of women had low concentrations of vitamin D in the winter, and by the end of the summer, 14 percent of the men and 13 percent of the women who returned continued to show low concentrations of vitamin D levels. More women (28 percent) than men (10 percent) had hypovitaminosis.
But the blame cannot solely be placed on geography. Some “fortified” foods do not actually contain the vitamin D they claim; data show that 70 percent of milk samples in North America do not contain 400 international units (IU) of vitamin D per quart as advertised. A newer cause of deficiency in select populations is bariatric surgery, which can result in inadequate dietary intake of vitamin D.
Osteoporosis, fracture patients show vitamin D deficiency
Among postmenopausal women, up to 76 percent of those with osteoporosis have a vitamin D inadequacy (less than 12 ng/mL). From one half to three quarters of individuals with a history of fracture have inadequate vitamin D. Hypovitaminosis D has been demonstrated in 86 percent of institutionalized women.
A study published in Osteoporosis International highlighted differences between ethnicities; a study of 185 patients with acute fragility fractures who received osteoporosis consultations found that African American and Hispanic patients were significantly younger than whites, but more likely to have serious comorbidities like diabetes or hypertension. African American patients had the highest rates of vitamin D deficiency and secondary hyperparathyroidism, even though they also had significantly higher bone mineral density.
Helping your patients
Adequate vitamin D intake has been proven to decrease the risk of fracture in women. In a study of 1,400 ambulatory women with a mean age of 84, patients who took 1.2 gm of calcium and 800 IU vitamin D daily had 23 percent fewer hip fractures after 36 months. Another study of 1,237 male and female elderly patients found that 22 percent showed a decrease in falls, presumably due to the positive influence of vitamin D on muscle strength.
Vitamin D deficiency is completely preventable and reversible. It is important to make sure that you, your family, and your patients receive adequate daily intake of vitamin D. Vitamin D is key for absorption of calcium and critical for bone health, and it plays an underappreciated role in muscle strength and fall prevention. Vitamin D is not just a treatment for women, because vitamin D deficiency is common in both males and females.
Current vitamin D recommendations from the U.S. Food and Nutrition Board and the Institute of Medicine are shown in Table 1 on page 37. Most researchers, however, consider these recommendations to be too low and believe minimum adult intake should be 1,000–2,000 IU daily.
It is time to include osteoporosis evaluations and recommendations for pharmacologic treatment and prevention of bone loss—for women and men—into your practice. We hope you appreciate the value of this information and take steps to ensure that your patients receive adequate vitamin D. Vitamin D is easy to prescribe and can make a world of difference in your patients’ musculoskeletal health.
This quarterly column from the AAOS Women’s Health Issues Advisory Board and the Ruth Jackson Orthopaedic Society provides important information for your practice about issues related to sex (determined by our chromosomes) and gender (how we present ourselves as male or female, which can be influenced by environment, families and peers, and social institutions). Mary I. O’Connor, MD, is chair of the AAOS Women’s Health Issues Advisory Board and past president of the Ruth Jackson Orthopaedic Society (RJOS); she can be reached at email@example.com. Laura L. Tosi, MD, is also an RJOS past president; she can be reached at firstname.lastname@example.org.
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