Why most of us should be taking Vitamin D supplements
When it comes to vitamin D, a few minutes in the sun is all you need, correct? Well, that depends. As it turns out, that is easier said than done for many of us. Draw a rough line across the country from San Francisco to Richmond, Virginia. If you live north of that line, it’s impossible to get enough sun exposure during the winter months to maintain adequate blood levels of vitamin D. And even during the summer, you may not be getting enough vitamin D. That’s especially true if you spend a great deal of time inside, out of the heat—or, ironically, if you’re particularly meticulous about using sunscreen, covering up, and seeking the shade when you’re outside.
Aging and racial background also affect vitamin D status. As we age, our skin doesn’t synthesize vitamin D as efficiently, and our kidneys are less able to convert vitamin D to its active hormone form. As for ethnicity, melanin—the pigment that gives skin its color—reduces the efficiency of vitamin D synthesis from sunlight; therefore dark-skinned individuals require even more sunlight to maintain adequate vitamin D levels.
Compounding the problem of lack of sunlight exposure is that there are not many dietary sources of vitamin D; supplements may be the most reliable way to achieve adequate vitamin D levels.
Why Vitamin D Is Critical for Bones
Vitamin D is actually a hormone that helps maintain bone strength by regulating the minerals calcium and phosphorus in bone. Vitamin D also regulates the absorption of calcium and phosporous from the intestines, thereby regulating bone turnover and mineralization. In children, a low blood concentration of vitamin D can lead to rickets. In adults, it leads to bone loss, osteoporosis, and an increase in fracture risk. Indeed, a number of studies have confirmed that vitamin D intake may help prevent osteoporosis in older adults and lower the risk of fractures.
The Role of Vitamin D in Preventing Falls
The lower risk of fractures may be due in part to another benefit of vitamin D: its role in muscle and leg strength. Leg weakness is a common symptom of severe vitamin D deficiency. But recent studies have found that even apparently healthy people may be negatively affected by less-than-optimal intake of vitamin D. In a study of more than 4,000 men and women age 60 years and older, people with lower vitamin D levels walked more slowly and had more trouble getting out of a chair than did those with higher levels. The study accounted for such variables as age, arthritis, and weight.
And in another study, of 1,200 older women, 400 IU of vitamin D per day cut a woman’s risk of being injured in a fall by more than 20%. Higher doses of vitamin D had an even greater effect.
How Much Vitamin D Do You Need?
The National Osteoporosis Foundation recommends 400-800 IU of vitamin D per day for those under age 50 and 800-1,000 IU pr day for men and women age 50 and over. Most people will need to rely on vitamin D supplements to ensure an adequate intake. (One note: Because of potential toxicity, the upper daily limit from supplemental vitamin D is currently set at 2,000 IU for all adults.)
Relying on fortified milk is an imperfect strategy, as studies over the years have found varying levels of vitamin D relative to the label claims. Moreover, many people don’t drink milk because of lactose intolerance, and cheese, yogurt, and other dairy foods often aren’t fortified. Many ready-to-eat cereals are fortified (albeit with modest amounts per serving), and some researchers are urging the government to institute mandatory fortification of more grain-based foods, such as breads and pasta. While the amounts are likely to be modest per serving, the overall number of servings per day might boost intake as much as 200 IU per day of vitamin D.
A serving of fatty fish—such as salmon, tuna, or mackerel—is another option for people interested in consuming foods high in vitamin D. In fact, it provides roughly two to three times more vitamin D than milk, depending on the particular fish. But taste and cost are considerations for many people.
Vitamin D Recommendations If You Have Osteoporosis
If you’ve been diagnosed with osteoporosis and are being treated with a bisphosphonate or another drug, that doesn’t excuse you from keeping an eye on your vitamin D intake. In a study of more than 1,500 postmenopausal women who were being treated for osteoporosis, researchers found that more than half of the women had inadequate vitamin D levels. This persisted across all age groups and geographic locations. The researchers noted that the women in the study, because of their osteoporosis diagnosis, “were expected to be more aware of the importance of vitamin D to bone health than the general population.” The fact that they let it slide might mean that they thought that whatever drug they were taking for osteoporosis was all they needed—or that vitamin D is still not getting the attention it deserves.
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