BY JENNIFER MOTL
As we age, our skin’s ability to produce vitamin D can drop by 50 percent, according to research at Harvard Medical School, so it’s crucial to get enough vitamin D.
Vitamin D has been a popular supplement for the last several years, for good reason. While vitamin D is best known for protecting bones, it also may reduce the risks of suffering Alzheimer’s disease, strokes and cancer.
People often turn to supplements because it’s hard to get enough vitamin D from food. Most adults need between 600 and 800 units of vitamin D a day—and possibly more depending on their bone health.
DIABETICS AND BONES
It’s especially important for people with diabetes to get enough vitamin D. That’s because diabetes can increase the risk of osteoporosis and fractures, according to many studies.
Even when their bone density tests are normal, people with diabetes still have a higher risk for fracture due to changes in the bone structure, according to Canadian researchers.
Getting enough vitamin D and calcium reduces the risk of most bone fractures by about 18 percent, according to Belgian researchers.
Just to be clear, vitamin D is not the only remedy for osteoporosis. Physical activity and medicines are critical for building up bones.
MEMORY AND STROKES
Beyond the bones, vitamin D works in the brain, too. Vitamin D stimulates cells to clean up memory-damaging plaques in the brain, according to scientists at University of California, Los Angeles.
The researchers found that combining vitamin D3 with curcumin, from the spice turmeric, stimulated helpful cells called macrophages. These cells destroy the harmful amyloid beta plaque that accumulates in the brain of people with Alzheimer’s disease.
Vitamin D intake also can affect the risk of stroke in some people. White people with vitamin D deficiency had double the risk of strokes compared with white people with normal vitamin D levels, according to data from the Third National Health and Nutrition Examination Survey. African–Americans with low vitamin D did not have higher stroke risk, for unknown reasons.
WHO’S AT RISK
Kidney problems, digestive problems such as Crohn’s disease, obesity and age put folks at higher risk for vitamin D deficiency. Having dark skin and taking certain medications for seizures and corticosteroids (such as prednisone) also affect vitamin D levels.
Dark skin naturally blocks some of the UV rays that produce vitamin D. That’s likely why African–Americans have the highest rates of vitamin D deficiency, at 31 percent, according to a report released this month by the Centers for Disease Control. About 12 percent of Mexican–Americans and 3 percent of whites of all ages had deficiencies.
Frail elderly folks are especially at risk for vitamin D deficiency. Not only does their skin produce less vitamin D, but they are often indoors. One study of Austrian women in nursing homes found that 93 percent were deficient in vitamin D.
If you think you might be at risk, ask your doctor about a blood test of your vitamin D level.
It’s challenging to get enough vitamin D from sunlight or food.
Sunlight shining on the skin causes vitamin D to form inside the body. But much of the year, the sun is too low in the sky to produce significant vitamin D for Americans anywhere but in the Deep South. And there, the risk of sunburn and skin cancer can be an issue.
As for food, fatty fish such as sockeye salmon (450 units vitamin D in 3 ounces) are good sources, as is fortified milk (100 units per cup). Mushrooms and fortified eggs contain some vitamin D. However, most foods are extremely low in vitamin D, making it hard to get to the daily goal of 600 to 800 units from food alone.
Because of the risks of skin cancer and the difficulty of getting enough vitamin D from foods, many physicians recommend vitamin D supplements.
GETTING ENOUGH D
Adults under 70 years of age need about 600 units of vitamin D daily, according to government guidelines. Once we reach age 70, needs rise to 800 units of vitamin D daily. People with osteoporosis may need more than 1,000 units, according to Spanish researchers.
Daily vitamin D is better absorbed than megadoses taken every week or month, according to Australian researchers.
It’s important to get adequate calcium when taking vitamin D. And Greek research suggests that getting adequate vitamin K along with vitamin D and calcium is even more effective and keeping bones strong. The Greek researchers found that the combo increased bone density in the spines of middle-age and older women.
Talk with your physician before taking any supplements.
Getting enough vitamin D is critical at every age to protect bones and memory and to help shield against cancer.
Jennifer Motl is a registered dietitian. Formerly of Fredericksburg, she now lives in Wisconsin. She welcomes reader questions via her website, brighteating.com, or by email at firstname.lastname@example.org.
Here’s another reason getting enough vitamin D matters: Low vitamin D levels have been linked to higher rates of some cancers. For example, women with the lowest levels were more than four times more likely to develop colon cancer than women with normal levels, according to the Women’s Health Initiative Calcium and Vitamin D Clinical Trial.
Also, taking calcium–vitamin D supplements reduced the risk of breast cancer in a study of 36,000 women who were middle-aged and older. They took 1,000 milligrams of calcium and 400 units of vitamin D.
An important note: Some breast cancer drugs can weaken bones, One study found that of women being treated with drugs called aromatase inhibitors, a whopping 35 percent were deficient in vitamin D. Deficiency was even more common in women of color and women who were overweight.