Are You Getting Enough Vitamin D?

Nearly 75 percent of Americans are deficient in vitamin D, according to a NIH-funded study. That’s dangerous because lack of the sunshine vitamin raises risk for a wide range of diseases, from multiple sclerosis to stroke, heart attack, kidney disease, autoimmune diseases, infertility, asthma, and breast, uterine, and prostate cancer.

What’s more, the most extreme form of deficiency—rickets, the crippling children’s bone disease—has reappeared in Britain and the U.S., where it was considered to be eradicated with the advent of fortified milk decades ago.

Most people don’t know if they’re short on this essential nutrient, which helps the body absorb the calcium needed for strong bones. Actress Gwyneth Paltrow was literally diagnosed by accident: After she broke her leg, doctors discovered that she had osteopenia, a precursor to osteoporosis, the brittle-bone disease more often found in older women. Her vitamin D levels, she told her fans, were the lowest her doctors had ever seen.

Read more about rickets and Vitamin D deficiency. 

What’s behind the deficiency epidemic?

Sunshine, once our main source of D, is no longer enough, particularly for people with dark skin who may need 20 to 30 times more exposure than those with fair skin. And most of us don’t soak up many rays because we work indoors and slather on sunscreen before venturing outside.

Ironically, our zeal to prevent skin cancer leaves prey to deficiency, since properly applied sunscreen blocks most of the skin’s production of vitamin D. In fact, people who use sunscreen daily are more likely to be deficient than those who don’t, Harvard School of Public Health reports.

However, that doesn’t mean you should head to the nearest tanning booth and start baking. The American Academy of Dermatology advises continuing to use sunscreen daily and get your vitamin D from food or a supplement.

Find out how to choose a healthy sunscreen. 

Who is most at risk?

If you avoid dairy foods, perhaps due to lactose intolerance, or follow a vegan diet, your risk of deficiency goes up. Vitamin D is naturally found in relatively few foods. Most of them—such as fish, fish oils, and egg yolks—come from animals. Vitamin D is also found in fortified foods, including dairy products, orange juice and cereals, but you’d have to drink 10 glasses of fortified milk a day to get your daily dose of  D.

Older and obese people are also at higher risk for deficiency, as are babies who are exclusively breastfed.

How can you tell if you have vitamin D deficiency?

You may experience bone pain, muscle weakness, headaches or unexplained fatigue, but most symptoms are subtle. You’ll need a blood test to know for sure. The 25-hydroxyvitamin D test measures the amount of vitamin D circulating in the blood.

For the most accurate results, schedule the test in late fall to late spring when you haven’t been exposed to sunlight for at least six weeks.

How much D do you need?

Some health experts advocate 2000 IU a day. In 2010, the Institute of Medicine recommended daily levels of 600 IU for children ages one and up and adults under age 70, and 800 IU for older adults, based on an analysis of nearly 1,000 studies.

Maximum daily intakes for adults can safely go up to 4,000 IU, according to the IOM, which advises an upper limit of 1,000 to 2,500 for kids, depending on age.  

What kind of health problems does deficiency cause?

Ten million Americans have osteoporosis, putting them at risk for fractures, deformity, disability, and loss of height; and another 34 million are at risk. The National Osteoporosis Foundation estimates that about half of women over age 50—and one in four men—will break a bone due to this disease.

Breast-fed infants who don’t receive vitamin D supplements or fortified food are particularly vulnerable to rickets. Chronic deficiency takes months of supplements and sunlight exposure to rebuild bone and the nervous system.

A 2011 study of more than 10,000 patients fount that those with low blood levels of D were twice as likely to have diabetes, 40 percent more likely to have high blood pressure, and about 30 percent more likely to suffer from cardiomyopathy—a diseased heart muscle—than those with normal levels.

The myriad health problems linked to deficiency may explain why patients in the study had triple the death rate from any cause than those who weren’t deficient, the researchers reported. Conversely, people who took vitamin D supplements had a 60 percent lower risk of death during the study period.

Learn how Vitamin D can help prevent falls.

Is too much vitamin D harmful?

Vitamin D toxicity is rare, but can have serious effects, particularly if you have other health problems, such as kidney or liver disease, the Mayo Clinic reports. The main risk is a buildup of excessive calcium in your blood, which can lead to heartbeat abnormalities. A new study also reports that both too little and too much vitamin D can harm the heart by increasing cardiovascular inflammation, creating a greater risk of cardiac problems, such as heart attack.

The researchers don’t know why high levels of D appear to be bad for the heart, but advise using supplements cautiously and sticking to the dosage advised by your doctor.

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