Back to basic: Get vitamins

This is almost like the return of tuberculosis or polio.

A health problem addressed long ago has re-emerged to threaten America’s children: a lack of vitamin D.

About 7.6 million children, adolescents and young adults — about 9 percent — have vitamin D levels so low they could be considered deficient. Another 61 percent — 50.8 million — have levels low enough to be insufficient, according to a new analysis of federal data.

“It’s astounding,” said Michal Mela-med of the Albert Einstein College of Medicine in New York, who helped conduct one of the analyses. “At first, we couldn’t believe the numbers. I think it’s very worrisome.”

Low vitamin levels were especially low among girls, adolescents and people with darker skin, making African-American teenage girls the group at the highest risk.

Anyone with low vitamin D levels is at risk for bone problems, heart disease, diabetes and other problems.

Researchers and others attribute the deficiencies to:

Children and young adults staying indoors more than ever to watch TV, play video games or play on computers. (Vitamin D is synthesized in the skin by exposure to sunlight.)

People covering up with sunscreen when they do go outdoors to protect from overexposure to sunlight. (Overexposure to sunlight is a cause of skin cancer, one of the most common forms of cancer.)

Children and adults drinking more soft drinks and less milk, which is fortified with vitamin D.

In the 1930s, the vitamin was added to commercially processed milk in order to reduce cases of rickets, which can cause bone malformations. That disease virtually disappeared — until the 1990s, when physicians began noticing a resurgence.

The new analysis of national data is viewed as dramatic by some, but not all, health experts. Some urge children to get outside and play more, while others continue to warn about sunlight and cancer.

We lean toward judicious amounts of sunlight and vigorous outdoor play, and not just to rev up vitamin D production in young bodies. Outdoor activities burn calories and build bone and muscle, counteracting today’s tendency toward childhood obesity. They also build at least some degree of understanding of, and hopefully sympathy for, the outdoor world of grass and trees and animals large and small.

Parents of course must make their own judgments about how much outdoor sunlight is good for their children.

But one thing’s for sure: Vitamin D is good for them — necessary, in fact. If children don’t get it through outdoor play, parents must find another way.

Millions of U.S. children have disturbingly low vitamin D levels, possibly increasing their risk for bone problems, heart disease, diabetes and other ailments, according to two new studies that provide the first national assessment of the crucial nutrient in young Americans.

About 9 percent of those ages 1 through 21 — about 7.6 million children, adolescents and young adults — have vitamin D levels so low they could be considered deficient, while another 61 percent — 50.8 million — have higher levels, but still low enough to be insufficient, according to the analysis of federal data being released Monday.

“It’s astounding,” said Michal Melamed of the Albert Einstein College of Medicine in New York, who helped conduct one of the studies published online by the journal Pediatrics. “At first, we couldn’t believe the numbers. I think it’s very worrisome.”

Low vitamin D levels are especially common among girls, adolescents and people with darker skin, including African Americans, according to the analysis of a nationally representative sample of more than 6,000 children. For example, 59 percent of black teenage girls were vitamin D deficient, Melamed’s study found.

The researchers and others blamed the low levels on a combination of factors, including children spending more time watching television and playing video games instead of going outside, covering up and using sunscreen when they do go outdoors, and drinking more soda and other beverages instead of consuming milk and other foods fortified with vitamin D.

“This appears to be another result of our unhealthy lifestyles, including a sedentary society that doesn’t go out in the sun much,” Melamed said.

The analysis and an accompanying federal study also found an association between low vitamin D levels and increased risk for high blood pressure, high blood sugar and a condition that increases the risk for heart disease and diabetes, known as the metabolic syndrome.

Taken together, the studies provide new evidence that low vitamin D levels may be putting a generation of children at increased risk for heart disease and diabetes, two of the nation’s biggest health problems that are also increased by the childhood obesity epidemic.

“These are very important studies,” said Richard Rivlin, a past president of the American Society for Clinical Nutrition who was not involved in the research. “They show the number of people who have high rates of vitamin D deficiency is really very frightening.”

Other researchers urged caution.

“The bottom line is that these numbers are interesting,” said Frank Greer of the University of Wisconsin in Madison, who served on a panel that recently doubled the American Academy of Pediatrics recommendations for daily vitamin D intake. “But I’m not ready to make a great hue and cry until we have more data. I think we should use them for further research to determine their significance.”

The findings come as the National Academy of Sciences Institute of Medicine is reviewing the federal government’s official guidelines for recommended daily intake of vitamin D. A public hearing is scheduled as part of that process at the National Academy of Sciences in Washington on Tuesday.

The most well-known health problem associated with vitamin D deficiency is rickets, which can cause bowlegs and other bone malformations. Milk was fortified with vitamin D in the 1930s to eliminate the disorder. But during the 1990s, doctors in several cities reported unusual numbers of cases, primarily in babies being breast-fed and mostly among African American children. A number of studies began to indicate that deficiencies might be common among adults — small studies found the same among children — and that deficiencies may be associated with a host of health problems. But the new studies are the first to examine the issue nationwide in young people.

Those who had low vitamin D levels were more likely to have lower levels of a hormone associated with healthy bones, higher blood pressure levels and lower levels of “good” cholesterol, which helps protect against heart disease, Melamed and her colleagues found.

In the second study, Jared Reis of the National Heart, Lung and Blood Institute analyzed data from about 3,500 adolescents from surveys conducted between 2001 and 2004, and found that compared with those with higher vitamin D levels, those with the lowest levels had more than double the risk of having high blood pressure and blood sugar and about four times the risk for the metabolic syndrome, a group of symptoms that increases the risk for heart disease and diabetes.

Some long-time proponents of the health benefits of vitamin D seized on the findings to urge parents to ask doctors to test their children’s vitamin D levels, consider increasing vitamin D supplementation or make sure children spend more time outdoors to boost their vitamin D levels.

“The sun has been demonized for years and as a result, people have avoided any direct exposure to sunlight,” said Michael Holick of the Boston University School of Medicine. “I think that’s the wrong message.”

But others said they worried that encouraging children to spend more time in the sun could lead to more skin cancer, which is already the leading cause of cancer.