CBS News Medical Correspondent Dr. Jennifer Ashton says low vitamin D levels mean those kids have a higher risk of developing heart, bone and other problems.
The study was conducted by researchers at Albert Einstein College of Medicine of Yeshiva University in New York. It appears in the journal Pediatrics.
Low vitamin D levels were found to be especially common among children who were older, female, African-American, Mexican-American, obese, drank milk less than once a week, or spent more than four hours a day watching TV, playing videogames, or using computers.
On "The Early Show" Monday, Ashton pointed out that the American Academy of Pediatrics recommends that infants, children, and teens get 400 IU (international units) a day. That's equal to four cups of milk or an amount you can easily get in one supplement.
"We expected the prevalence of vitamin D deficiency would be high, but the magnitude of the problem nationwide was shocking," says lead author Juhi Kumar, M.D., M.P.H., a fellow in pediatrics at Children's Hospital at Montefiore Medical Center, The University Hospital and Academic Medical Center for Albert Einstein College of Medicine.
She says diet, sunshine (without overexposure) and supplements are efficient means of raising Vitamin D levels.
The National Institutes of Health and American Dietetic Association say very few foods in nature contain Vitamin D. The flesh of fish such as salmon, tuna, and mackerel, and fish liver oils, are among the best sources. Small amounts of vitamin D are found in beef liver, cheese, and egg yolks. Some mushrooms provide vitamin D2 in variable amounts.
BEST FOODS FOR VITAMIN D:
Cod liver oil, 1 tablespoon 1,360 IU
Salmon, cooked, 3.5 ounces 360 IU
Mackerel, cooked, 3.5 ounces 345 IU
Tuna fish, canned in oil, 3 ounces 200 IU
Sardines, canned in oil, drained, 1.75 ounces 250 IU
Milk, nonfat, reduced fat, and whole, vitamin D-fortified, 1 cup 98 IU
Margarine, fortified, 1 tablespoon 60 IU
Ready-to-eat cereal, fortified with 10% of the DV for vitamin D, 0.75-1 cup (more heavily fortified cereals might provide more of the DV) 40 IU
Egg, 1 whole (vitamin D is found in yolk) 20 IU
Liver, beef, cooked, 3.5 ounces 15 IU
Cheese, Swiss, 1 ounce 12 IU
ASHTON DESCRIBED THREE VITAMIN D KID-FRIENDLY OPTIONS:
SALMON BURGER: a twist on a hamburger and easy to eat as a sandwich. One three-and-a-half ounce serving size of salmon and a glass of milk can give you enough Vitamin D to fulfill your daily recommended amount.
TUNA CASSEROLE is loaded with Vitamin D: The tuna is rich in vitamin D and it contains dairy, which has vitamin D and calcium; both are good for a child's bone development. It's also topped with Swiss cheese (a bonus of Vitamin D, which it contains naturally).
VITAMIN D SMOOTHIE: This could be great for a breakfast or snack - it has fortified orange juice, milk, yogurt - all of which can give your child a boost of Vitamin D at the beginning of their day.
WHAT ABOUT SUNSCREEN AND LOWER AMTS OF VITAMIN D: IS THERE A CONNECTION?
Kumar told CBS News it's "hard to say," noting "We didn't have data on sunscreen in our study, but we know that sunscreen levels have gone up and vitamin D has gone down. I'm sure they're related. For parents, they need to know their kid's skin: If they get red after 10 minutes, don't forgo sunscreen. But if they can withstand sun without getting burned or damaging their skin too much, let them play a little bit without the sunscreen, then apply it. The body was meant to get vitamin D from the sun.
The NIH says, "It has been suggested by some vitamin D researchers, for example, that approximately 5-30 minutes of sun exposure between 10 AM and 3 PM at least twice a week to the face, arms, legs, or back without sunscreen usually lead to sufficient vitamin D synthesis. Individuals with limited sun exposure need to include good sources of vitamin D in their diet or take a supplement. Despite the importance of the sun to vitamin D synthesis, it is prudent to limit exposure of skin to sunlight. UV radiation is a carcinogen responsible for most of the estimated 1.5 million skin cancers and the 8,000 deaths due to metastatic melanoma that occur annually in the United States.
WHAT SHOULD PARENTS KNOW ABOUT SUPPLEMENTS?
Most multivitamins are fortified with 400 IU of Vitamin D, Ashton says. Check the label to make sure the vitamin you choose is made with the D3 form (it may be listed as cholecalciferol). Kumar says, "We found very few kids were taking the vitamin D supplements. A multi-vitamin is fine to take it -- and may taste better too (because of the variety of flavors)."