Many Americans are sleep deprived, exercise deprived and fiber deprived. Now it turns out they are probably vitamin D deprived as well.

An American Academy of Pediatricians study found that people are getting far less vitamin D than they need. Especially at risk are older children and teens who live in northern climates. While the importance of vitamin C is widely understood, and many people take it in supplement form, the need for vitamin D may have been dramatically under estimated, says Dr. Susan Sullivan, who teaches food science and human nutrition at the University of Maine.

Some think the deficiency is a “public health emergency,” Dr. Sullivan said. Vitamin D helps supports the body’s immune system and has been shown to stave off certain kinds of cancer, diabetes, multiple sclerosis, and possibly colds and flu, among other diseases. Some research has suggested vitamin D deficiency leads to depression, though Dr. Sullivan cautions there are no conclusive findings on that theory.

For years, the federal government recommended that people of all ages get 200 international units of vitamin D each day, the amount that prevents rickets, a disease that results in a softening of bones in children.

While government standards have not yet changed, the American Academy of Pediatricians is now recommending that children and teenagers receive 400 units of vitamin D daily. But Dr. Sullivan and others in the field say 1,000 international units is a far better standard.

Vitamin D is synthesized by exposing skin to the sun. Just 10 minutes of bare-skin exposure — arms, legs, hands or face — to midday sun each day produces enough vitamin D, she said. The body stores the vitamin in fat. But for those living in Maine, the sun is too low from November to March; the atmosphere filters out the ultraviolet B rays that synthesize the vitamin. Without the sun, children typically get vitamin D by drinking milk or orange juice fortified with it; cereals, and some margarines and yogurts also add vitamin D.

But the problem is that the amount added to those foods is tied to the 200 international unit standard, so someone would have to drink 20, 8-ounce glasses of milk a day to get the amount of vitamin D Dr. Sullivan believes is needed. The answer is to buy the vitamin as a pill.

“I think we need widespread use of supplements,” she says. The supplement can be purchased in 1,000 IU form in stores like Wal-Mart for about $5, she says.

As a memory aid, just link the end of Daylight Savings Time with vitamin D supplement time.