Vitamin D facts
Figuring out all the factors that can affect your vitamin D level is complicated, says Harvard Medical School. Your body makes vitamin D when sunlight hits the skin. You can also get the vitamin from food or by taking a supplement.
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A number of factors influence a person's vitamin D levels. Here are six important ones.
Where you live. The farther away from the equator you live, the less vitamin D-producing UVB light reaches the earth's surface during the winter.
Air quality. Carbon particles in the air from the burning of fossil fuels, wood and other materials scatter UVB rays, diminishing vitamin D production.
Use of sunscreen. Sunscreen prevents sunburn by blocking UVB light. Theoretically, that means sunscreen use lowers vitamin D levels. But as a practical matter, very few people put on enough sunscreen to block all UVB light, so sunscreen's effects on vitamin D might not be that important.
Weight. Body fat sops up vitamin D, so it's been proposed that it might provide a source of the vitamin when intake is low or production is reduced.
Age. Compared with younger people, older people have lower levels of the substance in the skin that UVB light converts into the vitamin D precursor.
Reconsider chick lit
You might want to think twice before revisiting that old copy of "Bridget Jones's Diary."
Images in the media have long been blamed for low self-esteem among women, but a new report claims that the written word -- specifically, "chick lit" -- might be just as damaging, says The Washington Post.
Chick lit, the fiction genre aimed mainly at women, often features self-doubting heroines searching for the trifecta of love, career and a smaller pant size. According to a new study, protagonists who express negative feelings about their weight or body shape can make readers feel bad about themselves.
The researchers, from Virginia Tech, selected two popular novels -- Emily Giffin's "Something Borrowed" and Laura Jensen Walker's "Dreaming in Black and White" -- that feature female protagonists with a healthy body weight, but low self-esteem. They then rewrote passages from the novels, changing descriptions of the characters' sizes and comments reflecting self-esteem.
More than 150 college-aged women read the passages and rated how they felt about themselves after each. The researchers found that women who read versions about a slim character reported feeling less sexually attractive than participants who read about a heavier character. Those who read about an insecure heroine felt more concerned about their own weight.