Written by: Valerie Latona on Friday, March 15th, 2013

Known as the sunshine vitamin, vitamin D is actually a hormone produced by the body in response to sunlight. It is also occurs naturally in a few foods—including some fish, fish liver oils, and egg yolks—and in fortified dairy and grain products. It’s hard, though, to get enough vitamin D through food alone—unless you want to take a tablespoon of cod liver oil every day (it has 1,360 IU of D per tablespoon)! Ummm…no thanks!

But, according to The Mayo Clinic, the major biologic function of vitamin D is to maintain normal blood levels of calcium and phosphorus. Vitamin D aids in the absorption of calcium, helping to form and maintain strong bones—why getting enough calcium is only half of the strong bones equation. But preliminary research also indicates the importance of vitamin D for overall health and wellbeing:

1) It contributes to a healthy heart A recent analysis of research, published in the journal Osteoporosis International just this month (March 2013), found that there’s a link between low vitamin D levels and “stroke, myocardial infarction, diabetes mellitus, hypertension, and heart failure.” Enough reason for me to supplement with D…but if you need more proof, read on.

2) It may help stop the growth of cancer Preliminary research suggests that vitamin D has an anti-cancer benefit. It may stop the growth and progression of cancer cells and may be beneficial during cancer treatment, too.

3) It plays a critical role in youthful skin A recent study in the journal Dermo-Endocrinology, found that vitamin D seems to help regulate aging in many tissues, including the skin. Plus, researchers determined that “laboratory investigations have now convincingly shown that vitamin D compounds protect the skin against the hazardous effects of … ultraviolet (UV) radiation.”

4) It may help with hormonal problems Vitamin D influences the functions of hormones in body, including insulin, serotonin, and estrogen—hormones involved with health conditions such as diabetes, blood pressure, heart disease, stroke, depression, and premenstrual syndrome.

5) It’s key for healthy iron levels in the blood One study—conducted by Gangnam Severance Hospital and Yonsei University College of Medicine, both in Seoul, Korea—found that vitamin-D-deficient Korean women had a higher risk of anemia.

6) A deficiency of D may contribute to obesity Some research shows that a vitamin D deficiency can interfere with the “fullness” hormone leptin, which signals the brain that you’re full and should stop eating.

7) It may help control inflammation Vitamin D may help control the inflammation involved with periodontal disease, rheumatoid arthritis, and osteoarthritis.

Also, some research suggests that vitamin D may help strengthen the immune system—why I’m sure to take vitamin D during the cold and flu season or when I feel that I might be coming down with something. It’s also critical for breastfeeding moms: A recent review of studies, published in the Journal of Human Lactation, found that “Maternal vitamin D insufficiency during lactation, related to lack of sun exposure and minimal intake of vitamin D from the diet, contributes to low breast milk vitamin D content and, therefore, infant vitamin D deficiency.”

How do you get enough vitamin D?

Well, being in sunlight is the best way to get enough vitamin D. The sun’s energy turns a chemical in your skin into vitamin D₃, which is carried to your liver and then to your kidneys to transform it to active vitamin D. But no one should sit unprotected in the sun for long because doing so speeds up premature aging of the skin and can cause skin cancer.

The next best step is to eat plenty of foods with vitamin D, including fortified milk. But most experts agree that it’s hard to get enough D from food alone. (For adults under age 50, the National Osteoporosis Foundation [NOF] recommends 400 to 800 IU of vitamin D and 800 to 1,000 IU for adults age 50 and older. And for children, it’s generally recommended that infants and children get 400 to 600 IU daily.)

So the next step is usually to take a supplement.  Most multivitamins contain vitamin D—but you can also take a separate D supplement particularly if you’re deficient, as I am (in which case, your doctor may recommend you take a much higher dosage of D than what’s recommended by the NOF to bring up your levels). But this is key: Opt for vitamin D₃ over D₂, because research shows that D₃ is 87 percent more potent in raising and maintaining vitamin D concentrations. (If you’re vegan, though, know that most vitamin D₃ or cholecalciferol comes from animal sources [see picture above, and copy below for an exception], but vitamin D₂ or ergocalciferol comes from plant sources.)

An important note: you can take vitamin D supplements with or without food. While your body needs vitamin D to absorb calcium, you do not need to take vitamin D at the same time as a calcium supplement.

New sources of vitamin D

Ingenious experts at the skin-care brand SkinAuthority developed—with Dole Nutrition Institution—a vitamin D-fortified Whole Food Spice Powder. Just sprinkle it on your food and you can get up to 600 IU of vitamin D instantly. (Its nondescript taste easily blends with the flavors of a meal.) But why this is so brilliant: it’s a form of vitamin D₃ that’s 100% vegan—so now vegans can have their D₃ without eating animal-based products (or taking animal-based supplements)! So great! This powder also comes with an oil-free Vitamin D-based Topical Elixir ($79 for both powder and elixir; skinauthority.com) that you apply to skin to help nourish it. (It also contains vitamins A, E, and K.) I use both—and love them!

And because we know that vitamin D is so important for the skin (see point #3, above), you definitely want to be using a D serum on your skin—either this one from SkinAuthority or the one created by Manhattan board-certified dermatologist Dennis Gross, M.D.: Dr. Dennis Gross Skincare Active Vitamin D Serum ($65; dgskincare.com).

So be sure to get enough vitamin D daily. It’s a simple, easy way to do your body—and your health—a huge favor.