What foods are natural sources of vitamin D?
Very few foods are natural sources of vitamin D. Foods that do contain vitamin D include fatty fish, fish liver oils (cod liver oil) and eggs from hens that have been fed vitamin D. Almost all the vitamin D intake from foods comes from fortified milk and other foods, such as breakfast cereals, that have been fortified with vitamin D.
I spend a lot of time outdoors. Don't I get enough vitamin D from sun exposure?
Not likely. As people age, they often lose the ability to make Vitamin D3. In fact, Americans age 50 and older are believed to be at increased risk of developing vitamin D deficiency. Furthermore, season, geographic latitude, time of day, cloud cover, smog, and sunscreen can greatly affect UV ray exposure and consequently alter vitamin D synthesis.4
My multiple vitamin formula contains vitamin D2. Is that the same as vitamin D3?
No. The two forms of vitamin D used for nutritional supplementation are the secosterols ergocalciferol (vitamin D2) and cholecalciferolVitamin D3. Vitamin D2 is derived from fungal and plant sources. Most of our Vitamin D3 is produced in our bodies by the action of sunlight on 7-dehydrocholesterol in the skin. Vitamin D3 is superior to vitamin D2, as it has been shown to raise blood levels 70% better than D2.3
Why do I need vitamin D?
Your body must have vitamin D to absorb calcium and promote bone growth. Too little vitamin D results in soft bones in children (rickets) and fragile, misshapen bones in adults (osteomalacia). You also need vitamin D for other important body functions. Vitamin D deficiency has now been linked to breasy cancer, colon cancer, prostate cancer, heart disease, depression, weight gain, and other maladies. These studies show that people with higher levels of vitamin D have a lower risk of disease, although they do not definitively prove that lack of vitamin D causes disease -- or that vitamin D supplements would lower risk.
How can I get enough vitamin D?
Thirty minutes of sun exposure to the face, legs, or back -- without sunscreen -- at least twice a week should give you plenty of vitamin D.
But this much direct sun exposure might also expose you to potentially dangerous levels of cancer-causing UV radiation. And unless you live in the South or Southwest, you probably won't get enough sunlight during the winter months for your body to make enough vitamin D. The American Academy of Dermatology recommends against getting vitamin D from unprotected exposure to sunlight.
It's probably a better idea to get vitamin D from foods or from supplements.
Will a vitamin D test tell me if I need more vitamin D?
Yes. As part of your regular blood test, your health practitioner should order a test for 25-hydroxyvitamin D (25-OHD).
Everyone agrees that anyone with a 25-OHD level of less than 15 ng/mL or 37.5 nmol/L (depending on the units reported by a lab) needs more vitamin D. A 2002 study found that 42% of African-American women of childbearing age had vitamin D levels below 15 ng/mL.
The U.S. National Institutes of health notes that 25-OHD levels over 30 ng/mL are optimal, and that there is "insufficient data" to support recommendations for higher levels.
The Vitamin D Council considers the ideal 25-OHD level to be between 40 ng/mL and 70 ng/mL.
Which foods contain vitamin D?
Surprisingly few foods contain vitamin D -- unless it's added to the food. That's because your body is built to get vitamin D through your skin (from sunlight) rather than through your mouth (by food). But once your body has enough, it doesn't matter whether you got it through your skin or through your stomach.
There are three vitamin D super foods:
- Salmon (especially wild-caught)
- Mackerel (especially wild-caught; eat up to 12 ounces a week of a variety of fish and shellfish that are low in mercury)
- Mushrooms exposed to ultraviolet light to increase vitamin D
Other food sources of vitamin D include:
- Cod liver oil (warning: cod liver oil is rich in vitamin A; too much may be bad for you)
- Tuna canned in water
- Sardines canned in oil
- Milk or yogurt -- regardless of whether it's whole, nonfat, or reduced fat -- fortified with vitamin D
- Beef or calf liver
- Egg yolks
- Fortified breakfast cereals
How much vitamin D do I need?
The current recommended daily dose of vitamin D is 200 IU for people up to age 50, 400 IU for people aged 51 to 70, and 600 IU for people over age 70.