“Even major sun exposure does not guarantee vitamin D adequacy,” Binkley says. “There are large differences between individuals; most people still need supplements.”
What about multivitamins and fortified dairy foods?
Vitamin D is measured in international units (IUs). Amounts in multivitamins can vary widely from 50– 1,000 IUs. The U.S. Food and Nutrition Board recommends a vitamin D intake of 400 IUs a day. Experts, however, think that even 1,000–2,000 IUs a day may be a conservative estimate for older adults, especially women.
Getting that much vitamin D from food is practically impossible. “It’s true that many foods are fortified with vitamin D; but many that you would expect to be are not—like cheese, ice cream, and yogurts targeted to adults,” Binkley says.
“Foods cannot be fortified with more than 100 IUs of vitamin D per serving, so you can’t get enough D through diet alone. “In addition, many people think cod liver oil and other fish oils are good choices for vitamin D. But while cod liver oil is high in vitamin D, it’s also high in vitamin A—and too much vitamin A likely has a detrimental effect on bone health,” Binkley says.
Is too much vitamin D toxic?
Vitamin D is known as a fat-soluble vitamin, which means it’s a compound that can be stored in the liver and fatty body tissues. “Vitamin D is not so much stored in fat; rather, it’s sequestered,” Binkley says. “Studies indicate that it doesn’t build up the way people think—once it goes into fat, it doesn’t appear that we can get it back out to be used. “Toxicity cases have involved people taking doses of more than 10,000 IUs a day, so you’re very safe if you’re taking 1,000–2,000 IUs a day,” Binkley says.
Different kinds of vitamin D
“The only prescription vitamin D available in the U.S. is vitamin D2, or ergocalciferol,” Binkley says. “Multivitamin supplements contain either D2 or D3 (cholecalciferol).” Some studies indicate that vitamin D3 may be the type that the body uses best. Talk to your doctor about what’s best for you.
“Non-prescription preparations of vitamin D3 are available in some stores and online, but the doses are not standardized—you may be getting significantly more or less than what the bottle says,” according to Binkley.
Have your levels checked
You might have heard that lab testing for vitamin D is not accurate. “There used to be significant variation in laboratory testing, even as recently as four years ago,” Binkley says. “But methods have improved, and today’s testing is quite reliable and consistent.”
Even if you are already taking osteoporosis medications or calcium/vitamin D supplements, you still may be vitamin D deficient. “Vitamin D deficiency, like osteoporosis, tends to be one of those silent conditions— you don’t feel it; you don’t know you’re deficient,” Caudill says.
“We’ve been very vigilant in our screening of residents with osteoporosis or osteopenia [low bone mass],” says Mary Norman, M.D., Erickson Health physician at Highland Springs, an Erickson-built and -managed community in Dallas, Tex. “A simple blood test can let your doctor know if you are vitamin D deficient. Taking an extra vitamin D supplement might be all you need to help build stronger bones.”