Are you getting enough vitamin D?

Vitamin D is well known to be important for bone health. It has also been studied for its possible link to a lower risk of a wide variety of conditions. But although you can get vitamin D from food, supplements, or spending time in the sun, many people don’t get enough of it.

Why? Maybe you’re not getting enough from your diet. Other things that affect your body’s ability to produce vitamin D include season, time of day, where you live, air pollution, cloudiness, sunscreen, exposed body parts, skin color and age. Dermatologists recommend its use sunscreen and obtaining vitamin D from food and supplements instead of risking the sun’s harmful rays.

The role of vitamin D

Vitamin D is naturally present in few foods. But it is found in many fortified foods.

Since 1930, almost all cow’s milk in the US has been fortified with 100 IU of vitamin D per cup. Food manufacturers fortify other foods such as yogurt, cereal, and orange juice.

Ideally, vitamin D is added to a food or drink that contains it calcium. Vitamin D is necessary for the maximum absorption of calcium from the intestines, helping to build strong bones and teeth.

Vitamin D deficiency is associated with low bone mass and osteoporosiswhich is estimated to affect 10 million adults over the age of 50 in the US,” says Atlanta rheumatologist Eduardo Baetti, Ph.D. He says many of his patients — especially the elderly and those with dark skin — have low levels of vitamin D because the sun is not a reliable source.

How Much Vitamin D Do You Need?

The National Institutes of Health recommends that people get this amount of vitamin D daily:

  • Birth to 12 months: 10 micrograms (mcg) or 400 international units (IU)
  • Age 1-70 years: 15 mcg (600 IU)
  • Over 71 years: 20 mcg (800 IU)

Older people need more vitamin D because as they age, their skin does not produce vitamin D efficiently, they spend less time outdoors and tend not to get enough vitamin D.

Best sources of vitamin D

The sun is an excellent source of vitamin D, but it is difficult to quantify how much vitamin D you get from time in the sun, and the risk of skin cancer may outweigh the benefits.

Food comes first, says Baylor College of Medicine nutritionist Kelly Hawthorne. “Supplements can fill in the gaps, but it’s always better to try to meet your nutritional needs with foods that contain fiber, phytonutrientsand much more,” she says.

Unless you enjoy a diet that includes fatty fish or cod liver oil, it can be difficult to get enough vitamin D naturally without eating fortified foods or taking supplements. “The main dietary source of vitamin D comes from fortified dairy products, along with some yogurts and cereals,” says Hawthorne. Mushrooms, eggs, cheese and beef liver contain small amounts.

How much is too much?

Because vitamin D is a fat-soluble vitamin, it can build up in the body. So it’s possible to get too much of it.

The National Institutes of Health says these are the upper limits per day for vitamin D:

  • Birth to 6 months: 25 mcg (1000 IU)
  • Infants 7-12 months: 38 mcg (1500 IU)
  • Children 1-3 years: 63 mcg (2500 IU)
  • Children 4-8 years: 75 mcg (3000 IU)
  • Children 9-18 years: 100 mcg (4000 IU)
  • Adults 19 and older: 100 mcg (4,000 IU)
  • If you are pregnant or breastfeeding: 100 mcg (4000 IU)

“There is potential for harm if you overdose supplements over 4,000 IU/day, but there is no fear of overdosing from the sun because your skin acts as a regulatory system, allowing the production of just the right amount of vitamin D,” says Patsy Brannon, PhD, a Cornell University professor of nutritional science who has served on an Institute of Medicine committee revising vitamin D recommendations.

Acceptable levels of vitamin D in the blood

Your healthcare provider can check your vitamin D blood level with simple blood test.

Part of the confusion about whether or not you are getting enough vitamin D may be the definition of an acceptable blood level of vitamin D, clinically measured as 25-hydroxyvitamin D [25(OH)D].

Using blood levels of vitamin D is the best estimate of adequacy, which takes into account dietary intake and sunlight, but experts differ on what that level should be.

“A blood 25(OH)D level of at least 20 nanograms/ml was used by the IOM committee to set vitamin D recommendations because this level has shown adequacy for a wide variety of indicators of bone health,” Brannon says.

The Endocrine Society’s practice guidelines, as well as many laboratories and experts, recommend a minimum vitamin D blood level of 30 nanograms/ml as an acceptable level.

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