Reading Food Labels
Daily Values (DV) are on nutrition fact panels to help consumers compare nutrients in products and to choose a healthy diet. The DV for vitamin D is currently set at 400 IU by the FDA, which is less than the recommended 600 IU.
Hawthorne's advice: "Do the math: When one serving says it meets 100% DV, you still need an additional 200 IU to satisfy your requirement."
Amount of vitamin D in sample food sources:
- 1 Tbsp cod liver oil: 1,360 IU
- 3 oz. salmon: 800 IU
- 8 oz. fortified milk:100 IU
- 8 oz. fortified orange juice: 100 IU
- 3 oz. irradiated mushrooms: 400 IU
How Much Is Too Much?
Vitamin D is a fat-soluble vitamin. Fat-soluble vitamins can build up in the body and are not as easily excreted as water-soluble vitamins. The IOM committee set a level of 4,000 IU as the ‘tolerable upper limit' or the maximum amount that is safe to consume daily.
Vitamin D researcher and Creighton University professor Robert Heaney, MD, agrees with the new level but would like to see it even higher.
"I am delighted the upper limit for vitamin D has been doubled to 4,000 IUs per day, although this is a conservative level, considering the body of scientific evidence indicating it should be 10,000 IU," Heaney tells WebMD. "However, few people need more than 4,000 IUs, which will meet the needs of most healthy people, give physicians confidence to recommend supplementation, and allow research at higher vitamin D levels."
In July 2011, the Endocrine Society Practice Guidelines published recommendations for the evaluation, treatment, and prevention of vitamin D recommending an upper limit of 10,000 IU/day.
"There is a potential to cause harm if you overdose on supplements above 4,000 IU/day but there is no fear of overdosing from the sun because your skin acts like a regulatory system, only allowing production of the amount of vitamin D you need," Brannon says.
Acceptable Vitamin D Blood Levels
Part of the confusion about whether or not you are getting enough vitamin D may be the definition of the acceptable blood level of vitamin D, clinically measured as 25-hydroxyvitamin D [25(OH)D].
Using vitamin D blood levels is the best estimate of adequacy that accounts for dietary intake and sunshine, yet experts differ on what that level should be.
"A 25(OH)D blood level of at least 20 nanograms/ml was used by the IOM committee to set the recommendations for vitamin D because this level showed adequacy for a wide variety of bone health indicators" says Brannon.
The Endocrine Society Practice Guidelines, as well as many laboratories and experts (including Baetti), recommend a minimum vitamin D blood level of 30 nanograms/ml as an acceptable level.