Q&A Vitamin D

What happens when you cook foods rich in Vitamin D, like wild salmon? Do you lose their potency?

Vitamin D is relatively stable in foods. Storage, processing, and cooking have little effect on its activity. Vitamin D is stable when heated to boiling temperature of 212F.

If you fry fish in oil, does that remove the vitamin D?

Yes, more than 50 percent of the vitamin D is lost when you fry fish in oil. You would do well to bake, broil, or grill the fish.

Does vitamin D interact with any medications?

Vitamin D does not interact with any medications. However, some medications, such as antiseizure drugs, AIDS medications, and prednisone, will increase the destruction of 25-vitamin D, thus requiring patients to increase their vitamin D intake.

Does genetics play a role in the ability to maintain 25-vitamin D levels?

There is some evidence that genetics does play a small role in the ability to maintain vitamin D status. However, if you ingest between 1,500 and 2,000 IU of vitamin D a day, and you are not obese, this will satisfy your vitamin D requirement.

Can you receive vitamin D from sunlight through windows? What impact does cloud cover have?

Sunlight coming through window glass will not produce any vitamin D in the skin because the glass absorbs the vitamin D-producing UVB radiation. Your skin must be exposed to direct sunlight in order to make vitamin D. cloud cover will decrease the amount of UVB radiation penetrating to the earth and can reduce vitamin D synthesis by as much as 50 percent to 75 percent.

Is there an age at which vitamin D supplementation doesn’t work?

Absolutely not. Vitamin D supplementation is effective in children and adults of all ages. Aging does not affect the body’s ability to absorb vitamin D either from the diet or from supplements. At least 1,000 IU of vitamin day is appropriate for all ages, from children one year old to geriatric patients. Newborns during the first year of life should take at least 400 IU a day, and up to 1,000 IU is reasonable.

Does aging affect my ability to make vitamin D in my skin?

Yes, but the skin has such a large capacity that even with a 70 percent reduction by the time you’re seventy years old, you can still make enough just by exposing more skin.

I have heard that it is important to take magnesium along with vitamin D. is there any reason for this?

There is no need to take magnesium along with vitamin D. Vitamin D is efficiently absorbed with or without magnesium.

How much calcium should you have with 1,000 IU of vitamin D a day?

The Institute of Medicine recommends that all adults up to the age of fifty ingest 1,000 milligrams of calcium a day and adults over the age of fifty 1,200 milligrams of calcium a day. Teenagers require 1,300 milligrams a day to maximize their bone health.

Is it okay to take vitamin D without taking calcium supplements?
Yes. However, to maximize vitamin D’s effect on skeletal health, you need to ingest, either from supplements or from diet, 1,000 to 1,200 milligrams of calcium a day depending on your age. Teens need even more – 1,300 milligrams a day.

Do carbonated beverages affect vitamin D or calcium levels?

No. Carbonated beverages do not affect vitamin D or calcium levels.

Should you stop taking vitamin D supplements just before having your vitamin D status checked?

There is no need to stop your vitamin D to have your 25-vitamin D level checked.

How do you interpret different vitamin D lab numbers (i.e., do you look at 25-vitamin D2, 25-vitamin D3, or total 25-vitamin D)?

When you check the blood level of 25-vitamin D, the only number that is important is the total 25-vitamin D, which should be above 30 nanograms per milliliter. The 25-vitamin D2 level reflects vitamin D2 intake (usually from a vitamin D2 prescription), and the 25-vitamin D3 level reflects the vitamin D3 ingested from diet, supplements, and sun exposure. Adding together the 25-vitamin D2 and 25-vitamin D3 numbers gives the total 25-vitamin D number. For example, if your results show a vitamin D2 number of 15 nanograms per milliliter and a vitamin D3 of 20 nanograms per milliliter, then your total vitamin D would be 35 nanograms per milliliter.

Is it possible to get vitamin D toxicity with vitamin D supplementation and a diet high in vitamin D-fortified foods along with sun exposure?

Because very few foods contain vitamin D and the amount of vitamin D is relatively small in comparison to what the body requires, it is doubtful that you could become vitamin D toxic by taking a vitamin D supplement of 1,000 to 2,000 IU of vitamin D a day. You cannot get too much from the sun, either. Most of the literature suggests that adults have to ingest more than 10,000 IU of vitamin D a day for at least five months before they have to begin to be concerned about vitamin D toxicity. If you have sarcoidosis or another granulomatous disorder like tuberculosis, you could be more sensitive to vitamin D and need to check with your doctor.

Is farmed salmon a good source of vitamin D?

Farmed salmon has only about 10 percent to 25 percent of the vitamin D found in wild-caught salmon.

Why do some textbooks still call vitamin D the most toxic vitamin?

Indeed, most textbooks still call vitamin D the most toxic vitamin. It definitely is not. Vitamin A is much more toxic and can rapidly cause death in very high concentrations. (This was discovered by early explorers in Alaska who began eating polar bear liver and became severely vitamin A intoxicated, leading to death). Given the plethora of data emerging on the safety of vitamin D, the textbooks may be rewritten.