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Ask a Scientist -- Daily Dosing

Questions and Answers with Dr. Bruce Hollis, PhD
University Medical Center of South Carolina

This newsletter explained how vitamin D is processed and stored in the body – differently for bone health than immune health. The conclusion was that you need daily exposure to vitamin D (sunshine, food, supplements) in order to be fully protected against disease and in order to pass vitamin D along in breast milk.

Processing vitamin D in your body

Q: Is it possible that the vitamin D is not able to be converted into its active form either by the endocrine or the autocrine? If so what can be helpful?
A: It will be converted unless you suffer from extremely rare metabolic conditions.

Q: Is there evidence that the body down regulates its own synthesis from UVB exposure when oral D3 is supplemented regularly?
A: As far as I know this does not occur.
Q: Dr. Marty Makary, on his interview recently on Fox News, said that sunlight is required to convert Vitamin D into its active form.  Is that statement true?
A: If he said that he is confused. Sunlight is required to make vitamin D in the skin but not to further activate it in the body.

Daily Dosing

Q: What doses are appropriate for children? Specifically an 18 month old and a 3.5 year old.
A: 2,000 IU/d would be plenty.
Q: If I take 5000 IU of D3 a day, does that ensure my health?
A: As far as vitamin D status is involved it should.

A: 10,000 mg/d would kill you. 10,000 IU will not but it is unlikely you require this amount unless you have a specific disease. **If you meant 10,000 IU/day (not mg), that dose is considered safe by the IOM.

Q: What is the right daily vitamin D dosage (in a supplement) for a breast feeding woman that does not have sun exposure? 
A: Our recent publication on this subject tells us that you should take 6000 IU/d.

Q: What is the right daily vitamin D dosage for an adult healthy man that does not have sun exposure? 
A: 5,000-6,000 Iu/d.
Q: What is the right daily vitamin D dosage  (in a supplement) for an adult healthy woman that doesn't have sun exposure?
A: 4,000-6000 IU/d
Q: How long can I safely be on a regimen of 10,000 units of D3 per day?
A: As long as your blood level of 25(OH)D remains in the safe range, <100 ng/ml, then you are ok.
Q: I have read sun exposure at noon for about 15-20min will produce up to 20,000 IU of vitamin D, will you produce this amount each day of the week with sun exposure?
A: As you tan the amount of vitamin D generated by a given exposure will decrease.
Q: How does daily dosing affect fertility and the role of the multiple hormones in the female menstrual cycle?
A: Several studies suggest increased fertility in both females and males as vitamin D status normalizes.
Q: When is the ideal time to take a vitamin D supplement- with meals, in split doses, all at once or at bedtime?
A: I personally take mine all at once following my first meal of the day.
Q: I live in Argentina and here it is available a 2 ML monodosis Vitamin D3 vial presentation of 100,000 IU. Do I get the same benefit by taking 100,000 IU once a month than by taking 3,300 IU daily capsules?
A: Daily dosing is always preferable in my opinion.
Q: I take 5,000 IU daily. My goal is to have a D3 level of about 80, but your group says that level is too high. David Perlmutter MD likes that level. Why do you like a lower level?
A: Normal physiological levels of blood 25(OH)D is 30-100 ng/ml.
Q: Why does the D3 supplement say take with food?  And how much food? And before or after by how much time?  Thanks for taking the time to receive this type of question. 
A: I take mine with breakfast in the morning.
Q: Why is the daily dosage NOT so that people have 100ng/ml blood level?
A: If you have definable disease such as MS, prostate cancer or autoimmune problems then 100 ng/ml might be appropriate.  For primary prevention, 50-80 ng/ml is what I'd recommend.

Vitamin D and disease prevention

Q: A few studies point to increased risk of some cancers with high 25 (OH) D levels.  What is your optimal dose for adults and children?
A: As I had stated previously, levels of 25(OH)D in the range of 30-100 ng/ml would be considered normal. I know of a thousand biochemical papers on how vitamin D prevents cancer but NONE on how it would cause it. Thus, the observational studies that suggest it increases cancer rates make no sense to me.

Q: Is vitamin D supplement bad for people prone to kidney stones? If so is there any other supplement that can be included to counteract?
A: There is no evidence that vitamin D intake is related to kidney stone formation.

Vitamin D and other nutrients (magnesium, K)

Q: Hi, Do I have to take extra Magnesium with my daily dose of Vitamin D3?   I currently take a multivitamin that contains 100mg of Magnesium.
A: Recent studies suggest that Mg intakes up to 300 mg/d may be of benefit.

Q: I read that to take full advantage of Vitamin D3 a certain amount of Vitamin K2 is also necessary. How much daily Vitamin K2 do I need and how can I find out whether or not I am deficient at this vitamin too?
A: Recent studies suggest vitamin K intake may not be as important as thought in bone intake. Certainly some vitamin K is required for bone health but whether supplementation is required beyond endogenous production remains a question.
Q: Will including Vit. A and/or Magnesium augment our D3 daily dosing?
A: I suggest you not take extra vitamin A and about 300 mg/d of Mg.
Q; Can you please give us your thoughts about augmenting our daily D3 dosing with K-2?
A: Recent research suggests this is not required.
Q: What is the role of Magnesium in processing vitamin D, and is there a recommendation for daily intake and/or type of Magnesium?
A: Mg functions as a co factor for many enzyme systems probably including the vitamin D activating enzymes. Intakes of 300 mg/d will do the job.

Questions pertaining to individuals

Q: It is my personal belief and hypothesis that fruits and vegetables that get maximum exposure to sunlight are good for our health. Am I correct in my thinking?
A: There is absolutely no vitamin D in plants with the exception of irradiated mushrooms.
Q: My level of vitamin D dropped from 98 to 32 despite daily dosing with 4000 IU. I was recently diagnosed with IBS and wondering if this was the issue. How should I dose to ensure my level stays high enough since the vitamin D is probably not being absorbed? I have currently doubled my intake to hopefully compensate, but don't want to take too much.
A: Take as much as you need to raise your blood level of 25(OH)D to the desired level.
Q: As a senior citizen, what will forced immunizations do to my immune system?  I see this civil right slowly disappearing about making a choice. Thank you. 
A: I am not aware of forced immunization in adults. Flu vaccines are of questionable use while others like the shingles vaccine are highly desirable.
Q: my score is 39. what is the proper dose for me, a 66 year old, in general. and also would you dose differently for UV damaged skin and eyes, pre-cancerous in both cases?
A: If I were you I would take 5000-6000 IU/d.