Tuesday, February 9, 2010

Vitamin D follow-up

I skimmed the article that my pediatrician referred me to at the Vitamin D Council. I have to admit the author said a couple of things that bothered me. Granted, I did not read it deeply, so I may have glossed over some things.

But he suggested that there is some need to explain why identical twins are more likely to both have autism than fraternal twins. Really? Isn't the reason for that somewhat obvious? I will go back and read it again, maybe I misunderstood his point. But what is remarkable about this? Wouldn't you expect identical twins to be more similar than fraternal twins?

I was also bothered by his suggestion that african-americans "may be" more likely to have autism. I saw no actual data on this in his article, but I am pretty sure I read the precise opposite not long ago somewhere else, although maybe I'm mistaken about that. But he seems to be just guessing that African-Americans may have higher rates, and I did not like that. I found it particularly off-putting, actually, that his reasoning was partly based on an assertion that rates of mental retardation are higher among african-americans. I have no idea if that is true, but today, the majority of children diagnosed with an autism spectrum disorder are not retarded, nor do I think that the majority of retarded children have autism. So ... this left me less inclined to buy into his theory in general that Vitamin D deficiency might lead to autism or somthing that is autism-like.

But he pointed out that there seem to be more autistic children born in March, and that caught my attention, because my twins were born at the end of February. I haven't looked up the actual studies on this point yet, so I'm not sure if it's true. But did discover that there DO seem to have been a couple of small studies correlating autism rates with areas that are more cloudy or overcast.

It IS true that I was on modified bedrest and stayed in the house in the same lazboy chair for most of my last trimester. And it's also true that although I consumed gargantuan quanities of milk, I was carrying twins and wasn't taking Vitamin D supplements.

I started reading up some more, and I came across this article on Medscape: "Vitamin D Deficiency: Implications Across the Lifespan." I was struck by this statement:

"It has been shown that above 35° north latitude (Atlanta), little or no vitamin D3 can be produced from November to February."

I'm in Atlanta. So ... I looked it up. It turns out my house is actually at 33° 47' 50.1216," so ... what does that mean? fyi, the pediatrician told me some time back actually, that she thought we could not make enough vitamin d here in the wintertime, even if we stayed outside all day long. I'm just guessing that maybe she has a different opinion about how much of it we actually need?

Well, I can't really sort that out. And with regard to my pregnancy it's academic, because I rarely left the house. But it does make me wonder about whether we could get enough Vitamin D right now, if we went outside ... all day ...

A few other thoughts:

1. I was taking prenatal vitamins. However, it appears that some forms of Vitamin A really do interfere with absorption of Vitamin D, at least according to this report from the surgeon general. Apparently beta carotene is not a problem, though. I wonder what form was in the vitamins I took? I certainly have no idea.

2. I found out at my last doctor visit that I am calcium deficient. He actually said he figured I was probably Vitamin D deficient, because you can't absorb calcium efficiently if you don't have enough Vitamin D in your body. (again, see the helpful medscape article.)

3. The obstetrician sure did take a lot of blood while I was pregnant! Doesn't it seem like someone would have figured out if I was low on Vitamin D? Maybe not. I'll never know.

So ... I don't know. I'd like to do some more reading on it sometime.

But in the meantime ... my real question now is:

1. are we getting enough vitamin d?
2. is there any harm in giving T 5,000 IU a day, as my pediatrician recommended?

Well, I won't detail it here, but I think I am convinced that the answer to #1 is probably no. Even my physician thinks I'm probably low.

I think question #2 is maybe the most important then. How much can we safely take?

It really is possible to overdose on Vitamin D, and this can cause serious problems. According to the National Institute of Health Office of Dietary Supplements (who knew there was one??):

"Long-term intakes above the UL increase the risk of adverse health effects [4] (Table 4). Substantially larger doses administered for a short time or periodically (e.g., 50,000 IU/week for 8 weeks) do not cause toxicity. Rather, the excess is stored and used as needed to maintain normal serum 25(OH)D concentrations when vitamin D intakes or sun exposure are limited [11,90]."

-- Dietary Supplement Fact Sheet: Vitamin D.

But that number (50,000 IU per week for 8 weeks -- which is over 7,000 IU per day) refers to an adult. My son is only 2 (well, almost 3), so ...

To recap, my pediatrician suggeted 5000 per day. Is that really OK? I'm not sure. The NIH actually suggests that the upper limit for regular intake is 2,000 IU per day for everyone except infants under a year old. This is a lot lower than the pediatrician recommended, although again, she was talking short term use.

The NIH goes on to acknowledge that lots of researchers have challenged NIH's numbers as being too low. Apparently, clinical studies have demonstrated that as much as 10,000 IU per day seems safe in adults. However, NIH thinks that those studies were not adequate to assess harm, and that there are no studies assessing harm in children of increased levels. Still, they tell us they are considering whether to change the levels. I looked at their footnote -- apparently they have been considering this since 1997!

My pediatrician tells me they give children with rickets about 10,000 per day for months, and that I shouldn't worry.

I don't know. I am definitely going to up both boys to 2,000 IUs per day, though, since NIH thinks it's okay. They really have not been getting anything near that.

But as for the rest ... I plan to find out how much a blood test costs, how reliable it is, and look for more up to date information on toxicity levels in children. Stay tuned!


  1. awesome let me know how everything goes
    my son was also born in the winter time
    maybe they are on to something

  2. The comment from the Vitamin D Council about african-americans isn't racist. It was getting at something subtle that you might have missed- darker skin requires more exposure to sunlight to make the same amount of Vitamin D than white skin. The way it was assumed in that article might have put you off but that was not the intention.

  3. Bee, that's interesting. Maybe they really are on to something. thanks, Anonymous. I didn't actually think he was being racist, I did understand about the melatonin making it harder to make Vitamin D. It was just that his point struck me as not well supported, and it was really the supposed connection to the number of mentally retarded children that put me off. Plus, I am fairly certain that I just read somewhere else that there are fewer African American children with an autism diagnosis, although I can't remember where I saw it, so perhaps I am mistaken in that. But I really don't like equating autism to mental retardation. I just don't think that's accurate.

  4. You should consider reading the book "Survival of the Sickest" by Sharon Moalem. There is an entire chapter about Vitamin D, cholesterol, folic acid, and race. Nothing about autism, but it was suggested that African Americans with high cholesterol should go to the tanning salon.