Tuesday, January 12, 2010

Eat food. Not too much. Mostly plants. Plus Vitamin D.

Today I got results back from yesterday's check up, and it has led me to take action on two fronts. First, I will continue taking Vitamin D supplements. Second, I am putting myself on a diet.

I have been obsessed with vitamin D since doing my end of rotation project on it for Primary Care in November. About 50% of us are vitamin D deficient. This is largely because we don't get enough sun which is where we have evolved to get it from. There are very few dietary sources, cod liver oil, salmon, and fortified foods among them. But no one wants to eat cod liver oil, eating salmon every day is controversial, and a fortified food is just food with vitamins. So practically speaking we either have to get more sun or take supplements. More sun is problematic because of the whole skin cancer thing. It's also inconvenient and, in the winter, potentially uncomfortable.

Our evolutionary upper daily intake is around 10,000 IU (that's how much vitamin D can be synthesized in our skin if we stayed out in the sun all day with few clothes on). But the Institute of Medicine has settled on 2,000 IU as the maximum safe daily dose. At least as of today. They have been commissioned to make new recommendations with a planned announcement on May 2010. For reference, most doctors will tell you to take 400-800 IU/day just depending, but if you dig a bit you'll find that there's really little basis to that dose range.

Original vitamin D dosage was arrived at in the pediatric population for the treatment of rickets. The treatment way back when was a teaspoon of cod liver oil. Then someone determined that there's about 400 IU of vitamin D in cod liver oil and that became the standard recommended daily dose for all children. It wasn't thought that vitamin D was important for adults, but eventually someone brought it up and they arbitrarily set 200 IU/day as the minimum daily requirement for adults, the rationale being that adults probably need it less than children (not really true) and half the child dose sounds about right (ridiculous). Since then, the number has been creeping up. But it's important to remember that this is a minimum recommendation, not an optimum. An optimum has not been agreed on quite yet.

Most doctors I've talked to are uncomfortable with people in the general population taking more than 1,000 IU/day even though it is estimated that you need about 3,000 IU/day from all sources in order to have a normal level.

Anyway, a minimum dose could just be fine, but it's worth looking for an optimum dose since there's a lot of research going on suggesting that higher blood levels of vitamin D might be protective against many cancers, might protect your heart, might lead to more healthy muscles, might lead to more healthy bones, and might be useful for your immune system. Lots of mights, the jury is still out, but it is difficult to overdose on vitamin D (in contrast, it is easier to overdose on vitamins A, E, and K), and my feeling is that currently we, as a population, do not have the same vitamin D levels as our ancestors did since we're not out in the sun as often. So in order to get to more pre-modern levels, levels which the human body has evolved with, I try to take at least 2,000 IU/day. Even so, I have a low-normal level.

As for the diet, I am putting myself on the Michael Pollan diet. His mantra, "Eat food. Not too much. Mostly plants" has resonated with me ever since I read it in his Times Magazine article from 3 years ago, Unhappy Meals. But I suppose it resonated with me more in theory than in practice.

I have done fairly well with part one, eating real food, although now that I think about it I'm a sucker for Snickers bars. I'm pretty bad with the mostly plants. And I'm about average with the not too much. Anyway, for a little extra guidance, I'm buying his new book, Food Rules: An Eater's Manual, in which he expands on those 3 principles and tries to give common sense rules on how to adhere to them. This book really should not be necessary, but it obviously is.


dave said...

I was already sold on the first three sentences; now I think you've sold me on the fourth!

David said...