Wednesday, August 3, 2011
Lab ranges and RDAs are designed to avoid disease not create optimal health
I am reading all over the web about tired people. Many of them are tired enough that they've talked to their doctors about it. Or they have other weird symptoms but no diagnosis or maybe they just feel like something is not quite right. So they get some lab work done and it comes back "normal" and their doctor tells them there is nothing wrong with them. Others say that they take the recommended supplements as if that means that they are doing all they can.
The problem is that RDAs are designed to keep us disease free. They aren't designed to bring us to optimal health. This is one reason that the RDA for Vitamin D and the lab ranges are so low. The RDA was set originally as "get this much daily to avoid rickets". That's it. As long as you take this much, you won't get rickets. But that doesn't mean you are at optimal levels.
It's since been raised, but it's still pretty low and so are the recommended ranges on your labs. Some labs say that you want your vitamin D to be between 30 and 80 and then your doctor freaks when your Vitamin D goes over 75 -- a value that's pretty close to optimal for most people. Most labs say 30-100, but toxicity for Vitamin D is in the 200-250 range and optimal vitamin D levels are 50-150 according to the Vitamin D Council. (Some say bariatric patients aim for 80-100 to lower the risks of certain cancers.) According to the Vitamin D Council, anything above 75 is great and anything under 50 is low even if the lab says it's okay.
And that's just one supplement and one lab value that I happen to know a lot about.
Part of the problem is that the reference ranges on labs are created by studying normal people. They do the tests on thousands of people and then they set the range to be what 95% of the population falls into. (For the statisticians among us, they take everyone within 2 standard deviations of either side of the mid-point.) But what if the population being studied is skewed somehow? In the case of Vitamin D, decades of not getting enough has made most of us have very low results hence the "normal" range being lower than studies now show is optimal.
Or, more likely, what if the population doesn't apply to you?
As bariatric patients, we are not normies. Those with malabsorption can find their levels dropping dramatically in a short time so being at the low end of the "normal" range in certain values is more problematic for us. Even those of us with intact intestines can still have maldigestion issues that impact our supplement routines and what our levels should be to have optimal health.
Athletes are another population that is not normal. In particular, an athlete's iron levels need to be higher than the general population and often have resting pulse rates much lower than average. So, your iron could be "in range" but it could still be low for your needs as an athlete while having a resting pulse rate of 55 is no cause for concern in an athlete. (One article I read said our RDA for iron should be 30% higher than the general population.)
Finally, we are all individuals and what is normal for us may not be what is normal for everyone. Perhaps our ranges fall outside the two standard deviations. This could be a cause for concern, but maybe that's "just the way we are." This is why it's good to establish a baseline. Getting regular lab work and keeping track of trends can tell you if your lab results are abnormal for you.
For example, my hemoglobin and hematocrit levels have always been on the high end of the normal range for a woman. Medical personnel have always exclaimed over how awesome they were. But now they are right in the middle of the range. Doctors tell me that's fine or even excellent or "perfect." But it's not perfect for me. It's low for me. Luckily, people get that measure tested all the time so I know I'm lower than normal.
But on a lot of lab tests, the first time I had it tested was pre-op two weeks before surgery. So I don't really know. My protein levels, which have been out of range for 2.5 years now are a measure that I'd love to have known what the values were since I was 12, like I do with my hemoglobin. All I can do now is watch and look for other signs that whatever my values are now is either right for me or not.
To find out more
This article is aimed at triathletes but it talks about this issue and gives some sources for where to find different ranges and recommendations from what you see on your labwork:
Exhausted? Take a second look at your blood tests
This page talks about the reference ranges and how they are developed:
What are reference ranges?
And this page gives reference ranges for a large number of lab tests:
Reference ranges for blood tests