Are you taking way too much Vitamin D for good health?

It is important for those with RNY to supplement with Vitamin D because research shows that serum levels will drop over time if you don't.  You can only really increase your vitamin D levels from sun or supplementation (food is not a good source).  Since most people use sunscreen, that leaves supplementation.  But the question is, how high do you want to take those levels with vitamin D supplements?

Note that to find your Vitamin D level, you will get a blood test called "25(OH)D" (also called "Vitamin D 25 Hydroxy"), and the units will be either "ng/mL" or "nmol/L". LabCorp uses ng/mL.

Now even though many people on this forum and elsewhere push for super high blood levels, the bottom line is there is a lack of definitive evidence for any health benefit when serum 25(OH)D levels are above 75 nmol/L (30 ng/mL).

But fortunately you don't have to take my word for it.  Here is what is on the U.S. Gov's NIH (National Institutes of Health) dietary website: "50 nmol/L (20 ng/mL) is the serum 25(OH)D level that covers the needs of 97.5% of the population. Serum concentrations >125 nmol/L (>50 ng/mL) are associated with potential adverse effects...Emerging evidence links potential adverse effects to such high levels, particularly >150 nmol/L (>60 ng/mL)"  ods.od.nih.gov/factsheets/vitamind

And this U.S. NIH recommendation is in keeping with the latest consensus recommendation of the following British orgs: Cancer Research UK, Diabetes UK, the National Heart Forum, the National Osteoporosis Society, British Association of Dermatologists, the Multiple Sclerosis Society, and others.

Various studies have found that 25(OH)D levels tend to plateau at around 70-80 nmol/L (30-32 ng/mL) in the absence of very large supplementation or extreme sun exposure. In fact, a Hawaiian study found that half of young surfers had levels below 75 nmol/L (30 ng/mL) despite extensive unprotected outdoor exposure and being very tanned. The question you have to ask is, do you really want to take your levels that much higher than your body seems to want them to go?

To reinforce this "nature knows best" wisdom, there is increasing evidence that serum levels above 125 nmol/L (50 ng/mL) have adverse health effects. Not only did a meta-analysis find no benefit for exceeding 75 (30 ng/mL) nmol/L when looking at half a dozen different kinds of cancer -- it also found that exceeding 100 nmol/L (40 ng/ mL) doubled the risk of developing pancreatic cancer, and that is not a cancer you want. Another recent study also found excessive amounts of vitamin D linked to the onset of atrial fibrillation.

Some suggest that most people may need to take 10,000 IU per day to get adequate blood levels. Now about the richest food source of vitamin D — wild salmon — would require 2.2 lbs a day to provide 10,000 IU. And again, even consistent sun exposure will usually not get levels above 80 nmol/L (32 ng/mL) without RNY.  So how do proponents of ultra-high levels figure that a human in a state of nature (without any supplements to be had) would get enough vitamin D?

Perhaps you have noticed, as I have, that balance is where things invariably seem to settle even after decades of extremist recommendations in the health arena.

Now, you may have seen I've gone out of my way here to use two different units.  This is because different labs use different units to measure your vitamin D level in your bloodwork.

To convert from ng/mL to nmol/L, multiply by 2.5 (2.496 to be precise).

To convert from nmol/L to ng/mL, multiply by 0.4 (0.4006 to be precise).

Why are the units so important? Because countless people on this forum and elsewhere quote what your Vitamin D level should be, or what their reading was, without giving the units. I have seen people say, "the optimum level is 75", for example. But if that is 75 nmol/L, it should actually be converted to 30 for LabCorp results in ng/mL. Conversely, if they mean 75 ng/mL, then that would be 188 nmol/L (which the bulk of the research suggests is too high).

This might explain why some people who are taking a whopping 10,000 IU every day are still disappointed in their low vitamin D levels, when in fact if they converted their units properly, they might decide their levels are actually too high.

I should note to give comfort for those wanting to take their levels very high that LabCorp gives a normal reference range of 32-100 ng/mL (which is 80-250 nmol/L).  Since LabCorp states that 32 ng/mL (80 nmol/L) is the threshold for optimum health, it would seem that would be a safe place to start, given the health concerns linked with excessive levels.

For what it is worth, I personally am shooting for 90 nmol/L (36 ng/mL), so as to err just a tad on the higher side re calcium absorption post RNY, but not so high as to pose any other health risks.

Some people on this forum apparently have religious zeal on this issue, and that may be putting it mildly. And since I am not zealous about this, there is no need to comment if you are all up in arms and don't want to have rational discourse.

Finally, just because the NIH says it doesn't make it so -- if in the end you want to go higher with your vitamin D levels, then go for it.  Just do your research, ask your doctor, and come to your own decision that is best for you -- and best wishes for your good health!