Risks of excess vitamin D supplementation
Vitamin D status is measured by 25(OH)D in blood. We’ll dive further into vitamin D metabolism later, but for now, just understand that this is the precursor to active vitamin D and is generally considered the most accurate single marker to assess vitamin D status. The U.S. laboratory reference range for adequate 25(OH)D is 30 to 74 ng/mL, while the Vitamin D Council suggests a higher range of 40 to 80 ng/mL, with a target of 50 ng/mL (17).
But a large body of evidence in the medical literature strongly suggests that optimal vitamin D levels might be lower than these figures. There is little to no evidence showing benefit to 25(OH)D levels above 50 ng/mL, and increasing evidence to suggest that levels of this magnitude may cause harm. Consequences of vitamin D toxicity include heart attack, stroke, kidney stones, headache, nausea, vomiting, diarrhea, anorexia, weight loss, and low bone density (18).
Furthermore, in most studies, taking vitamin D supplements does not decrease risk of death, cardiovascular disease, or other conditions. Based on an exhaustive review of over 1,000 studies in 2011, the Institute of Medicine recommends a much more conservative range of 20 to 50 ng/mL (19).
Are we overdoing Vitamin D?
Moderators: Rosie, Stanz, Jean, CAMary, moremuscle, JFR, Dee, xet, Peggy, Matthew, Gabes-Apg, grannyh, Gloria, Mars, starfire, Polly, Joefnh
Are we overdoing Vitamin D?
https://chriskresser.com/vitamin-d-more ... paign=blog
Hi Deb,
IMO the answer to your question is "yes and no". Yes, we are overdoing vitamin D if we take relatively large daily doses without balancing it with a corresponding intake of magnesium. The same question could be asked of calcium supplements. And the answer would be the same. But no, we are not taking too much vitamin D as long as we take a matching dose of magnesium also.
IMO Chris Kresser is making the same mistake that virtually all doctors make. They view every issue as if it were independent of all other issues. And as we all know, that's simply not true. Every time that one body system is affected, other body systems are affected, also. And if our vitamin or mineral balance becomes upset by disease, genetics, vitamin or mineral supplementation, or whatever, trying to correct the problem by taking a massive amount of a single element is a simplistic approach that can lead to problems, especially when carried to extremes.
First off, the reason why there is little to no evidence showing benefit to 25(OH)D levels above 50 ng/mL is mostly because research in that category is as scarce as hen's teeth. So few people today have a level of vitamin D above 50 ng/mL that whenever studies are made, no conclusions can be drawn about that category because of insufficient data. And here again, Chris makes the same mistakes as other physicians by assuming that lack of data implies a negative consequence. It most definitely does not. What it does imply is a clear bias in the industry. For example, here is a recent study on high doses of vitamin D for treating IBS:
Study finds high dose vitamin D supplementation significantly improves irritable bowel syndrome
Look at the listed consequences of taking enough vitamin D to be considered toxic: heart attack, stroke, kidney stones, headache, nausea, vomiting, diarrhea, anorexia, weight loss, and low bone density.
Do you recognize those symptoms in red? They are all symptoms of magnesium deficiency. I have posted many times about how magnesium deficiency causes these symptoms. And I have posted many times about how taking large doses of vitamin D without taking an adequate amount of magnesium can cause those symptoms (because vitamin D enhances calcium absorption, and magnesium is depleted in removing calcium from the blood). Out of all those symptoms, only diarrhea is actually a symptom of true vitamin D toxicity, and it takes a heck of a lot of vitamin D to reach the toxicity level (above 150 ng/mL). So the problem is not taking too much vitamin D — the problem is failing to take enough magnesium.
And when he says:
Thanks for pointing out his misleading blog. It's not so much that his claims are not true (under certain conditions). The problem is that they are half-truths, by omission. The other half of the equation is magnesium, and if you overlook half the equation, then obviously such math is worthless.
Don't get me wrong — I'm a Chris Kresser fan. But he dropped the ball on this one because he is well aware of the effects of the interdependency of vitamin D, magnesium, and calcium. Maybe he was half-asleep when he wrote that article.
Tex
IMO the answer to your question is "yes and no". Yes, we are overdoing vitamin D if we take relatively large daily doses without balancing it with a corresponding intake of magnesium. The same question could be asked of calcium supplements. And the answer would be the same. But no, we are not taking too much vitamin D as long as we take a matching dose of magnesium also.
IMO Chris Kresser is making the same mistake that virtually all doctors make. They view every issue as if it were independent of all other issues. And as we all know, that's simply not true. Every time that one body system is affected, other body systems are affected, also. And if our vitamin or mineral balance becomes upset by disease, genetics, vitamin or mineral supplementation, or whatever, trying to correct the problem by taking a massive amount of a single element is a simplistic approach that can lead to problems, especially when carried to extremes.
First off, the reason why there is little to no evidence showing benefit to 25(OH)D levels above 50 ng/mL is mostly because research in that category is as scarce as hen's teeth. So few people today have a level of vitamin D above 50 ng/mL that whenever studies are made, no conclusions can be drawn about that category because of insufficient data. And here again, Chris makes the same mistakes as other physicians by assuming that lack of data implies a negative consequence. It most definitely does not. What it does imply is a clear bias in the industry. For example, here is a recent study on high doses of vitamin D for treating IBS:
Study finds high dose vitamin D supplementation significantly improves irritable bowel syndrome
Look at the listed consequences of taking enough vitamin D to be considered toxic: heart attack, stroke, kidney stones, headache, nausea, vomiting, diarrhea, anorexia, weight loss, and low bone density.
Do you recognize those symptoms in red? They are all symptoms of magnesium deficiency. I have posted many times about how magnesium deficiency causes these symptoms. And I have posted many times about how taking large doses of vitamin D without taking an adequate amount of magnesium can cause those symptoms (because vitamin D enhances calcium absorption, and magnesium is depleted in removing calcium from the blood). Out of all those symptoms, only diarrhea is actually a symptom of true vitamin D toxicity, and it takes a heck of a lot of vitamin D to reach the toxicity level (above 150 ng/mL). So the problem is not taking too much vitamin D — the problem is failing to take enough magnesium.
And when he says:
he's not only wrong, but he's attempting to twist the facts to meet his agenda. If he's statistically correct (about the use of the term "most"), then it's only because most studies are not designed to meet those specific criteria. That said, I have bookmarked hundreds of references that verify that taking vitamin D supplements is associated with significant reductions in diseases ranging from most types of cancer, to autism, osteoporosis, immune system issues, cardiovascular issues, etc. And does quality of life mean nothing? Or is the only measure of the benefits of supplements increased longevity?Chris Kresser wrote:Furthermore, in most studies, taking vitamin D supplements does not decrease risk of death, cardiovascular disease, or other conditions.
Thanks for pointing out his misleading blog. It's not so much that his claims are not true (under certain conditions). The problem is that they are half-truths, by omission. The other half of the equation is magnesium, and if you overlook half the equation, then obviously such math is worthless.
Don't get me wrong — I'm a Chris Kresser fan. But he dropped the ball on this one because he is well aware of the effects of the interdependency of vitamin D, magnesium, and calcium. Maybe he was half-asleep when he wrote that article.
Tex
It is suspected that some of the hardest material known to science can be found in the skulls of GI specialists who insist that diet has nothing to do with the treatment of microscopic colitis.
Thanks for this Tex. I have wondered where I should be with vitamin D since I really upped my magnesium with ReMag. My magnesium levels are good according to my recent RBC test. I seem to be able to increase my Vitamin D levels pretty easily. Pre supplements I was in the upper 20's. I added 2,000 units of Vitamin D daily and got to mid 50's within a few months. Since I increased my magnesium I cut back on my Vitamin D (now about 5,000 units per week) to see what would happen. I am south for the winter so am getting more sun than at home. My recent vitamin D test showed me at 37, so I am increasing the dosage. I think I will aim for 50's.
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Gabes-Apg
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Deb
what each person needs to take dosage wise for supplements can depend on many factors
- how much inflammation there is
- where we live and how much quality UVA / UVB time we get (further to this age and how well we process the UVA/UVB into useable Vit D3 in the cells)
- stress / lifestyle in our day to day lives
- contact with cold / flu / sick people
- medications
each year, I increase Vit D3 intake as winter / cold and flu season approaches.
week to week I will increase the intake if there are indicators of inflammation in my body or if there is increased stress going on.
what each person needs to take dosage wise for supplements can depend on many factors
- how much inflammation there is
- where we live and how much quality UVA / UVB time we get (further to this age and how well we process the UVA/UVB into useable Vit D3 in the cells)
- stress / lifestyle in our day to day lives
- contact with cold / flu / sick people
- medications
each year, I increase Vit D3 intake as winter / cold and flu season approaches.
week to week I will increase the intake if there are indicators of inflammation in my body or if there is increased stress going on.
Gabes Ryan
"Anything that contradicts experience and logic should be abandoned"
Dalai Lama
"Anything that contradicts experience and logic should be abandoned"
Dalai Lama
Deb,
I agree that the 50s is a good target for vitamin D level. You probably recall me posting about having kidney stones and various other problems in the fall of 2014. Back in those days my vitamin D level ranged from the 40s to the 90s, depending on the season and how much supplemental vitamin D I was taking. Chris Kressor would have said, "See, I told you so". But when I had the kidney stones my vitamin D level was in the 40s. About 6 months after that I finally figured out that I had a chronic magnesium deficiency. And after I corrected that problem, everything smoothed out. When the kidney stones initially showed up (3 weeks apart), I was afraid that they would be a regular problem. But eliminating my magnesium deficiency apparently eliminated the kidney stone problem. 3 years have passed with no signs of another.
You probably also remember me posting about having a couple of TIAs (in July, 2009 and May, 2010). Back in those days I took very little vitamin D (maybe 2, 000 IU during the winter only), and no magnesium, and I have no idea what my vitamin D or magnesium levels were, because even with the TIAs, none of my doctors every checked either one.
But in hindsight, it certainly appears that those TIAs might have been associated with my chronic magnesium deficiency. The first one occurred first thing in the morning (before breakfast), and the second occurred late at night (after 11 pm). Both of those times overlap the time of the day/night when magnesium levels are at their lowest.
Tex
I agree that the 50s is a good target for vitamin D level. You probably recall me posting about having kidney stones and various other problems in the fall of 2014. Back in those days my vitamin D level ranged from the 40s to the 90s, depending on the season and how much supplemental vitamin D I was taking. Chris Kressor would have said, "See, I told you so". But when I had the kidney stones my vitamin D level was in the 40s. About 6 months after that I finally figured out that I had a chronic magnesium deficiency. And after I corrected that problem, everything smoothed out. When the kidney stones initially showed up (3 weeks apart), I was afraid that they would be a regular problem. But eliminating my magnesium deficiency apparently eliminated the kidney stone problem. 3 years have passed with no signs of another.
You probably also remember me posting about having a couple of TIAs (in July, 2009 and May, 2010). Back in those days I took very little vitamin D (maybe 2, 000 IU during the winter only), and no magnesium, and I have no idea what my vitamin D or magnesium levels were, because even with the TIAs, none of my doctors every checked either one.
But in hindsight, it certainly appears that those TIAs might have been associated with my chronic magnesium deficiency. The first one occurred first thing in the morning (before breakfast), and the second occurred late at night (after 11 pm). Both of those times overlap the time of the day/night when magnesium levels are at their lowest.Tex
It is suspected that some of the hardest material known to science can be found in the skulls of GI specialists who insist that diet has nothing to do with the treatment of microscopic colitis.
I forgot to mention: For decades, physicians have wondered why most heart attacks occur early in the day, often when the patient first gets out of bed and begins to prepare for the day. Many doctors have written, offering many "explanations" for why this happens, but none of them hold up under close scrutiny because all of them ignore the fact that this is the time of day when magnesium levels are at their absolute minimum — just before breakfast.
This is extremely puzzling because physicians clearly understand that if a heart attack patient is alive when reached by paramedics, or when arriving at the hospital, a magnesium infusion is typically life-saving. Yet they still fail to make the connection that magnesium deficiency is a prime reason why most heart attacks occur first thing in the morning.
Tex
This is extremely puzzling because physicians clearly understand that if a heart attack patient is alive when reached by paramedics, or when arriving at the hospital, a magnesium infusion is typically life-saving. Yet they still fail to make the connection that magnesium deficiency is a prime reason why most heart attacks occur first thing in the morning.
Tex
It is suspected that some of the hardest material known to science can be found in the skulls of GI specialists who insist that diet has nothing to do with the treatment of microscopic colitis.
Hi Polly,
Thanks for pointing that out. Are you referring to 50 nmol/l (20 ng/ml) or 50 ng/ml (125 nmol/l)? I suspect that the jury is still out on this one because researchers seem to be confused about what the data actually say regarding specific situations. For example, a 2016 systematic review and meta-analysis of 11 different studies was reviewed in Medscape.
But when you read the comments, the evidence is not clear cut in either direction — there seem to be a lot of ifs, ands, and buts involved. In part the article says:
For anyone reading this, remember that the 50 nmol/L level (using international units) mentioned in the article is equivalent to only 20 ng/mL (using U.S. units).
My takeaway from this is that based on blood levels of vitamin D, those in the highest 20 % had the lowest odds of age-related macular degeneration when compared with those in the lowest 20% (in one analysis). Those with the highest vitamin D levels had an 83% reduced risk of AMD. However, as you suggested, this is based on relatively low vitamin D levels (in the deficiency range) in that lower 20 % of cases, and even the top 20 % may have had only slightly better vitamin D levels (possibly well below the 50 ng/ml level).
But presumably, "Late" AMD is what we are the most concerned about, and that same study showed that those who had less than 50 nmol/l (20 ng/ml) circulating vitamin D had more than twice the odds of developing late AMD compared with those who had higher vitamin D concentrations. Of course, we're still talking about relatively low vitamin D serum levels (not quantitatively high levels)
I find this comment to be somewhat akin to grasping at straws, as it is highly unlikely that macular degeneration causes low vitamin D blood levels (rather than the other way around).
But all of this ignores a very important fact. The Vitamin D Council bases their recommendation of 40–80 ng/ml as a "sufficient" range, based on real life data including actual test levels of people who still live a basic hunter-gatherer lifestyle. This is as close as we can get to valid evolutionary archaeological data. IMO Mother Nature is virtually always the best source of valid data where the rubber meets the road (outside of the laboratories and the ivory towers of the academic world).
At least that's how I view the controversy.
Tex
Thanks for pointing that out. Are you referring to 50 nmol/l (20 ng/ml) or 50 ng/ml (125 nmol/l)? I suspect that the jury is still out on this one because researchers seem to be confused about what the data actually say regarding specific situations. For example, a 2016 systematic review and meta-analysis of 11 different studies was reviewed in Medscape.
But when you read the comments, the evidence is not clear cut in either direction — there seem to be a lot of ifs, ands, and buts involved. In part the article says:
Low Vitamin D Levels Linked to Macular Degeneration RiskIn a second analysis, those in the highest quintile of circulating vitamin D levels had the lowest odds of AMD compared with those in the lowest quintile. Those with the highest vitamin D levels had 83% lower odds of AMD (odds ratio [OR], 0.83; 95% CI, 0.71 - 0.97) and 47% lower odds of late AMD (OR, 0.47; 95% CI, 0.28 - 0.79) compared with those with the lowest levels.
In addition, participants with less than 50 nmol/L circulating vitamin D had more than twice the odds of late AMD (OR, 2.18; 95% CI, 1.34 - 3.56) than those with higher concentrations. However, this association dropped out of significance when all AMD cases, regardless of stage, were considered (OR, 1.26; 95% CI, 0.90 - 1.76).
Although the authors argue for the possibility that low vitamin D levels may contribute to AMD, they state that vitamin D deficiency may not fully explain development and worsening of the condition. Further, it is unclear whether vitamin D supplementation would be protective against developing AMD.
They also acknowledge that no validated theory currently exists that can fully explain an association between circulating vitamin D levels and late-stage AMD, and that lower vitamin D levels may result from macular degeneration.
For anyone reading this, remember that the 50 nmol/L level (using international units) mentioned in the article is equivalent to only 20 ng/mL (using U.S. units).
My takeaway from this is that based on blood levels of vitamin D, those in the highest 20 % had the lowest odds of age-related macular degeneration when compared with those in the lowest 20% (in one analysis). Those with the highest vitamin D levels had an 83% reduced risk of AMD. However, as you suggested, this is based on relatively low vitamin D levels (in the deficiency range) in that lower 20 % of cases, and even the top 20 % may have had only slightly better vitamin D levels (possibly well below the 50 ng/ml level).
But presumably, "Late" AMD is what we are the most concerned about, and that same study showed that those who had less than 50 nmol/l (20 ng/ml) circulating vitamin D had more than twice the odds of developing late AMD compared with those who had higher vitamin D concentrations. Of course, we're still talking about relatively low vitamin D serum levels (not quantitatively high levels)
I find this comment to be somewhat akin to grasping at straws, as it is highly unlikely that macular degeneration causes low vitamin D blood levels (rather than the other way around).
Considering that researchers almost never "think out of the box" except to promote their own agendas, Comments such as that lead me to wonder if these guys really know what they're doing or if they're just trying to promote preconceived ideas.and that lower vitamin D levels may result from macular degeneration
But all of this ignores a very important fact. The Vitamin D Council bases their recommendation of 40–80 ng/ml as a "sufficient" range, based on real life data including actual test levels of people who still live a basic hunter-gatherer lifestyle. This is as close as we can get to valid evolutionary archaeological data. IMO Mother Nature is virtually always the best source of valid data where the rubber meets the road (outside of the laboratories and the ivory towers of the academic world).
For health professionals: Position statement on supplementation, blood levels and sun exposureThe Vitamin D Council makes a recommendation of 50 ng/ml and defines the above reference ranges for the following reasons:
The human genome was selected with abundance of vitamin D. Humans evolved in the sun near the equator, synthesizing robust quantities of vitamin D in the skin. Research has shown that lifeguards, farmers near the equator, and sun dwelling hunter gatherers maintain blood levels between 40-80 ng/ml on sun exposure alone1,2,3.
The Vitamin D Council believes that the maternal 25(OH)D status necessary to provide antirachitic activity for offspring should be considered a biomarker for optimal vitamin D status in humans. Research shows that antirachitic activity in breast milk occurs at 45 ng/ml or higher, but not at 38.4 ng/ml or lower4.
Research has generally shown that parathyroid hormone is maximally suppressed at 40 ng/ml or higher, another finding that the Vitamin D Council considers a biomarker for optimal vitamin D status5,3.
The human body is usually unable to achieve 25(OH)D levels above 100 ng/ml on UVB exposure alone3. There are no studies to date to suggest that 25(OH)D levels over 100 ng/ml are beneficial, so the Vitamin D Council believes that the upper limit should be set at 100 ng/ml.
Vitamin D toxicity manifests itself by hypercalcuria and hypercalcemia. Research has shown that serum calcium levels are not related to 25(OH)D levels up to 257 ng/ml6, but cases of toxicity have been reported at levels as low as 194 ng/ml7. The Vitamin D Council believes that a conservative threshold of 150 ng/ml should be considered the lower limit of toxicity.
The Vitamin D Council recognizes that there are not enough controlled trials at this time to either support these recommendation or oppose these recommendations.
At least that's how I view the controversy.
Tex
It is suspected that some of the hardest material known to science can be found in the skulls of GI specialists who insist that diet has nothing to do with the treatment of microscopic colitis.
Hiya Tex,
Very nice discussion of the issue! Actually, I don't know whether my comment referred to ng/ml or nmol/L. I had only jotted down the "50" in my brief notes on the topic....didn't even note the article. lol.
Polly xo
Very nice discussion of the issue! Actually, I don't know whether my comment referred to ng/ml or nmol/L. I had only jotted down the "50" in my brief notes on the topic....didn't even note the article. lol.
Polly xo
Blessed are they who can laugh at themselves, for they shall never cease to be amused.
So I found out you can get various lab tests done here in Colorado just going into the lab and ordering it. Was off last Thursday so went into Quest Labs in my local Safeway (the lady said they opened in there like 8 months ago or something..) and got Vit D done as it had been at least 3 years since the last one which had been in the 50's at 5,000 a day. Got the results online last night and I'm at 75. I have been doing 10,000/day per the recommendation here for maybe 6 weeks or so in addition to the increased magnesium in various forms..
My question is...do I need to back off some?
Laine
My question is...do I need to back off some?
Laine
"Do what you can, with what you have, where you are"-Teddy Roosevelt
Hi Laine,
In my strictly unprofessional opinion, your current level is OK, but at your current dosage (after only 6 weeks) your serum level is almost surely still increasing, so unless you want your level to go higher, you could probably afford to back off a few thousand IU without much risk of losing more than a small percentage of your current level.
How much to reduce your dosage depends on your goal. Do you have an optimal target level above or below your current level? Data are available to aid in estimating dosage increases needed to boost serum vitamin D levels from one known level to another. And this information could also be used to estimate the needed dosage reduction in order to lower one's serum vitamin D level by a given amount. But unfortunately the table of data only goes up to a blood level of 60 ng/ml (150 nmol/l).
http://grassrootshealth.net/media/image ... single.pdf
But based on your test history, you could probably assume that if 5,000 IU will maintain a serum level of 50 ng/ml, and 10,000 IU correlates with 100 ng/ml, then about 7,500 IU might correlate with a long-term serum level of about 75 ng/ml. 6,000 IU would correlate with a long-term level of 60 ng/ml, etc. I estimated the 100 ng/ml from the fact that 10,000 IU should get you approximately half-way to homeostasis in 6 weeks. It might not boost the level that much because at the half-way point (time-wise), your blood level may be more than half-way to homeostasis, but it's best to err on the conservative side.
If I were in that situation and everything was going well, I would probably drop my dosage to about 6,000 IU. However, if I were having problems with acid reflux/GERD/heartburn, I might continue at the current dose for a few more weeks. It depends on your goals.
And if anyone uses the table at that link to estimate vitamin D dosage increases (or decreases), remember that the data are for someone who weighs about 150 lbs. (roughly 68 kilos). If you weigh significantly less, then you will respond faster (or a greater amount) than the data indicate. Likewise, if you weigh more than 150 lbs, then your response will be slightly slower (less) than the indicated amount.
Tex
In my strictly unprofessional opinion, your current level is OK, but at your current dosage (after only 6 weeks) your serum level is almost surely still increasing, so unless you want your level to go higher, you could probably afford to back off a few thousand IU without much risk of losing more than a small percentage of your current level.
How much to reduce your dosage depends on your goal. Do you have an optimal target level above or below your current level? Data are available to aid in estimating dosage increases needed to boost serum vitamin D levels from one known level to another. And this information could also be used to estimate the needed dosage reduction in order to lower one's serum vitamin D level by a given amount. But unfortunately the table of data only goes up to a blood level of 60 ng/ml (150 nmol/l).
http://grassrootshealth.net/media/image ... single.pdf
But based on your test history, you could probably assume that if 5,000 IU will maintain a serum level of 50 ng/ml, and 10,000 IU correlates with 100 ng/ml, then about 7,500 IU might correlate with a long-term serum level of about 75 ng/ml. 6,000 IU would correlate with a long-term level of 60 ng/ml, etc. I estimated the 100 ng/ml from the fact that 10,000 IU should get you approximately half-way to homeostasis in 6 weeks. It might not boost the level that much because at the half-way point (time-wise), your blood level may be more than half-way to homeostasis, but it's best to err on the conservative side.
If I were in that situation and everything was going well, I would probably drop my dosage to about 6,000 IU. However, if I were having problems with acid reflux/GERD/heartburn, I might continue at the current dose for a few more weeks. It depends on your goals.
And if anyone uses the table at that link to estimate vitamin D dosage increases (or decreases), remember that the data are for someone who weighs about 150 lbs. (roughly 68 kilos). If you weigh significantly less, then you will respond faster (or a greater amount) than the data indicate. Likewise, if you weigh more than 150 lbs, then your response will be slightly slower (less) than the indicated amount.
Tex
It is suspected that some of the hardest material known to science can be found in the skulls of GI specialists who insist that diet has nothing to do with the treatment of microscopic colitis.
Thanks Tex...
I took 5,000/day for years. I think I will go and buy some 1,000s tomorrow and back down to maybe 6,000/day. I haven't weighed myself for probably a month and a half cause I know it's not good...but I'm thinking I'm probably 110# now..usually am at 123# when I am feeling good. No Gerd/reflux/heartburn stuff going on....
Laine
I took 5,000/day for years. I think I will go and buy some 1,000s tomorrow and back down to maybe 6,000/day. I haven't weighed myself for probably a month and a half cause I know it's not good...but I'm thinking I'm probably 110# now..usually am at 123# when I am feeling good. No Gerd/reflux/heartburn stuff going on....
Laine
"Do what you can, with what you have, where you are"-Teddy Roosevelt
My doctor (hematologist/oncologist) likes the Vitamin D level on the high side of the spectrum. He went to a seminar at Harvard University last summer and he said this was the general consensus. Mine was in the high 80's and that is where he'd like me to keep it. I've been taking 2,000 IU's a day and it dropped to 60 when I had labs done last week. Now I know I need to increase it over the winter months and drop a little in the summer.
Nancy
Nancy