October 22, 2007

Vitamin D lowers Insulin Resistance?


Research published after this blog post was written finds that supplementing with Vitamin D, even in intravenous megadoses does NOT improve blood sugar or insulin resistance in any significant way. You can find citations to that research HERE.

Vitamin D may have some positive effects on heath, and I continue to take it, but it will not reverse any already existing autoimmune condition nor is it a diabetes cure. In fact, my own blood sugar stopped responding to Vitamin D within a week after I wrote this blog post.

If you found this page searching for help with lowering blood sugars, please check out this page: How To Get Your Blood Sugar Under Control. I hear every week from people who have used this technique to lower their blood sugars dramatically.

Original Post

At my recent visit to the endocrinologist, the doctor suggested I add 1000 I.U. of Vitamin D to my daily regimen because of some recent data suggesting that it helps the body eliminate cells that have developed melanoma.

I followed her advice and started taking a pill every day around 10:30 when I take my metformin. A few days later I started to experience dramatic lows around 3 PM. Lows have rarely been a problem for me, as my body usually mounts an aggressive counterregulatory response at the first hint my blood sugar is dropping. All of a sudden I was seeing blood sugars in the 60s, and they were not resolving with the usual 2-4 grams of glucose. At one point as I battled a low I ended up eating 25 grams of Halloween candy and still only found myself in the 80s ninety minutes later.

It took me a few days to connect the lows with the addition of Vitamin D to my daily regimen. When I did, I started to read up on the relationship of Vitamin D to diabetes. It turns out that the relationship is a strong one, not only for people with Type 2,as a recent metastudy discovered--people with Type 2 appear to have low blood levels of Vitamin D and there is some suggestion that the combination of Vitamin D and Calcium may delay the diagnosis of Type 2, but also for people with Type 1. A Finnish study found that children who received Vitamin D supplementation appear to have a lower rate of Type 1 than those who did not.

There is also some data suggesting that Vitamin D may also be protective against Multiple Sclerosis, a disease that has long been known to be more prevalent in northern latitudes, as well as the data connecting it with cancer prevention.

The large dose of Vitamin D I am now taking appears to increase my sensitivity to insulin even though I am already insulin sensitive. It potentiates a dose as low as 1 unit of insulin, making it several times more powerful than usual. When I have skipped my insulin for a couple meals to see what the Vitamin D it might do when I don't use insulin (while eating very low carb meals) I did not experience the dramatic drop, but I did end up very slowly drifting down into the high 70s a few hours after dinner, rather than ending up in the 90s or low 100s as I would have expected to do.

I have read that it takes many months to completely restore Vitamin D levels to normal, so I'm going to keep supplementing and see what happens,though I'm thinking I might look for a lower dose pill and split the dose to see if I can avoid the dramatic drop all at once, as they are quite disturbing and leave me feeling jittery and off center for hours afterwards.

If you have had any interesting experiences with Vitamin D let me hear about them. I don't know if my sensitivity to Vitamin D is another of the things that grow out of my own, oddball form of Genetic diabetes or something that might be common among people with diabetes in general


John Phillip said...

Hi Jenny:
Your experience with Vitamin D is in line with my experience. I am a type 2, and have been on Vitamin D supplementation now for 1 year (2000 IU/day), started primarily for cardiovascular and cancer prevention reasons. I noticed that my fasting and postprandial (1 & 2 Hour) dropped about 20 - 25% after about 30 days of beginning supplementation. Now after a year, I am consistently at 70 - 75 fasting and rarely above 100 postprandial (low carb diet, of course).
Also, as recommended by Dr. Davis of the Track your Plaque blog, I have switched from a powder based version to a gelcap to improve delivery. It is critical to have the Vitamin D blood test to ensure you remain in the Dr. Davis recommended range of 50 - 60 ng/Ml.
I would also like to say that reading your posts have had a major impact on how I test by glucose lately with regular testing at the 1 & 2 hour intervals after eating. It was an eye opener to me, as I had only been checking fasting and pre-meal levels at the suggestion of my 'former' doctor. Your blog is consistently filled with practical and highly informative information which I look forward to receiving. Thanks!

Jenny said...


Thanks for your very kind words.

Testing fasting and before meals is ONLY appropriate for patients who use insulin. Unfortunately, few doctors know WHY those times were chosen. I ran into the same thing when I first was diagnosed. Since my fasting was normal and my post-meal numbers in the mid-200s this delayed my being able to get doctors to treat me appropriately.

Paul Anderson said...

Hi Jennie,

I find this topic very interesting.

There seems to be a suggestion that for those people with low vitamin D levels supplementation will help with diabetes control ( I am not absolutely sure if this is by reducing insulin resistance or somehow helping beta cell function - or a combination of both).

For many reasons it would be useful to have your vitamin D-levels measured. After all, if there is an optimal level I guess thta's the place to be.

My understanding is that fish oil supplementation is more effective. It also would help with cell structure by boosting the omega 3 content of cell membranes.

How do you assess your insulin resistance. I guess its botha relative and an absolute thing. Short of measuring the measuring BG and insulin levels in repsonse to a glucose challenge its not very easy. Alternatively I guess there are proxy markers for IR like trigliceride levels, HDL, body fat, etc, and maybe blood pressure.

I hope you get a chance to follow this up and that it continues to have positive effects.

I, also, find your blog and website a very good read.


Jenny said...


I measure my insulin resistance by noting what my insulin/carb ratio is.

That's the number of grams of carbs that one unit of insulin will cover.

Mine is currently about 1/15 - 1/120, a bit less in the morning and sometimes a bit more.

Unknown said...

I've read that vitamin D helps improve lipids (Dr Davis.) Could it be that improvement that lowers insulin resistance? Maybe it has an effect on the enzyme, lipoprotein lipase (can you tell I've been reading Taubes?) If your insulin is peaking around that time then LPL activity would be higher in your fat cells, soaking up all those triglycerides.

Dr. William Davis said...

Hi, Jenny--

Getting up to date on your delightful and insightful blog, I came across your vit D discussion.

I've been fussing with this issue for nearly two years now and have never looked back. In the northern midwest (I'm in Milwaukee), the average dose for a woman is 4000 units per day, for a male 5000-6000 units per day to generate desirable serum levels of 25-OH-vitamin D3 of >50 ng/ml. It's shocking what some people require. I've seen people take 12,000 units for several months, for instance, yet still have levels of 30 ng/ml.

The positive effects of doing this are astounding. Lipid effects, enhanced insulin responses, improved bone density are only the start.

As J Phillip pointed out above, a gelcap is essential, though an internist recently flew in to see me from Kansas City to show me the phenomenal effects he's experienced on his spinal disease taking a tablet form along with a tablespoon of olive oil. (He's tougher than me!)

The effects are so impressive that I've re-directed our program for heart disease reversal and our research to incorporate much more exploration of the vitamin D question.

(Love your discussions of Taubes' book!)

Unknown said...

Thanks for bringing this subject up, I was headed in for some blood tests anyway and asked my doc to check my vitamin D levels, turns out that I am low, so thanks to you.


Tammy said...

Why am I just now learning about this? My Husband is Type 1. We finally found got him on the Pump and he is doing much better on that. He has been a diabetic for 15 years.
Anyway, this stuff is great. I'm going to subscribe to this blog!
Way to go Jenny!

Terry said...

Hi Jenny,
It is something about vit D. I have been diabetic for almost 30 years, on insulin for 10. I stumbled on the vit D thing after reading about natural vit D. From the sun. I have a blocked vain in my leg and read a lot of info about the affect of D on the vains. I have been sitting out for about 40 to 60 min a day for 2 weeks. The pains in my leg has almost gone away. The last few days I have come off my short acting insulin. My fasting is around 70 and bed time around 130 to 150. I think vit D has alot of good benefits we may not know about. I go to my endro Dr in 3 weeks it will be interesting to see my A1C. I hope this is typed correctly as I am vision impaired from diabetes problems with my retina. Today I have noticed some inprovement in my vision. HMMMM I wonder. I hope I can find this blog again. It is very interesting.

Sarah said...

I,m so interested in this blog regarding vitamin D. I suffer from P.C.O.S and insulin resistance. I have been following a low carb diet for years now and am very nearly type 2 diabetic. I have been holding weight around my middle which even on a very low calorie and high protein diet , I just could not shift. I have been researching alot over the years and suddenly came across info concerning vit D and insulin resistance. I thought -why not - ive tried just about averything else and the research seemed exremely promising. I have been taking 100iu per day now for approximately 3weeks and already im feeling better. I have far more energy, my brain seems far clearer and less foggy in my thinking. I have noticed my wieght is also suddenly starting to shift. I have done nothing else to change my routine except take vit D and busy bee b vit complex. I can scarcley contain my enthusiasm and am so scared that it will stop working and all will go back as it was. However, i just can not recommend taking this combination enough to help regulate weight loss and insuling resistance. My lows in blood sugar have also been far less regular.I almost forgot!- I have also been making sure that i have been drinking upto 3litres of spring water per day and this seems to help shift the weight too. My skin also has benefitted and far softer and smoother and hardly any wrinkles too!(always great news!) Keepup the great blogs-thank you so much for all your great information.
love Sarah x

Sarah said...

just realised i said 100iu a day! of course - i meant 1000IU per day!
Sarah xx

Little Kiwi said...

What can I say other than Wow....
For the past 18 months since being diagnosed with insulin resistance (seemed to be a contributing factor in why I could not budge weight around my waste), I am on a low GI diet and am a vegetarian.

Just had the first followup blood test since being diagnosed and have the same issue with blood sugar and insulin resistance, plus raised cholesteral, and guess what, have a sever Vitamin D deficiency.

Reading these blogs has been a real eye opener and I am leaving the office to buy a supplement and also taking all my newly gained knowledge back to mt Doctor...

Thankyou for having such a great blog, and I will keep you updated on my progress with the insulin resistance and the waist size

Unknown said...

Thanks for all the valuable information.
I suffer with diabetes II as a result of being exposed to Agent Orange in Vietnam. It jumped up all at once and now my sugar is very hard to control. I have been put on "Ergocalciferol (vit D2) 50,000 unit capsule" to be taken once a month. Can I get some input from somione on this dosage?

Jenny said...


If a doctor put you on that dose for a short time to raise your very low Vitamin D level it is probably fine.

It should be used in conjunction with testing of your levels to make sure they stay in the safe range.

Jim Sutton said...

Joyce: "Ergocalciferol (vit D2) 50,000 unit capsule" is NOT the form of vitamin D found in our body. The correct form is "Cholecalciferol" or Vitamin D3. Please see Dr William Davis' heartscanblog and do a search for "Ergocalciferol" or "Vitamin D2" for an informed presentation on this topic. Hope this helps you.

Unknown said...

I am amazed to have finally found this connection. I'm very much in Sarah's situation, except I have another additional complication. I had gastric bypass surgery in February of last year, lost 30 pounds in 3 months after that, and then stopped. I have been doing months and months of research and blood tests. The only supplement the doctors have said is low has always been Vitamin D.

When I went back to my surgeon, I point blank asked him if my lack of weight loss was caused by Vitamin D. He said it wasn't. That was over a year ago.

In the last two weeks I have done EXTENSIVE reading about insulin resistance and leptin resistance. In the last 48 hours I have become convinced from my symptoms that that's what's going on with me. Fasting insulin was 9, I can't lose fat -- only water -- no matter how many calories I lower to, and no matter how long I exercise.

My insurance company's lab doesn't do leptin testing, although they acknowledge that leptin is a major factor in obesity. Go figure.

It wasn't until today I decided to cross reference the two issues -- my low Vitamin D and Insulin Resistance/Leptin Resistance. I was astonished! I'm experiencing these I/L resistance symptoms, most likely DUE TO my low Vitamin D levels!!

Even my two endocrinologists NEVER EVER mentioned that Vitamin D could interfere with your insulin and/or leptin levels! I was almost looking at a revision surgery until I came upon this yesterday.

I've been going through this for two years and have been so, so frustrated. It's been devastating. I felt like I've been chained to a tree. For all my running and exercising (an hour 6 days a week at 240 lbs), I was running and running only to stay where I was.

When I tell doctors I stopped losing weight, their mouths drop open in absolute shock. It's embarassing to tell people I even had surgery. You don't let someone cut you open so you can lose weight unless you're serious. I felt like such a failure, even though I'd invested so much money in various things to keep track of calories!

At first I really thought it was my thyroid, but all the tests proved normal. Last week I bought a Bodybugg ($200) to check my burn. I was SO shocked to find that I'm burning 2500 calories/day when I don't exercise, and closer to 2900 when I do! And then I'm only eating 1000-1400 calories a day, meaning some days I burn everything I eat! It just wasn't making any sense.

SOMETHING was blocking my fat burning, but doctors kept telling me I was fine and NEVER associated my Vitamin D with my inability to lose weight, and never felt I was insulin or leptin resistant.

Now that I'm onto this . . . I'm a little discouraged, because I read it could take several months to get right again!!! After two years of misery, I have to say I'm just a little impatient to see results from all my hard work. :)

I've been on Metformin (for PCOS, which is one of the things which qualified me for surgery). I've noticed some changes once I stay on a low-carb diet. But I understand that Vitamin D is far more efficient than even Metformin!

I'm so thrilled, but now have to pay for patience. :)

I have a prescription for 50,000 IUs of Vitamin D -- but don't know what form it is. The bottle just says Vitamin D. Is there any way to really know??

Unknown said...

Oh, correction! Fasting insulin level was 10 -- but my lab's range is 3-11, so doctors have been convinced that I'm fine.

terriergal said...

Hi - interesting! I don't know if you were looking only for diabetes-specific stories re:vitaminD but here goes: I am 39 and have three kids. I do not have diabetes but have had my glucose tolerance tested while pregnant and while not pregnant. I had it tested a few years ago when I was on pain killers for a pelvic pain problem - and while on pain killers EVERYTHING felt bad in general but I couldn't figure it out. I would get jittery and weak, typical of blood sugar lows...which is why I asked to have it tested. It was normal... everything is always 'normal' even when i feel like dirt. But surgery resolved my looong trial with pelvic pain thankfully so I am no longer on pain killers except for the occasional bad migraine. I stopped eating a lot of junk, and no longer really have an appetite for what I used to crave. I also get analgesic rebound headaches and so have to be careful not to use them too much, as well as avoid caffeine for the same reason.

My mom has Type 2 diabetes however, and she is on a lot of medication for rheumatoid arthritis. Hard to say if one caused the other or if it is genetic or what and whether I am manifesting a bit of that. But it doesn't show up in tests, just in how I feel, sometimes.

I had read about vitamin D and i know that I am MUCH more energetic and positive minded when I get some direct sunshine, so I thought that I would try it to see if I can combat the winter blues this year. I took 2000 IU per day for about a week before I started to feel chilled, achy, and foggy headed and had a roaring sound in my head like very loud low tinnitus (I do have tinnitus normally). I had muscle cramps in my back that were killers. A bit of research turned up this is not unheard of in vitamin D sensitive individuals. A few days of of the D supplementing resolved this.

I also am highly allergic to fish so I switched to a non-allergenic vitamin D in a smaller dose and take it once or twice a week. I still start to feel a lot of that rumbling sound in my head and muscle tension if I do too much however, but now I know or at least am pretty sure what it is.

nimsy said...

My experience matches terriergal's. I suffer from SAD and some auto immune problems. My mum has diabetes type 2 and I am doing my best not to develop it by being very careful with my diet.
I came across the vitamin D Action campaign and did lots of research on vitamin D and felt that I would really benefit from it. So I got a test done via their website and found my levels were really low (19ng/ml) and started to supplement with vit D.
But after a few weeks,I started getting severe headaches that wouldn't go away, body ache, shivers, chills, fever etc. I was only supplementing with 800iu of vit D a day. When I stopped, the symptoms took 3 weeks to go away. I tested this by taking vit D again and after about 3 weeks of supplementation, same problems as before and again it took approx 2-3 weeks for them to subside.
I have read that you can be sensitive to vit D, so that is probably what has happened with me.
I feel really upset and desperate, because I am sure that a higher level of vit D would really benefit me but don't know how to acheive this without getting ill.
Has anyone who is sensitive to vit d managed to find a way to increase their vit d levels without problems?
Is it better to take a small dose daily or a bigger dose less frequently?

Unknown said...

Did you guys look at the fillers for your vit D capsules? It could be something besides the D that is doing that, or maybe it's the source of the D if you are sensitive to seafood. Anyway 800IU wouldn't help much anyway, try 1000IU per 25 lbs of body weight. ex. 150 lbs = 6000IU

Anonymous said...


Just wanted to say that I also have a huge Vit D deficiency and have the opposite problem with weight gain. Until I started taking vitamin D, I couldn't gain any weight--I lost most of my fat and muscle, and doctors who saw me for the first time would ask me if I could possible have AIDS or an eating disorder. As soon as I started supplementing, I was able to gain weight again, both fat and muscle. Joints and bones aren't hurting as much. Nerve pain is lessening. Lots of infections clearing up.

Peter Snowdon said...

Dear Jenny

I just caught up with the discussion you have here of Vitamin D and insulin sensitivity, after having finally started taking my diabetes diagnosis seriously, AND having discovered I am severly deficient in Vitamin D (8 ng/ml). Thanks for your blog, and for all the valuable information you have gathered.

I'd just like to comment on the two studies you cite here as refuting the Vitamin D/insulin connection:

(Caveat: I am not a scientists, but my university degree is in philosophy, so I'm quite prone to looking for logical flaws).

It seems to me that these two studies do NOT adequately demonstrate that there can be no impact of Vitamin D levels on insulin production and/or sensitivity, because they only cover a small range of cases for the key variables. The Tai et al study defines Vitamin D deficiency as less than 50 nmol/l, which is well within the healthy range recommended by a broad consensus of scientists participating in the D-Action study. Moreover, average D levels at the start of the experiment were only a fraction under 40 nmol/l. This is also more or less within the level which D Action is calling for as 'normal'. So at least prima facie, this study was examining the impact of increasing the Vitamin D levels of people with adequate Vitamin D. It also relies on a glucose tolerance test to determine insulin resistance. It is impossible to tell from the abstract if other factors which may influence response to this particular test were also isolated out during the study.

The Women's Health study, OTOH, gave only 400iu/d of Vitamin D, and does not seem to have tracked Vitamin D levels, only supplementation. 400 iu/d is a very weak dose: I know for instance that many doctors believe that to have a lasting impact on my Vitamin D levels, starting from such a low baseline, I would need to take 8000 iu/d.

So, it seems to me that neither study provides ANY data on what happens if you give large doses of D3 over long periods of time to people who are already diabetic or pre-diabetic.

Good wishes

Shane Mac said...

Hey all
I have had uncontrolled diabetes since 2008. Blood sugar levels ranged from 240 to 400 with insulin and meds. Feb 2010 had a visit to docs office , blood test revealed very low vitamin D.
Doctor started me in D2 50,000 units twice a week (50,000 is correct). Took about a week to see any results but the results were huge. Started to have blood sugar levels crash down to 40 & 50 range – never had that to happen before (scary) . Cut my insulin injections down to 10 units twice a day , before D2, I was injecting 60 units twice a day and also 15 units of fast acting insulin after meals. Cut the fast acting insulin out altogether.
I know everyone’s body chemistry is different, but for me D2 was heaven sent. Kind of has me wondering why the doctors hasn’t test my D levels in the past 2 years . I myself would have never thought I was vitamin D deficient as I spend a lot of time outside and in the sun.
I hope this info serves to help others.
Thanks for your Wonderful Blog Jenny!
PS - Prescription reads = VIT D2 1.25mg (50,000 unit) .

Jenny said...


Interesting! Do make sure that you keep monitoring your levels, because too-high Vitamin D is associated with brittle bones and possibly higher risk of some cancers. Check out the next-to-last paragraph of this review:


Dianne said...

Sheryl and Terrigirl's negative experiences with Vitamin D sounds like the Vitamin D supplementation uncovered an underlying magnesium deficiency. Magnesium, along with other co-factors (zince, vitamin K2, boron, and a small amount of vitamin A) is required to metabolize vitamin D and to produce the active form, (vitamin D hormone), although magnesium is the the most important of these. It is also required for all the body processes that vitamin D influences. So if a person has an underlying deficiency of magnesium, supplementing with vitamin D will cause them to feel worse rather than better with prolonged supplementation, as existing magnesium stores are used up to metabolize and utilize the vitamin D. Because magnesium insufficiency or deficiency is quite common, this scenario is not unusual.