Here is the revised text of the section on Vitamin D:
Vitamin D is Low in People Diagnosed with Diabetes But Supplementation Doesn't Help
Evidence is accumulating that suggests that Vitamin D is low in people who develop Type 2 diabetes. Because of this there has been speculation that Vitamin D improves insulin sensitivity. Unfortunately, there is not a scintilla of evidence that supplementing with Vitamin D in any form will reverse diabetes.
I am temporarily leaving Vitamin D in the "helpful" category, because it is possible it has some value in countering heart disease, but the evidence is accumulating that it may be just another overhyped simplistic cure promoted by unscrupulous celebrity doctors looking to earn fortunes selling products to people suffering serious chronic illnesses.
The early enthusiasm for Vitamin D as a treatment for diabetes occurred after a November 2007 a study headed by Dr. Paul Knekt published in Diabetes Care found that over 17 years in a population of roughly 4,000 Finnish men and women, individuals with higher blood levels of vitamin D had a 40 percent lower risk of developing type 2 diabetes than those with lower levels of this vitamin.
Serum 25-Hydroxyvitamin D Concentration and Subsequent Risk of Type 2 Diabetes. Catharina Mattila, Paul Knekt, et al. Diabetes Care 30:2569-2570, 2007
A review of earlier work pointing to the same conclusion can be found in:
The Role of Vitamin D and Calcium in Type 2 Diabetes. A Systematic Review and Meta-Analysis. Anastassios G. Pittas, Joseph Lau, Frank B. Hu and Bess Dawson-Hughes.J Clin Endo & Metab Vol. 92, No. 6 2017-2029.
Vitamin D Has No Effect On Early Type 1 DiabetesLow levels of Vitamin D have also been linked with increased incidence of autoimmune disease, including both Type 1 diabetes and multiple schlerosis. One meta-study concluded that supplementation with Vitamin D had a preventative effect on the development of Type 1 (autoimmune) diabetes.
Vitamin D supplementation in early childhood and risk of type 1 diabetes: a systematic review and meta-analysis.C S Zipitis, A K Akobeng. Archives of Disease in Childhood 2008;93:512-517
Unfortunately, Vitamin D in this context is preventative, but does not reverse the condition.
Giving Vitamin D to people recently diagnosed with Type 1 (autoimmune) diabetes for two years made zero difference in their outcomes.
No Protective Effect of Calcitriol on ß-Cell Function in Recent-Onset Type 1 Diabetes
The IMDIAB XIII trial Diabetes Care September 2010 vol. 33 no. 9 1962-1963. doi: 10.2337/dc10-0814
Vitamin D Infusion Does NOT Improve Glucose MetabolismHere's another result that points to the possibility that it may be that something about having diabetes lowers Vitamin D levels, rather than that Vitamin D improves insulin sensitivity.
A study in which people who were deficient in Vitamin D were given glucose tolerance tests and then given a massive dose of Vitamin D which raised their levels to normal after which they were given follow up glucose tolerance tests found no change in blood sugar or insulin sensitivity after Vitamin D was normalized.
Glucose tolerance and vitamin D: Effects of treating vitamin D deficiency Kamilia Tai. Nutrition. Volume 24, Issue 10, Pages 950-956 (October 2008).
Vitamin D May Not Be Significant in Loss of Blood Sugar ControlA study of 446 European subjects diagnosed with metabolic syndrome found no relationship between blood concentrations of vitamin D and insulin secretion or sensitivity. In this group 20% had vitamin D levels over 30 ng/ml (75 nmol/L). This may suggest that the low vitamin D levels seen in people with diabetes are a result, not a cause of their blood sugar disorder.
Serum Vitamin D Concentration Does Not Predict Insulin Action or Secretion in European Subjects With the Metabolic Syndrome. Hanne L. Gulseth et al. Diabetes Care April 2010 vol. 33 no. 4 923-925. doi: 10.2337/dc09-1692
Womens Health Study Finds No Effect on Diabetes of Vitamin D and Calcium SupplementationThe Womens Health Study--the people who put an end to the myth that the low fat diet prevents heart disease--came up with the finding that, in 33,951 women, supplementation with 400 IU Vitamin D and 1000 mg Calcium made no difference in the number of people who developed diabetes. The finding was described as "robust."
Calcium Plus Vitamin D Supplementation and the Risk of Incident Diabetes in the Women's Health Initiative. WHI investigators. Diabetes Care 31:701-707, 2008
Those who champion Vitamin D claim that much higher doses are required to see an effect. This may be true as the amount of Vitamin D used in this study was well under the amount that is necessary to raise low levels into the normal range.
High Dose Vitamin D Increased Fractures in Older WomenAdouble-blind, placebo-controlled trial of 2256 community-dwelling women, aged 70 years or older, given Intervention 500,000 IU of cholecalciferol or placebo by injection saw a 26% higher risk of fracture in the group receiving the supplementation. So much for the theory that doses were too low in other studies.
Annual High-Dose Oral Vitamin D and Falls and Fractures in Older WomenKerrie M. Sanders et al. JAMA 2010;303(18):1815-1822.
Vitamin D's Connection with Cardiovascular DiseaseRecent research has linked low levels of Vitamin D with higher risk of cardiovascular disease. An analysis of the Framingham data found that "Vitamin D deficiency is associated with incident cardiovascular disease."
Vitamin D Deficiency and Risk of Cardiovascular Disease. Thomas J. Wang et al.Circulation. 2008;117:503-511 The research that has not yet been done is the well-conducted study that would investigate whether supplementing with Vitamin D would lower the incidence of heart disease. Dr. Davis of The Heart Scan Blog claims to have seen vitamin D supplementation improve cardiac health. He believes that it is a vital part, along with Vitamin K, of the metabolic process that directs dietary calcium where it belongs--on the bones, rather than being deposited in arterial plaque which is part of the process that leads to heart attack.
Vitamin D May Have an Effect on MoodThere is some evidence that Vitamin D reverses the depression many people experience in the dark months of winter.
Vitamin D3 enhances mood in healthy subjects during winter Allen T. G. Lansdowne, S. C. Provost. Psychopharmacology, DOI 10.1007/s002130050517
Because Vitamin D has a positive effect on mood--similar to that burst of good feeling we experience when we step out into the sun, it is possible that the low levels of Vitamin D found in people with Diabetes may be related to the increased incidence of depression associated with Type 2 diabetes.
Vitamin D Improves Outcome in Chronic Kidney DiseaseA study published in May of 2008 found that patients with chronic kidney disease given Calcitriol (a form of Vitamin D) had a 26% lower mortality and a 20% lower rate of going onto dialysis over a period of almost two years.
Association of Oral Calcitriol with Improved Survival in Nondialyzed CKD Abigail B. Shoben et. al. Journal of the American Society of Nephrology Published online May 7, 2008. doi: 10.1681/ASN.2007111164
A Danger with Vitamin D: High Blood Calcium Which May Cause Hardened ArteriesIf you supplement with the very high Vitamin D levels being promoted by celebrity doctors you run the risk of experiencing very high blood calcium levels if you take calcium supplements. Even blood calcium levels in the high normal level have been associated with increased heart disease so this is a serious concern.
Rampant Vitamin D supplementation is causing a revival in what used to be a rare condition, Milk Alkali syndrome, which can be fatal.
Got Calcium? Welcome to the Calcium-Alkali Syndrome Ami M. Patel and Stanley Goldfarb. J Am Soc Nephrol 21: 1440-1443, 2010
I personally experienced a serious problem with a high blood calcium level after supplementing with 2000 IU of Vitamin D for about 9 months in my doctor's suggestion. I was NOT taking any calcium supplements, but I was eating several servings of cheese each day as part of my lower carbohydrate diet. My Vitamin D level tested well above the low end of normal but at a level that the lab considered normal, but the lab high is the level at which Vitamin D toxicity occurs.
If you do supplement with more than 1000 IU a day of calcium you must get your blood calcium levels checked from time to time and if they are at the high end, you should back off both Vitamin D and foods high in calcium until they come down.
As is always the case, our metabolisms are too complex to be "cured" with any supplement. It is possible that supplementation with Vitamin D in those with measured low levels is helpful for heart disease, but it is foolish to supplement with massive doses of Vitamin D when you don't know your levels and are not tracking your blood calcium.
In addition, I have see a healthy person experience a hormonal reaction similar to "roid rage" when they supplemented with high doses of Vitamin D. Dr. William Davis confirmed to me, via email that Vitamin D can raise Testosterone levels.
Recommended Dose:1000 IU per day. The oil based versions of Vitamin D are better absorbed than those found in hard calcium-based pills. There is no need to buy overpriced special versions of Vitamin D, such as Vitamin D2,as they may actually be less effective than the regular ones.
There is some controversy about what level constitutes an overdose but if you are not getting a lot of sun, adults should be fine taking 1000 IU. If you are taking Vitamin D, ask your doctor to test your Vitamin D level when you get your other blood tests just to be safe.
Doses higher than 1000 IU may cause problems if you already have normal levels of Vitamin D and may unbalance your blood calcium levels.