In Israel, some researchers still think that 1,000 IUs of vitamin D is “high dose.” However, Doctor Breslavsky, working under the supervision of Professor Shargorodsky at Tel Aviv University, did find out some very interesting facts about 1,000 IU/day and changes in heart health and general health of diabetic patients, despite the low supplementation amounts.
Breslavsky A, Frand J, Matas Z, Boaz M, Barnea Z, Shargorodsky M. Effect of high doses of vitamin D on arterial properties, adiponectin, leptin and glucose homeostasis in type 2 diabetic patients. Clin Nutr. 2013 Feb 27.
They did a randomized controlled trial of 1,000 IU/day versus placebo in 47 diabetic patients, 32 of whom completed the study. They looked at changes in various hormones and in glucose resistance. Of course they found no changes with their tiny dose of vitamin D. However, they did manage to find some beneficial changes in arterial stiffness.
First of all, 1,000 IU/day for a year only raised 25(OH)D levels from 12 ng/ml to 17 ng/ml, so the patients in the treatment group remained vitamin D deficient. None of the measurements of metabolic activity or hormone levels changed over the year except a trend for higher adiponectin levels (p=.053). However, aortic stiffness decreased significantly (p=.01) in the 19 patients in the treatment group.
I certainly liked what the authors said about vitamin D and cardiovascular disease:
“Previous clinical and experimental data show that the vitamin D affects the renin angiotensin aldosterone system, vascular smooth muscle cell proliferation as well as vascular calcification and inflammation. Furthermore, decreased serum vitamin D levels relate to increased blood pressure and impaired glucose homeostasis, which directly affect risk of cardiovascular disease. Recent epidemiologic data have shown that low levels of 25- hydroxy vitamin D and 1,25-dihydroxyvitamin D are correlated with increased risk in all-cause and cardiovascular mortality. Moreover, low levels of 25(OH) D are associated with higher risk of myocardial infarction in a graded manner, even after controlling for factors known to be associated with coronary artery disease.”
I hope the authors have learned that dosing vitamin D is like dosing thyroid hormone. The two hormones share the same type of receptor super family. With thyroid hormone, like cholecalciferol, 125 ug/day is needed in most people (5,000 IU/day), but some people will require 250 ug/day (10,000 IU) and a few obese people might even require 375 ug/day or 15,000 IU. Such doses will result in normal thyroid hormone levels and will also result in natural vitamin D levels.