Those of you taking high doses of D3 should consider taking K2 also :
Vitamin D and K2 Work in Tandem to Slow Arterial Calcification
"The study was designed to compare the effect of oral administration of vitamin K2 (MK-7) plus vitamin D, or vitamin D alone, on the progression of coronary artery calcification score and carotid intima media thickness (the lining of the main arteries in your neck that feed blood to your brain), which are hallmarks of potentially lethal heart disease and stroke. The data revealed a slower progression of calcification in those taking both vitamin K2 and vitamin D compared to those taking vitamin D alone.1 The study’s lead author said:"
“In this study, the K2 and D protected against cardiovascular calcification, while the D group alone did not. Clearly, this has positive implications for human health." "
Definitely always take K with your D. You are right. They are together in cod liver oil naturally. So if we supplement with actual synthetic d, we need to add the k.
I was wondering if 5000 iu / day was too much... then I found this:
If you’re fair skinned, experts say going outside for 10 minutes in the midday sun—in shorts and a tank top with no sunscreen—will give you enough radiation to produce about 10,000 international units of the vitamin.