Historically, 400 IU (10 ug) of vitamin D was recommended for better health because it closely approximated the amount of vitamin D in a teaspoonful of cod liver oil. However, 800 to 1,000 IU is ...
Over the past few decades, the "normal" blood level of vitamin D (25-OH vitamin D) was based on the amount needed to keep PTH from becoming abnormally high. Again, PTH at high levels can cause ...