Bigger Leaner Stronger: The Simple Science of Building the Ultimate Male Body

by Michael Matthews

According to Dr. Michael Holick, however, even 2,000 IU per day is suboptimal. Research shows that 2,000 IU per day is the minimum needed to maintain vitamin D sufficiency (30 milligrams per milliliter), but Dr. Holick maintains that optimal vitamin D status is between 50 and 80 milligrams per milliliter, which would call for a daily intake closer to 5,000 IU.11 So, I recommend that you start at 2,000 IU per day and then get blood tested for your 25-hydroxyvitamin D levels (the usable form of vitamin D your body creates) to ascertain your vitamin D status. Chances are, you’ll come in below 50 to 80 milligrams per milliliter. Research shows that you need to increase intake of vitamin D by 100 IU to increase blood concentration by 1 milligram per milliliter, so you can then calculate how much additional vitamin D you’ll need to take to reach optimal levels.12 For instance, if your test came back at 30 milligrams per milliliter and you wanted to raise it to 50 milligrams per milliliter, you would need to increase your current intake by 2,000 IU.