Tip: Take This Vitamin or Get a Hernia

Researchers nabbed 216 college football players who were participating in the NFL Scouting Combine. They wanted to find out if there was a relationship between vitamin D levels and muscle strains, including core muscle injuries (sports hernias).

Using blood tests, they found that 126 players (more than half) had abnormally low serum vitamin D levels, and 22 of them had severe deficiencies. Here's how they defined that:

• Normal: 32 ng/mL
• Insufficient: 20-31 ng/mL
• Deficient: Below 20 ng/mL

Was there a relationship between low D and muscle injuries? In short, yes.

"Our primary finding is that NFL combine athletes at greatest risk for lower extremity muscle strain or core muscle injury had lower levels of vitamin D. This could be related to physiologic changes that occur to muscle composition in deficient states," said Dr. Scott Rodeo, the senior investigator.

The scientists here defined normal D levels as those being at least 32 ng/mL. That's 32 nanograms per milliliter... but that's just barely normal.

Progressive doctors go a bit further and say that the OPTIMAL range is between 50 and 70 nanograms per milliliter. And some shoot for as high as 100 ng/mL. Those higher ranges seem to be where the real health benefits kick in.

Now, the average American in late winter (after months of little sun exposure) averages about 15 to 18 ng/ml – a serious deficiency. So, chances are, unless you're a lifeguard in Kona who doesn't wear much sunscreen, you'll need to supplement with Vitamin D.

Experts suggest supplementing with 1000 to 5000 IU of Vitamin D3 per day. You can adjust that amount based on your non-sunscreened sun exposure, the time of the year, your location on the planet, etc. If you want to see where you're at and how much you need in order to maintain a healthy level, you'll need ask your doctor for a couple of blood tests for 25-hydroxyvitamin D.

Can you get too much vitamin D? Technically, yes, but it would very difficult to do unless you were swallowing over 20,000 IU daily for months on end. So, no need to worry about it really.

Old recommendations said 2000 IU daily was the safe upper limit, but today most agree that was unnecessarily low and say that 10,000 IU is more like it. (Government agencies and antiquated dietician schools will take a while to catch up and reluctantly change their recommendations, of course.)

1. Hospital for Special Surgery. More than half of college football athletes have inadequate levels of vitamin D: Vitamin D deficiency linked to muscle injuries. ScienceDaily. 17 March 2017.