Dr. Clemens is concerned because vitamin D plays a big part in so many bodily functions.
"We have realized now that vitamin D has a major role in so many other conditions including: hypertension, blood pressure regulation, heart health, maintaining bone structure, and maybe part of the obesity/diabetes story as well," said Dr. Clemens.
With no obvious indicators we're deficient, it is a silent crisis. Dietitian Elizabeth Somer points out who among us is more at risk.
"As we get older we get less and less efficient at making vitamin D," said Somer. "Most of us wear sunscreen because we're concerned about getting skin cancer. So as you get older, if you're skin is dark, if you wear sunscreen or your indoors a lot, it's just a given you're going to be vitamin D deficient.
So how much vitamin D do you need? The current recommendation for vitamin D is 400 IUs, but that's something experts say falls short of our needs.
Now some experts are recommending between 800 and 1000 IUs, but keep in mind we don't get so much from our food. Some of the highest sources like dried shiitake mushrooms and a serving a salmon are only around 240 IUs. Keep in mind we don't eat these foods every day. The ones that we do, fortified milk and juice, you are just not getting that much.
When the RDA for vitamin D is increased, which Clemens say should change by year's end, then and only then will you see greater fortification in the food supply.
Until then many are taking higher doses, which doesn't appear to be toxic. And there's a simple blood test that may be the best indicator for what you need.
"The clinical literature indicates there are no side effects to 1000 IUs, in fact the toxicological data indicate that we can take upwards of 50,000 IUs without adverse effects," said Dr. Clemens.