For better or worse, vitamin D is in the limelight these days. In headline after headline, it comes off looking like a white-gloved nutritional rock star, a solo artist who doesn't need a band.

But in nature, there are no solo acts. There never have been. Only symphonies and duets. 

So here we go again. Back to the truth, back to nuance. Vitamin D is going to need some help.

I'll tell you all about that help in a moment, but first, let's give vitamin D its due. Because vitamin D really is "the sunshine vitamin". You may already know the studies showing how just 30 minutes of full-body midday summer sun exposure is equivalent to consuming 10,000–20,000 IU of vitamin D. And you may have heard how important vitamin D is for optimizing calcium uptake, bone health, immune health, mood maintenance, synaptogenesis in the brain, and muscle strength.

All true. But here's the catch: one of vitamin D's key benefits requires an entirely different nutrient to work be safe.

Because it's not good enough to simply absorb more and more calcium. That could be dangerous. You have to tell calcium where to go! Vitamin D doesn't care where calcium could go to your arteries for all vitamin D cares (ever heard of "hardening of the arteries" or a "Coronary Calcium Score" to assess your heart attack risk?)

The truth is, you need a co-factor with your vitamin D, something to help partition calcium into the right compartments in your body. You need something to help direct calcium away from soft tissues like blood vessels and joints (so they stay supple) and toward hard tissues like bones and teeth (so they stay strong).

This co-factor is called vitamin K2...vitamin K2 MK-7, to be exact.

Vitamin K2 MK-7 is the long-forgotten vitamin you need to help you get all the benefits from vitamin D without the risk.

In fact, Dale Bredesen, MD, author of The End of Alzheimer's, now recommends at least 100 mcg of vitamin K2 MK-7 for anyone taking more than 1000 IU of vitamin D3 daily.

Have you checked your supplements lately? Is vitamin K2 included in your favorite brand of vitamin D3? Probably not.

How about your food? Does it contain significant amounts of K2? Maybe. Take a closer look. You may be familiar with K1 found in plant foods. But K2 is different: it is found in animal and fermented foods.

Good dietary sources of vitamin K2 include:

  • natto, fermented soy
  • goose liver
  • cheese
  • egg yolks
  • dark chicken meat
  • butter

You may have heard that if you have the right gut bacteria you can convert some of your dietary K1 into K2. That's correct. But the current data suggest this process is inefficient—especially if you have ever been treated with broad-spectrum antibiotics. So it's best to ingest your K2 directly.

Now back to your endless summer.

I hope you are enjoying the halcyon sunshine and liquid summer nights as much as I am. I hope your body is too. Ensure that it is by balancing the system that was designed to balance you.

Start thinking about K2.