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What Is Vitamin D And Why Do We Need It?

What is Vitamin D and why do we need it? Nutrient breakdown by Laura Ligos RD


I have given you a background on who I am and how I deal with real food in real life. I think it’s time I geek out with you now, what do you think? I want to start a series of nutrient breakdown posts to give you more tangible takeaways as it applies to nutrition and your health.

This past week I was in Boston for training for work. As a team, we went to Boston’s Escape the Room and it was a blast. No, we did not escape, albeit we were close. We had a blast BUT we almost couldn’t figure out a clue that should have been easy for a bunch of nutrition nuts.

The clue was basically leading us to an answer that was revolved around VITAMINS. I shouted this to my teammates and we all started cracking up. We talk about vitamins DAILY and remind each other to take our vitamin D because HELLO NORTHEAST WINTERS.

I digress.

Let’s learn a little about vitamin D, shall we?

What is Vitamin D?


Vitamin D is actually a hormone, not a vitamin, more specifically a steroid hormone.

That being said, we are actually able to make our own vitamin D if all goes right. All we need is some sunlight and cholesterol and we are on our way to sufficient vitamin D. Yes, in fact, cholesterol is beneficial to our health, although you probably already knew that.

When our skin is exposed to ultraviolet light from the sun it gets absorbed with the help of cholesterol and is converted into vitamin D, which we can then use in the body for its many uses.

Note: I over simplified this process so that you know enough to know what’s good.

We do not actually have to consume any source of vitamin D in order to have it, making it much closer to a hormone, but alas we still call it a vitamin, as we can also gain it from food and supplementation.

Vitamin D is a fat-soluble vitamin so that means it NEEDS fat (aka lipids) in order to be absorbed in your body. So skim milk fortified with vitamin D is literally a waste of money, you’re welcome. Same goes with your orange juice, seriously what’s the deal?

Vitamin D’s Role & Benefit in the Body


I won’t get into the specific pathways and how the hormone/nutrient does all the magical things it can do for our body. However, I wanted you all to see how much this ONE nutrient can do for you and why it’s important to care.

Vitamin D:

  • Helps the body absorb calcium
  • Maintains strong and healthy bones
  • Increases muscle mass and strength
  • Improves lower body strength
  • Regulates the immune system
  • Protects against chronic disease (including heart disease, asthma, cancer and more)

Where can we get Vitamin D?


Most food sources of Vitamin D are not sufficient for most, so sunlight exposure or supplementation tends to be recommended. Of course, if you live in the arctic tundra in the winter (read: UPSTATE NY), it is almost impossible to get enough sun exposure to support your vitamin D needs.

Here is a list of ways you can get Vitamin D:

  • Sunlight
  • Fatty Fish (i.e. sardines, mackerel, salmon)
  • Egg yolks
  • Butter
  • Beef Liver
  • Cheese
  • Fish Oil
  • Mushrooms (only those grown in direct sunlight)
  • Full Fat Milk
  • Fortified Dairy Alternatives (i.e. Almond milk)
  • D3 Supplements

How do you know if you need Vitamin D?


Test. Don’t Guess.

Pro tip: the majority of my clients who I run blood tests on, need to supplement with Vitamin D and are deficient. However, I still recommend testing, as we don’t want to be supplementing just because someone said so.

Want to get tested? Check out InsideTracker and receive a Health Geeks Discount while you’re at it! Here:  Test Your Vitamin D Levels