Vitamin D: The Vitamin Most U.S. Adults are Low in

By Don

February 14, 2025

Blog

Reading Time: 3 minutes

My Introduction to Vitamin D

In December of 2015 my wife and I moved across the country from a college town in Texas to a town 40 minutes north of New York City.

It was an exciting time in life… newly married, new job, new location, etc…

But there was one change in particular that caught me flat footed.

The lack of sunshine.

New York City has just 5 hours of daily sunshine in January… and I bet you we had less than that during the winter we moved.

Most days I left for the office at 6:30am and left the office by 5p… so for the first time in my life there were days I didn’t see the sun.

All of a sudden I became a more melancholy, irritable, and moody.

This was my introduction to Vitamin D.

Most U.S. Adults Don’t Get Enough Vitamin D

Adults need at least 600 international units (IU) of Vitamin D every day.

For adults over 70 the recommendation is at least 800 IU’s.

So how many U.S. adults get enough?

While the answer depends on the study you look at (and how it was run), here’s what a 2018 study published by Cambridge found:

  • 28.9% of U.S. adults were vitamin D deficient (< 20ng/ML)

  • 41.4% of U.S. adults were vitamin D insufficient (21-29 ng/ML)

To quote their conclusion:

“… fewer than 30% of U.S. adults had sufficient vitamin D for optimal health outcomes”

These are staggering numbers.

P.S. Depending on the study you look at, you’ll find a range…

Some say ~60% are deficient & insufficient… some say 90%+ don’t get enough…

While the truth is probably somewhere in the middle… it’s undeniably far lower than recommended levels.

The Critical Supporting Role of Vitamin D

 

Vitamin D creation is remarkable… it’s one of those processes that happens without us having to consciously think about it.

Diving into this displays the brilliance of God.

Here’s what happens.

When UV light from the sun hits your skin, a reaction takes place that begins to create Vitamin D…. but it’s not quite ready to do it’s job yet.

So this Vitamin D compound is sent through your blood stream to the liver for the first conversion process.

Then this new compound is sent again through the blood stream to your kidneys for the second conversion process.

And then it’s sent to your small intestines to do one of it’s primary roles, which is helping the small intestines absorb calcium.

Calcium ensures bone strength and health, proper functioning of nervous tissue, muscle tissue, and much more.

For instance, if you have low Vitamin D and can’t absorb calcium from your food, your body starts pulling calcium from your bones… which leads to weaker and more porous bones.

Low levels of Vitamin D have also been linked to things like:

  • Bone softening

  • Mood changes

  • Seasonal affective disorder

  • Fatigue

  • Anxiety

  • Loss of appetite

  • Trouble sleeping

The body really is a system (1 Corinthians 12-14)… and each component, down to the tiniest vitamin, all have a pivotal role to play in this God designed, synergistic system.

P.S. Shoutout to the this video Institute of Human Anatomy for their helpful video on this process

How To Get Enough Vitamin D

So… how do we get enough Vitamin D?

There are two primary sources: sunlight and food.

Here’s a breakdown for both.

Vitamin D from sunlight

Here are the recommendations.

Daily sun exposure

10-15 minutes outside each day produces enough vitamin D for most adults.

  • Optimal time is 10a-2p (when UV light is strongest), but other times work too

  • Expose face, arms, and hands

  • Get outside. Windows can block UV light

  • Works best in clear or partly cloudy weather. Overcast reduces UV exposure

  • 30 minutes, 2-3x a week can also produce adequate amounts of Vitamin D

  • Total time depends on skin pigmentation

P.S. While sunscreen blocks UV light, not enough is typically used to block all Vitamin D production

Vitamin D from foods

Unlike other vitamins, not a lot of foods are high in Vitamin D.

Here are the some of the main ones.

Foods with High Vitamin D

  • Mackerel: 3oz = 600 – 1,000 IU

  • Wild-caught Salmon: 3oz = 570 – 1,000 IU

  • Trout: 3oz = 500-600 IU

  • Herring: 3oz = 400 – 600 IU

  • UV-exposed mushrooms: ½ cup = 450 – 1,000 IU

  • Sardines: 3oz = 300 IU

  • Tuna: 3oz = 230 IU

  • Eel: 3oz = 200 IU

  • Halibut: 3oz = 200 IU

  • Shrimp: 3oz = 50 IU

  • Beef liver: 3oz = 50 IU

  • Egg yolks: 1 egg yolk = 40 IU

  • Cheese (Swiss, Cheddar, Gouda): 1oz = 10-20 IU

P.S. There are other ways to get Vitamin D from consumption, like multi-vitamins, direct supplements, or fortified dairy products.

➡️ The Takeaway

Vitamin D plays a critical supporting role in calcium absorption, muscular, nervous, and mood regulation processes.

10-15 minutes of sun per day is enough to get what your body needs.

Some foods have Vitamin D, primarily fatty fish (salmons, mackerel, sardines, etc…)

God designed this incredible system to produce what we need on auto-pilot.

“I praise You, for I am fearfully and wonderfully made. Wonderful are Your works; my soul knows it very well”

Psalm 139:14

To Him be the glory forever.

If you liked this, check out the Layman’s Fitness Newsletter, where I release similar content like this every week.

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