Shining a Light on Vitamin D: Everything You Need to Know

Curated by Claudia Shannon / Research Scientist / ishonest

Here’s what getting a good dose of the D naturally or via a supplement, can do for you.

What is vitamin D exactly?

Vitamin D is considered a fat-soluble vitamin, but by definition it’s a hormone. That’s because our body makes it. Vitamin D helps to control our blood calcium levels, which is a nutrient that’s very important for strong, healthy bones. It also plays a part in helping our immune system stay tough.

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About 50 to 90 percent of your vitamin D comes from sunlight, with the rest coming from food.

When sunshine hits our skin and a chemical reaction produces cholecalciferol (a form of vitamin D). From there our liver coverts it to calcidiol (another form of vitamin D). The last step is when our kidneys convert these forms to the active form of vitamin D that our body can use.

Since a lot of us live in regions where winter clouds the sun (or we protect our skin with sunscreen), vitamin D absorption from the sun is often prevented or impossible.

If your locale also gets visits from Jack Frost, you may not even make vitamin D from the sun for half the year. That’s why vitamin D deficiency impacts about 50 percent of the world’s population.

Take a bite: Food sources of vitamin D

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When it comes to food, there are limited choices that naturally contain vitamin D. That’s why you’ll find some foods fortified with added vitamin D.

Foods that contain the most vitamin D include:

  • Fatty fish (salmon, tuna, mackerel). 1 ounce of raw salmon contains 3 micrograms (about 120 IU).
  • Eggs. 1 whole egg contains 1 microgram (about 40 IU).
  • Milk (including many plant-based options). Each quart contains 10 micrograms (about 400 IU).
  • Breakfast cereal (can vary so check the label). 1 cup of the OG cheerios contains 1 microgram (about 40 IU).

You can also get some vitamin D from mushrooms, especially when they’re grown in areas that allow them to absorb ultraviolet light from the sun or lamps.

Help your health: Vitamin D benefits

You’re not going to want to be the half of the population that has vitamin D deficiency, because this vitamin offers a bunch of vital health benefits.

Healthy bones
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Vitamin D helps calcium absorb, and both of these nutrients give us a solid skeletal structure. A 2019 meta-analysis found that people supplementing with vitamin D and calcium daily had a 16 percent reduced chance of hip fracture.

Boosted immune system

Vitamin D is vital for a healthy immune system because it helps your immune response fight off disease and infection.

A 2017 article describes how vitamin D can trigger the innate immune response (first line of defense when a foreign object enters our body) and also fine- tunes our adaptive immunity (immunity that jumps in when the innate response can’t handle it).

Mental health

Low vitamin D levels may be to blame for your winter blues. Seasonal affective disorder (SAD) is a legit major depressive disorder that follows the changes of the seasons. The American Psychological Association notes that about 5 percent of the U.S. population experiences SAD for 40 percent of the year.

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As the seasons change and winter arrives so does our chance at getting enough vitamin D from the sunshine. A 2017 review states that individuals with vitamin D levels under 50 nanomoles per liter (nmol/L) are more prone to depression than those that have levels above 75 nmol/L.

Keeping you vitamin D levels happy, might help curb depression symptoms and boost your mood.

The deets on Vitamin D deficiency

There are many factors that can put us at risk of vitamin D deficiency beyond where you live, including:

  • Age. Older adults typically spend less time outdoors and the skin’s ability to synthesize vitamin D declines with age.
  • Skin tone. If you have a darker skin tone, you have more pigment in the skin called melanin. This protects the skin from harsh UV rays, but it also reduces the skins ability to produce vitamin D in a cloud-covered climate.

Certain medical conditions can also impact the absorption of vitamin D, such as:

  • cystic fibrosis
  • crohn’s disease
  • celiac disease
  • weight loss surgeries
  • obesity
  • Kidney and liver diseases

Vitamin D deficiency symptoms

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If you’re deficient in vitamin D, your body may give you a heads up. Symptoms that point to a vitamin D deficiency could include:

  • fatigue
  • muscle weakness, aches, or cramps
  • pain in your bones
  • mood changes (like depression)

Over time, the deficiency will lead to the bone-weakening condition osteomalacia in adults and the skeletal disorder rickets in children. This is when bones start to soften, which causes growth complications in children and increases fractures in adults.

What about vitamin D and coronavirus?

Research has shown there may be a relationship between the novel coronavirus and vitamin D levels. But it’s not a done deal that vitamin D can prevent a COVID-19 infection.

A 2020 review states that vitamin D has the ability of reducing risk of infections.

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That’s because it can lower viral replication rates and reduce pro-inflammatory cytokines (small proteins released by cells that have a specific effect on other cells). These pro-inflammatory proteins can lead to pneumonia since they injure the lining of the lungs.

The review also states that the evidence between vitamin D in reducing risk of COVID-19 includes:

  • The COVID-19 outbreak started in winter, which as we know, is when many people are vitamin D deficient.
  • There were a lower number of COVID-19 cases in the Southern Hemisphere at the end of summer (if the sun’s out, so is vitamin D).
  • Low vitamin D levels has been found to contribute to acute respiratory distress syndrome (COVID-19 attacks our respiratory system).
  • Fatality rates with COVID-19 increase with age and chronic disease (both associated with low levels of vitamin D).

How much vitamin D can you take?

First things first: Always talk to your doc before popping a vitamin D supplement. It’s important to know the proper dosage and make sure it won’t interact with any meds you’re taking.

More than likely, you don’t need a supplement that is over 600 to 800 IU per day. Some people might require more, like individuals dealing with a bone health disorder or a condition that interferes with vitamin D absorption.

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Unless your doc gives you the go ahead, avoid taking a supplement that is over 4,000 IU per day, which is the safe upper limit.

Vitamin D side effects

Reaching toxic levels of vitamin D is hard to do. Unless you’re taking insanely large doses of 60,000 IU per day for several months (the RDA for most adults is 600 IU), then you should be in the clear.

But if your vitamin D levels are higher than 150 ng/mL (375 nmol/L), then you’re overdoing it with the supplements.

Since vitamin D is a fat-soluble vitamin, it’s stored in fat and released into the bloodstream over time. Our body regulates how much vitamin D we get when we’re out in the sun, but doesn’t have that ability when we take supplements.

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One of the biggest consequences of too much vitamin D is the buildup of calcium. This can result in the formation of calcium stones and lead to kidney problems.

Symptoms of vitamin D toxicity could include:

  • confusion
  • recurrent vomiting
  • abdominal pain
  • dehydration
  • polyuria (urination more than usual)
  • polydipsia (excessive thirst)

Here comes the sun

Don’t be in the half of the population that is D deficient. Without it you’re putting yourself at risk for brittle bones, low energy, and a lackluster immune system.

If the sun’s out where you live, take advantage. Otherwise, it’s not a bad idea to chat with your doc about whether a supplement your next route.

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