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Here's why you might need to take a vitamin D supplement

It’s the second week of January. I can only see three colors out my window: whitish-grey, brownish grey-and grey-grey. The blue sky has been hidden behind a curtain of clouds for weeks and I’m missing the sun.

This south facing snowman out my front window will melt quickly if he ever sees the sun. We've been in an inversion in Vernal, and haven't seen the sun for weeks.

Unlike the snowman in this photo (which will melt if the sun ever comes out), my body is literally craving sunshine.

I'm craving the sun's warmth, light and it's vitamin-D-creating powers. Yes, I'm a dietitian, so I think about these things regularly. Human skin creates vitamin D when it is exposed to sunlight. When we have limited sun exposure (during a winter inversion), we must rely on food for vitamin D.

Unfortunately, there isn’t much vitamin D in the typical American diet. How do you know if you getting enough vitamin D in the winter? Keep reading to find out.

In this article:

What is vitamin D and why do we need it?

The simple answer: Vitamin D is a nutrient that helps build bones. Children and adults who don’t get enough vitamin D are at risk for weak bones.

Vitamin D might also help prevent cancer, heart disease, autoimmune diseases and depression. Getting enough Vitamin D improves your overall well-being. Click here to learn more.

Where does vitamin D come from?

The Sun:

  • During the summer, exposure to 5-30 minutes of sunlight on your hands, face, arms and legs will meet vitamin D needs.

  • During the winter: It’s too cold to expose your arms and legs outside + Because of Utah’s latitude, winter sunlight isn’t “strong” enough to make vitamin D


  • Vitamin D is naturally found in fatty fish (trout, salmon, cod liver oil), egg yolks and UV-light-exposed-mushrooms.

  • Vitamin D is added to fortified foods: Milk (dairy and non-dairy), orange juice, and cereal.

  • See the infographic at the bottom of this blog post for more info.

How much vitamin D does my family need?

The recommended amount of vitamin D depends on your age.

Infants age 0-12 months: 10 mcg (400IU)

kids + adults 1-70 years: 15 mcg (600 IU)

Pregnant/nursing women:15 mcg (600 IU)

Older adult at 70+ years: 20 mcg (800 IU)

Vitamin D is labeled in units called micrograms (mcg) and International Units (IU)

You'll usually see mcg on food labels.

You’ll usually see IU on supplement labels (confusing!)

How do I know if my family getting enough vitamin D?

It's tricky to know if you are getting enough vitamin D. Here are 3 things to consider:

1. How much vitamin D are you getting from the sun?

  • Winter sunlight isn't "strong" enough to make vitamin D

  • Wearing sunscreen stops your skin from making vitamin D (but it's still important for preventing skin cancer!)

  • Darker pigmented skin makes less vitamin D.

  • Clouds and pollution block the sun's rays that make vitamin D.

Summary: Being outside for 5-30 minutes in the summer will give you enough vitamin D. Your skin probably doesn't make enough vitamin D during a Utah winter.

2. How much vitamin D are you getting from food?

  • 1 cup fortified milk = about 3 mcg

  • 3 ounces fatty fish = 14.5 mcg

  • 1 can tuna = 2.25 mcg

  • 1 Egg yolk = 1 mcg

People age 1-70 need 15 mcg/day

  • 3 oz = the size of a deck of cards

  • Check food labels to see how much you get from fortified foods you regularly eat

Summary: If you don't eat fish 2 times/week or drink 4-5 cups of fortified milk/day, you don't get enough vitamin D from food. Check labels of foods you commonly eat to see how much you are getting.

3. How much vitamin D is your infant getting?

  • Breast milk is usually low in vitamin D.

  • Exclusively breastfed infants need to take 400 IU of vitamin D from birth until 12 months.

  • Don't give an infant anything but formula or breastmilk in their bottle until 12 months.

  • Exclusively formula-fed babies get all the vitamin D they need from infant formula.

Summary: If your breastfed child age 0-1 year is not taking a vitamin D supplement, check with your pediatrician about starting one. Infant formula provides all of your child’s vitamin D needs.

How do I choose a Vitamin D supplement if I need one?

Here are 2 things to look for in a Vitamin D supplement

1. USP Mark

Supplements are not regulated like drugs. To make sure a supplement is safe and effective, I look for the USP mark on a supplement label before I buy it. Here is an online list of USP-certified supplements:

image from

2. Take an amount less than 1,000 IU

Taking too much vitamin D is dangerous and can cause high calcium levels in the blood. High calcium levels can cause nausea, vomiting, muscle weakness, kidney stones, and other problems.

Do not take more than this amount of Vitamin D

Children age 0-7 months: 1,000 IU

Children age 7-12 months: 1,500 IU

Children age 1-3 years: 2,500 IU

Children age 4-8 years: 3,000 IU

Children AND adults age 9+ years: 4,000 IU

Remember that you only need to take this amount

Infants age 0-12 months: 10 mcg (400IU)

kids + adults 1-70 years: 15 mcg (600 IU)

Pregnant/nursing women: 15 mcg (600 IU)

Older adult at 70+ years: 20 mcg (800 IU)

It is common for Vitamin D supplements to contain 2,000 IU of vitamin D. Don't take that much if you drink milk and eat fish. Look for a supplement with 600 IU. If you can’t find one, take a higher dose less often, or buy a gummy supplement and only eat part of it each day.

Summary: Find a vitamin D supplement with USP on the label and aim to take only 600 IU or 15mcg per day. Take less if you drink fortified milk and eat fatty fish.

Final Review:

  • Vitamin D is important for bone health and general wellness.

  • You probably get enough during the summer from sun exposure (but you should definitely wear sunscreen to prevent skin cancer)

  • If you don't eat fish twice a week or drink 4 cups of milk/day (dairy or non-dairy), you probably don't get enough vitamin D during the winter.

  • If your infant is breastfed, check with your doctor about vitamin D drop supplements.

To get enough vitamin D during the winter: drink more milk, eat fatty fish 2 times/week (salmon is a good choice) or choose a USP approved supplement that is between 400 IU and 1,000 IU.

Have questions? Email Nicole:


NIH Vitamin D Fact Sheet for Professionals:

Harvard School of Public; The Nutrition Source; Vitamin D:

American Academy of Pediatrics;; Vitamin D and Iron Supplements for Babies:

PS: My mealplan for the week

Monday: whole wheat spaghetti, jarred red sauce, garlic bread, canned peaches, canned green beans

Tuesday: skillet pizza topped with cheese, spinach and bell peppers, canned applesauce

Wednesday: soft lentil tacos with whole wheat tortillas, orange slices, canned corn + black beans

Thursday: Peanut noodles with tofu (recipe coming soon to the website), sliced bell peppers and spinach, orange slices

Friday: veggie noodle soup + grapefruit slices

Wondering how I get enough vitamin D?

  1. I eat oatmeal cooked in 1 cup of milk for breakfast every morning,

  2. I have a green smoothie made with milk for my morning snack,

  3. I eat tuna fish for lunch 2-3 days per week

  4. I drink warm vanilla milk for an afternoon snack every day

  5. I try to eat salmon once per week

  6. I eat 1/2 of a nature-made gummy supplement every other day (1/2 gummy = 500mg)

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