Everything You Need to Know About Vitamin D

Vitamin D: Benefits, Dosage and Sources

Have you noticed the recent spike in Vitamin D’s popularity? You may have read food packages boasting “added vitamin D” or seen stores selling Vitamin D in supplemental form? If so, you might wonder what all the fuss is about and if you should take it. 

Vitamin D and You

Vitamin D is essential for good health. It’s responsible for many vital body processes. Vitamin D strengthens your bones by adding minerals, supports your immune system, and protects you from certain chronic diseases like autoimmune disorders or diabetes. 

You can find Vitamin D in two forms, D2 and D3. D2, or Ergocalciferol, in certain types of mushrooms, while D3, cholecalciferol is found in oily fish, egg yolks, and fish liver oil. D3 is the  preferred type as it is used much more effectively by your body. 

You can get vitamin D from dietary sources, but the best Vitamin D source is sunlight! When UV rays from the sun come in contact with your skin, your body creates vitamin D. Not everyone gets enough sun exposure, however, which can make it difficult to get enough vitamin D. 

Are You At Risk for a Vitamin D Deficiency? 

It’s estimated in the US around 42% of adults have low vitamin D levels, and nearly 60% of children are either insufficient or deficient in this crucial vitamin.

Vitamin D Sources

If you have darker skin, you are at a high risk of deficiency because Darker pigments can block the sun’s vitamin D synthesis. If you’re Black, Hispanic, or Pacific Islander, you may want to be tested for a deficiency.

The latitude at which you live can also play a role in getting enough vitamin D. The farther you are from the equator, the less direct sunlight you will be exposed to, raising your risk of deficiency. In non-summer months, your skin makes little vitamin D if you live above 37 degrees north or below 37 degrees south of the equator. Wearing hats, long sleeves, and sunscreen throughout the year can further block the sun’s rays needed to create vitamin D.

Lastly, if you don’t eat enough fat, you could be at risk for a vitamin D deficiency. Vitamin D is a fat-soluble nutrient, meaning it requires fat to be fully utilized by the body. If you avoid fat-containing foods like avocados, fish, nuts, or oil, it can make it more challenging for you to absorb and use this nutrient.

Vitamin D Deficiency Consequences

A vitamin D deficiency can adversely affect everything from your bones, to your thyroid, to your heart. In children, vitamin D deficiency may stunt their growth or cause ‘rickets,’ a disease that causes bones to become soft and bend out of shape. Children are also at risk for cardiac problems if vitamin D levels are too low.

As an adult, vitamin D deficiency can cause osteoporosis and increase your risk of fractures which can lead to falls for the elderly. Low vitamin D levels are also associated with developing hyperparathyroidism, multiple sclerosis, high blood pressure, diabetes, and certain cancers.

How Much Vitamin D is Adequate? 

You’ll need a blood test to determine your levels of vitamin D. The test will measure the amount of vitamin D you store in your body (25 (OH) D). You can ask your doctor to perform this simple test and create a plan to correct any deficiencies.

 Blood levels on the following scale

  • Sufficient: 25(OH)D greater than 20 ng/ml (50 nmol/l).
  • Insufficient: 25(OH)D less than 20 ng/ml (50 nmol/l).
  • Deficient: 25(OH)D less than 12 ng/ml (25 nmol/l) 

If you are deficient, your doctor can help you decide how much vitamin supplementation you’ll need to restore your vitamin D to essential levels. If you choose to supplement, taking 400-800IU (10-20 micrograms) per day is usually adequate. If you are concerned about your levels due to limited sun exposure, your race, or age, it’s wise to work with a medical professional that can tailor recommendations to fit you.

How Much Is Too Much?

As with everything, too much of something can have adverse side effects. Excessive amounts of Vitamin D can be detrimental to your health. While toxicity is uncommon, too high of a dose taken over long periods can cause unsafe levels of vitamin D to build up in your system. 4000 IU (100mcg) per day is the safe upper limit, according to the Institute of Medicine. Consult with your doctor before you take more. If you take toxic levels of vitamin D, you may experience nausea, confusion, digestive upset, and poor appetite. If left untreated, toxicity can cause elevated blood calcium leading to bone loss and even kidney failure.

Vitamin D Dosage

If you fear that you may have taken too much vitamin D, stop taking your supplement and immediately call a health professional. Tell them the dosage and length of time you’ve been taking the dosage and they can help you decide what to do to avoid toxicity.

Can You Get Your Vitamin D From Food? 

Sunlight is your best source of vitamin D, and you’ll need about 10-minutes of direct sun exposure per day to keep your vitamin D at healthy levels. But it’s challenging during the winter months to get your vitamin D from the sun. In the colder months, you spend less time outdoors and likely wear protective clothing.

Sunscreen and UV-blocking makeup also limit your exposure. If you add foods with vitamin D  or take a supplement, it can help you bridge the gap. Food sources include fatty fish (such as salmon or mackerel), beef liver, cheese, egg yolks, and fortified foods. If you are vegetarian, you may obtain vitamin D from mushrooms and fortified foods such as tofu. Fortified foods such as milk or plant-milks provide most vitamin D in American eating plans. Most fortified milk and milk products provide around 120IU (3mcg) of Vitamin D, only one-fifth of the recommended daily amount. If you suspect you aren’t eating many of these food sources that are high in vitamin D, you might benefit from supplementation.

Recommended Daily Allowances of Vitamin D:

  • Age 0-12 months old 400IU (10mcg) 
  • Age 1-70 years old 600IU (15mcg)
  • Age 70 and older 800IU (20mcg)

If you’re elderly, pregnant or nursing, or have an immune system disorder, you’ll benefit significantly from a vitamin D supplement. Supplementation isn’t for everyone. Some medical conditions or medications may contraindicate the use of vitamin D supplements, so it’s always wise to consult your doctor before you assume that you should take a supplement of any kind.

Vitamin D and Your Health

Vitamin D plays a role in many of your body’s processes and is critical for good health. Nearly every cell in your body contains a vitamin D receptor, making it one of the most crucial nutrients your body requires. Intakes of this essential vitamin are commonly insufficient and you may benefit from supplementation. If you have darker skin, live far from the equator, are older than 70, or spend little time in direct sunlight you are more likely to be deficient. Vitamin D provides enormous benefits to your health. If you suspect you aren’t getting enough, have a conversation with your doctor so they can help you create a plan to ensure you’re getting enough of this vital nutrient.

Author's bio


Hayley Harris, RD

Hayley is a Registered Dietitian Nutritionist, recipe developer, and nutrition coach. She writes killer nutrition content for websites including Recover Zone and KetoVale, and Whole Foods, Catalina Crunch, and Colours of Nature have featured her recipes. During her studies for a Bachelor of ...