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Vitamin D, also known as the sunshine vitamin, is primarily known for its role in assisting with calcium absorption and building strong bones. But Vitamin D also plays a vital role in a variety of other bodily processes such as immune health, sleep and mood, muscle maintenance, and prevention of osteoporosis, cancer, cardiovascular disease, diabetes, and a number of other chronic diseases. Knowingthis, most of us should be flocking to stock up on this powerful vitamin. But with all of the conflicting information on recommendations and intake sources, it is difficult to know exactly how much Vitamin D you should be getting and from where.

Conflicting Views on Vitamin D

There is a lot of confusing information out there on the proper dosage of Vitamin D. When Vitamin D first arrived on the scene in the early 20th century, doctors began to liberally recommend Vitamin D through the consumption of cod-liver and spending time in the sun. Food manufacturers began to enhance a variety of foods with Vitamin D. But in the 1950’s health officials began to become cautious of lifestyles and diets overloaded with Vitamin D after an outbreak of hypercalcemia, a condition in which the body has too much-circulating calcium, and stopped promoting it as much.

Vitamin D made a re-entrance in the health scene in the early 2000’s as research demonstrated its need for optimal bodily functions. In 2010, the Food and Nutrition Board of the Institute of Medicine, now known as the National Academy of Medicine, recommended adequate amounts of Vitamin D blood serum levels be at 20 ng/mL, far below the 30 ng/mL recommended by researchers.

So what exactly is Vitamin D, why is it important, and how much should we actually get?

Vital Roles of Vitamin D

Vitamin D is a nutrient we intake from both food and the sun when our skin is exposed to UVB rays. Once Vitamin D is in your body, it makes the hormone calcitriol, a hormone necessary for calcium and phosphorus absorption. Every cell in our bodies, including immune cells, contain Vitamin D receptors. This explains Vitamin D has a vital role in immune function and prevention of diseases such as cancer and autoimmune diseases.

Assessing Your Need of Vitamin D

Before assessing how much Vitamin D you feel you need to get, it is important to know that everyone is different in their Vitamin D needs. Factors such as how much time you spend outside vs. inside, where you live, how often you apply sunscreen, and how much Vitamin D are you actually getting from your diet, all influence your Vitamin D needs.

The best way to know how much Vitamin D you, as an individual, need is to get tested. It is recommended you get tested each year, or ideally, every 6 months. Most doctors include lab work to measure the active form of Vitamin D, 25-hydroxyvitamin D, or 25(OH) D, during an annual exam. You can also purchase a direct-to-consumer lab for about $60.
An accurate way of assessing your personal Vitamin D levels is to check your parathyroid hormone (PTH) levels. If you are deficient in Vitamin D, your parathyroid gland releases more PTH. So if your PTH levels are high, it may be an indication of low Vitamin D levels.

The important thing to remember is that everyone is different in their Vitamin D levels and needs. Vitamin D levels can fluctuate based on nutrition, sun exposure, and geographical location.

Too Much or Too Little Vitamin D

Since Vitamin D affects multiple bodily functions, it is important to remain within a range that is ideal for your body. If Vitamin D levels are too low, it can affect hormones such as cortisol and thyroid. If it is too high, it can throw off other hormones in the body. About 70% of the world’s population is deficient in Vitamin D. Low levels of Vitamin D can cause migraines, muscle and joint pain, depression, and inflammation.

Too much vitamin D, however, can also cause adverse side effects. Excessive levels of Vitamin D can lead to hypercalcemia. Other symptoms associated with excess Vitamin D include poor appetite, nausea, vomiting, frequent urination, and kidney problems.

Practical Ways to Boost Vitamin D Levels

One of the easiest ways to get Vitamin D into your life is to get outside and expose your skin to natural sunlight. The amount of unprotected sun exposure you need depends on your skin tone. If your skin tone is fairly light, 10-15 minutes outside is enough time for your skin to absorb the sun’s benefits. For those of you with darker skin tones, it may take up to two hours.

Another way to get Vitamin D is through your diet. Vitamin D is a fat-soluble vitamin, meaning you need dietary fat in order for Vitamin D to be properly absorbed in the body. Whole food sources of Vitamin D include cod-liver, fatty fish such as salmon, sardines, and mackerel, and eggs.

Lastly, supplementation is another way to get Vitamin D when sun exposure or diet sources are limited. It is best to choose Vitamin D3 when choosing to use supplements. Vitamin D3 is the most bioavailable for of Vitamin D and is 85% more effective at raising Vitamin D blood serum levels than Vitamin D2. Supplements can be found in both pill form and liquid forms.

Vitamin D from the sun stays in our bodies 24-48 hours and 12-24 hours from food sources. It is important to get adequate amounts daily via a combination of sources. Below are recommendations for Vitamin D supplementation from the Institute for Functional Medicine.

Supplementing Wisely


25(OH) D Level Supplement Dose
<10 ng/mL 10,000 IU/day
10-20 ng/mL 10,000 IU/day
20-30 ng/mL 8,000 IU/day
30-40 ng/mL 5,000 IU/day
40-50 ng/mL 2,000 IU/day

Daniela Serna, CPT, HC, is a health advocate, certified personal trainer, and health coach.