Vitamin D

Vitamin D3 – Cholecalciferol

Vitamin D is the most unique vitamin of the vitamins. What makes it unique is that it is a hormone. In particular it’s a secosteroid, which means it functions in a way that is very similar to a steroid. As a hormone it can interact with our DNA. It can interact with at least 200 different genes to turn them on or off.

Vitamin D3

The primary way our bodies get the vitamin D it needs is through sunlight. As cholesterol travels through your body and reaches your skin, UVB rays from the sun help transform it into a precursor of vitamin D. This vitamin D precursor eventually travels to the liver and kidneys where it’s turned into the active form of vitamin D. This active form has a few names but it’s more simply known as Vitamin D3.

Vitamin D2

The other active form of vitamin D is known as Vitamin D2 or ergocalciferol. This form of vitamin D is manufactured by exposing plant sterols to UV light. It’s usually manufactured in factories and used pharmaceutically but there are a few natural food sources out there. Vitamin D2 and D3 have nearly identical functions in our bodies. There are some studies that indicate that vitamin D2 may not be as effiective as vitamin D3 but results are conflicting. It’s important to note that the form of vitamin D we get from sunlight exposure and food sources such as Mushrooms and Dairy is Vitamin D3.

Vitamin D and Calcium

Vitamin D helps us absorb calcium from the food we eat. Without sufficient levels of vitamin D in our body we can only absorb a fraction of the calcium from food. This can have a significant impact on your body over time since your body will begin to take calcium from your bones or teeth in order to keep your calcium levels normal.

What does Vitamin D do?

Vitamin D helps keep our bones and teeth strong. It does this by helping our body absorb calcium from food. Without enough calcium in our diet, our body can start taking it from our bones and teeth. This is one reason why people who are vitamin D and calcium deficient may develop osteoporosis as they age or be more likely to develop cavities. People who have celiac disease may be deficient in both vitamin D and calcium.
Vitamin D can help prevent cancer by helping to reduce chronic inflammation. It can help keep your eyes healthy along with with vitamin A.

Vitamin D can help your body burn fat through specific pathways in the body.

  1. It may help reduce insulin resistance, which is linked to overeating, diabetes and obesity.
  2. Vitamin D may signal your body to stop storing fat. When vitamin D levels in your blood are low, your body produces a hormone called PTH (parathyroid hormone), which signals the body to store fat. The presence of vitamin D, which is a hormone itself, helps keep PTH at bay. Our skin absorbs sunlight and uses it to make vitamin D (scroll down to read more). Since our vitamin D levels are lowest during the fall and winter months, it’s no surprise that the body would want to store fat instead of burn it off. Food became much harder to come by during the winter when our ancestors were hunter-gatherers so it’s possible this relationship between PTH and vitamin D levels developed as a way for our bodies to store up fat as an energy source when food was scarce and also as a layer of insulation from the cold.


How much Vitamin D do we need?

We should aim to get 1,000 IU’s of vitamin D daily. Normally, our vitamin D levels should be between 50-70 ng/ml. However, if your vitamin D levels are are below this range, you may be considered vitamin D deficient. This can vary depending on the individual. Your doctor can check your vitamin D levels with a simple blood test and determine what action you should take. Vitamin D deficiency is a widespread and silent problem in the U.S. Millions of people across the country, especially during the winter months, are deficient in vitamin D. Having insufficient levels of vitamin D can increase your risk of cancer, especially breast, cervical, and colorectal cancers. Some other conditions linked with a lack of vitamin D are Parkinson’s disease, osteoporosis and celiac disease.

Recommended Dietary Allowances (RDA) for Vitamin D
Age Male Female Pregnant Lactating
0-12 Months 400 IU (10 mcg) 400 IU (10 mcg)    
1-13 Years 600 IU (10 mcg) 600 IU (10 mcg)    
14-18 Years 600 IU (10 mcg) 600 IU (10 mcg) 600 IU (10 mcg)  
19-50 Years 600 IU (10 mcg) 600 IU (10 mcg) 600 IU (10 mcg)  
51-70 Years 600 IU (10 mcg) 600 IU (10 mcg)    
70+ Years 800 IU (10 mcg) 800 IU (10 mcg)    


Ximagination / istockphoto



How much direct sunlight we get on our skins depends on several factors. We seem to reach our peak vitamin D levels in the month of August, while we hit our lows in February. The further north you are on the earth in the northern hemisphere the less opportunity you have to produce vitamin D since the angle of the sun is lower in the sky. Likewise, the same applies in the southern hemisphere the further south you go. The equator regions and desert climates are the primary places to get the maximum amount of sunlight exposure all year round.

Note: Please use good judgement. Do not stop using sunscreen if you burn easily or tend to burn after a short time. Even though sunscreens can block UVB rays from the sun you should not abandon it. Try spending a few minutes in the sun especially during the summer months without sunscreen to help you get the vitamin D you need for the day. For help, you can refer to the daily UV index to see how long it’s safe to stay in the sun.

Vitamin D Rich Foods




Skin Color

Another major factor that is seldom discussed is skin color. You skin color can significantly impact how much vitamin D you will produce when you’re out in the sun.
There is still some debate about how far south you need to be for the sun to be able to help you produce vitamin D during the fall and winter months. Studies based on millions of blood samples show that the cutoff line is around 37 to 40 degrees latitude. (Click here for an article from the Harvard Women’s Health Watch newsletter about the importance of getting enough vitamin D.) However, this line is based on blood samples and does not take into account how often you go outside, how long you are outside, weather, skin color and your overall health.


As a supplement you should take vitamin D3 with calcium. This is important because vitamin D and calcium’s roles in your body are linked. Without vitamin D you can only absorb a small amount of calcium from the food you eat. When your vitamin D levels are normal you can absorb much more calcium from your food. If you are deficient in vitamin D it may be likely that your body needs more calcium as well. It may actually be better to take magnesium with calcium and vitamin D as well. Magnesium stimulates your nerves while calcium relaxes it. To maintain balance, it’s strongly recommended that calcium and magnesium be taken together. Your best bet is to find a supplement that gives you your daily dose of magnesium, calcium and vitamin D all together.

To sum it all up:

  • Vitamin D is an important vitamin/hormone that affects our genes, calcium absorption and our risks for cancer.
  • We can get it through sunlight, food and supplements.
  • Foods high in vitamin D are Fish, Dairy, and Mushrooms
  • If you use supplements, it’s recommended that you get one that contains Vitamin D, Calcium and Magnesium.
  • People of color produce little, if any, vitamin D from the sun during the later fall and winter months in the U.S (Generally October through March)
  • Normal blood serum levels of Vitamin D are at or between 20 to 40ng/ml
  • Low vitamin D levels have been linked to increases in cancer risks




  2. Hanley, David A., and K. Shawn Davison. “Vitamin D insufficiency in North America.” The Journal of nutrition 135.2 (2005): 332-337.
  4. Dr. Oz Show
  5. Payne C. (2013, July 1) Vitamin D levels in USA peak in August, study finds. USA Today. Retrieved from:
  8. Evatt ML, DeLong MR, Kumari M, et al. High Prevalence of Hypovitaminosis D Status in Patients With Early Parkinson Disease. Arch Neurol. 2011;68(3):314-319. 

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