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Recently there has been a lot of talk that vitamin D3 is more effective than vitamin D2 in raising the level of the circulating form of total vitamin D in the blood. Even Dr. Mehmet Oz in this video suggests that you should prefer vitamin D3 to vitamin D2.

Is that really true?

Before we dig into the research, let us take a closer look at these two forms of vitamin D.

Vitamin D3, also known as cholecalciferol, is produced when ultraviolet rays (UVB) react with 7-dehydrocholesterol. This cholesterol molecule is naturally present in the skin of animals, including humans, and in milk.

Vitamin D2, also known as ergocalciferol, is derived from plant and fungal sources, such as mushrooms. Again, these plants contain a precursor molecule which converts to vitamin D2 when exposed to UVB rays.

Chemically, the difference between vitamin D2 and vitamin D3 molecule is very subtle.

According to a paper from Dr Michael Holick and coworkers, the notion of vitamin D2 not being as effective as vitamin D3 came about because of two recent reports which found that:

  1. vitamin D2 was less effective when given as 4000 IU/day for 2 weeks or as a single dose of 50,000 IU; and
  2. when a single dose of 50,000 IU was given to healthy adults, the serum level of vitamin D decreased more rapidly than the placebo group.

In the same paper, Dr Holick reports the results of his own research which divided the test subjects in 4 groups, each receiving one of the following for 11 weeks:

  1. a placebo
  2. 1000 IU/day of vitamin D2
  3. 1000 IU/day of vitamin D3
  4. 500 IU/day of vitamin D2 and 500 IU/day of vitmain D3

Sample size in each group ranged from 14 to 20.

The serum levels of the circulating form of vitamin D (25 hydroxy vitamin D) did not increase for the placebo group even though some of them took a multivitamin and drank milk.

The serum level of the vitamin D2 only group and the vitamin D3 only group increased to about the same level after 11 weeks. Same result was seen for the group that received both D2 and D3. In general, it was found that each 100 IU/day increased the serum level by 1 ng/mL over 11 weeks.

This result shows that both vitamin D2 and vitamin D3 are almost equally effective and that vitamin D2.

All subjects were vitamin D deficient at the start of the study; that is there average starting vitamin D level was about 17 – 20. After 11 weeks, the final average serum levels were less than 30 ng/mL. Dr Holick concludes that a higher level of vitamin D supplementation is needed to increase the serum level to the optimal range of 40 -60 ng/mL.

Although these results do show that both vitamin D2 and vitamin D3 are equally effective in raising serum levels, there are several limitations in this study which should prompt further investigation:

  1. Sample size in each group is small
  2. Standard deviation of both starting and final 25(OH)D levels are very high
  3. All starting levels were below 20 ng/mL. It would be interesting to see if vitamin D2 and D3 behave differently in subjects whose starting levels are high. There is a link between starting vitamin D level and increase in serum level per 1000 IU/day and it should be carefully evaluated.

The question still remains, but only from an academic point of view. Practically speaking, it doesn’t really matter whether you take vitamin D2 or vitamin D3. Always check your starting serum level and talk to your doctor before taking supplements.




Copyright Robert P. Heaney, 2011. Used with permission.

This chart is interesting! It shows that the effectiveness of vitamin D supplements in terms of actual rise in blood level of vitamin D depends on the starting level. For example, if your starting level is at 20 ng/mL, taking a 1000 IU per day supplement can raise your blood level by about 10 ng/mL. But the same 1000 IU per day increase your blood level by only 4 ng/mL if you are already at 60 ng/mL. And it practically does nothing if you are at 80 ng/mL.

This knowledge can help consumers and doctors decide an appropriate level of vitamin D supplementation.

Many people take vitamin D supplements, either on their own, or because they have been prescribed to them by their doctors. The media is full of news about vitamin D deficiency and a common response is to take a daily vitamin supplement. But does it work?

According to this chart, the answer is it depends! If you are in the 40 -60 ng/mL range, which most experts believe to be ideal, popping a pill because of the media frenzy about vitamin D deficiency is completely useless. You are better off watching your diet and lifestyle by consuming vitamin D rich foods (dairy, fortified juices, fatty fish and mushrooms) and getting limited sun exposure without sun screen. Your body creates a reserve of vitamin D in your fat cells, which can help you go through the winter months when you are not able to get much sun. The vitamin D calculator can help you estimate your vitamin D intake from food and sun exposure.

If you are clinically diagnosed as having insufficient or deficient levels of vitamin D, you should look at your baseline blood level of vitamin D and talk to your doctor about an appropriate amount of supplementation. Use the above chart as a starting point of discussion. Do not blindly accept a high dose of vitamin D supplement because it can cause toxicity. Your doctor will use a try-and-wait approach, but you need to ask questions and convince yourself that the prescribed treatment makes sense for you.

Treat supplements as drugs,  not nutrition in a pill!

If you want to read more about the data behind this chart, click here for the complete research paper.


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Recent research has shown a link between low vitamin D and increased rate of Multiple Sclerosis (MS). Now researchers are trying to establish a safe and effective dose to help MS patients.

MS is a debilitating disease with no cure. The video below does a great job of explaining MS and the role of vitamin D (thanks @DougCookRD  for providing the link on Twitter).

According to the National Multiple Sclerosis Society, about 8000 – 10000 children in the United States under the age of 18 have MS. Another 10000 – 15000 have experienced at least one symptom of MS. In general, it is difficult to have an accurate diagnosis of MS in children and as high as 5% of people with MS have a history of symptoms before the age of 18. Overall rate of MS in the world population ranges between 2 – 150 per 100,000.

A recent paper by Dr. Jodie Burton and colleagues in the journal Neurology presented some interesting results. High amounts of vitamin D over a period of nearly one year were found to be safe. Although sample size was small, and results not statistically significant,  there was a 41% decrease in the annualized relapse rate (ARR) and a slight decrease in the expanded disability status scale (EDSS) in the treatment group, which received the vitamin D supplementation compared to the control group, which did not receive the vitamin D supplementation.The full text of the article is available here.

This is an encouraging development and it appears that vitamin D can help against MS. I would love to see more research in this area, especially with pediatric MS patients.



Yes, that is correct…well almost!

The term vitamin is used for a nutrient which is essential for the body but the body cannot produce it in sufficient amounts. That is why it must be obtained from food or a nutritional supplement.

The deal with vitamin D is that our body is fully capable of producing it when our skin is exposed to the sun. Ultraviolet radiation (UVB) from the sun converts cholesterol in the skin to a form of vitamin D called Vitamin D3. The amount of vitamin D3 produced by this photochemical reaction depends on the skin type, location, time of the day and year, cloud cover, ozone level etc. This is how nature intended us to make this important chemical even though she gave us different shades of skin colors. It has worked remarkably well for thousands of years, until recently, when vitamin D deficiency has become so common.

The second reason why vitamin D is not really a vitamin is because it is a prohormone; that means it is converted to an active form inside our body which has hormonal activity. New research is now helping us understand the importance of vitamin D and its link to various medical conditions such as diabetes, heart diseases and even cancer.

Since we are no longer getting enough sun exposure, either due to geography, or due to our lifestyle which includes excessive use of sunscreens when outdoors, vitamin D has become an essential nutrient. That is where it fits the definition of a vitamin.

Collectively, vitamin D refers to both vitamin D2 and D3. Vitamin D2 comes from plant sources, such as UV treated mushrooms, while vitamin D3 comes from animal sources.

Here are 10 facts about vitamin D you will find interesting.



The vitamin D calculator is now available for a free download from the app store! Download it on your iPhone and/or iPad from here.