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What's the Difference Between Vitamin D2 and Vitamin D3?

What's the Difference Between Vitamin D2 and Vitamin D3?

The main difference between vitamin D2 and vitamin D3 lies in their potency. The former is less potent and has lower affinity and shorter half-life than the latter. Read the following HealthHearty article to know more about their differences.
Nicks J
Did You Know?
Vitamin D is often referred to as a hormone as it is synthesized by our body.
When you decide to take vitamin D supplements, know that it is available in 2 forms; vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol). It is commonly prescribed to treat medical conditions associated with vitamin D deficiency. Both forms of vitamin D cannot be considered as equivalent and using them interchangeably can be troublesome. This is because vitamin D2 and vitamin D3 have different properties as far as drug affinity, efficacy, and half-life is concerned.
Vitamin D can be easily obtained from sun exposure, but taking it in supplemental form becomes necessary when one is suffering from its deficiency. According to the Food and Nutrition Board, the average daily recommended amount of vitamin D in adults between the ages of 19-70 is 600 IU.
Although which supplement to take is entirely a doctor's prerogative, the following write-up informs the better between the two.
Vitamin D3
Vitamin D2

Synthesis
♦ When the human body is exposed to sunlight, the skin produces vitamin D3.
♦ The skin does not create vitamin D2, after coming in direct contact with sunlight. To put it simply, synthesis of vitamin D2 does not take place in the human body.
Source
♦ Supplemental vitamin D3 is a lanolin-based product, meaning it is derived from sheep's wool. So, one can say that it is essentially an animal-based supplement.
♦ Supplemental vitamin D2 is a fungus/ yeast derived product. It is a naturally occurring vitamin in plants and fungus and is synthetically manufactured by irradiating fungus.
Efficacy
♦ A 2004 study published in the Journal of Clinical Endocrinology and Metabolism observed that vitamin D3 is significantly more effective than vitamin D2 when taken in large doses (50,000 IU). 25-hydroxyvitamin D (25OHD) (a form of vitamin D) is an indicator of the amount of vitamin D present in the body. In the study, it was observed that people taking vitamin D3 for a specified duration tend to have substantially higher 25OHD concentration than those taking vitamin D2. In another study conducted in the same year, when the supplements were given in regular doses of 4000 IU for 2 weeks, 25OHD levels were found to be 0.7 times more with vitamin D3 than vitamin D2.
♦ In the study, based on their capability to increase levels of serum 25 OHD, vitamin D2's potency was less than 33% as compared to vitamin D3's potency.
Half-life
♦ The length of time a medication remains effective is referred to as half-life. It is observed that vitamin D3 has a longer half-life as it keeps the level of 25 OHD raised for a longer duration.
♦ Vitamin D2 has a shorter half-life and its circulation time is less than vitamin D3.
Affinity
♦ Affinity refers to the drug's ability to hold to its receptor. Vitamin D3 has higher affinity, meaning its strength of binding is superior to vitamin D2. Vitamin D3 remains attached to its receptors for a prolonged duration; hence, has a longer action time.
♦ Vitamin D2 has a lower affinity, meaning its attachment to the receptors is comparatively weak. Hence, it does not stay for long in the body and has a shorter action time.
Shelf Life
♦ Vitamin D3 tablets certainly have longer shelf life and are better at withstanding varied environmental conditions.
♦ The shorter shelf life of vitamin D2 is well-known; hence, it is not the first choice for fortifying food products.

With studies indicating vitamin D3 to be more potent, doctors prescribing vitamin D2 may be advocating less effective form of vitamin D. Recent research has also proven that increasing serum 25OHD levels has led to better absorption of calcium. In that context, taking vitamin D3 appear to be more prudent as it is more effective in improving serum 25OHD levels, which may further boost calcium absorption and alleviate risk of osteoporosis.
Disclaimer: The information provided in this article is solely for educating the reader. It is not intended to be a substitute for the advice of a medical expert.