Vitamin D2 vs. D3: What’s the Difference?

What Is Vitamin D?

Vitamin D is a fat-soluble vitamin that promotes the absorption of calcium, regulates bone growth and plays a role in immune function.

Your skin produces vitamin D when it’s exposed to sunlight. However, if you spend most of your time indoors or live at a high latitude, you’ll need to get this vitamin from your diet.

To prevent deficiency symptoms, make sure to eat vitamin D-rich foods regularly, get some sunlight or take supplements.

Since vitamin D is fat-soluble, it is better to choose oil-based supplements or take them with food that contains some fat.

Vitamin D comes in two main forms:

  - Vitamin D2 (Ergocalciferol) Comes from Plants

  - Vitamin D3 (Cholecalciferol) Comes from Animals

The two forms of vitamin D differ depending on their food sources.

Vitamin D3 is only found in animal-sourced foods, whereas D2 mainly comes from plant sources and fortified foods.

Sources of Vitamin D3: Oily fish and fish oil – Liver - Egg yolk – Butter - Dietary supplements.

Sources of Vitamin D2: Mushrooms (grown in UV light) -Fortified foods - Dietary supplements.

Your skin makes vitamin D3 when it’s exposed to sunlight.

Specifically, ultraviolet B (UVB) radiation from sunlight triggers the formation of vitamin D3 from the compound 7-dehydrocholesterol in skin.

A similar process takes place in plants and mushrooms, where UVB light leads to the formation of vitamin D2 from ergosterol, a compound found in plant oils.

If you regularly spend time outdoors, lightly clad and without sunscreen, you may be getting all the vitamin D you need.

Be careful not to spend too much time in the sun without sunscreen. This is especially important if you have light-colored skin. Sunburns are a major risk factor for skin cancer.

Unlike dietary vitamin D, you cannot overdose on vitamin D3 produced in your skin. If your body already has enough, your skin simply produces less.

Both are effectively absorbed into the bloodstream. However, the liver metabolizes them differently.

The liver metabolizes vitamin D2 into 25-hydroxyvitamin D2 and vitamin D3 into 25-hydroxyvitamin D3. Both known as calcifediol.

Calcifediol is the main circulating form of vitamin D, and its blood levels reflect your body’s stores of this nutrient.

For this reason, your health care provider can estimate your vitamin D status by measuring your levels of calcifediol.

However, vitamin D2 seems to yield less calcifediol than an equal amount of vitamin D3.

If you are taking vitamin D supplements, consider choosing vitamin D3.

In fact, studies suggest vitamin D2 is more sensitive to humidity and fluctuations in temperature. For this reason, vitamin D2 supplements may be more likely to degrade over time.

How to Improve Your Vitamin D Status:

  - Select mushrooms that have been exposed to ultraviolet light

  - Take fish oil supplements such as cod liver oil

  - Eat fatty fish twice a week

  - Choose milk or orange juice that’s been fortified with vitamin D

  - Eat some eggs and butter

  - Spend at least half an hour in the sun daily, if possible

  - If you take vitamin D supplements, make sure not to exceed the safe upper intake evel, which is (100 micrograms) per day for adults.

According to the US Institute of Medicine, the recommended daily allowance is (10–20 micrograms), but common supplemental doses range from (25–50 micrograms) per day.