Vitamin D2 vs. Vitamin D3: What to Consider

Vitamin D (calciferol) is a fat-soluble vitamin that plays a crucial role in maintaining strong bones and teeth and supporting the immune system, heart health, and mental well-being.

Vitamin D2 and vitamin D3 are the two primary forms of vitamin D. D2 is typically synthetic and found in fortified foods, while D3 is found in animal-sourced foods and can also be produced by the body when the skin is exposed to sunlight. While the body easily absorbs both, research shows that D3 is more effective at raising and maintaining vitamin D levels than D2.

Read on to learn more about the differences and similarities between Vitamin D2 and D3. 

Vitamin D2 vs. Vitamin D3

When shopping for vitamin D supplements, you may notice two versions of vitamin D lining the shelves: D2 and D3, which are:

• Vitamin D2 (ergocalciferol) is typically produced through the ultraviolet (UV) irradiation of a type of yeast called ergosterol. It is also found in fortified foods, such as milk, cereal, and orange juice.
• Vitamin D3 (cholecalciferol) is produced by the body when the skin is exposed to sunlight. It can also be absorbed by eating animal-sourced foods, such as fatty fish, egg yolks, and liver. 

Though both types of vitamin D can help you reach the recommended daily intake of vitamin D, there are some differences between the two. 

Absorption 

Both vitamins D2 and D3 effectively absorb into the bloodstream, but there are differences in how the body metabolizes them. 

When D2 and D3 are consumed, the liver converts them to 25-hydroxyvitamin D2 and 25-hydroxyvitamin D3. These two compounds are called calcifediol. Then, the kidneys convert calcifediol into calcitriol—the active form of vitamin D. Calcifediol helps support the body’s immune system and boosts calcium absorption to support bone health.

Several studies have compared the absorption and utilization of vitamin D2 and vitamin D3 and found vitamin D3 to be more efficiently absorbed and utilized by the body. A research review of 24 studies also found that vitamin D3 is more effective at raising and maintaining vitamin D levels in the body.

Do You Need Both?

After consumption, vitamins D2 and D3 are converted into the same active compound (calcitriol). Though you don’t need both, experts recommend getting vitamin D through various sources. This includes spending time outdoors when it is sunny and eating foods rich in vitamin D.

People who have difficulty getting sufficient amounts of vitamin D from sun exposure and diet alone may benefit from vitamin D supplements. 

Which Is Preferred By Healthcare Providers?

If you have low vitamin D levels in your blood, your healthcare provider may recommend a vitamin D supplement to get your levels back up within the normal range. Both vitamins D2 and D3 are available as over-the-counter (OTC) dietary supplements. 

While most people don’t need a prescription for vitamin D, your healthcare provider may prescribe a high-dose supplement to take on a short-term basis. They usually prescribe vitamin D2 because it is more widely available and less expensive than vitamin D3. That said, higher doses of D3 are available in OTC supplements, so talk to your healthcare provider about supplementing if you prefer D3 over D2. 

Benefits Compared

Both vitamins D2 and D3 help keep bones strong, maintain muscle function, and support the immune system to help fight off viruses and bacteria. For the most part, the two offer the same benefits, though researchers are exploring how they may differ.

Research from 2022 found differences in how vitamin D2 and vitamin D3 impact genes that affect immune function. One study found the active form of vitamin D3 more potent in regulating the expression of genes involved in innate and acquired immunity than vitamin D2. More research is needed to understand how D2 and D3 interact with genes that regulate immune function. 

Most research suggests that vitamin D3 supplementation is superior to vitamin D2 supplementation. However, one study showed that vitamin D2 was more effective for people with autoimmune conditions who were on low-dose steroid therapy.

Though vitamin D3 supplements seem better at increasing and maintaining vitamin D levels in the body, both vitamins D2 and D3 can help boost vitamin D levels in people with a deficiency.

Vitamin D2 Sources

Dietary vitamin D2 comes from plant-based sources, primarily yeast and mushrooms. Common sources of vitamin D2 include:

• Yeast: Vitamin D2 is produced by exposing yeast to UV light and is used as a source of vitamin D2 to fortify foods.
• Fortified foods: Vitamin D2 is often added to fortified foods, such as milk, cereal, and orange juice, to help people reach their recommended daily vitamin D intake.
• Mushrooms: Some mushrooms, such as shiitake and portobello, contain vitamin D2 naturally.
• Supplements: Vitamin D2 supplements are widely available in various forms, such as tablets, capsules, and liquids.

Vitamin D3 Sources

Sources of vitamin D3 include:

• Sunlight: The body produces vitamin D3 when the skin is exposed to sunlight.
• Animal-based foods: Fatty fish (such as salmon, tuna, and trout), egg yolks, and beef liver contain D3.
• Supplements: Vitamin D3 supplements are available in liquid, capsule, and tablet forms.

So, Which One Is Better?

Both vitamins D2 and D3 can help bring vitamin D levels within a normal range. Still, research suggests that vitamin D3 supplements may be the better option for maintaining sufficient vitamin D levels to support your health.

Possible Side Effects 

Consuming excessive amounts of vitamin D supplements can lead to vitamin D toxicity and unpleasant side effects, such as:

• Nausea 
• Vomiting 
• Muscle weakness
• Confusion
• Pain
• Loss of appetite
• Dehydration
• Excessive urination and thirst
• Kidney stones

Signs of Vitamin D Deficiency

Most people with vitamin D deficiency do not have symptoms. Those who do may have subtle signs that are not immediately noticeable, but a prolonged and severe deficiency can lead to a wide range of symptoms, including:

• Fatigue
• Bone pain
• Weakness 
• Muscle twitches
• Impaired wound healing
• Bone loss (osteoporosis)
• Increased risk of infections
• Depression

Getting Enough Vitamin D

Vitamin D deficiency is a common problem, affecting an estimated 40% of the U.S. population and 1 billion people worldwide. Some people are at a higher risk of vitamin D deficiency, including older adults, people living in areas with limited sunlight, those with darker skin tones, breastfed infants, and people with certain health conditions (e.g., celiac disease).

Here are some things you can do to ensure you get enough vitamin D: 

• Get some sun: The body can produce vitamin D3 when the skin is exposed to sunlight. However, it is important to balance sun exposure with other sources to avoid skin damage.
• Eat a balanced diet: Eating a diet that includes foods rich in vitamin D3, such as fatty fish, egg yolks, and liver, can help. Some fortified foods are good sources of vitamin D3, such as milk, cereal, and orange juice.
• Take supplements: Vitamin D3 supplements are widely available and can help you reach the recommended daily vitamin D intake.
  

Summary

Vitamin D is essential to maintaining strong bones and teeth and supporting immune function, heart health, and other processes. While vitamins D2 and D3 can both help boost vitamin D levels in people with a deficiency, research suggests that vitamin D3 is more efficiently absorbed and utilized by the body and may be better at increasing and maintaining vitamin D levels in the body.

Vitamin D deficiency is common worldwide. Speak with your healthcare provider to determine whether you should take a vitamin D supplement and how to incorporate more vitamin D into your diet.