Vitamin D4 (22-Dihydroergocalciferol) | Benefits, Sources, Dosage, Safety & Complete Guide

Vitamin D4 is one of the lesser-known forms of vitamin D. Also known as 22-dihydroergocalciferol, it is a vitamin D compound found primarily in certain mushrooms and fungi.

Most people are familiar with vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol) because these are the forms commonly discussed in nutrition, supplements, and clinical practice. Vitamin D4, however, has received considerably less attention.

Research has shown that some edible mushrooms contain vitamin D4, particularly when they are exposed to ultraviolet (UV) light. Scientists have also studied how UV-B exposure can increase vitamin D4 formation in mushrooms.

But what exactly is vitamin D4, and how does it differ from other forms of vitamin D? In this complete guide, we’ll explore vitamin D4 benefits, sources, foods, dosage, safety, supplements, and its differences from vitamins D2 and D3, based on current scientific evidence. 

What Is Vitamin D4?

Vitamin D4 is a fat-soluble vitamin D compound scientifically known as 22-dihydroergocalciferol.

It belongs to the same broader family of vitamin D compounds as vitamin D2 and vitamin D3, but its chemical structure is slightly different.

Fungi and mushrooms contain vitamin D4. Mushrooms contain a sterol called 22,23-dihydroergosterol, which ultraviolet radiation can convert into vitamin D4.

The process can be simplified as:

22,23-dihydroergosterol + UV exposure → Vitamin D4

This is similar to the formation of vitamin D2:

Ergosterol + UV exposure → Vitamin D2

Researchers identified vitamin D4 in edible mushrooms after detecting a compound that behaved like a vitamin D compound during laboratory analysis. Further testing confirmed it as 22-dihydroergocalciferol.

Vitamin D4: Key Facts 

Feature	Vitamin D4
Chemical name	22-Dihydroergocalciferol
Vitamin D family	Yes
Main natural sources studied	Mushrooms and fungi
Precursor	22,23-Dihydroergosterol
UV-dependent formation	Yes
Established RDA	No
Established D4 supplement dose	No
Human research	Limited
Most established vitamin D forms	D2 and D3

How Is Vitamin D4 Produced?

Vitamin D4 formation starts with a fungal sterol called 22,23-dihydroergosterol.

UV radiation triggers photochemical changes in this precursor, producing vitamin D4 in mushrooms.

This is one reason mushrooms are particularly interesting in vitamin D research.

Researchers have found vitamin D4 in mushrooms grown or processed under conditions involving UV exposure, and laboratory studies have demonstrated that UV-B treatment can increase vitamin D4 concentrations.

However, vitamin D4 production is not identical in every mushroom.

Its concentration can depend on:

• Mushroom species
• UV wavelength
• UV intensity
• Exposure time
• Growing conditions
• Processing methods
• Moisture content
• Storage conditions

Therefore, simply eating mushrooms does not guarantee a specific amount of vitamin D4.

Vitamin D4 Sources | Which Foods Contain Vitamin D4?

The most notable vitamin D4 food sources identified so far are mushrooms.

Researchers have detected vitamin D4 in several edible mushroom varieties, including:

• Portabella mushrooms
• Maitake mushrooms
• Oyster mushrooms
• Shiitake mushrooms
• Enoki mushrooms
• Crimini mushrooms
• Morel mushrooms
• Chanterelle mushrooms

However, the amount can vary significantly between samples.

In a study of mushroom samples from U.S. retailers and producers, vitamin D4 was detected in 18 composites, with the highest concentrations occurring in some mushrooms known to have received UV exposure. Vitamin D4 was not detected in the white button mushroom composites studied.

Vitamin D4 in UV-Exposed Mushrooms

UV exposure is particularly important when discussing vitamin D4 mushrooms.

A study examining oyster mushrooms found that UV-B treatment increased vitamin D4 concentration, alongside changes in other vitamin D-related compounds. The vitamin D4 concentration reached approximately 20 μg/g of dry matter under the experimental conditions used.

Other research has also investigated UV treatment of mushrooms as a way of increasing vitamin D compounds, particularly vitamin D2. Human research has demonstrated that vitamin D2 from UV-B-treated mushrooms can improve vitamin D status, although that study investigated vitamin D2—not vitamin D4.

This distinction is important because we should not automatically interpret evidence about UV-treated mushrooms and vitamin D2 as evidence that vitamin D4 has the same effect.

Vitamin D4 Benefits | What Does the Research Say?

Searches for vitamin D4 benefits often produce claims that go far beyond the available evidence.

At present, there is not enough high-quality human research to establish a specific list of health benefits unique to vitamin D4.

Vitamin D as a broader family is important for several biological functions, including calcium and phosphorus regulation, bone health, and normal physiological processes. However, most established human evidence concerns vitamin D2, vitamin D3, and their metabolites.

Therefore, it is more accurate to describe vitamin D4 as a potentially biologically active vitamin D compound under investigation, rather than claiming that it has proven therapeutic benefits.

Potential role in vitamin D biology

Because vitamin D4 belongs to the vitamin D family, researchers are interested in how it is metabolized and whether it can participate in vitamin D signaling.

Experimental research has investigated vitamin D4 metabolism and biological activity, but these findings do not yet provide enough evidence to establish clinical benefits in humans.

Possible relevance to bone health

Vitamin D is essential for normal calcium absorption and bone mineralization.

However, there is currently insufficient evidence to conclude that vitamin D4 supplementation can prevent or treat:

• Vitamin D deficiency
• Rickets
• Osteomalacia
• Osteoporosis
• Fractures

Established vitamin D recommendations and clinical practice primarily concern vitamin D2 and D3.

Potential immune and cellular effects

Vitamin D signalling is involved in several biological processes, including immune regulation and cellular functions.

Because vitamin D4 is a related compound, scientists continue to investigate whether it has unique biological effects.

However, claims that vitamin D4 specifically boosts immunity, prevents cancer, improves heart health, or treats chronic diseases are not currently supported by sufficient human clinical evidence.

Does Vitamin D4 Help With Vitamin D Deficiency?

There is currently not enough evidence to recommend vitamin D4 as a treatment for vitamin D deficiency. Vitamin D status is commonly evaluated using blood 25-hydroxyvitamin D [25(OH)D] measurements. Established vitamin D recommendations and clinical supplementation primarily involve vitamin D2 and vitamin D3.

If laboratory testing confirms vitamin D deficiency, treatment should follow evidence-based medical guidance rather than relying on vitamin D4.

How Much Vitamin D4 Do You Need Per Day?

There is currently no established recommended daily allowance (RDA) specifically for vitamin D4.

This is an important topic because searches for “vitamin D4 dosage” may suggest that a standard dosage exists. It does not.

The established recommendations are for vitamin D overall, based on the available evidence and commonly supplied through vitamin D2 and D3.

Established vitamin D intake recommendations

Age	Recommended vitamin D intake
Birth–12 months	10 mcg (400 IU)/day*
1–70 years	15 mcg (600 IU)/day
Over 70 years	20 mcg (800 IU)/day
Pregnancy	15 mcg (600 IU)/day
Breastfeeding	15 mcg (600 IU)/day

*Adequate Intake (AI) rather than RDA.

These are vitamin D recommendations, not vitamin D4-specific recommendations. The NIH lists these values based on established Dietary Reference Intakes.

Vitamin D4 Supplements | Are They Available?

A Vitamin D supplements are commonly available as:

• Vitamin D2
• Vitamin D3

Vitamin D4 is not a standard supplement form with an established clinical dosing protocol.

This is largely because research has not yet established the optimal dose, long-term safety, clinical effectiveness, or appropriate blood-level targets for isolated vitamin D4.

Therefore, vitamin D4 should not be marketed or used as though it has the same evidence base as vitamin D2 or D3.

Vitamin D4 Side Effects and Safety

There is currently insufficient human evidence to establish a comprehensive safety profile for high-dose vitamin D4 supplementation.

That does not mean that naturally occurring vitamin D4 in mushrooms is known to be unsafe. It means that researchers do not yet have the same amount of long-term safety data available for vitamin D4 as they do for conventional vitamin D supplements.

Excessive intake of vitamin D in established forms can cause toxicity and hypercalcemia. Therefore, high-dose vitamin D supplements should not be taken without appropriate medical guidance.

Vitamin D4 vs Vitamin D2 vs Vitamin D3

Although all three belong to the vitamin D family, they are not identical.

Vitamin D2	Vitamin D3	Vitamin D4
Vitamin D2, or ergocalciferol, is primarily associated with fungi and yeast. It is also used in some fortified foods and dietary supplements.	Vitamin D3, or cholecalciferol, is produced in human skin following exposure to UVB radiation. It is also naturally present in foods such as fatty fish and egg yolks and is widely available as a supplement.	Vitamin D4, or 22-dihydroergocalciferol, has been detected in several edible mushrooms. Its formation is linked to UV exposure and the presence of its fungal precursor.

Unlike D2 and D3, vitamin D4 does not currently have the same level of clinical evidence or established nutritional recommendations.

Read more about: Vitamin D1 | Ergocalciferol and Lumisterol |

Vitamin D4 vs D2 vs D3

Feature	Vitamin D2	Vitamin D3	Vitamin D4
Chemical name	Ergocalciferol	Cholecalciferol	22-Dihydroergocalciferol
Associated sources	Fungi and yeast	Skin and animal foods	Mushrooms and fungi
UV-related formation	Yes	Yes	Yes
Common supplement form	Yes	Yes	Not routinely used
Human evidence	Extensive	Extensive	Limited
Established nutritional recommendations	Yes	Yes	No separate recommendation

Bottom line: Vitamin D4 is scientifically interesting, but it should not currently be considered a replacement for vitamin D2 or D3.

Vitamin D4 vs Vitamin D3 | Which One Is Better?

If you are comparing vitamin D4 vs D3, the answer depends on what you mean by “better.”

For correcting or preventing vitamin D deficiency, vitamin D3 has a much stronger evidence base.

Vitamin D4 vs Vitamin D3

Aspect	Vitamin D3	Vitamin D4
Chemical name	Cholecalciferol	22-Dihydroergocalciferol
Research	Extensively studied in humans	Limited human research
Availability	Widely available	Not commonly available
Supplements	Commonly used	Not a standard supplement form
Nutritional guidance	Included in established recommendations	No specific recommendations
Deficiency treatment	Well established	Insufficient evidence
Overall evidence	Strong	Limited

Vitamin D4 vs Vitamin D2 | What’s the Difference?

A Vitamin D2 and vitamin D4 are both associated with fungi, but they are chemically different vitamin D compounds. Vitamin D2 has a much more established role in nutrition and supplementation, while vitamin D4 remains an emerging area of research. 

Vitamin D4 vs Vitamin D3

Aspect	Vitamin D2	Vitamin D4
Chemical name	Ergocalciferol	22-Dihydroergocalciferol
Main sources	Fungi and yeast	Mushrooms and fungi
Precursor	Ergosterol	22,23-Dihydroergosterol
UV conversion	Ergosterol → Vitamin D2	22,23-Dihydroergosterol → Vitamin D4
Research	Extensively studied	Limited research
Supplements	Commonly used	Not a standard supplement form
Fortified foods	Used in some fortified foods	Not routinely used
Current status	Established nutritional form	Emerging area of research

How Does Vitamin D Work in the Body?

To understand vitamin D4 research, it helps to understand the general vitamin D pathway.

Vitamin D obtained through food, supplements, or skin production undergoes metabolic changes in the body.

For the established vitamin D2 and D3 pathways:

Vitamin D → Liver → 25-hydroxyvitamin D → Kidney → 1,25-dihydroxyvitamin D

The liver converts vitamin D into 25-hydroxyvitamin D [25(OH)D], the main circulating form used to assess vitamin D status.

The kidneys can then convert it into 1,25-dihydroxyvitamin D, also called calcitriol, the hormonally active form.

Calcitriol plays an important role in calcium and phosphorus regulation.

The metabolism and biological significance of vitamin D4 in humans are considerably less understood, which is why more research is needed.

Who Should Be Interested in Vitamin D4?

Vitamin D4 is particularly interesting for:

• Nutrition researchers
• Food scientists
• Researchers studying mushrooms
• Mycologists
• Vitamin D researchers
• People interested in emerging nutrition science

For the general public, however, vitamin D4 should currently be viewed as an emerging research topic rather than a replacement for established vitamin D nutrition.

Frequently Asked Questions