Is there a natural form of vitamin D? Exploring the 'Sunshine Vitamin' and Food Sources

November 21, 2025 •

3 min read

According to the National Institutes of Health, very few foods naturally contain significant amounts of vitamin D. Yes, there is a natural form of vitamin D, primarily synthesized by the body from sunlight exposure and found in some foods, with the two main types being D2 and D3.

Quick Summary

Natural vitamin D is acquired primarily through sunlight exposure (D3) and certain foods (D2 and D3). The article explores the differences between the two forms, natural dietary sources, and the role of UV exposure in the body's synthesis of the crucial nutrient.

Key Points

Sunlight is a Primary Natural Source: The body naturally synthesizes vitamin D3 (cholecalciferol) when skin is exposed to UVB radiation from the sun.
Two Main Natural Forms Exist: The two major forms are vitamin D2 (ergocalciferol), from plants and fungi, and vitamin D3, from animal sources and sun exposure.
Natural Food Sources are Limited: Few foods naturally contain high levels of vitamin D, but key sources include fatty fish, fish liver oils, egg yolks, and certain UV-exposed mushrooms.
D3 is Considered More Potent: Research suggests that vitamin D3 is more effective than D2 at increasing and sustaining blood vitamin D concentrations.
Fortified Foods are Common Sources: Many products like milk, cereal, and orange juice are fortified with vitamin D to help people meet their daily needs, especially when natural sources are insufficient.
Sun Exposure Requires Caution: Relying solely on sunlight for vitamin D is often not advised due to variations in synthesis and the increased risk of skin cancer from excessive exposure.
Supplements Can Bridge the Gap: For those with limited access to sun or sufficient natural food sources, supplementation is a safe and effective way to maintain healthy vitamin D levels.

The Body's Primary Source: Vitamin D from Sunlight

The most significant and direct natural source of vitamin D is the sun. When bare skin is exposed to ultraviolet B (UVB) radiation, a form of cholesterol in the skin is converted into previtamin D3, which then becomes vitamin D3 (cholecalciferol). This is the same D3 found in animal foods and many supplements. Factors like season, latitude, skin tone, and amount of skin exposed influence production.

Sunlight provides sufficient vitamin D for most people from April to September. However, sunscreen blocks UVB rays, reducing production, and synthesis decreases with age. Relying solely on the sun is often not recommended due to these limitations and the risk of skin cancer from excessive exposure.

The Two Main Natural Forms: D2 vs. D3

Vitamin D exists mainly as D2 (ergocalciferol) and D3 (cholecalciferol) in foods and supplements, differing in their chemical structure. Both are converted in the body to the active form, calcitriol. D3 is generally more effective at increasing and maintaining blood vitamin D levels.

Vitamin D3 (Cholecalciferol): This form is made in human skin from sunlight and found in animal-based foods. It is considered more potent.
Vitamin D2 (Ergocalciferol): Produced by plants, yeast, and mushrooms exposed to UV light. It is found in many fortified foods and is suitable for vegans and vegetarians.

Natural Dietary Sources of Vitamin D

Getting enough vitamin D from unfortified food sources is difficult. The best natural sources are typically animal-based, especially fatty fish.

High-Vitamin D Foods

Fatty Fish and Fish Oils: Salmon, trout, tuna, and mackerel are excellent sources of D3. Cod liver oil is also very high in D3.
Beef Liver: Contains a smaller amount of natural D3.
Egg Yolks: The D3 in eggs is in the yolk, with higher levels in eggs from sun-exposed chickens.
Certain Mushrooms: A natural plant-based source (D2). Mushrooms exposed to UV light have increased vitamin D content.

The Role of Fortified Foods

Since few foods naturally contain much vitamin D, fortification is common. Fortified foods are a significant source for many, especially those with limited sun exposure.

Common fortified products include:

Dairy and Plant-Based Milks: Cow's milk and many plant-based alternatives are fortified.
Cereals and Orange Juice: Many brands add vitamin D.
Margarine: Some spreads are fortified.

Comparison of Vitamin D2 and D3


Feature	Vitamin D2 (Ergocalciferol)	Vitamin D3 (Cholecalciferol)
Natural Source	Plants, fungi, and yeast exposed to UV light.	Animal products and human skin from sun exposure.
Effectiveness	Less effective at raising and sustaining blood vitamin D levels.	More effective at raising and sustaining blood vitamin D levels.
Source for Supplements	Manufactured using UV irradiation of yeast.	Typically produced from lanolin (sheep's wool) or lichen for vegan options.
Metabolism	Metabolized into 25-hydroxyvitamin D2.	Metabolized into 25-hydroxyvitamin D3, contributing to the body's main circulating form.
Cost	Generally cheaper to produce for fortification purposes.	Often used in higher-potency supplements.
Bioavailability	Well absorbed, but less potent than D3.	Well absorbed and generally considered more potent.

Conclusion

Yes, there are natural forms of vitamin D. The most direct natural source is the synthesis of vitamin D3 in the skin from UVB sunlight exposure. Natural food sources are limited but include D3 from fatty fish and egg yolks, and D2 from certain UV-exposed mushrooms. Fortified foods are important, but understanding natural sources is key. D3 is generally more effective at boosting vitamin D status. Supplementation can help those with insufficient sun or dietary intake. Learn more from the NIH Office of Dietary Supplements.

Frequently Asked Questions

The vitamin D3 produced by your skin from sun exposure is chemically identical to the D3 found in animal-based foods and supplements. While both are effective, relying solely on sun exposure is not recommended due to skin cancer risks, making food and supplements safer, more consistent alternatives.

The main difference is their origin: vitamin D2 (ergocalciferol) comes from plants and fungi, while vitamin D3 (cholecalciferol) comes from animal sources and human skin. Studies indicate D3 is more effective at raising and maintaining overall blood vitamin D levels than D2.

Good natural food sources include fatty fish like salmon, trout, and mackerel, fish liver oils, egg yolks from free-range chickens, beef liver, and some UV-treated mushrooms.

Yes, mushrooms naturally contain ergosterol, which converts to vitamin D2 when exposed to UV light, similar to how human skin produces D3. Many commercially grown mushrooms are now intentionally exposed to UV light to boost their vitamin D content significantly.

Many foods are fortified with vitamin D because few foods naturally contain significant amounts, and public health campaigns aim to reduce the prevalence of vitamin D deficiency. This provides a reliable source of the nutrient for people who may not get enough sun exposure.

No, you cannot get too much vitamin D from sun exposure. Your skin has a regulatory mechanism that limits the amount of vitamin D it produces, and excess sunlight breaks down vitamin D rather than producing more. Vitamin D toxicity almost always occurs from over-supplementation.

Several groups are at higher risk of deficiency, including breastfed infants, older adults, individuals with limited sun exposure, people with darker skin pigmentation, those with conditions affecting fat absorption (like Crohn's disease), and people with obesity.