Understanding Your Nutrition Diet: Where did vitamin D3 come from?

November 11, 2025 •

4 min read

An estimated one billion people worldwide have vitamin D deficiency, emphasizing the need to understand its origins. The vital nutrient vitamin D3 is primarily synthesized in the skin from sunlight exposure, but it also comes from specific dietary sources and supplements.

Quick Summary

The main origin of vitamin D3 is the skin's synthesis using sunlight's UVB rays. Lesser amounts come from animal-based foods like fatty fish and eggs. Supplementation, often sourced from lanolin or lichen, provides a reliable alternative.

Key Points

Skin Synthesis: The body's main source of Vitamin D3 is the skin, which produces it from 7-dehydrocholesterol when exposed to sunlight's UVB rays.
Dietary Sources: Naturally occurring Vitamin D3 is found in animal products, primarily fatty fish like salmon, sardines, and mackerel, as well as fish liver oils, egg yolks, and beef liver.
Supplements from Lanolin: Most commercial Vitamin D3 supplements are derived from lanolin, a waxy substance found on sheep's wool, which is irradiated to produce cholecalciferol.
Vegan D3 from Lichen: A vegan-friendly alternative to lanolin-based supplements is Vitamin D3 extracted from lichens.
Key Differences from D2: Vitamin D3 from animal sources is generally considered more effective at raising and sustaining blood vitamin D levels than vitamin D2, which is derived from plants and fungi.
Historical Discovery: The link between sunlight, diet (like cod liver oil), and the prevention of rickets led to the discovery and structural identification of vitamin D3 in the early 20th century.

The Primary Origin: Sunlight and Your Skin

The most natural and significant source of vitamin D3 (cholecalciferol) for most people is synthesis within the skin triggered by exposure to ultraviolet B (UVB) radiation from sunlight. The process involves a chemical reaction that starts in the epidermis, the outer layer of skin, where a precursor molecule known as 7-dehydrocholesterol (7-DHC) is present.

When UVB rays with wavelengths between 290 and 320 nm penetrate the skin, they break a bond in the 7-DHC molecule, converting it into pre-vitamin D3. This pre-vitamin D3 then undergoes a temperature-dependent process called thermal isomerization, which takes several hours to convert it into the stable form, vitamin D3. The body then transports this newly formed vitamin D3 to the liver and kidneys for further conversions into its active form, calcitriol.

Several factors influence the skin's ability to produce vitamin D3 from sunlight:

Latitude and Season: For those living in higher latitudes, the sun's angle during winter months is too low for the necessary UVB rays to penetrate the atmosphere effectively. This makes winter-time sun exposure an inefficient source of D3 for many.
Time of Day: The most effective time for synthesis is around midday when the sun is highest and UVB exposure is strongest.
Skin Pigmentation: Melanin, the pigment that causes darker skin, acts as a natural sunscreen. People with darker skin tones require significantly more sun exposure to produce the same amount of vitamin D3 as those with lighter skin.
Clothing and Sunscreen: Both physical barriers effectively block UVB radiation, preventing D3 synthesis. The use of SPF 15 sunscreen can reduce vitamin D production by 99.9%.
Age: As people age, the amount of 7-DHC in the skin decreases, reducing their capacity to produce vitamin D3 from sun exposure.

Dietary Sources from the Animal Kingdom

Beyond sunlight, where did vitamin D3 come from historically and in modern diets? Vitamin D3 is naturally found in very few foods, almost exclusively from animal sources. Incorporating these items into your nutrition diet can help maintain healthy vitamin D levels, especially for those with limited sun exposure.

Key dietary sources of vitamin D3 include:

Fatty Fish: Fish are one of the richest natural sources. Excellent options include:
- Salmon (especially sockeye)
- Sardines
- Mackerel
- Rainbow trout
Fish Liver Oils: Cod liver oil is particularly concentrated and has historically been used to treat rickets.
Egg Yolks: While the amount is smaller, the yolk of one large egg contains some vitamin D3.
Beef Liver: This is another natural source, though with lower concentrations compared to fatty fish.

The Role of Supplements and Fortified Foods

Given that most people can't rely solely on sun exposure or a few specific foods, supplements and fortified products play a crucial role in preventing deficiency. The industrial production of vitamin D3 for supplements and fortification primarily comes from two main sources: lanolin and lichen.

Lanolin-Derived D3: The majority of commercially available vitamin D3 is produced by irradiating 7-dehydrocholesterol extracted from lanolin, the waxy substance found in sheep's wool. The process mimics the natural synthesis in the skin.
Lichen-Derived D3: For those seeking a vegan-friendly option, a plant-based vitamin D3 extracted from lichens is now available.

Many foods are artificially fortified with vitamin D to help boost public intake. In the US, for example, milk is commonly fortified with D3. Other fortified items can include cereals, plant-based milks, and orange juice. Checking the nutrition label is key, as some products may use the plant-derived vitamin D2 instead of D3.

A Comparison of Vitamin D Sources

To better understand the different ways to get your vitamin D3, consider this comparison:


Feature	Sunlight Exposure	Animal-Based Foods	Supplements	Fortified Foods
Primary Form	D3	D3	D3 or D2	D3 or D2
Key Precursor	7-dehydrocholesterol in skin	Natural synthesis in animals	7-dehydrocholesterol from lanolin/lichen	D3/D2 added artificially
Availability	Dependent on season, latitude, time, and skin type	Limited number of foods	Wide availability, various forms	Common for milk, cereal, and some plant milks
Reliability	Variable, unreliable in many regions	Can contribute, but hard to meet needs alone	Highly reliable	Adds consistent, small amounts to diet
Risk of Toxicity	Extremely low; body self-regulates	Low, unlikely from food alone	Possible at very high, unsupervised doses	Low
Efficacy	Highly effective when conditions are right	Good, but often insufficient alone	Generally more potent than D2, very effective	Depends on fortification amount; D3 more effective than D2

The History Behind the Discovery

The story of vitamin D is closely tied to the history of rickets. In the mid-17th century, the disease became prevalent in industrialized cities where sunlight was scarce. While cod liver oil was used as a treatment in the 1800s, the underlying reason remained a mystery. It wasn't until the early 20th century that the link was fully understood.

In the 1920s, German physician Kurt Huldschinsky observed that ultraviolet light could cure rickets, suggesting an unknown substance was produced by the body.
In 1922, American scientist Elmer McCollum isolated the nutrient from cod liver oil and named it vitamin D, distinguishing it from vitamin A.
By the 1930s, Adolf Windaus and his colleagues at the University of Göttingen were instrumental in identifying the chemical structure of vitamin D3 (cholecalciferol) and its skin precursor, 7-dehydrocholesterol. For this and related work on sterols, Windaus received the Nobel Prize in Chemistry in 1928.

Conclusion

The question of where did vitamin D3 come from has a multi-faceted answer, encompassing both the natural processes of our bodies and modern advancements in food science. For most, the primary and most efficient source is cutaneous synthesis from sunlight. However, geographical location, season, and lifestyle often make dietary intake and supplementation necessary. By understanding these diverse origins—from the ancient power of the sun to the nutrients in fatty fish and scientifically-developed supplements—individuals can build a comprehensive nutrition diet to ensure they meet their vitamin D needs and support their overall health.

Frequently Asked Questions

For most people, the most effective way to produce vitamin D3 is through natural synthesis in the skin via sun exposure. The body is highly efficient at this process when conditions like latitude, season, and time of day are favorable.

Fatty fish are the best animal food sources of vitamin D3. This includes salmon, sardines, mackerel, and rainbow trout. Fish liver oils, egg yolks, and beef liver also provide smaller amounts.

Most vitamin D3 for supplements is produced by extracting 7-dehydrocholesterol from lanolin (sheep's wool fat) and irradiating it with ultraviolet light. A vegan version is sourced from lichens.

Most evidence indicates that vitamin D3 is more effective at raising and maintaining blood levels of vitamin D than vitamin D2, making D3 the generally preferred form for supplements.

No, it is difficult to get enough vitamin D3 from diet alone, as very few foods naturally contain significant amounts. Sun exposure or supplementation is often necessary to meet adequate levels.

The amount of vitamin D3 produced from sunlight is limited by skin pigmentation, age, latitude, season, time of day, and the use of clothing and sunscreen.

The discovery was linked to observations of rickets, which correlated with insufficient sunlight exposure. Research in the early 20th century confirmed that UV light cured the condition and led to the isolation and identification of the vitamin's chemical structure.