Where does cholecalciferol come from?

November 21, 2025 •

3 min read

Over 40% of US adults are considered vitamin D deficient, highlighting the importance of understanding its sources. The human body obtains cholecalciferol, or vitamin D3, from two primary pathways: natural production in the skin upon sun exposure and exogenous intake from certain foods and supplements.

Quick Summary

Cholecalciferol, also known as vitamin D3, originates from both natural and manufactured sources. Humans synthesize it in the skin via UVB radiation, while dietary intake comes from fatty fish, eggs, and fortified foods. Supplements are also a common source, often derived from lanolin or lichen.

Key Points

Endogenous Synthesis: Cholecalciferol (vitamin D3) is naturally produced in the skin when a cholesterol precursor is exposed to UVB radiation from sunlight.
Dietary Animal Sources: Key food sources for cholecalciferol include fatty fish (salmon, tuna), fish oils (cod liver oil), eggs, and beef liver.
Commercial Supplement Production: Most non-vegan cholecalciferol supplements are derived from lanolin, a wax found in sheep's wool.
Vegan Alternatives: Vegan-friendly vitamin D3 supplements are available, sourced from lichen.
Fortified Foods: Many everyday foods, such as milk, cereals, and orange juice, are fortified with vitamin D to aid public health.
D3 vs. D2 Potency: Cholecalciferol (D3) is generally more effective than ergocalciferol (D2) at increasing and sustaining vitamin D levels in the body.
Factors Affecting Production: Melanin in darker skin tones and advanced age can both decrease the efficiency of the body's natural cholecalciferol production from sunlight.

Endogenous Production in Human Skin

For most people, the primary source of cholecalciferol is the body's own production triggered by sunlight. The skin contains 7-dehydrocholesterol, which converts to pre-vitamin D3 and then cholecalciferol when exposed to ultraviolet B (UVB) light. Factors like latitude, season, cloud cover, and altitude influence this process. Darker skin with more melanin reduces production, as does age.

Dietary Sources: From Animal Products to Fortified Foods

Cholecalciferol can also be obtained through diet, although few foods naturally contain significant amounts.

Natural Animal Sources

Fatty Fish and Fish Oils: Fatty fish such as salmon, mackerel, and trout, as well as cod liver oil, are excellent sources.
Egg Yolks: Contain small amounts, varying with the hen's diet and sun exposure.
Beef Liver: Provides a modest amount along with other nutrients.

Fortified Foods

Many foods are fortified with vitamin D, often D2 or D3, to help prevent deficiency:

Milk and Dairy Products: Cow's milk, yogurt, and dairy alternatives are often fortified.
Plant-Based Milks: Soy, almond, and oat milk frequently have added vitamin D.
Breakfast Cereals and Orange Juice: Many brands fortify these products.

Commercial Production: From Lanolin to Lichen

Supplements are a common source of cholecalciferol, with production methods varying based on source material.

Lanolin-Derived D3 (Non-Vegan)

Most commercial D3 supplements are made from lanolin, found in sheep's wool. Cholesterol extracted from lanolin is converted to 7-dehydrocholesterol and then to cholecalciferol using UV light, mimicking natural synthesis.

Lichen-Derived D3 (Vegan)

Vegan D3 is extracted from lichen using water and plant ethanol. This provides a plant-based alternative to D2, which usually comes from UV-irradiated yeast and fungi.

Comparison: D2 vs. Cholecalciferol (D3)

Cholecalciferol (D3) is generally considered more effective than ergocalciferol (D2) at increasing and maintaining blood vitamin D levels.


Feature	Cholecalciferol (Vitamin D3)	Ergocalciferol (Vitamin D2)
Primary Source	Animal-based (sun exposure, fatty fish, lanolin)	Plant-based (UV-irradiated yeast/fungi)
Metabolic Potency	More effective at raising serum vitamin D levels	Less effective than D3
Source for Vegans	Lichen-derived options available	Standard D2 is vegan-friendly
Supplement Stability	More stable and longer-acting	Less stable

Conclusion

Cholecalciferol, vital for bone health and immune function, comes from internal body production via sun exposure, dietary sources like fatty fish and fortified foods, and supplements. Supplements are often derived from lanolin for non-vegan options or lichen for vegan alternatives. Understanding these sources helps individuals ensure adequate vitamin D intake.

MedlinePlus: Cholecalciferol (Vitamin D3)

How does the human body produce its own cholecalciferol?

The body's skin synthesizes cholecalciferol when 7-dehydrocholesterol is exposed to UVB light from the sun.

What are the best dietary sources of cholecalciferol?

Fatty fish (salmon, mackerel, trout) and fish liver oils are the best dietary sources. Egg yolks and beef liver contain smaller amounts.

Can vegans get cholecalciferol from food sources?

Natural cholecalciferol is in animal products, but vegans can find fortified foods like plant-based milks and cereals. Lichen-based supplements are also a vegan option.

What is the difference between ergocalciferol (D2) and cholecalciferol (D3)?

D2 comes from plants/fungi, while D3 is from animal sources and skin synthesis. D3 is generally more effective at raising blood vitamin D levels.

Where does the cholecalciferol in supplements come from?

Most non-vegan supplements use cholecalciferol derived from lanolin (sheep's wool) via UV irradiation of extracted cholesterol. Vegan supplements use lichen-derived D3.

How does skin pigmentation affect cholecalciferol production from the sun?

More melanin in darker skin reduces vitamin D production from UVB exposure, meaning darker-skinned individuals may need more sun exposure.

Is it possible to get too much cholecalciferol from sunlight?

The skin regulates production to prevent toxicity from sun exposure, but prolonged sun exposure increases skin cancer risk.

Frequently Asked Questions

Without sun exposure, the body gets cholecalciferol from dietary sources such as fatty fish, egg yolks, and fortified foods like milk and cereal, or from supplements.

For most humans, the primary natural source is endogenous synthesis in the skin when exposed to ultraviolet B (UVB) light from the sun.

Yes, vegan-friendly cholecalciferol supplements are available. These are produced commercially by extracting vitamin D3 from lichen.

The most common method for commercial supplement production involves extracting cholesterol from lanolin (sheep's wool) and irradiating it with ultraviolet light to convert it into cholecalciferol.

Clinical evidence suggests that cholecalciferol (D3) is more potent and more effective than ergocalciferol (D2) at raising and maintaining vitamin D levels in the blood.

Milk is fortified by adding vitamin D, which is often commercially produced cholecalciferol (D3) or ergocalciferol (D2), during the manufacturing process.

Some mushrooms exposed to ultraviolet (UV) light can produce significant amounts of vitamin D, mostly D2 but sometimes D3. Wild or specially treated mushrooms are the best source, as most commercially grown ones are cultivated in the dark.