Two Primary Ways We Can Obtain Vitamin D

December 17, 2025 •

4 min read

According to the National Institutes of Health, vitamin D is a fat-soluble vitamin that plays a vital role in bone health and immune function. Fortunately, there are two primary ways we can obtain vitamin D, allowing people to meet their needs through a combination of sun exposure and diet, which can include both natural foods and fortified products.

Quick Summary

The two main sources for acquiring vitamin D are sunlight and food. Sun exposure triggers the body's natural production, while dietary sources include fatty fish, fortified foods, and supplements.

Key Points

Sunlight is a natural source: The body produces vitamin D3 when the skin is exposed to UVB rays from the sun.
Dietary intake is an alternative: You can get vitamin D from a limited number of naturally occurring foods, as well as many fortified foods and supplements.
Production varies with location: Your ability to synthesize vitamin D from sunlight depends heavily on factors like your geographic latitude, the time of year, and the amount of clothing you wear.
Supplements are a reliable option: For those with limited sun exposure or dietary restrictions, supplements, particularly vitamin D3, are an effective way to maintain adequate levels.
A balanced approach is best: A combination of moderate sun exposure, a balanced diet including fortified foods, and potentially a supplement is often the best strategy for ensuring sufficient vitamin D.
Skin pigmentation affects synthesis: Individuals with darker skin tones have more melanin, which reduces the skin's efficiency in producing vitamin D from sunlight.
Fortified foods bridge the gap: Since very few foods naturally contain vitamin D, fortified cereals, milk, and juices are a major source in many diets.

The Sunlight Connection: A Natural Vitamin D Source

The most common and efficient way the human body obtains vitamin D is through direct exposure to sunlight. When your skin is exposed to the sun's ultraviolet B (UVB) rays, it triggers the synthesis of vitamin D3 (cholecalciferol) from a precursor molecule. This natural process is incredibly effective, and for most people, just 5–30 minutes of sun exposure to the face, arms, legs, or back, a few times per week, can be enough to produce sufficient vitamin D.

Factors Influencing Sun-Synthesized Vitamin D

Several factors affect how much vitamin D your body can produce from sunlight alone. These include:

Season and latitude: The angle of the sun's rays varies by season and proximity to the equator. People living in northern latitudes, for instance, are less able to produce vitamin D from sunlight during the winter months when the sun is lower in the sky.
Time of day: The optimal time for vitamin D synthesis is typically midday, between 10 a.m. and 4 p.m., when UVB rays are strongest.
Skin pigmentation: Melanin, the pigment responsible for darker skin tones, acts as a natural sunblock and reduces the skin's ability to produce vitamin D from sunlight. As a result, individuals with darker skin may require more sun exposure to produce the same amount of vitamin D as someone with lighter skin.
Age: The skin's efficiency in synthesizing vitamin D declines with age, making older adults more susceptible to deficiency.
Sunscreen and clothing: Using sunscreen or wearing clothing that covers most of the skin can significantly block the UVB rays needed for vitamin D production. However, experts advise balancing sensible sun exposure with skin cancer prevention.

Dietary Intake: The Food and Supplement Route

The second way to obtain vitamin D is through dietary sources, which is particularly important for those with limited sun exposure due to lifestyle, location, or skin type. While few foods naturally contain significant amounts of vitamin D, many products are fortified with it.

Naturally Occurring and Fortified Food Sources

Fatty fish: Oily fish like salmon, mackerel, trout, and sardines are some of the best natural food sources of vitamin D3.
Mushrooms: Certain types of mushrooms, particularly those exposed to UV light, can be a good plant-based source of vitamin D2.
Egg yolks: The yolks of eggs contain a small amount of vitamin D.
Fortified dairy and alternatives: Cow's milk, along with plant-based milks like soy, almond, and oat milk, are often fortified with vitamin D.
Fortified cereals and juices: Many breakfast cereals and orange juices have added vitamin D.

Supplements for Consistent Intake

For many, especially those who struggle to meet their needs through sun and diet alone, supplements are a reliable option. Vitamin D supplements come in two main forms: vitamin D2 (ergocalciferol, from plants) and vitamin D3 (cholecalciferol, from animals or lichen). Research suggests that vitamin D3 is more effective at raising and sustaining blood vitamin D levels than D2. A healthcare provider can determine the appropriate dosage for an individual based on their specific needs and blood test results.

Comparing Vitamin D Sources: Sun vs. Diet


Feature	Sun Exposure	Dietary Intake	Supplements
Primary Form	Produces Vitamin D3 in the skin.	Both Vitamin D2 (plant-based) and D3 (animal-based).	Typically Vitamin D3 for higher efficacy, but D2 is also available.
Dependence on Variables	Highly dependent on latitude, season, time of day, skin tone, and age.	Less dependent on external factors; intake is controlled.	Intake is easily controlled and not subject to environmental factors.
Risk of Overdose	Virtually none; the body self-regulates production to prevent toxicity.	Possible with overconsumption of fortified foods, though rare.	Possible with excessive daily intake; should be monitored by a doctor.
Suitability for All	Limited for infants, older adults, individuals with dark skin, or those with limited outdoor access.	Suitable for most, but difficult to get enough from food alone.	Excellent for filling nutritional gaps, especially in winter or for high-risk groups.
Other Considerations	Associated with skin cancer risk from overexposure.	Dietary sources offer additional nutrients.	Purity and absorption can vary by brand.

Conclusion

In conclusion, the two fundamental ways to obtain vitamin D are through cutaneous synthesis from sunlight and through dietary consumption. While sun exposure is the most efficient natural method, factors like geography, season, and skin pigmentation mean it isn't a reliable year-round option for everyone. Dietary sources, including a variety of fortified foods and supplements, provide a consistent and controllable way to ensure adequate vitamin D intake, especially when sun exposure is insufficient. For optimal health, most experts recommend a balanced approach that combines safe, moderate sun exposure with vitamin D-rich foods or supplements as needed to maintain adequate levels for strong bones, a healthy immune system, and overall well-being.

An authoritative resource for additional information on recommended intake levels is the Office of Dietary Supplements at the National Institutes of Health, which provides detailed fact sheets on vitamin D for consumers and health professionals.

Frequently Asked Questions

It is difficult for most people to get sufficient vitamin D from food sources alone because few foods naturally contain significant amounts. While some foods are fortified, many people require a supplement, especially in seasons with limited sunlight.

Yes. Vitamin D2 is derived from plant sources like fungi, while vitamin D3 comes from animals and is also synthesized by human skin upon sun exposure. Studies indicate that D3 is more effective at raising and maintaining overall vitamin D levels in the body.

For many people, about 5–30 minutes of sun exposure to the face, arms, legs, or back between 10 a.m. and 4 p.m. at least twice a week is enough to produce sufficient vitamin D. However, this varies based on factors like skin tone, location, and season.

No, you cannot get toxic levels of vitamin D from sun exposure alone. The body has a built-in mechanism that regulates production and prevents excessive amounts from being synthesized.

Foods naturally rich in vitamin D include fatty fish such as salmon, tuna, and mackerel, as well as cod liver oil, egg yolks, and beef liver. Some mushrooms exposed to UV light also contain vitamin D.

Groups at higher risk for vitamin D deficiency include breastfed infants, older adults, individuals with dark skin, people with limited sun exposure, and those with certain medical conditions that affect fat absorption.

Foods are fortified with vitamin D to help increase the population's intake of this essential nutrient, particularly since few foods contain it naturally. This practice helps to combat widespread deficiency.